Start migration of writer code

moor_generator/lib/src/analyzer/dart/parser.dart

@@ -7,14 +7,19 @@ import 'package:moor/sqlite_keywords.dart';
 import 'package:moor_generator/src/analyzer/errors.dart';
 import 'package:moor_generator/src/analyzer/session.dart';
 import 'package:moor_generator/src/model/specified_column.dart';
+import 'package:moor_generator/src/model/specified_dao.dart';
+import 'package:moor_generator/src/model/specified_database.dart';
 import 'package:moor_generator/src/model/specified_table.dart';
 import 'package:moor_generator/src/model/used_type_converter.dart';
 import 'package:moor_generator/src/utils/names.dart';
 import 'package:moor_generator/src/utils/type_utils.dart';
 import 'package:recase/recase.dart';
+import 'package:source_gen/source_gen.dart';
 
 part 'column_parser.dart';
 part 'table_parser.dart';
+part 'use_dao_parser.dart';
+part 'use_moor_parser.dart';
 
 class MoorDartParser {
   final DartTask task;

moor_generator/lib/src/analyzer/dart/use_dao_parser.dart

@@ -1,12 +1,9 @@
-import 'package:analyzer/dart/element/element.dart';
+part of 'parser.dart';
-import 'package:moor_generator/src/model/specified_dao.dart';
-import 'package:moor_generator/src/state/session.dart';
-import 'package:source_gen/source_gen.dart';
 
 class UseDaoParser {
-  final GeneratorSession session;
+  final DartTask dartTask;
 
-  UseDaoParser(this.session);
+  UseDaoParser(this.dartTask);
 
   /// If [element] has a `@UseDao` annotation, parses the database model
   /// declared by that class and the referenced tables.
@@ -24,11 +21,11 @@ class UseDaoParser {
             ?.map((e) => e.toStringValue()) ??
         {};
 
-    final parsedTables = await session.parseTables(tableTypes, element);
+    final parsedTables = await dartTask.parseTables(tableTypes, element);
-    parsedTables.addAll(await session.resolveIncludes(includes));
+    parsedTables.addAll(await dartTask.resolveIncludes(includes));
 
     final parsedQueries =
-        await session.parseQueries(queryStrings, parsedTables);
+        await dartTask.parseQueries(queryStrings, parsedTables);
 
     return SpecifiedDao(element, parsedTables, parsedQueries);
   }

moor_generator/lib/src/analyzer/dart/use_moor_parser.dart

@@ -1,13 +1,9 @@
-import 'package:analyzer/dart/element/element.dart';
+part of 'parser.dart';
-import 'package:analyzer/dart/element/type.dart';
-import 'package:moor_generator/src/model/specified_database.dart';
-import 'package:moor_generator/src/state/session.dart';
-import 'package:source_gen/source_gen.dart';
 
 class UseMoorParser {
-  final GeneratorSession session;
+  final DartTask task;
 
-  UseMoorParser(this.session);
+  UseMoorParser(this.task);
 
   /// If [element] has a `@UseMoor` annotation, parses the database model
   /// declared by that class and the referenced tables.
@@ -25,11 +21,10 @@ class UseMoorParser {
             ?.map((e) => e.toStringValue()) ??
         {};
 
-    final parsedTables = await session.parseTables(tableTypes, element);
+    final parsedTables = await task.parseTables(tableTypes, element);
-    parsedTables.addAll(await session.resolveIncludes(includes));
+    parsedTables.addAll(await task.resolveIncludes(includes));
 
-    final parsedQueries =
+    final parsedQueries = await task.parseQueries(queryStrings, parsedTables);
-        await session.parseQueries(queryStrings, parsedTables);
     final daoTypes = _readDaoTypes(annotation);
 
     return SpecifiedDatabase(element, parsedTables, daoTypes, parsedQueries);

moor_generator/lib/src/analyzer/errors.dart

@@ -1,22 +1,34 @@
 import 'package:analyzer/dart/element/element.dart';
 import 'package:collection/collection.dart';
+import 'package:meta/meta.dart';
+import 'package:source_span/source_span.dart';
 
 /// Base class for errors that can be presented to an user.
 class MoorError {
   final Severity severity;
+  final String message;
 
-  MoorError(this.severity);
+  MoorError({@required this.severity, this.message});
 }
 
 class ErrorInDartCode extends MoorError {
-  final String message;
   final Element affectedElement;
 
   ErrorInDartCode(
-      {this.message,
+      {String message,
       this.affectedElement,
       Severity severity = Severity.warning})
-      : super(severity);
+      : super(severity: severity, message: message);
+}
+
+class ErrorInMoorFile extends MoorError {
+  final FileSpan span;
+
+  ErrorInMoorFile(
+      {@required this.span,
+      String message,
+      Severity severity = Severity.warning})
+      : super(message: message, severity: severity);
 }
 
 class ErrorSink {

moor_generator/lib/src/analyzer/moor/create_table_reader.dart

@@ -1,40 +1,17 @@
+import 'package:moor_generator/src/analyzer/sql_queries/type_mapping.dart';
 import 'package:moor_generator/src/model/specified_column.dart';
 import 'package:moor_generator/src/model/specified_table.dart';
 import 'package:moor_generator/src/model/used_type_converter.dart';
-import 'package:moor_generator/src/parser/sql/type_mapping.dart';
 import 'package:moor_generator/src/utils/names.dart';
 import 'package:moor_generator/src/utils/string_escaper.dart';
 import 'package:recase/recase.dart';
 import 'package:sqlparser/sqlparser.dart';
 
-/*
+class CreateTableReader {
-We're in the process of defining what a .moor file could actually look like.
-At the moment, we only support "CREATE TABLE" statements:
-``` // content of a .moor file
-CREATE TABLE users (
-  id INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT,
-  name VARCHAR(100) NOT NULL,
-)
-```
-
-In the future, we'd also like to support
-- import statements between moor files
-- import statements from moor files referencing tables declared via the Dart DSL
-- declaring statements in these files, similar to how compiled statements work
-  with the annotation.
- */
-
-class ParsedMoorFile {
-  final List<CreateTable> declaredTables;
-
-  ParsedMoorFile(this.declaredTables);
-}
-
-class CreateTable {
   /// The AST of this `CREATE TABLE` statement.
   final ParseResult ast;
 
-  CreateTable(this.ast);
+  CreateTableReader(this.ast);
 
   SpecifiedTable extractTable(TypeMapper mapper) {
     final table =

moor_generator/lib/src/analyzer/moor/parser.dart

@@ -0,0 +1,45 @@
+import 'package:moor_generator/src/analyzer/errors.dart';
+import 'package:moor_generator/src/analyzer/moor/create_table_reader.dart';
+import 'package:moor_generator/src/analyzer/results.dart';
+import 'package:moor_generator/src/analyzer/session.dart';
+import 'package:sqlparser/sqlparser.dart';
+
+class MoorParser {
+  final MoorTask task;
+
+  MoorParser(this.task);
+
+  Future<ParsedMoorFile> parseAndAnalyze() {
+    final results =
+        SqlEngine(useMoorExtensions: true).parseMultiple(task.content);
+
+    final createdReaders = <CreateTableReader>[];
+
+    for (var parsedStmt in results) {
+      if (parsedStmt.rootNode is CreateTableStatement) {
+        createdReaders.add(CreateTableReader(parsedStmt));
+      } else {
+        task.reportError(ErrorInMoorFile(
+            span: parsedStmt.rootNode.span,
+            message: 'At the moment, only CREATE TABLE statements are supported'
+                'in .moor files'));
+      }
+    }
+
+    // all results have the same list of errors
+    final sqlErrors = results.isEmpty ? <ParsingError>[] : results.first.errors;
+
+    for (var error in sqlErrors) {
+      task.reportError(ErrorInMoorFile(
+        span: error.token.span,
+        message: error.message,
+      ));
+    }
+
+    final createdTables =
+        createdReaders.map((r) => r.extractTable(task.mapper)).toList();
+    final parsedFile = ParsedMoorFile(createdTables);
+
+    return Future.value(parsedFile);
+  }
+}

moor_generator/lib/src/analyzer/session.dart

@@ -1,18 +1,37 @@
 import 'dart:async';
 
