Generate selectable for custom queries

This makes is easier to use getSingle() and watchSingle()
on them.
Fixes #120

extras/integration_tests/tests/lib/suite/transactions.dart

@@ -8,6 +8,7 @@ void transactionTests(TestExecutor executor) {
   test('transactions write data', () async {
     final db = Database(executor.createExecutor());
 
+    // ignore: invalid_use_of_protected_member, invalid_use_of_visible_for_testing_member
     await db.transaction((_) async {
       final florianId = await db.writeUser(People.florian);
 
@@ -30,6 +31,7 @@ void transactionTests(TestExecutor executor) {
     final db = Database(executor.createExecutor());
 
     try {
+      // ignore: invalid_use_of_protected_member, invalid_use_of_visible_for_testing_member
       await db.transaction((_) async {
         final florianId = await db.writeUser(People.florian);
 

moor/example/example.g.dart

@@ -832,22 +832,23 @@ abstract class _$Database extends GeneratedDatabase {
     );
   }
 
+  Selectable<TotalWeightResult> _totalWeightQuery(
+      {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
+          QueryEngine operateOn}) {
+    return (operateOn ?? this).customSelectQuery(
+        '      SELECT r.title, SUM(ir.amount) AS total_weight\n        FROM recipes r\n        INNER JOIN recipe_ingredients ir ON ir.recipe = r.id\n      GROUP BY r.id\n     ',
+        variables: [],
+        readsFrom: {recipes, ingredientInRecipes}).map(_rowToTotalWeightResult);
+  }
+
   Future<List<TotalWeightResult>> _totalWeight(
       {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
           QueryEngine operateOn}) {
-    return (operateOn ?? this).customSelect(
-        '      SELECT r.title, SUM(ir.amount) AS total_weight\n        FROM recipes r\n        INNER JOIN recipe_ingredients ir ON ir.recipe = r.id\n      GROUP BY r.id\n     ',
-        variables: []).then((rows) => rows.map(_rowToTotalWeightResult).toList());
+    return _totalWeightQuery(operateOn: operateOn).get();
   }
 
   Stream<List<TotalWeightResult>> _watchTotalWeight() {
-    return customSelectStream(
-        '      SELECT r.title, SUM(ir.amount) AS total_weight\n        FROM recipes r\n        INNER JOIN recipe_ingredients ir ON ir.recipe = r.id\n      GROUP BY r.id\n     ',
-        variables: [],
-        readsFrom: {
-          recipes,
-          ingredientInRecipes
-        }).map((rows) => rows.map(_rowToTotalWeightResult).toList());
+    return _totalWeightQuery().watch();
   }
 
   @override

moor/lib/src/runtime/database.dart

@@ -111,6 +111,7 @@ mixin QueryEngine on DatabaseConnectionUser {
   /// although it is very likely that the user meant to call it on the
   /// [Transaction] t. We can detect this by calling the function passed to
   /// `transaction` in a forked [Zone] storing the transaction in
+  @protected
   bool get topLevel => false;
 
   /// We can detect when a user called methods on the wrong [QueryEngine]
@@ -169,6 +170,8 @@ mixin QueryEngine on DatabaseConnectionUser {
   /// You can use the [updates] parameter so that moor knows which tables are
   /// affected by your query. All select streams that depend on a table
   /// specified there will then issue another query.
+  @protected
+  @visibleForTesting
   Future<int> customUpdate(String query,
       {List<Variable> variables = const [], Set<TableInfo> updates}) async {
     final engine = _resolvedEngine;
@@ -190,11 +193,12 @@ mixin QueryEngine on DatabaseConnectionUser {
   /// Executes a custom select statement once. To use the variables, mark them
   /// with a "?" in your [query]. They will then be changed to the appropriate
   /// value.
+  @protected
+  @visibleForTesting
+  @Deprecated('use customSelectQuery(...).get() instead')
   Future<List<QueryRow>> customSelect(String query,
       {List<Variable> variables = const []}) async {
-    return CustomSelectStatement(
-            query, variables, <TableInfo>{}, _resolvedEngine)
-        .get();
+    return customSelectQuery(query, variables: variables).get();
   }
 
