Typealiases and easier defaults for scoped components

Closes #1993.

drift/test/generated/custom_tables.g.dart

@@ -1606,12 +1606,13 @@ abstract class _$CustomTablesDb extends GeneratedDatabase {
   }
 
   Selectable<Config> readMultiple(List<String> var1,
-      {OrderBy Function(ConfigTable config) clause = _$moor$default$0}) {
+      {ReadMultiple$clause? clause}) {
     var $arrayStartIndex = 1;
     final expandedvar1 = $expandVar($arrayStartIndex, var1.length);
     $arrayStartIndex += var1.length;
-    final generatedclause =
-        $write(clause(this.config), startIndex: $arrayStartIndex);
+    final generatedclause = $write(
+        clause?.call(this.config) ?? const OrderBy.nothing(),
+        startIndex: $arrayStartIndex);
     $arrayStartIndex += generatedclause.amountOfVariables;
     return customSelect(
         'SELECT * FROM config WHERE config_key IN ($expandedvar1) ${generatedclause.sql}',
@@ -1625,12 +1626,11 @@ abstract class _$CustomTablesDb extends GeneratedDatabase {
         }).asyncMap(config.mapFromRow);
   }
 
-  Selectable<Config> readDynamic(
-      {Expression<bool> Function(ConfigTable config) predicate =
-          _$moor$default$1}) {
+  Selectable<Config> readDynamic({ReadDynamic$predicate? predicate}) {
     var $arrayStartIndex = 1;
-    final generatedpredicate =
-        $write(predicate(this.config), startIndex: $arrayStartIndex);
+    final generatedpredicate = $write(
+        predicate?.call(this.config) ?? const CustomExpression('(TRUE)'),
+        startIndex: $arrayStartIndex);
     $arrayStartIndex += generatedpredicate.amountOfVariables;
     return customSelect('SELECT * FROM config WHERE ${generatedpredicate.sql}',
         variables: [
@@ -1643,10 +1643,11 @@ abstract class _$CustomTablesDb extends GeneratedDatabase {
   }
 
   Selectable<String> typeConverterVar(SyncType? var1, List<SyncType?> var2,
-      {Expression<bool> Function(ConfigTable config) pred = _$moor$default$2}) {
+      {TypeConverterVar$pred? pred}) {
     var $arrayStartIndex = 2;
-    final generatedpred =
-        $write(pred(this.config), startIndex: $arrayStartIndex);
+    final generatedpred = $write(
+        pred?.call(this.config) ?? const CustomExpression('(TRUE)'),
+        startIndex: $arrayStartIndex);
     $arrayStartIndex += generatedpred.amountOfVariables;
     final expandedvar2 = $expandVar($arrayStartIndex, var2.length);
     $arrayStartIndex += var2.length;
@@ -1694,9 +1695,7 @@ abstract class _$CustomTablesDb extends GeneratedDatabase {
     });
   }
 
-  Selectable<MultipleResult> multiple(
-      {required Expression<bool> Function(WithDefaults d, WithConstraints c)
-          predicate}) {
+  Selectable<MultipleResult> multiple({required Multiple$predicate predicate}) {
     var $arrayStartIndex = 1;
     final generatedpredicate = $write(
         predicate(
@@ -1734,8 +1733,7 @@ abstract class _$CustomTablesDb extends GeneratedDatabase {
         }).asyncMap(email.mapFromRow);
   }
 
-  Selectable<ReadRowIdResult> readRowId(
-      {required Expression<int> Function(ConfigTable config) expr}) {
+  Selectable<ReadRowIdResult> readRowId({required ReadRowId$expr expr}) {
     var $arrayStartIndex = 1;
     final generatedexpr =
         $write(expr(this.config), startIndex: $arrayStartIndex);
@@ -1865,11 +1863,9 @@ abstract class _$CustomTablesDb extends GeneratedDatabase {
       const DriftDatabaseOptions(storeDateTimeAsText: true);
 }
 
-OrderBy _$moor$default$0(ConfigTable _) => const OrderBy.nothing();
-Expression<bool> _$moor$default$1(ConfigTable _) =>
-    const CustomExpression('(TRUE)');
-Expression<bool> _$moor$default$2(ConfigTable _) =>
-    const CustomExpression('(TRUE)');
+typedef ReadMultiple$clause = OrderBy Function(ConfigTable config);
+typedef ReadDynamic$predicate = Expression<bool> Function(ConfigTable config);
+typedef TypeConverterVar$pred = Expression<bool> Function(ConfigTable config);
 
 class JsonResult extends CustomResultSet {
   final String key;
@@ -1927,6 +1923,9 @@ class MultipleResult extends CustomResultSet {
   }
 }
 