+import 'package:analyzer/dart/constant/value.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
+import 'package:moor/moor.dart' show Table;
+import 'package:moor_generator/src/analyzer/dart/parser.dart';
 import 'package:moor_generator/src/analyzer/errors.dart';
+import 'package:moor_generator/src/analyzer/moor/parser.dart';
 import 'package:moor_generator/src/analyzer/results.dart';
+import 'package:moor_generator/src/analyzer/sql_queries/sql_parser.dart';
+import 'package:moor_generator/src/analyzer/sql_queries/type_mapping.dart';
 import 'package:moor_generator/src/backends/backend.dart';
+import 'package:moor_generator/src/model/specified_dao.dart';
+import 'package:moor_generator/src/model/specified_database.dart';
+import 'package:moor_generator/src/model/specified_table.dart';
+import 'package:moor_generator/src/model/sql_query.dart';
+import 'package:source_gen/source_gen.dart';
 
 /// Will store cached data about files that have already been analyzed.
 class MoorSession {
   MoorSession();
 
-  Future<DartTask> startDartTask(BackendTask backendTask) async {
+  Future<DartTask> startDartTask(BackendTask backendTask, {String uri}) async {
-    final library = await backendTask.resolveDart(backendTask.entrypoint);
+    final input = uri ?? backendTask.entrypoint;
+    final library = await backendTask.resolveDart(input);
     return DartTask(this, backendTask, library);
   }
+
+  Future<MoorTask> startMoorTask(BackendTask backendTask, {String uri}) async {
+    final input = uri ?? backendTask.entrypoint;
+    final source = await backendTask.readMoor(input);
+    return MoorTask(backendTask, this, source);
+  }
 }
 
 /// Used to parse and analyze a single file.
@@ -31,27 +50,89 @@ abstract class FileTask<R extends ParsedFile> {
 
 /// Session used to parse a Dart file and extract table information.
 class DartTask extends FileTask<ParsedDartFile> {
+  static const tableTypeChecker = const TypeChecker.fromRuntime(Table);
+
   final LibraryElement library;
+  MoorDartParser _parser;
+  MoorDartParser get parser => _parser;
 
   DartTask(MoorSession session, BackendTask task, this.library)
-      : super(task, session);
+      : super(task, session) {
+    _parser = MoorDartParser(this);
+  }
 
   @override
   FutureOr<ParsedDartFile> compute() {
     // TODO: implement compute
     return null;
   }
+
+  /// Parses a [SpecifiedDatabase] from the [ClassElement] which was annotated
+  /// with `@UseMoor` and the [annotation] reader that reads the `@UseMoor`
+  /// annotation.
+  Future<SpecifiedDatabase> parseDatabase(
+      ClassElement element, ConstantReader annotation) {
+    return UseMoorParser(this).parseDatabase(element, annotation);
+  }
+
+  /// Parses a [SpecifiedDao] from a class declaration that has a `UseDao`
+  /// [annotation].
+  Future<SpecifiedDao> parseDao(
+      ClassElement element, ConstantReader annotation) {
+    return UseDaoParser(this).parseDao(element, annotation);
+  }
+
+  /// Resolves a [SpecifiedTable] for the class of each [DartType] in [types].
+  /// The [initializedBy] element should be the piece of code that caused the
+  /// parsing (e.g. the database class that is annotated with `@UseMoor`). This
+  /// will allow for more descriptive error messages.
+  Future<List<SpecifiedTable>> parseTables(
+      Iterable<DartType> types, Element initializedBy) {
+    return Future.wait(types.map((type) {
+      if (!tableTypeChecker.isAssignableFrom(type.element)) {
+        reportError(ErrorInDartCode(
+          severity: Severity.criticalError,
+          message: 'The type $type is not a moor table',
+          affectedElement: initializedBy,
+        ));
+        return null;
+      } else {
+        return parser.parseTable(type.element as ClassElement);
+      }
+    })).then((list) => List.from(list)); // make growable
+  }
+
+  /// Reads all tables declared in sql by a `.moor` file in [paths].
+  Future<List<SpecifiedTable>> resolveIncludes(Iterable<String> paths) {
+    return Stream.fromFutures(
+            paths.map((path) => session.startMoorTask(backendTask, uri: path)))
+        .asyncMap((task) => task.compute())
+        .expand((file) => file.declaredTables)
+        .toList();
+  }
+
+  Future<List<SqlQuery>> parseQueries(
+      Map<DartObject, DartObject> fromAnnotation,
+      List<SpecifiedTable> availableTables) {
+    // no queries declared, so there is no point in starting a sql engine
+    if (fromAnnotation.isEmpty) return Future.value([]);
+
+    final parser = SqlParser(this, availableTables, fromAnnotation)..parse();
+
+    return Future.value(parser.foundQueries);
+  }
 }
 
 class MoorTask extends FileTask<ParsedMoorFile> {
-  final List<String> content;
+  final String content;
+  final TypeMapper mapper = TypeMapper();
 
   MoorTask(BackendTask task, MoorSession session, this.content)
       : super(task, session);
 
   @override
   FutureOr<ParsedMoorFile> compute() {
-    // TODO: implement compute
+    final parser = MoorParser(this);
-    return null;
+    return parser.parseAndAnalyze();
   }
 }

moor_generator/lib/src/analyzer/sql_queries/query_handler.dart

@@ -1,11 +1,14 @@
 import 'package:moor_generator/src/model/sql_query.dart';
 import 'package:moor_generator/src/model/used_type_converter.dart';
-import 'package:moor_generator/src/parser/sql/type_mapping.dart';
+import 'package:moor_generator/src/analyzer/sql_queries/type_mapping.dart';
 import 'package:moor_generator/src/utils/type_converter_hint.dart';
 import 'package:sqlparser/sqlparser.dart' hide ResultColumn;
 
 import 'affected_tables_visitor.dart';
 
+/// Maps an [AnalysisContext] from the sqlparser to a [SqlQuery] from this
+/// generator package by determining its type, return columns, variables and so
+/// on.
 class QueryHandler {
   final String name;
   final AnalysisContext context;

moor_generator/lib/src/analyzer/sql_queries/sql_parser.dart

@@ -1,16 +1,16 @@
 import 'package:analyzer/dart/constant/value.dart';
 import 'package:build/build.dart';
-import 'package:moor_generator/src/state/errors.dart';
+import 'package:moor_generator/src/analyzer/errors.dart';
+import 'package:moor_generator/src/analyzer/session.dart';
 import 'package:moor_generator/src/model/specified_table.dart';
 import 'package:moor_generator/src/model/sql_query.dart';
-import 'package:moor_generator/src/parser/sql/query_handler.dart';
+import 'package:moor_generator/src/analyzer/sql_queries/query_handler.dart';
-import 'package:moor_generator/src/parser/sql/type_mapping.dart';
+import 'package:moor_generator/src/analyzer/sql_queries/type_mapping.dart';
-import 'package:moor_generator/src/state/session.dart';
 import 'package:sqlparser/sqlparser.dart' hide ResultColumn;
 
 class SqlParser {
   final List<SpecifiedTable> tables;
-  final GeneratorSession session;
+  final FileTask task;
   final Map<DartObject, DartObject> definedQueries;
 
   final TypeMapper _mapper = TypeMapper();
@@ -18,7 +18,7 @@ class SqlParser {
 
   final List<SqlQuery> foundQueries = [];
 