   /// Creates a stream from a custom select statement.To use the variables, mark
@@ -202,15 +206,36 @@ mixin QueryEngine on DatabaseConnectionUser {
   /// appropriate value. The stream will re-emit items when any table in
   /// [readsFrom] changes, so be sure to set it to the set of tables your query
   /// reads data from.
+  @protected
+  @visibleForTesting
+  @Deprecated('use customSelectQuery(...).watch() instead')
   Stream<List<QueryRow>> customSelectStream(String query,
       {List<Variable> variables = const [], Set<TableInfo> readsFrom}) {
-    final tables = readsFrom ?? <TableInfo>{};
-    final statement =
-        CustomSelectStatement(query, variables, tables, _resolvedEngine);
-    return statement.watch();
+    return customSelectQuery(query, variables: variables, readsFrom: readsFrom)
+        .watch();
+  }
+
+  /// Creates a custom select statement from the given sql [query]. To run the
+  /// query once, use [Selectable.get]. For an auto-updating streams, set the
+  /// set of tables the ready [readsFrom] and use [Selectable.watch]. If you
+  /// know the query will never emit more than one row, you can also use
+  /// [Selectable.getSingle] and [Selectable.watchSingle] which return the item
+  /// directly or wrapping it into a list.
+  ///
+  /// If you use variables in your query (for instance with "?"), they will be
+  /// bound to the [variables] you specify on this query.
+  @protected
+  @visibleForTesting
+  Selectable<QueryRow> customSelectQuery(String query,
+      {List<Variable> variables = const [],
+      Set<TableInfo> readsFrom = const {}}) {
+    readsFrom ??= {};
+    return CustomSelectStatement(query, variables, readsFrom, _resolvedEngine);
   }
 
   /// Executes the custom sql [statement] on the database.
+  @protected
+  @visibleForTesting
   Future<void> customStatement(String statement) {
     return _resolvedEngine.executor.runCustom(statement);
   }
@@ -226,6 +251,8 @@ mixin QueryEngine on DatabaseConnectionUser {
   ///     might be different than that of the "global" database instance.
   ///  2. Nested transactions are not supported. Creating another transaction
   ///     inside a transaction returns the parent transaction.
+  @protected
+  @visibleForTesting
   Future transaction(Future Function(QueryEngine transaction) action) async {
     final resolved = _resolvedEngine;
     if (resolved is Transaction) {

moor/lib/src/runtime/statements/query.dart

@@ -120,6 +120,33 @@ abstract class Selectable<T> {
   Stream<T> watchSingle() {
     return watch().transform(singleElements());
   }
+
+  /// Maps this selectable by using [mapper].
+  ///
+  /// Each entry emitted by this [Selectable] will be transformed by the
+  /// [mapper] and then emitted to the selectable returned.
+  Selectable<N> map<N>(N Function(T) mapper) {
+    return _MappedSelectable<T, N>(this, mapper);
+  }
+}
+
+class _MappedSelectable<S, T> extends Selectable<T> {
+  final Selectable<S> _source;
+  final T Function(S) _mapper;
+
+  _MappedSelectable(this._source, this._mapper);
+
+  @override
+  Future<List<T>> get() {
+    return _source.get().then(_mapResults);
+  }
+
+  @override
+  Stream<List<T>> watch() {
+    return _source.watch().map(_mapResults);
+  }
+
+  List<T> _mapResults(List<S> results) => results.map(_mapper).toList();
 }
 
 mixin SingleTableQueryMixin<T extends Table, D extends DataClass>

moor/test/data/tables/todos.g.dart

@@ -1303,22 +1303,26 @@ abstract class _$TodoDb extends GeneratedDatabase {
     );
   }
 
-  Future<List<AllTodosWithCategoryResult>> allTodosWithCategory(
+  Selectable<AllTodosWithCategoryResult> allTodosWithCategoryQuery(
       {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
           QueryEngine operateOn}) {
-    return (operateOn ?? this).customSelect(
-        'SELECT t.*, c.id as catId, c."desc" as catDesc FROM todos t INNER JOIN categories c ON c.id = t.category',
-        variables: []).then((rows) => rows.map(_rowToAllTodosWithCategoryResult).toList());
-  }
-
-  Stream<List<AllTodosWithCategoryResult>> watchAllTodosWithCategory() {
-    return customSelectStream(
+    return (operateOn ?? this).customSelectQuery(
         'SELECT t.*, c.id as catId, c."desc" as catDesc FROM todos t INNER JOIN categories c ON c.id = t.category',
         variables: [],
         readsFrom: {
           categories,
           todosTable
-        }).map((rows) => rows.map(_rowToAllTodosWithCategoryResult).toList());
+        }).map(_rowToAllTodosWithCategoryResult);
+  }
+
+  Future<List<AllTodosWithCategoryResult>> allTodosWithCategory(
+      {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
+          QueryEngine operateOn}) {
+    return allTodosWithCategoryQuery(operateOn: operateOn).get();
+  }
+
+  Stream<List<AllTodosWithCategoryResult>> watchAllTodosWithCategory() {
+    return allTodosWithCategoryQuery().watch();
   }
 