+typedef Multiple$predicate = Expression<bool> Function(
+    WithDefaults d, WithConstraints c);
+
 class ReadRowIdResult extends CustomResultSet {
   final int rowid;
   final String configKey;
@@ -1966,6 +1965,8 @@ class ReadRowIdResult extends CustomResultSet {
   }
 }
 
+typedef ReadRowId$expr = Expression<int> Function(ConfigTable config);
+
 class NestedResult extends CustomResultSet {
   final WithDefault defaults;
   final List<WithConstraint> nestedQuery0;

drift_dev/lib/src/model/sql_query.dart

@@ -827,6 +827,12 @@ class FoundDartPlaceholder extends FoundElement {
       type is ExpressionDartPlaceholderType &&
       (type as ExpressionDartPlaceholderType).defaultValue != null;
 
+  bool get hasDefaultOrImplicitFallback =>
+      hasDefault ||
+      (type is SimpleDartPlaceholderType &&
+          (type as SimpleDartPlaceholderType).kind ==
+              SimpleDartPlaceholderKind.orderBy);
+
   FoundDartPlaceholder(this.type, this.name, this.availableResultSets);
 
   @override

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

@@ -4,6 +4,7 @@ import 'package:drift_dev/src/analyzer/sql_queries/explicit_alias_transformer.da
 import 'package:drift_dev/src/analyzer/sql_queries/nested_queries.dart';
 import 'package:drift_dev/src/utils/string_escaper.dart';
 import 'package:drift_dev/writer.dart';
+import 'package:recase/recase.dart';
 import 'package:sqlparser/sqlparser.dart' hide ResultColumn;
 
 import 'sql_writer.dart';
@@ -254,20 +255,25 @@ class QueryWriter {
   void _writeParameters(SqlQuery query) {
     final namedElements = <FoundElement>[];
 
+    String scopedTypeName(FoundDartPlaceholder element) {
+      return '${ReCase(query.name).pascalCase}\$${ReCase(element.name).camelCase}';
+    }
+
     String typeFor(FoundElement element) {
-      var type = element.dartTypeCode();
+      return element.dartTypeCode();
+    }
 
-      if (element is FoundDartPlaceholder &&
-          element.writeAsScopedFunction(options)) {
-        // Generate a function providing result sets that are in scope as args
+    String writeScopedTypeFor(FoundDartPlaceholder element) {
+      final root = scope.root;
+      final type = typeFor(element);
+      final scopedType = scopedTypeName(element);
 
-        final args = element.availableResultSets
-            .map((e) => '${e.argumentType} ${e.name}')
-            .join(', ');
-        type = '$type Function($args)';
-      }
+      final args = element.availableResultSets
+          .map((e) => '${e.argumentType} ${e.name}')
+          .join(', ');
+      root.leaf().write('typedef $scopedType = $type Function($args);');
 
-      return type;
+      return scopedType;
     }
 
     var needsComma = false;
@@ -285,7 +291,11 @@ class QueryWriter {
       } else {
         if (needsComma) _buffer.write(', ');
 
-        final type = typeFor(element);
+        var type = typeFor(element);
+        if (element is FoundDartPlaceholder &&
+            element.writeAsScopedFunction(options)) {
+          type = writeScopedTypeFor(element);
+        }
         _buffer.write('$type ${element.dartParameterName}');
         needsComma = true;
       }
@@ -302,62 +312,27 @@ class QueryWriter {
         needsComma = true;
 
         String? defaultCode;
+        var isNullable = false;
+        var type = typeFor(optional);
 
         if (optional is FoundDartPlaceholder) {
-          final kind = optional.type;
-          if (kind is ExpressionDartPlaceholderType &&
-              kind.defaultValue != null) {
-            // Wrap the default expression in parentheses to avoid issues with
-            // the surrounding precedence in SQL.
-            final sql = SqlWriter(scope.options)
-                .writeNodeIntoStringLiteral(Parentheses(kind.defaultValue!));
-            defaultCode = 'const CustomExpression($sql)';
-          } else if (kind is SimpleDartPlaceholderType &&
-              kind.kind == SimpleDartPlaceholderKind.orderBy) {
-            defaultCode = 'const OrderBy.nothing()';
-          }
+          // If optional Dart placeholders are written as functions, they are
+          // generated as nullable parameters. The default is handled with a
+          // `??` in the method's body.
+          if (optional.writeAsScopedFunction(options)) {
+            isNullable = optional.hasDefaultOrImplicitFallback;
+            type = writeScopedTypeFor(optional);
 