-  SqlParser(this.session, this.tables, this.definedQueries);
+  SqlParser(this.task, this.tables, this.definedQueries);
 
   void _spawnEngine() {
     _engine = SqlEngine();
@@ -36,14 +36,15 @@ class SqlParser {
       try {
         context = _engine.analyze(sql);
       } catch (e, s) {
-        session.errors.add(MoorError(
+        task.reportError(MoorError(
-            critical: true,
+            severity: Severity.criticalError,
             message: 'Error while trying to parse $sql: $e, $s'));
         return;
       }
 
       for (var error in context.errors) {
-        session.errors.add(MoorError(
+        task.reportError(MoorError(
+          severity: Severity.warning,
           message: 'The sql query $sql is invalid: $error',
         ));
       }

moor_generator/lib/src/backends/build/build_backend.dart

@@ -0,0 +1,28 @@
+import 'package:analyzer/dart/element/element.dart';
+import 'package:build/build.dart';
+import 'package:moor_generator/src/backends/backend.dart';
+
+class BuildBackend extends Backend {}
+
+class BuildBackendTask extends BackendTask {
+  final BuildStep step;
+
+  BuildBackendTask(this.step);
+
+  @override
+  String get entrypoint => step.inputId.path;
+
+  AssetId _resolve(String uri) {
+    return AssetId.resolve(uri, from: step.inputId);
+  }
+
+  @override
+  Future<String> readMoor(String path) {
+    return step.readAsString(_resolve(path));
+  }
+
+  @override
+  Future<LibraryElement> resolveDart(String path) {
+    return step.resolver.libraryFor(_resolve(path));
+  }
+}

moor_generator/lib/src/backends/build/moor_builder.dart

@@ -1,10 +1,14 @@
 import 'package:build/build.dart';
+import 'package:moor_generator/src/backends/build/build_backend.dart';
 import 'package:moor_generator/src/dao_generator.dart';
 import 'package:moor_generator/src/moor_generator.dart';
-import 'package:moor_generator/src/state/options.dart';
 import 'package:source_gen/source_gen.dart';
 
+part 'options.dart';
+
 class MoorBuilder extends SharedPartBuilder {
+  final BuildBackend backend = BuildBackend();
+
   factory MoorBuilder(BuilderOptions options) {
     final parsedOptions = MoorOptions.fromBuilder(options.config);
 

moor_generator/lib/src/backends/build/options.dart

@@ -1,3 +1,5 @@
+part of 'moor_builder.dart';
+
 class MoorOptions {
   final bool generateFromJsonStringConstructor;
 

moor_generator/lib/src/parser/column_parser.dart

@@ -1,223 +0,0 @@
-import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/element/element.dart';
-import 'package:analyzer/dart/element/type.dart';
-import 'package:moor_generator/src/model/used_type_converter.dart';
-import 'package:moor_generator/src/state/errors.dart';
-import 'package:moor_generator/src/model/specified_column.dart';
-import 'package:moor_generator/src/parser/parser.dart';
-import 'package:moor_generator/src/state/session.dart';
-import 'package:moor_generator/src/utils/type_utils.dart';
-import 'package:recase/recase.dart';
-
-const String startInt = 'integer';
-const String startString = 'text';
-const String startBool = 'boolean';
-const String startDateTime = 'dateTime';
-const String startBlob = 'blob';
-const String startReal = 'real';
-
-final Set<String> starters = {
-  startInt,
-  startString,
-  startBool,
-  startDateTime,
-  startBlob,
-  startReal,
-};
-
-const String _methodNamed = 'named';
-const String _methodReferences = 'references';
-const String _methodAutoIncrement = 'autoIncrement';
-const String _methodWithLength = 'withLength';
-const String _methodNullable = 'nullable';
-const String _methodCustomConstraint = 'customConstraint';
-const String _methodDefault = 'withDefault';
-const String _methodMap = 'map';
-
-const String _errorMessage = 'This getter does not create a valid column that '
-    'can be parsed by moor. Please refer to the readme from moor to see how '
-    'columns are formed. If you have any questions, feel free to raise an issue.';
-
-class ColumnParser extends ParserBase {
-  ColumnParser(GeneratorSession session) : super(session);
-
-  SpecifiedColumn parse(MethodDeclaration getter, Element getterElement) {
-    /*
-      These getters look like this: ... get id => integer().autoIncrement()();
-      The last () is a FunctionExpressionInvocation, the entries before that
-      (here autoIncrement and integer) are MethodInvocations.
-      We go through each of the method invocations until we hit one that starts
-      the chain (integer, text, boolean, etc.). From each method in the chain,
-      we can extract what it means for the column (name, auto increment, PK,
-      constraints...).
-     */
-
-    final expr = returnExpressionOfMethod(getter);
-
-    if (!(expr is FunctionExpressionInvocation)) {
-      session.errors.add(MoorError(
-        affectedElement: getter.declaredElement,
-        message: _errorMessage,
-        critical: true,
-      ));
-
-      return null;
-    }
-
-    var remainingExpr =
-        (expr as FunctionExpressionInvocation).function as MethodInvocation;
-
-    String foundStartMethod;
-    String foundExplicitName;
-    String foundCustomConstraint;
-    Expression foundDefaultExpression;
-    Expression createdTypeConverter;
-    DartType typeConverterRuntime;
-    var nullable = false;
-
-    final foundFeatures = <ColumnFeature>[];
-
-    while (true) {
-      final methodName = remainingExpr.methodName.name;
-
-      if (starters.contains(methodName)) {
-        foundStartMethod = methodName;
-        break;
-      }
-
-      switch (methodName) {
-        case _methodNamed:
-          if (foundExplicitName != null) {
-            session.errors.add(
-              MoorError(
-                critical: false,
-                affectedElement: getter.declaredElement,
-                message:
-                    "You're setting more than one name here, the first will "
-                    'be used',
-              ),
-            );
-          }
-
-          foundExplicitName =
-              readStringLiteral(remainingExpr.argumentList.arguments.first, () {
-            session.errors.add(
-              MoorError(
-                critical: false,
-                affectedElement: getter.declaredElement,
-                message:
-                    'This table name is cannot be resolved! Please only use '
-                    'a constant string as parameter for .named().',
-              ),
-            );
-          });
-          break;
-        case _methodReferences:
-          break;
-        case _methodWithLength:
-          final args = remainingExpr.argumentList;
-          final minArg = findNamedArgument(args, 'min');
-          final maxArg = findNamedArgument(args, 'max');
-
-          foundFeatures.add(LimitingTextLength.withLength(
-            min: readIntLiteral(minArg, () {}),
-            max: readIntLiteral(maxArg, () {}),
-          ));
-          break;
-        case _methodAutoIncrement:
-          foundFeatures.add(AutoIncrement());
-          // a column declared as auto increment is always a primary key
-          foundFeatures.add(const PrimaryKey());
-          break;
-        case _methodNullable:
-          nullable = true;
-          break;
-        case _methodCustomConstraint:
-          foundCustomConstraint =
-              readStringLiteral(remainingExpr.argumentList.arguments.first, () {
-            session.errors.add(
-              MoorError(
-                critical: false,
-                affectedElement: getter.declaredElement,
-                message:
-                    'This constraint is cannot be resolved! Please only use '
-                    'a constant string as parameter for .customConstraint().',
-              ),
-            );
-          });
-          break;
-        case _methodDefault:
-          final args = remainingExpr.argumentList;
-          final expression = args.arguments.single;
-          foundDefaultExpression = expression;
-          break;
-        case _methodMap:
-          final args = remainingExpr.argumentList;
-          final expression = args.arguments.single;
-
-          // the map method has a parameter type that resolved to the runtime
-          // type of the custom object
-          final type = remainingExpr.typeArgumentTypes.single;
-
-          createdTypeConverter = expression;
-          typeConverterRuntime = type;
-          break;
-      }
-
-      // We're not at a starting method yet, so we need to go deeper!
-      final inner = (remainingExpr.target) as MethodInvocation;
-      remainingExpr = inner;
-    }
-
-    ColumnName name;
-    if (foundExplicitName != null) {
-      name = ColumnName.explicitly(foundExplicitName);
-    } else {
-      name = ColumnName.implicitly(ReCase(getter.name.name).snakeCase);
-    }
-
-    final columnType = _startMethodToColumnType(foundStartMethod);
-
-    UsedTypeConverter converter;
-    if (createdTypeConverter != null && typeConverterRuntime != null) {
-      converter = UsedTypeConverter(
-          expression: createdTypeConverter,
-          mappedType: typeConverterRuntime,
-          sqlType: columnType);
-    }
-
-    return SpecifiedColumn(
-        type: columnType,
-        dartGetterName: getter.name.name,
-        name: name,
-        overriddenJsonName: _readJsonKey(getterElement),
-        customConstraints: foundCustomConstraint,
-        nullable: nullable,
-        features: foundFeatures,
-        defaultArgument: foundDefaultExpression?.toSource(),
-        typeConverter: converter);
-  }
-
-  ColumnType _startMethodToColumnType(String startMethod) {
-    return const {
-      startBool: ColumnType.boolean,
-      startString: ColumnType.text,
-      startInt: ColumnType.integer,
-      startDateTime: ColumnType.datetime,
-      startBlob: ColumnType.blob,
-      startReal: ColumnType.real,
-    }[startMethod];
-  }
-
-  String _readJsonKey(Element getter) {
-    final annotations = getter.metadata;
-    final object = annotations.singleWhere((e) {
-      final value = e.computeConstantValue();
-      return isFromMoor(value.type) && value.type.name == 'JsonKey';
-    }, orElse: () => null);
-
-    if (object == null) return null;
-
-    return object.constantValue.getField('key').toStringValue();
-  }
-}