   Future<int> deleteTodoById(
@@ -1344,7 +1348,7 @@ abstract class _$TodoDb extends GeneratedDatabase {
     );
   }
 
-  Future<List<TodoEntry>> withIn(
+  Selectable<TodoEntry> withInQuery(
       String var1,
       String var2,
       List<int> var3,
@@ -1353,21 +1357,7 @@ abstract class _$TodoDb extends GeneratedDatabase {
     var $highestIndex = 3;
     final expandedvar3 = $expandVar($highestIndex, var3.length);
     $highestIndex += var3.length;
-    return (operateOn ?? this).customSelect(
-        'SELECT * FROM todos WHERE title = ?2 OR id IN ($expandedvar3) OR title = ?1',
-        variables: [
-          Variable.withString(var1),
-          Variable.withString(var2),
-          for (var $ in var3) Variable.withInt($),
-        ]).then((rows) => rows.map(_rowToTodoEntry).toList());
-  }
-
-  Stream<List<TodoEntry>> watchWithIn(
-      String var1, String var2, List<int> var3) {
-    var $highestIndex = 3;
-    final expandedvar3 = $expandVar($highestIndex, var3.length);
-    $highestIndex += var3.length;
-    return customSelectStream(
+    return (operateOn ?? this).customSelectQuery(
         'SELECT * FROM todos WHERE title = ?2 OR id IN ($expandedvar3) OR title = ?1',
         variables: [
           Variable.withString(var1),
@@ -1376,29 +1366,46 @@ abstract class _$TodoDb extends GeneratedDatabase {
         ],
         readsFrom: {
           todosTable
-        }).map((rows) => rows.map(_rowToTodoEntry).toList());
+        }).map(_rowToTodoEntry);
+  }
+
+  Future<List<TodoEntry>> withIn(
+      String var1,
+      String var2,
+      List<int> var3,
+      {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
+          QueryEngine operateOn}) {
+    return withInQuery(var1, var2, var3, operateOn: operateOn).get();
+  }
+
+  Stream<List<TodoEntry>> watchWithIn(
+      String var1, String var2, List<int> var3) {
+    return withInQuery(var1, var2, var3).watch();
+  }
+
+  Selectable<TodoEntry> searchQuery(
+      int id,
+      {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
+          QueryEngine operateOn}) {
+    return (operateOn ?? this).customSelectQuery(
+        'SELECT * FROM todos WHERE CASE WHEN -1 = :id THEN 1 ELSE id = :id END',
+        variables: [
+          Variable.withInt(id),
+        ],
+        readsFrom: {
+          todosTable
+        }).map(_rowToTodoEntry);
   }
 
   Future<List<TodoEntry>> search(
       int id,
       {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
           QueryEngine operateOn}) {
-    return (operateOn ?? this).customSelect(
-        'SELECT * FROM todos WHERE CASE WHEN -1 = :id THEN 1 ELSE id = :id END',
-        variables: [
-          Variable.withInt(id),
-        ]).then((rows) => rows.map(_rowToTodoEntry).toList());
+    return searchQuery(id, operateOn: operateOn).get();
   }
 
   Stream<List<TodoEntry>> watchSearch(int id) {
-    return customSelectStream(
-        'SELECT * FROM todos WHERE CASE WHEN -1 = :id THEN 1 ELSE id = :id END',
-        variables: [
-          Variable.withInt(id),
-        ],
-        readsFrom: {
-          todosTable
-        }).map((rows) => rows.map(_rowToTodoEntry).toList());
+    return searchQuery(id).watch();
   }
 
   FindCustomResult _rowToFindCustomResult(QueryRow row) {
@@ -1408,20 +1415,23 @@ abstract class _$TodoDb extends GeneratedDatabase {
     );
   }
 
+  Selectable<FindCustomResult> findCustomQuery(
+      {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
+          QueryEngine operateOn}) {
+    return (operateOn ?? this).customSelectQuery(
+        'SELECT custom FROM table_without_p_k WHERE some_float < 10',
+        variables: [],
+        readsFrom: {tableWithoutPK}).map(_rowToFindCustomResult);
+  }
+
   Future<List<FindCustomResult>> findCustom(
       {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
           QueryEngine operateOn}) {
-    return (operateOn ?? this).customSelect(
-        'SELECT custom FROM table_without_p_k WHERE some_float < 10',
-        variables: []).then((rows) => rows.map(_rowToFindCustomResult).toList());
+    return findCustomQuery(operateOn: operateOn).get();
   }
 
