Warning for identifiers looking like strings

Contextualize the error message for double-quoted identifiers that can't
be resolved, because those should potentially have been single-quoted
string literals.

Closes #3631

Author: simolus3

sqlparser/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.41.2
+
+- Improve error message on unknown columns when it looks like the identifier
+  should have been a string literal.
+
 ## 0.41.1
 
 - Support new features introduced in SQLite version 3.50.0.

sqlparser/lib/src/analysis/steps/reference_resolver.dart

@@ -121,7 +121,11 @@ class ReferenceResolver
 
   void _reportUnknownColumnError(Reference e, {Iterable<Column>? columns}) {
     final msg = StringBuffer('Unknown column.');
-    if (columns != null) {
+
+    if (e.isSingleDoubleQuotedToken) {
+      msg.write(' Note: Double-quotes define an identifier in SQL. '
+          'If you meant to write a string literal, use single quotes instead.');
+    } else if (columns != null) {
       final columnNames =
           columns.map((c) => c.humanReadableDescription()).join(', ');
       msg.write(' These columns are available: $columnNames');

sqlparser/lib/src/ast/expressions/reference.dart

@@ -28,6 +28,27 @@ class Reference extends Expression with ReferenceOwner {
           'When setting a schemaName, entityName must not be null either.',
         );
 
+  /// Returns whether this [Reference] is syntactically derived from a single
+  /// identifier token wrapped in double quotes.
+  ///
+  /// Because the strict "double quotes are identifiers and never string
+  /// literals" rule enabled by drift and sqlparser can be surprising, we use
+  /// this information to improve error messages and point this out
+  /// specifically.
+  bool get isSingleDoubleQuotedToken {
+    if (schemaName != null || entityName != null) {
+      return false;
+    }
+
+    if (first == last) {
+      if (first case final IdentifierToken singleToken) {
+        return singleToken.escaped;
+      }
+    }
+
+    return false;
+  }
+
   @override
   R accept<A, R>(AstVisitor<A, R> visitor, A arg) {
     return visitor.visitReference(this, arg);

sqlparser/pubspec.yaml

@@ -1,6 +1,6 @@
 name: sqlparser
 description: Parses sqlite statements and performs static analysis on them
-version: 0.41.1
+version: 0.41.2-dev
 homepage: https://github.com/simolus3/drift/tree/develop/sqlparser
 repository: https://github.com/simolus3/drift
 #homepage: https://drift.simonbinder.eu/

sqlparser/test/analysis/reference_resolver_test.dart

@@ -440,4 +440,14 @@ CREATE TABLE routes (
     expect(fromReferenced!.source.containingSet,
         result.rootScope.knownTables['points']);
   });
+
+  test('warns about identifiers that should have been strings', () {
+    final result = SqlEngine().analyze('''SELECT 'hello ' || "world";''');
+
+    result.expectError(
+      '"world"',
+      type: AnalysisErrorType.referencedUnknownColumn,
+      message: contains('Note: Double-quotes define an identifier in SQL.'),
+    );
+  });
 }