moor_generator/lib/src/parser/moor/moor_analyzer.dart

@@ -1,63 +0,0 @@
-import 'package:moor_generator/src/parser/moor/parsed_moor_file.dart';
-import 'package:source_span/source_span.dart';
-import 'package:sqlparser/sqlparser.dart';
-
-/// Parses and analyzes the experimental `.moor` files containing sql
-/// statements.
-class MoorAnalyzer {
-  /// Content of the `.moor` file we're analyzing.
-  final String content;
-
-  MoorAnalyzer(this.content);
-
-  Future<MoorParsingResult> analyze() {
-    final results = SqlEngine().parseMultiple(content);
-
-    final createdTables = <CreateTable>[];
-    final errors = <MoorParsingError>[];
-
-    for (var parsedStmt in results) {
-      if (parsedStmt.rootNode is CreateTableStatement) {
-        createdTables.add(CreateTable(parsedStmt));
-      } else {
-        errors.add(
-          MoorParsingError(
-            parsedStmt.rootNode.span,
-            message:
-                'At the moment, only CREATE TABLE statements are supported in .moor files',
-          ),
-        );
-      }
-    }
-
-    // all results have the same list of errors
-    final sqlErrors = results.isEmpty ? <ParsingError>[] : results.first.errors;
-
-    for (var error in sqlErrors) {
-      errors.add(MoorParsingError(error.token.span, message: error.message));
-    }
-
-    final parsedFile = ParsedMoorFile(createdTables);
-
-    return Future.value(MoorParsingResult(parsedFile, errors));
-  }
-}
-
-class MoorParsingResult {
-  final ParsedMoorFile parsedFile;
-  final List<MoorParsingError> errors;
-
-  MoorParsingResult(this.parsedFile, this.errors);
-}
-
-class MoorParsingError {
-  final FileSpan span;
-  final String message;
-
-  MoorParsingError(this.span, {this.message});
-
-  @override
-  String toString() {
-    return span.message(message, color: true);
-  }
-}

moor_generator/lib/src/parser/parser.dart

@@ -1,64 +0,0 @@
-import 'package:analyzer/dart/ast/ast.dart';
-import 'package:moor_generator/src/state/errors.dart';
-import 'package:moor_generator/src/model/specified_table.dart';
-import 'package:moor_generator/src/state/session.dart';
-
-class Parser {
-  List<SpecifiedTable> specifiedTables;
-
-  void init() async {}
-}
-
-class ParserBase {
-  final GeneratorSession session;
-
-  ParserBase(this.session);
-
-  Expression returnExpressionOfMethod(MethodDeclaration method) {
-    final body = method.body;
-
-    if (!(body is ExpressionFunctionBody)) {
-      session.errors.add(MoorError(
-          affectedElement: method.declaredElement,
-          critical: true,
-          message:
-              'This method must have an expression body (use => instead of {return ...})'));
-      return null;
-    }
-
-    return (method.body as ExpressionFunctionBody).expression;
-  }
-
-  String readStringLiteral(Expression expression, void onError()) {
-    if (!(expression is StringLiteral)) {
-      onError();
-    } else {
-      final value = (expression as StringLiteral).stringValue;
-      if (value == null) {
-        onError();
-      } else {
-        return value;
-      }
-    }
-
-    return null;
-  }
-
-  int readIntLiteral(Expression expression, void onError()) {
-    if (!(expression is IntegerLiteral)) {
-      onError();
-      // ignore: avoid_returning_null
-      return null;
-    } else {
-      return (expression as IntegerLiteral).value;
-    }
-  }
-
-  Expression findNamedArgument(ArgumentList args, String argName) {
-    final argument = args.arguments.singleWhere(
-        (e) => e is NamedExpression && e.name.label.name == argName,
-        orElse: () => null) as NamedExpression;
-
-    return argument?.expression;
-  }
-}

