Parse MAPPED BY constraints for moor files

sqlparser/lib/src/ast/schema/column_definition.dart

@@ -40,6 +40,7 @@ abstract class ColumnConstraint extends AstNode {
     T Function(Default) isDefault,
     T Function(CollateConstraint) collate,
     T Function(ForeignKeyColumnConstraint) foreignKey,
+    T Function(MappedBy) mappedBy,
   }) {
     if (this is NotNull) {
       return notNull?.call(this as NotNull);
@@ -55,6 +56,8 @@ abstract class ColumnConstraint extends AstNode {
       return collate?.call(this as CollateConstraint);
     } else if (this is ForeignKeyColumnConstraint) {
       return foreignKey?.call(this as ForeignKeyColumnConstraint);
+    } else if (this is MappedBy) {
+      return mappedBy?.call(this as MappedBy);
     } else {
       throw Exception('Did not expect $runtimeType as a ColumnConstraint');
     }
@@ -164,3 +167,20 @@ class ForeignKeyColumnConstraint extends ColumnConstraint {
   @override
   Iterable<AstNode> get childNodes => [clause];
 }
+
+/// A `MAPPED BY` constraint, which is only parsed for moor files. It can be
+/// used to declare a type converter for this column.
+class MappedBy extends ColumnConstraint {
+  /// The Dart expression creating the type converter we use to map this token.
+  final InlineDartToken mapper;
+
+  MappedBy(String name, this.mapper) : super(name);
+
+  @override
+  bool _equalToConstraint(MappedBy other) {
+    return other.mapper.dartCode == mapper.dartCode;
+  }
+
+  @override
+  final Iterable<AstNode> childNodes = const [];
+}

sqlparser/lib/src/engine/sql_engine.dart

@@ -46,7 +46,7 @@ class SqlEngine {
   /// Parses the [sql] statement into an AST-representation.
   ParseResult parse(String sql) {
     final tokens = tokenize(sql);
-    final parser = Parser(tokens);
+    final parser = Parser(tokens, useMoor: useMoorExtensions);
 
     final stmt = parser.statement();
     return ParseResult._(stmt, parser.errors, sql);

sqlparser/lib/src/reader/parser/parser.dart

@@ -43,9 +43,13 @@ class ParsingError implements Exception {
 abstract class ParserBase {
   final List<Token> tokens;
   final List<ParsingError> errors = [];
+
+  /// Whether to enable the extensions moor makes to the sql grammar.
+  final bool enableMoorExtensions;
+
   int _current = 0;
 
-  ParserBase(this.tokens);
+  ParserBase(this.tokens, this.enableMoorExtensions);
 
   bool get _isAtEnd => _peek.type == TokenType.eof;
   Token get _peek => tokens[_current];
@@ -145,7 +149,7 @@ abstract class ParserBase {
 
 class Parser extends ParserBase
     with ExpressionParser, SchemaParser, CrudParser {
-  Parser(List<Token> tokens) : super(tokens);
+  Parser(List<Token> tokens, {bool useMoor = false}) : super(tokens, useMoor);
 
   Statement statement({bool expectEnd = true}) {
     final first = _peek;

sqlparser/lib/src/reader/parser/schema.dart

@@ -153,6 +153,15 @@ mixin SchemaParser on ParserBase {
       return ForeignKeyColumnConstraint(resolvedName, clause)
         ..setSpan(first, _previous);
     }
+    if (enableMoorExtensions && _matchOne(TokenType.mapped)) {
+      _consume(TokenType.by, 'Expected a MAPPED BY constraint');
+
+      final dartExpr = _consume(
+          TokenType.inlineDart, 'Expected Dart expression in backticks');
+
+      return MappedBy(resolvedName, dartExpr as InlineDartToken)
+        ..setSpan(first, _previous);
+    }
 
     // no known column constraint matched. If orNull is set and we're not
     // guaranteed to be in a constraint clause (started with CONSTRAINT), we

sqlparser/test/parser/create_table_test.dart

@@ -1,5 +1,6 @@
 import 'package:sqlparser/sqlparser.dart';
 import 'package:sqlparser/src/ast/ast.dart';
+import 'package:sqlparser/src/utils/ast_equality.dart';
 import 'package:test_core/test_core.dart';
 
 import '../common_data.dart';
@@ -115,4 +116,24 @@ void main() {
       ),
     );
   });
+
+  test('parses MAPPED BY expressions when in moor mode', () {
+    const stmt = 'CREATE TABLE a (b NOT NULL MAPPED BY `Mapper()` PRIMARY KEY)';
+    final parsed = SqlEngine(useMoorExtensions: true).parse(stmt).rootNode;
+
+    enforceEqual(
+      parsed,
+      CreateTableStatement(tableName: 'a', columns: [
+        ColumnDefinition(
+          columnName: 'b',
+          typeName: null,
+          constraints: [
+            NotNull(null),
+            MappedBy(null, inlineDart('Mapper()')),
+            PrimaryKeyColumn(null),
+          ],
+        ),
+      ]),
+    );
+  });
 }

sqlparser/test/parser/utils.dart

@@ -10,6 +10,11 @@ Token token(TokenType type) {
   return Token(type, null);
 }
 
+InlineDartToken inlineDart(String dartCode) {
+  final fakeFile = SourceFile.fromString('`$dartCode`');
+  return InlineDartToken(fakeFile.span(0));
+}
+
 IdentifierToken identifier(String content) {
   final fakeFile = SourceFile.fromString(content);
   return IdentifierToken(false, fakeFile.span(0));