-          // If the parameter is converted to a scoped function, we also need to
-          // generate a scoped function as a default value. Since defaults have
-          // to be constants, we generate a top-level function which is then
-          // used as a tear-off.
-          if (optional.writeAsScopedFunction(options) && defaultCode != null) {
-            final root = scope.root;
-            final counter = root.counter++;
-            // ignore: prefer_interpolation_to_compose_strings
-            final functionName = r'_$moor$default$' + counter.toString();
-
-            final buffer = root.leaf()
-              ..write(optional.dartTypeCode(scope.generationOptions))
-              ..write(' ')
-              ..write(functionName)
-              ..write('(');
-            var i = 0;
-            for (final arg in optional.availableResultSets) {
-              if (i != 0) buffer.write(', ');
-
-              buffer
-                ..write(arg.argumentType)
-                ..write(' ')
-                ..write('_' * (i + 1));
-              i++;
+            if (isNullable) {
+              type += '?';
             }
-            buffer
-              ..write(') => ')
-              ..write(defaultCode)
-              ..write(';');
-
-            // With the function being written, the default code is just a tear-
-            // off of that function
-            defaultCode = functionName;
+          } else {
+            defaultCode = _defaultForDartPlaceholder(optional, scope);
           }
         }
 
-        final type = typeFor(optional);
-
         // No default value, this element is required if it's not nullable
         var isMarkedAsRequired = false;
-        var isNullable = false;
         if (optional is FoundVariable) {
           isMarkedAsRequired = optional.isRequired;
           isNullable = optional.nullableInDart;
@@ -382,7 +357,7 @@ class QueryWriter {
   }
 
   void _writeExpandedDeclarations(SqlQuery query) {
-    _ExpandedDeclarationWriter(query, options, _buffer)
+    _ExpandedDeclarationWriter(query, options, scope, _buffer)
         .writeExpandedDeclarations();
   }
 
@@ -441,13 +416,15 @@ String _converter(UsedTypeConverter converter) {
 class _ExpandedDeclarationWriter {
   final SqlQuery query;
   final DriftOptions options;
+  final Scope _scope;
   final StringBuffer _buffer;
 
   bool indexCounterWasDeclared = false;
   bool needsIndexCounter = false;
   int highestIndexBeforeArray = 0;
 
-  _ExpandedDeclarationWriter(this.query, this.options, this._buffer);
+  _ExpandedDeclarationWriter(
+      this.query, this.options, this._scope, this._buffer);
 
   void writeExpandedDeclarations() {
     // When the SQL query is written to a Dart string, we give each variable an
@@ -532,7 +509,17 @@ class _ExpandedDeclarationWriter {
             return table;
           }
         }).join(', ');
-        return '${element.dartParameterName}($args)';
+
+        final defaultValue = _defaultForDartPlaceholder(element, _scope);
+
+        if (defaultValue != null) {
+          // Optional elements written as a function are generated as nullable
+          // parameters. We need to emit the default if the actual value is
+          // null at runtime.
+          return '${element.dartParameterName}?.call($args) ?? $defaultValue';
+        } else {
+          return '${element.dartParameterName}($args)';
+        }
       } else {
         // We can just use the parameter directly
         return element.dartParameterName;
@@ -694,3 +681,21 @@ class _ExpandedVariableWriter {
     _buffer.write('...${placeholderContextName(element)}.introducedVariables');
   }
 }
+
+String? _defaultForDartPlaceholder(
+    FoundDartPlaceholder placeholder, Scope scope) {
+  final kind = placeholder.type;
+  if (kind is ExpressionDartPlaceholderType && kind.defaultValue != null) {
+    // Wrap the default expression in parentheses to avoid issues with
+    // the surrounding precedence in SQL.
+    final sql = SqlWriter(scope.options)
+        .writeNodeIntoStringLiteral(Parentheses(kind.defaultValue!));
+    return 'const CustomExpression($sql)';
+  } else if (kind is SimpleDartPlaceholderType &&
+      kind.kind == SimpleDartPlaceholderKind.orderBy) {
+    return 'const OrderBy.nothing()';
+  } else {
+    assert(!placeholder.hasDefaultOrImplicitFallback);
+    return null;
+  }
+}

extras/integration_tests/drift_testcases/lib/database/database.g.dart

@@ -2,19 +2,6 @@
 
 part of 'database.dart';
 
-// **************************************************************************
-// JsonSerializableGenerator
-// **************************************************************************
-
-Preferences _$PreferencesFromJson(Map<String, dynamic> json) => Preferences(
-      json['receiveEmails'] as bool,
-    );
-
-Map<String, dynamic> _$PreferencesToJson(Preferences instance) =>
-    <String, dynamic>{
-      'receiveEmails': instance.receiveEmails,
-    };
-
 // **************************************************************************
 // DriftDatabaseGenerator
 // **************************************************************************
@@ -665,3 +652,16 @@ class FriendshipsOfResult {
         .toString();
   }
 }
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+Preferences _$PreferencesFromJson(Map<String, dynamic> json) => Preferences(
+      json['receiveEmails'] as bool,
+    );
+
+Map<String, dynamic> _$PreferencesToJson(Preferences instance) =>
+    <String, dynamic>{
+      'receiveEmails': instance.receiveEmails,
+    };