moor_generator/lib/src/parser/table_parser.dart

@@ -1,129 +0,0 @@
-import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/element/element.dart';
-import 'package:moor_generator/src/state/errors.dart';
-import 'package:moor_generator/src/model/specified_column.dart';
-import 'package:moor_generator/src/model/specified_table.dart';
-import 'package:moor_generator/src/parser/parser.dart';
-import 'package:moor_generator/src/state/session.dart';
-import 'package:moor_generator/src/utils/names.dart';
-import 'package:moor_generator/src/utils/type_utils.dart';
-import 'package:recase/recase.dart';
-import 'package:moor/sqlite_keywords.dart';
-
-class TableParser extends ParserBase {
-  TableParser(GeneratorSession session) : super(session);
-
-  Future<SpecifiedTable> parse(ClassElement element) async {
-    final sqlName = await _parseTableName(element);
-    if (sqlName == null) return null;
-
-    final columns = await _parseColumns(element);
-
-    final table = SpecifiedTable(
-      fromClass: element,
-      columns: columns,
-      sqlName: escapeIfNeeded(sqlName),
-      dartTypeName: _readDartTypeName(element),
-      primaryKey: await _readPrimaryKey(element, columns),
-    );
-
-    var index = 0;
-    for (var converter in table.converters) {
-      converter
-        ..index = index++
-        ..table = table;
-    }
-
-    return table;
-  }
-
-  String _readDartTypeName(ClassElement element) {
-    final nameAnnotation = element.metadata.singleWhere(
-        (e) => e.computeConstantValue().type.name == 'DataClassName',
-        orElse: () => null);
-
-    if (nameAnnotation == null) {
-      return dataClassNameForClassName(element.name);
-    } else {
-      return nameAnnotation.constantValue.getField('name').toStringValue();
-    }
-  }
-
-  Future<String> _parseTableName(ClassElement element) async {
-    // todo allow override via a field (final String tableName = '') as well
-
-    final tableNameGetter = element.getGetter('tableName');
-    if (tableNameGetter == null) {
-      // class does not override tableName. So just use the dart class name
-      // instead. Will use placed_orders for a class called PlacedOrders
-      return ReCase(element.name).snakeCase;
-    }
-
-    // we expect something like get tableName => "myTableName", the getter
-    // must do nothing more complicated
-    final tableNameDeclaration =
-        await session.loadElementDeclaration(tableNameGetter);
-    final returnExpr = returnExpressionOfMethod(
-        tableNameDeclaration.node as MethodDeclaration);
-
-    final tableName = readStringLiteral(returnExpr, () {
-      session.errors.add(MoorError(
-          critical: true,
-          message:
-              'This getter must return a string literal, and do nothing more',
-          affectedElement: tableNameGetter));
-    });
-
-    return tableName;
-  }
-
-  Future<Set<SpecifiedColumn>> _readPrimaryKey(
-      ClassElement element, List<SpecifiedColumn> columns) async {
-    final primaryKeyGetter = element.getGetter('primaryKey');
-    if (primaryKeyGetter == null) {
-      return null;
-    }
-
-    final resolved = await session.loadElementDeclaration(primaryKeyGetter);
-    final ast = resolved.node as MethodDeclaration;
-    final body = ast.body;
-    if (body is! ExpressionFunctionBody) {
-      session.errors.add(MoorError(
-          affectedElement: primaryKeyGetter,
-          message: 'This must return a set literal using the => syntax!'));
-      return null;
-    }
-    final expression = (body as ExpressionFunctionBody).expression;
-    final parsedPrimaryKey = <SpecifiedColumn>{};
-
-    if (expression is SetOrMapLiteral) {
-      for (var entry in expression.elements) {
-        if (entry is Identifier) {
-          final column = columns
-              .singleWhere((column) => column.dartGetterName == entry.name);
-          parsedPrimaryKey.add(column);
-        } else {
-          print('Unexpected entry in expression.elements: $entry');
-        }
-      }
-    } else {
-      session.errors.add(MoorError(
-          affectedElement: primaryKeyGetter,
-          message: 'This must return a set literal!'));
-    }
-
-    return parsedPrimaryKey;
-  }
-
-  Future<List<SpecifiedColumn>> _parseColumns(ClassElement element) {
-    final columns = element.fields
-        .where((field) => isColumn(field.type) && field.getter != null);
-
-    return Future.wait(columns.map((field) async {
-      final resolved = await session.loadElementDeclaration(field.getter);
-      final node = resolved.node as MethodDeclaration;
-
-      return await session.parseColumn(node, field.getter);
-    }));
-  }
-}

moor_generator/lib/src/state/errors.dart

@@ -1,17 +0,0 @@
-import 'package:analyzer/dart/element/element.dart';
-
-class MoorError {
-  final bool critical;
-  final String message;
-  final Element affectedElement;
-
-  MoorError({this.critical = false, this.message, this.affectedElement});
-}
-
-class ErrorStore {
-  final List<MoorError> errors = [];
-
-  void add(MoorError error) => errors.add(error);
-
-  bool get hasCriticalError => errors.any((e) => e.critical);
-}

moor_generator/lib/src/state/generator_state.dart

@@ -1,39 +0,0 @@
-import 'package:analyzer/dart/element/type.dart';
-import 'package:build/build.dart';
-import 'package:moor/moor.dart';
-import 'package:moor_generator/src/model/specified_table.dart';
-import 'package:moor_generator/src/state/session.dart';
-import 'package:source_gen/source_gen.dart';
-
-import 'options.dart';
-
-GeneratorState _state;
-
-/// Uses the created instance of the generator state or creates one via the
-/// [create] callback if necessary.
-GeneratorState useState(GeneratorState Function() create) {
-  return _state ??= create();
-}
-
-class GeneratorState {
-  final MoorOptions options;
-
-  final Map<DartType, Future<SpecifiedTable>> _foundTables = {};
-  final tableTypeChecker = const TypeChecker.fromRuntime(Table);
-
-  GeneratorState(this.options);
-
-  GeneratorSession startSession(BuildStep step) {
-    return GeneratorSession(this, step);
-  }
-
-  /// Parses the [SpecifiedTable] from a [type]. As this operation is very
-  /// expensive, we always try to only perform it once.
-  ///
-  /// The [resolve] function is responsible for performing the actual analysis
-  /// and it will be called when the [type] has not yet been resolved.
-  Future<SpecifiedTable> parseTable(
-      DartType type, Future<SpecifiedTable> Function() resolve) {
-    return _foundTables.putIfAbsent(type, resolve);
-  }
-}