   Stream<List<FindCustomResult>> watchFindCustom() {
-    return customSelectStream(
-            'SELECT custom FROM table_without_p_k WHERE some_float < 10',
-            variables: [],
-            readsFrom: {tableWithoutPK})
-        .map((rows) => rows.map(_rowToFindCustomResult).toList());
+    return findCustomQuery().watch();
   }
 
   @override
@@ -1453,19 +1463,11 @@ mixin _$SomeDaoMixin on DatabaseAccessor<TodoDb> {
     );
   }
 
-  Future<List<TodoEntry>> todosForUser(
+  Selectable<TodoEntry> todosForUserQuery(
       int user,
       {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
           QueryEngine operateOn}) {
-    return (operateOn ?? this).customSelect(
-        'SELECT t.* FROM todos t INNER JOIN shared_todos st ON st.todo = t.id INNER JOIN users u ON u.id = st.user WHERE u.id = :user',
-        variables: [
-          Variable.withInt(user),
-        ]).then((rows) => rows.map(_rowToTodoEntry).toList());
-  }
-
-  Stream<List<TodoEntry>> watchTodosForUser(int user) {
-    return customSelectStream(
+    return (operateOn ?? this).customSelectQuery(
         'SELECT t.* FROM todos t INNER JOIN shared_todos st ON st.todo = t.id INNER JOIN users u ON u.id = st.user WHERE u.id = :user',
         variables: [
           Variable.withInt(user),
@@ -1474,6 +1476,17 @@ mixin _$SomeDaoMixin on DatabaseAccessor<TodoDb> {
           todosTable,
           sharedTodos,
           users
-        }).map((rows) => rows.map(_rowToTodoEntry).toList());
+        }).map(_rowToTodoEntry);
+  }
+
+  Future<List<TodoEntry>> todosForUser(
+      int user,
+      {@Deprecated('No longer needed with Moor 1.6 - see the changelog for details')
+          QueryEngine operateOn}) {
+    return todosForUserQuery(user, operateOn: operateOn).get();
+  }
+
+  Stream<List<TodoEntry>> watchTodosForUser(int user) {
+    return todosForUserQuery(user).watch();
   }
 }

moor_flutter/example/lib/database/database.dart

@@ -91,14 +91,14 @@ class Database extends _$Database {
   Stream<List<CategoryWithCount>> categoriesWithCount() {
     // select all categories and load how many associated entries there are for
     // each category
-    return customSelectStream(
+    return customSelectQuery(
       'SELECT c.id, c.desc, '
       '(SELECT COUNT(*) FROM todos WHERE category = c.id) AS amount '
       'FROM categories c '
       'UNION ALL SELECT null, null, '
       '(SELECT COUNT(*) FROM todos WHERE category IS NULL)',
       readsFrom: {todos, categories},
-    ).map((rows) {
+    ).watch().map((rows) {
       // when we have the result set, map each row to the data class
       return rows.map((row) {
         final hasId = row.data['id'] != null;

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

@@ -1,5 +1,6 @@
 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';
@@ -33,6 +34,8 @@ class CreateTable {
   /// The AST of this `CREATE TABLE` statement.
   final ParseResult ast;
 
+  CreateTable(this.ast);
+
   SpecifiedTable extractTable(TypeMapper mapper) {
     final table =
         SchemaFromCreateTable().read(ast.rootNode as CreateTableStatement);
@@ -47,6 +50,7 @@ class CreateTable {
       final dartName = ReCase(sqlName).camelCase;
       final constraintWriter = StringBuffer();
       final moorType = mapper.resolvedToMoor(column.type);
+      UsedTypeConverter converter;
       String defaultValue;
 
       for (var constraint in column.constraints) {
@@ -65,6 +69,12 @@ class CreateTable {
           defaultValue = '$expressionName(${asDartLiteral(sqlDefault)})';
         }
 
+        if (constraint is MappedBy) {
+          converter = _readTypeConverter(constraint);
+          // don't write MAPPED BY constraints when creating the table
+          continue;
+        }
+
         if (constraintWriter.isNotEmpty) {
           constraintWriter.write(' ');
         }
@@ -79,6 +89,7 @@ class CreateTable {
         features: features,
         customConstraints: constraintWriter.toString(),
         defaultArgument: defaultValue,
+        typeConverter: converter,
       );
 
       foundColumns[column.name] = parsed;
@@ -114,5 +125,8 @@ class CreateTable {
     );
   }
 