moor_generator/lib/src/state/session.dart

@@ -1,129 +0,0 @@
-import 'package:analyzer/dart/analysis/results.dart';
-import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/constant/value.dart';
-import 'package:analyzer/dart/element/element.dart';
-import 'package:analyzer/dart/element/type.dart';
-import 'package:build/build.dart';
-import 'package:moor_generator/src/model/specified_column.dart';
-import 'package:moor_generator/src/model/specified_dao.dart';
-import 'package:moor_generator/src/model/specified_database.dart';
-import 'package:moor_generator/src/model/specified_table.dart';
-import 'package:moor_generator/src/model/sql_query.dart';
-import 'package:moor_generator/src/parser/column_parser.dart';
-import 'package:moor_generator/src/parser/moor/moor_analyzer.dart';
-import 'package:moor_generator/src/parser/sql/sql_parser.dart';
-import 'package:moor_generator/src/parser/sql/type_mapping.dart';
-import 'package:moor_generator/src/parser/table_parser.dart';
-import 'package:moor_generator/src/parser/use_dao_parser.dart';
-import 'package:moor_generator/src/parser/use_moor_parser.dart';
-import 'package:source_gen/source_gen.dart';
-
-import 'errors.dart';
-import 'generator_state.dart';
-import 'options.dart';
-import 'writer.dart';
-
-class GeneratorSession {
-  final GeneratorState state;
-  final ErrorStore errors = ErrorStore();
-  final BuildStep step;
-
-  final Writer writer = Writer();
-
-  TableParser _tableParser;
-  ColumnParser _columnParser;
-
-  MoorOptions get options => state.options;
-
-  GeneratorSession(this.state, this.step) {
-    _tableParser = TableParser(this);
-    _columnParser = ColumnParser(this);
-  }
-
-  Future<ElementDeclarationResult> loadElementDeclaration(
-      Element element) async {
-    final resolvedLibrary = await element.library.session
-        .getResolvedLibraryByElement(element.library);
-
-    return resolvedLibrary.getElementDeclaration(element);
-  }
-
-  /// Parses a [SpecifiedDatabase] from the [ClassElement] which was annotated
-  /// with `@UseMoor` and the [annotation] reader that reads the `@UseMoor`
-  /// annotation.
-  Future<SpecifiedDatabase> parseDatabase(
-      ClassElement element, ConstantReader annotation) {
-    return UseMoorParser(this).parseDatabase(element, annotation);
-  }
-
-  /// Parses a [SpecifiedDao] from a class declaration that has a `UseDao`
-  /// [annotation].
-  Future<SpecifiedDao> parseDao(
-      ClassElement element, ConstantReader annotation) {
-    return UseDaoParser(this).parseDao(element, annotation);
-  }
-
-  /// Resolves a [SpecifiedTable] for the class of each [DartType] in [types].
-  /// The [initializedBy] element should be the piece of code that caused the
-  /// parsing (e.g. the database class that is annotated with `@UseMoor`). This
-  /// will allow for more descriptive error messages.
-  Future<List<SpecifiedTable>> parseTables(
-      Iterable<DartType> types, Element initializedBy) {
-    return Future.wait(types.map((type) {
-      if (!state.tableTypeChecker.isAssignableFrom(type.element)) {
-        errors.add(MoorError(
-          critical: true,
-          message: 'The type $type is not a moor table',
-          affectedElement: initializedBy,
-        ));
-        return null;
-      } else {
-        return _tableParser.parse(type.element as ClassElement);
-      }
-    })).then((list) => List.from(list)); // make growable
-  }
-
-  Future<List<SpecifiedTable>> resolveIncludes(Iterable<String> paths) async {
-    final mapper = TypeMapper();
-    final foundTables = <SpecifiedTable>[];
-
-    for (var path in paths) {
-      final asset = AssetId.resolve(path, from: step.inputId);
-      String content;
-      try {
-        content = await step.readAsString(asset);
-      } catch (e) {
-        errors.add(MoorError(
-            critical: true,
-            message: 'The included file $path could not be found'));
-      }
-
-      final parsed = await MoorAnalyzer(content).analyze();
-      foundTables.addAll(
-          parsed.parsedFile.declaredTables.map((t) => t.extractTable(mapper)));
-
-      for (var parseError in parsed.errors) {
-        errors.add(MoorError(message: "Can't parse sql in $path: $parseError"));
-      }
-    }
-
-    return foundTables;
-  }
-
-  /// Parses a column from a getter [e] declared inside a table class and its
-  /// resolved AST node [m].
-  Future<SpecifiedColumn> parseColumn(MethodDeclaration m, Element e) {
-    return Future.value(_columnParser.parse(m, e));
-  }
-
-  Future<List<SqlQuery>> parseQueries(
-      Map<DartObject, DartObject> fromAnnotation,
-      List<SpecifiedTable> availableTables) {
-    // no queries declared, so there is no point in starting a sql engine
-    if (fromAnnotation.isEmpty) return Future.value([]);
-
-    final parser = SqlParser(this, availableTables, fromAnnotation)..parse();
-
-    return Future.value(parser.foundQueries);
-  }
-}

moor_generator/lib/src/writer/database_writer.dart

@@ -1,11 +1,8 @@
 import 'package:moor_generator/src/model/sql_query.dart';
-import 'package:moor_generator/src/state/session.dart';
+import 'package:moor_generator/src/writer/utils/memoized_getter.dart';
-import 'package:moor_generator/src/writer/query_writer.dart';
-import 'package:moor_generator/src/writer/result_set_writer.dart';
 import 'package:recase/recase.dart';
 import 'package:moor_generator/src/model/specified_database.dart';
 import 'package:moor_generator/src/writer/table_writer.dart';
-import 'utils.dart';
 
 class DatabaseWriter {
   final SpecifiedDatabase db;
@@ -19,13 +16,6 @@ class DatabaseWriter {
       TableWriter(table, session).writeInto(buffer);
     }
 
-    // Write additional classes to hold the result of custom queries
-    for (final query in db.queries) {
-      if (query is SqlSelectQuery && query.resultSet.matchingTable == null) {
-        ResultSetWriter(query).write(buffer);
-      }
-    }
-
     // Write the database class
     final className = '_\$${db.fromClass.name}';
     buffer.write('abstract class $className extends GeneratedDatabase {\n'

moor_generator/lib/src/writer/queries/query_writer.dart

@@ -1,9 +1,11 @@
 import 'dart:math' show max;
 
+import 'package:moor_generator/src/backends/build/moor_builder.dart';
 import 'package:moor_generator/src/model/specified_column.dart';
 import 'package:moor_generator/src/model/sql_query.dart';
-import 'package:moor_generator/src/state/session.dart';
 import 'package:moor_generator/src/utils/string_escaper.dart';
+import 'package:moor_generator/src/writer/queries/result_set_writer.dart';
+import 'package:moor_generator/src/writer/writer.dart';
 import 'package:recase/recase.dart';
 import 'package:sqlparser/sqlparser.dart';
 
@@ -16,13 +18,18 @@ const highestAssignedIndexVar = '\$highestIndex';
 /// should be included in a generated database or dao class.
 class QueryWriter {
   final SqlQuery query;
-  final GeneratorSession session;
+  final Scope scope;
   SqlSelectQuery get _select => query as SqlSelectQuery;
   UpdatingQuery get _update => query as UpdatingQuery;
 
+  MoorOptions get options => scope.writer.options;
+  StringBuffer _buffer;
+
   final Set<String> _writtenMappingMethods;
 
-  QueryWriter(this.query, this.session, this._writtenMappingMethods);
+  QueryWriter(this.query, this.scope, this._writtenMappingMethods) {
+    _buffer = scope.leaf();
+  }
 
   /// The expanded sql that we insert into queries whenever an array variable
   /// appears. For the query "SELECT * FROM t WHERE x IN ?", we generate
@@ -36,19 +43,25 @@ class QueryWriter {
     return 'expanded${v.dartParameterName}';
   }
 
-  void writeInto(StringBuffer buffer) {
+  void writeInto() {
     if (query is SqlSelectQuery) {
-      _writeSelect(buffer);
+      final select = query as SqlSelectQuery;
+      if (select.resultSet.matchingTable == null) {
+        // query needs its own result set - write that now
+        final buffer = scope.findScopeOfLevel(DartScope.library).leaf();
+        ResultSetWriter(select).write(buffer);
+      }
+      _writeSelect();
     } else if (query is UpdatingQuery) {
-      _writeUpdatingQuery(buffer);
+      _writeUpdatingQuery();
     }
   }
 
-  void _writeSelect(StringBuffer buffer) {
+  void _writeSelect() {
-    _writeMapping(buffer);
+    _writeMapping();
-    _writeSelectStatementCreator(buffer);
+    _writeSelectStatementCreator();
-    _writeOneTimeReader(buffer);
+    _writeOneTimeReader();
-    _writeStreamReader(buffer);
+    _writeStreamReader();
   }
 