-  CreateTable(this.ast);
+  UsedTypeConverter _readTypeConverter(MappedBy mapper) {
+    // todo we need to somehow parse the dart expression and check types
+    return null;
+  }
 }

moor_generator/lib/src/writer/query_writer.dart

@@ -46,6 +46,7 @@ class QueryWriter {
 
   void _writeSelect(StringBuffer buffer) {
     _writeMapping(buffer);
+    _writeSelectStatementCreator(buffer);
     _writeOneTimeReader(buffer);
     _writeStreamReader(buffer);
   }
@@ -54,6 +55,10 @@ class QueryWriter {
     return '_rowTo${_select.resultClassName}';
   }
 
+  String _nameOfCreationMethod() {
+    return '${_select.name}Query';
+  }
+
   /// Writes a mapping method that turns a "QueryRow" into the desired custom
   /// return type.
   void _writeMapping(StringBuffer buffer) {
@@ -87,27 +92,50 @@ class QueryWriter {
     }
   }
 
+  /// Writes a method returning a `Selectable<T>`, where `T` is the return type
+  /// of the custom query.
+  void _writeSelectStatementCreator(StringBuffer buffer) {
+    final returnType = 'Selectable<${_select.resultClassName}>';
+    final methodName = _nameOfCreationMethod();
+
+    buffer.write('$returnType $methodName(');
+    _writeParameters(buffer);
+    buffer.write(') {\n');
+
+    _writeExpandedDeclarations(buffer);
+    buffer
+      ..write('return (operateOn ?? this).')
+      ..write('customSelectQuery(${_queryCode()}, ');
+    _writeVariables(buffer);
+    buffer.write(', ');
+    _writeReadsFrom(buffer);
+
+    buffer.write(').map(');
+    buffer.write(_nameOfMappingMethod());
+    buffer.write(');\n}\n');
+  }
+
+  /*
+    Future<List<AllTodosWithCategoryResult>> allTodos(String name,
+      {QueryEngine overrideEngine}) {
+    return _allTodosWithCategoryQuery(name, engine: overrideEngine).get();
+  }
+   */
+
   void _writeOneTimeReader(StringBuffer buffer) {
     buffer.write('Future<List<${_select.resultClassName}>> ${query.name}(');
     _writeParameters(buffer);
-    buffer.write(') {\n');
-    _writeExpandedDeclarations(buffer);
-    buffer
-      ..write('return (operateOn ?? this).') // use custom engine, if set
-      ..write('customSelect(${_queryCode()},');
-    _writeVariables(buffer);
-    buffer
-      ..write(')')
-      ..write(
-          '.then((rows) => rows.map(${_nameOfMappingMethod()}).toList());\n')
-      ..write('\n}\n');
+    buffer..write(') {\n')..write('return ${_nameOfCreationMethod()}(');
+    _writeUseParameters(buffer);
+    buffer.write(').get();\n}\n');
   }
 
   void _writeStreamReader(StringBuffer buffer) {
-    // turning the query name into pascal case will remove underscores
     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('_')) {
       methodName = '_watch$upperQueryName';
     } else {
@@ -115,23 +143,10 @@ class QueryWriter {
     }
 
     buffer.write('Stream<List<${_select.resultClassName}>> $methodName(');
-    // don't supply an engine override parameter because select streams cannot
-    // be used in transaction or similar context, only on the main database
-    // engine.
     _writeParameters(buffer, dontOverrideEngine: true);
-    buffer.write(') {\n');
-
-    _writeExpandedDeclarations(buffer);
-    buffer..write('return customSelectStream(${_queryCode()},');
-
-    _writeVariables(buffer);
-    buffer.write(',');
-    _writeReadsFrom(buffer);
-
-    buffer
-      ..write(')')
-      ..write('.map((rows) => rows.map(${_nameOfMappingMethod()}).toList());\n')
-      ..write('\n}\n');
+    buffer..write(') {\n')..write('return ${_nameOfCreationMethod()}(');
+    _writeUseParameters(buffer, dontUseEngine: true);
+    buffer.write(').watch();\n}\n');
   }
 
   void _writeUpdatingQuery(StringBuffer buffer) {
@@ -177,6 +192,17 @@ 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}) {
+    into.write(query.variables.map((v) => v.dartParameterName).join(', '));
+    if (!dontUseEngine) {
+      if (query.variables.isNotEmpty) into.write(', ');
+      into.write('operateOn: operateOn');
+    }
+  }
+
   // Some notes on parameters and generating query code:
   // We expand array parameters to multiple variables at runtime (see the
   // documentation of FoundVariable and SqlQuery for further discussion).