   String _nameOfMappingMethod() {
@@ -61,11 +74,11 @@ class QueryWriter {
 
   /// Writes a mapping method that turns a "QueryRow" into the desired custom
   /// return type.
-  void _writeMapping(StringBuffer buffer) {
+  void _writeMapping() {
     // avoid writing mapping methods twice if the same result class is written
     // more than once.
     if (!_writtenMappingMethods.contains(_nameOfMappingMethod())) {
-      buffer
+      _buffer
         ..write('${_select.resultClassName} ${_nameOfMappingMethod()}')
         ..write('(QueryRow row) {\n')
         ..write('return ${_select.resultClassName}(');
@@ -84,35 +97,35 @@ class QueryWriter {
           code = '$field.mapToDart($code)';
         }
 
-        buffer.write('$fieldName: $code,');
+        _buffer.write('$fieldName: $code,');
       }
 
-      buffer.write(');\n}\n');
+      _buffer.write(');\n}\n');
       _writtenMappingMethods.add(_nameOfMappingMethod());
     }
   }
 
   /// Writes a method returning a `Selectable<T>`, where `T` is the return type
   /// of the custom query.
-  void _writeSelectStatementCreator(StringBuffer buffer) {
+  void _writeSelectStatementCreator() {
     final returnType = 'Selectable<${_select.resultClassName}>';
     final methodName = _nameOfCreationMethod();
 
-    buffer.write('$returnType $methodName(');
+    _buffer.write('$returnType $methodName(');
-    _writeParameters(buffer);
+    _writeParameters();
-    buffer.write(') {\n');
+    _buffer.write(') {\n');
 
-    _writeExpandedDeclarations(buffer);
+    _writeExpandedDeclarations();
-    buffer
+    _buffer
       ..write('return (operateOn ?? this).')
       ..write('customSelectQuery(${_queryCode()}, ');
-    _writeVariables(buffer);
+    _writeVariables();
-    buffer.write(', ');
+    _buffer.write(', ');
-    _writeReadsFrom(buffer);
+    _writeReadsFrom();
 
-    buffer.write(').map(');
+    _buffer.write(').map(');
-    buffer.write(_nameOfMappingMethod());
+    _buffer.write(_nameOfMappingMethod());
-    buffer.write(');\n}\n');
+    _buffer.write(');\n}\n');
   }
 
   /*
@@ -122,34 +135,35 @@ class QueryWriter {
   }
    */
 
-  void _writeOneTimeReader(StringBuffer buffer) {
+  void _writeOneTimeReader() {
-    buffer.write('Future<List<${_select.resultClassName}>> ${query.name}(');
+    _buffer.write('Future<List<${_select.resultClassName}>> ${query.name}(');
-    _writeParameters(buffer);
+    _writeParameters();
-    buffer..write(') {\n')..write('return ${_nameOfCreationMethod()}(');
+    _buffer..write(') {\n')..write('return ${_nameOfCreationMethod()}(');
-    _writeUseParameters(buffer);
+    _writeUseParameters();
-    buffer.write(').get();\n}\n');
+    _buffer.write(').get();\n}\n');
   }
 
-  void _writeStreamReader(StringBuffer buffer) {
+  void _writeStreamReader() {
     final upperQueryName = ReCase(query.name).pascalCase;
 
     String methodName;
     // turning the query name into pascal case will remove underscores, add the
     // "private" modifier back in if needed
-    if (session.options.fixPrivateWatchMethods && query.name.startsWith('_')) {
+    if (scope.writer.options.fixPrivateWatchMethods &&
+        query.name.startsWith('_')) {
       methodName = '_watch$upperQueryName';
     } else {
       methodName = 'watch$upperQueryName';
     }
 
-    buffer.write('Stream<List<${_select.resultClassName}>> $methodName(');
+    _buffer.write('Stream<List<${_select.resultClassName}>> $methodName(');
-    _writeParameters(buffer, dontOverrideEngine: true);
+    _writeParameters(dontOverrideEngine: true);
-    buffer..write(') {\n')..write('return ${_nameOfCreationMethod()}(');
+    _buffer..write(') {\n')..write('return ${_nameOfCreationMethod()}(');
-    _writeUseParameters(buffer, dontUseEngine: true);
+    _writeUseParameters(dontUseEngine: true);
-    buffer.write(').watch();\n}\n');
+    _buffer.write(').watch();\n}\n');
   }
 
-  void _writeUpdatingQuery(StringBuffer buffer) {
+  void _writeUpdatingQuery() {
     /*
       Future<int> test() {
     return customUpdate('', variables: [], updates: {});
@@ -157,24 +171,23 @@ class QueryWriter {
      */
     final implName = _update.isInsert ? 'customInsert' : 'customUpdate';
 
-    buffer.write('Future<int> ${query.name}(');
+    _buffer.write('Future<int> ${query.name}(');
-    _writeParameters(buffer);
+    _writeParameters();
-    buffer.write(') {\n');
+    _buffer.write(') {\n');
 
-    _writeExpandedDeclarations(buffer);
+    _writeExpandedDeclarations();
-    buffer
+    _buffer
       ..write('return (operateOn ?? this).')
       ..write('$implName(${_queryCode()},');
 
-    _writeVariables(buffer);
+    _writeVariables();
-    buffer.write(',');
+    _buffer.write(',');
-    _writeUpdates(buffer);
+    _writeUpdates();
 
-    buffer..write(',);\n}\n');
+    _buffer..write(',);\n}\n');
   }
 
-  void _writeParameters(StringBuffer buffer,
+  void _writeParameters({bool dontOverrideEngine = false}) {
-      {bool dontOverrideEngine = false}) {
     final paramList = query.variables.map((v) {
       var dartType = dartTypeNames[v.type];
       if (v.isArray) {
@@ -183,13 +196,13 @@ class QueryWriter {
       return '$dartType ${v.dartParameterName}';
     }).join(', ');
 
-    buffer.write(paramList);
+    _buffer.write(paramList);
 
     // write named optional parameter to configure the query engine used to
     // execute the statement,
     if (!dontOverrideEngine) {
-      if (query.variables.isNotEmpty) buffer.write(', ');
+      if (query.variables.isNotEmpty) _buffer.write(', ');
-      buffer.write('{@Deprecated(${asDartLiteral(queryEngineWarningDesc)}) '
+      _buffer.write('{@Deprecated(${asDartLiteral(queryEngineWarningDesc)}) '
           'QueryEngine operateOn}');
     }
   }
@@ -197,11 +210,11 @@ class QueryWriter {
   /// Writes code that uses the parameters as declared by [_writeParameters],
   /// assuming that for each parameter, a variable with the same name exists
   /// in the current scope.
-  void _writeUseParameters(StringBuffer into, {bool dontUseEngine = false}) {
+  void _writeUseParameters({bool dontUseEngine = false}) {
-    into.write(query.variables.map((v) => v.dartParameterName).join(', '));
+    _buffer.write(query.variables.map((v) => v.dartParameterName).join(', '));
     if (!dontUseEngine) {
-      if (query.variables.isNotEmpty) into.write(', ');
+      if (query.variables.isNotEmpty) _buffer.write(', ');
-      into.write('operateOn: operateOn');
+      _buffer.write('operateOn: operateOn');
     }
   }
 
@@ -217,7 +230,7 @@ class QueryWriter {
   // "vars" variable twice. To do this, a local var called "$currentVarIndex"
   // keeps track of the highest variable number assigned.
 
-  void _writeExpandedDeclarations(StringBuffer buffer) {
+  void _writeExpandedDeclarations() {
     var indexCounterWasDeclared = false;
     var highestIndexBeforeArray = 0;
 
@@ -228,12 +241,12 @@ class QueryWriter {
           // add +1 because that's going to be the first index of the expanded
           // array
           final firstVal = highestIndexBeforeArray + 1;
-          buffer.write('var $highestAssignedIndexVar = $firstVal;');
+          _buffer.write('var $highestAssignedIndexVar = $firstVal;');
           indexCounterWasDeclared = true;
         }
 
         // final expandedvar1 = $expandVar(<startIndex>, <amount>);
-        buffer
+        _buffer
           ..write('final ')
           ..write(_expandedName(variable))
           ..write(' = ')
@@ -244,7 +257,7 @@ class QueryWriter {
           ..write('.length);\n');
 
         // increase highest index for the next array
-        buffer
+        _buffer
           ..write('$highestAssignedIndexVar += ')
           ..write(variable.dartParameterName)
           ..write('.length;');
@@ -256,8 +269,8 @@ class QueryWriter {
     }
   }
 
-  void _writeVariables(StringBuffer buffer) {
+  void _writeVariables() {
-    buffer..write('variables: [');
+    _buffer..write('variables: [');
 
     for (var variable in query.variables) {
       // for a regular variable: Variable.withInt(x),
@@ -266,15 +279,15 @@ class QueryWriter {
       final name = variable.dartParameterName;
 
       if (variable.isArray) {
-        buffer.write('for (var \$ in $name) $constructor(\$)');
+        _buffer.write('for (var \$ in $name) $constructor(\$)');
       } else {
-        buffer.write('$constructor($name)');
+        _buffer.write('$constructor($name)');
       }
 
-      buffer.write(',');
+      _buffer.write(',');
     }
 
-    buffer..write(']');
+    _buffer..write(']');
   }
 
   /// Returns a Dart string literal representing the query after variables have
@@ -295,29 +308,29 @@ class QueryWriter {
           .singleWhere((f) => f.variable.resolvedIndex == sqlVar.resolvedIndex);
       if (!moorVar.isArray) continue;
 
-      // write everything that comes before this var into the buffer
+      // write everything that comes before this var into the_buffer
       final currentIndex = sqlVar.firstPosition;
       final queryPart = query.sql.substring(lastIndex, currentIndex);
-      buffer.write(escapeForDart(queryPart));
+      _buffer.write(escapeForDart(queryPart));
       lastIndex = sqlVar.lastPosition;
 
       // write the ($expandedVar) par
-      buffer.write('(\$${_expandedName(moorVar)})');
+      _buffer.write('(\$${_expandedName(moorVar)})');
     }
 
     // write the final part after the last variable, plus the ending '
-    buffer..write(escapeForDart(query.sql.substring(lastIndex)))..write("'");
+    _buffer..write(escapeForDart(query.sql.substring(lastIndex)))..write("'");
 
     return buffer.toString();
   }
 
-  void _writeReadsFrom(StringBuffer buffer) {
+  void _writeReadsFrom() {
     final from = _select.readsFrom.map((t) => t.tableFieldName).join(', ');
-    buffer..write('readsFrom: {')..write(from)..write('}');
+    _buffer..write('readsFrom: {')..write(from)..write('}');
   }
 
-  void _writeUpdates(StringBuffer buffer) {
+  void _writeUpdates() {
     final from = _update.updates.map((t) => t.tableFieldName).join(', ');
-    buffer..write('updates: {')..write(from)..write('}');
+    _buffer..write('updates: {')..write(from)..write('}');
   }
 }

moor_generator/lib/src/writer/queries/result_set_writer.dart

@@ -1,6 +1,7 @@
 import 'package:moor_generator/src/model/specified_column.dart';
 import 'package:moor_generator/src/model/sql_query.dart';
 
+/// Writes a class holding the result of an sql query into Dart.
 class ResultSetWriter {
   final SqlSelectQuery query;
 

moor_generator/lib/src/writer/tables/data_class_writer.dart

@@ -1,13 +1,17 @@
 import 'package:moor_generator/src/model/specified_table.dart';
-import 'package:moor_generator/src/state/session.dart';
 import 'package:moor_generator/src/writer/utils/hash_code.dart';
+import 'package:moor_generator/src/writer/writer.dart';
 import 'package:recase/recase.dart';
 
 class DataClassWriter {
   final SpecifiedTable table;
-  final GeneratorSession session;
+  final Scope scope;
 
-  DataClassWriter(this.table, this.session);
+  StringBuffer _buffer;
+
+  DataClassWriter(this.table, this.scope) {
+    _buffer = scope.leaf();
+  }
 
   void writeInto(StringBuffer buffer) {
     buffer.write(

moor_generator/lib/src/writer/tables/table_writer.dart

@@ -4,7 +4,7 @@ import 'package:moor_generator/src/state/session.dart';
 import 'package:moor_generator/src/utils/string_escaper.dart';
 import 'package:moor_generator/src/writer/data_class_writer.dart';
 import 'package:moor_generator/src/writer/update_companion_writer.dart';
-import 'package:moor_generator/src/writer/utils.dart';
+import 'package:moor_generator/src/writer/memoized_getter.dart';
 
 class TableWriter {
   final SpecifiedTable table;

moor_generator/lib/src/writer/writer.dart

@@ -1,4 +1,5 @@
 import 'package:meta/meta.dart';
+import 'package:moor_generator/src/backends/build/moor_builder.dart';
 
 /// Manages a tree structure which we use to generate code.
 ///
@@ -10,6 +11,9 @@ import 'package:meta/meta.dart';
 /// passing a [Scope] we will always be able to write code in a parent scope.
 class Writer {
   final Scope _root = Scope(parent: null);
+  final MoorOptions options;
+
+  Writer(this.options);
 
   String writeGenerated() => _leafNodes(_root).join();
 
@@ -41,8 +45,13 @@ abstract class _Node {
 /// we just pass a single [StringBuffer] around, this is annoying to manage.
 class Scope extends _Node {
   final List<_Node> _children = [];
+  final DartScope scope;
+  final Writer writer;
 
-  Scope({@required Scope parent}) : super(parent);
+  Scope({@required Scope parent, Writer writer})
+      : scope = parent?.scope?.nextLevel ?? DartScope.library,
+        writer = writer ?? parent?.writer,
+        super(parent);
 
   Scope get root {
     var found = this;
@@ -52,6 +61,19 @@ class Scope extends _Node {
     return found;
   }
 
+  Iterable<Scope> get _thisAndParents sync* {
+    var scope = this;
+    do {
+      yield scope;
+      scope = scope.parent;
+    } while (scope != null);
+  }
+
+  Scope findScopeOfLevel(DartScope level) {
+    return _thisAndParents
+        .firstWhere((scope) => scope.scope.isSuperScope(level));
+  }
+
   Scope child() {
     final child = Scope(parent: this);
     _children.add(child);
@@ -70,3 +92,27 @@ class _LeafNode extends _Node {
 
   _LeafNode(Scope parent) : super(parent);
 }
+
+class DartScope {
+  static const DartScope library = DartScope._(0);
+  static const DartScope topLevelMember = DartScope._(1);
+  static const DartScope inner = DartScope._(2);
+
+  static const List<DartScope> values = [library, topLevelMember, inner];
+
+  final int _id;
+
+  const DartScope._(this._id);
+
+  DartScope get nextLevel {
+    if (_id == values.length - 1) {
+      // already in innermost level
+      return this;
+    }
+    return values[_id + 1];
+  }
+
+  bool isSuperScope(DartScope other) {
+    return other._id >= _id;
+  }
+}