Add `IS` operator to Dart query builder

drift/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 2.5.0-dev
+
+- Add `isExp`, `isValue`, `isNotExp` and `isNotValue` methods to `Expression`
+  to generate the `IS` operator in SQL.
+
 ## 2.4.2
 
 - Fix an exception when a client disconnects from a drift remote server while

drift/lib/src/runtime/query_builder/expressions/expression.dart

@@ -42,6 +42,9 @@ abstract class Expression<D extends Object> implements FunctionParameter {
   bool get isLiteral => false;
 
   /// Whether this expression is equal to the given expression.
+  ///
+  /// This generates an equals operator in SQL. To perform a comparison
+  /// sensitive to `NULL` values, use [isExp] instead.
   Expression<bool> equalsExp(Expression<D> compare) =>
       _Comparison.equal(this, compare);
 
@@ -52,7 +55,7 @@ abstract class Expression<D extends Object> implements FunctionParameter {
   ///
   /// This method only supports comparing the value of the column to non-
   /// nullable values and translates to a direct `=` comparison in SQL.
-  /// To compare this column to `null`, use [equalsNullable].
+  /// To compare this column to `null`, use [isValue].
   Expression<bool> equals(D compare) =>
       _Comparison.equal(this, Variable<D>(compare));
 
@@ -91,6 +94,51 @@ abstract class Expression<D extends Object> implements FunctionParameter {
     return _CastInSqlExpression<D, D2>(this);
   }
 
+  /// Generates an `IS` expression in SQL, comparing this expression with the
+  /// Dart [value].
+  ///
+  /// This is the SQL method most closely resembling the [Object.==] operator in
+  /// Dart. When this expression and [value] are both non-null, this is the same
+  /// as [equals]. Two `NULL` values are considered equal as well.
+  Expression<bool> isValue(D value) {
+    return isExp(Variable<D>(value));
+  }
+
+  /// Generates an `IS NOT` expression in SQL, comparing this expression with
+  /// the Dart [value].
+  ///
+  /// This the inverse of [isValue].
+  Expression<bool> isNotValue(D value) {
+    return isNotExp(Variable<D>(value));
+  }
+
+  /// Expression that is true if the inner expression resolves to a null value.
+  Expression<bool> isNull() => isExp(const Constant(null));
+
+  /// Expression that is true if the inner expression resolves to a non-null
+  /// value.
+  Expression<bool> isNotNull() => isNotExp(const Constant(null));
+
+  /// Generates an `IS` expression in SQL, comparing this expression with the
+  /// [other] expression.
+  ///
+  /// This is the SQL method most closely resembling the [Object.==] operator in
+  /// Dart. When this expression and [other] are both non-null, this is the same
+  /// as [equalsExp]. Two `NULL` values are considered equal as well.
+  Expression<bool> isExp(Expression<D> other) {
+    return BaseInfixOperator(this, 'IS', other,
+        precedence: Precedence.comparisonEq);
+  }
+
+  /// Generates an `IS NOT` expression in SQL, comparing this expression with
+  /// the [other] expression.
+  ///
+  /// This the inverse of [isExp].
+  Expression<bool> isNotExp(Expression<D> other) {
+    return BaseInfixOperator(this, 'IS NOT', other,
+        precedence: Precedence.comparisonEq);
+  }
+
   /// An expression that is true if `this` resolves to any of the values in
   /// [values].
   Expression<bool> isIn(Iterable<D> values) {
@@ -279,31 +327,27 @@ class Precedence implements Comparable<Precedence> {
 /// [_Comparison].
 enum _ComparisonOperator {
   /// '<' in sql
-  less,
+  less('<'),
 
   /// '<=' in sql
-  lessOrEqual,
+  lessOrEqual('<='),
 
   /// '=' in sql
-  equal,
+  equal('='),
 
   /// '>=' in sql
-  moreOrEqual,
+  moreOrEqual('>='),
 
   /// '>' in sql
-  more
+  more('>');
+
+  final String operator;
+
+  const _ComparisonOperator(this.operator);
 }
 
 /// An expression that compares two child expressions.
 class _Comparison extends InfixOperator<bool> {
-  static const Map<_ComparisonOperator, String> _operatorNames = {
-    _ComparisonOperator.less: '<',
-    _ComparisonOperator.lessOrEqual: '<=',
-    _ComparisonOperator.equal: '=',
-    _ComparisonOperator.moreOrEqual: '>=',
-    _ComparisonOperator.more: '>'
-  };
-
   @override
   final Expression left;
   @override
@@ -313,7 +357,7 @@ class _Comparison extends InfixOperator<bool> {
   final _ComparisonOperator op;
 
   @override
-  String get operator => _operatorNames[op]!;
+  String get operator => op.operator;
 
   @override
   Precedence get precedence {

drift/lib/src/runtime/query_builder/expressions/null_check.dart

@@ -1,24 +1,13 @@
 part of '../query_builder.dart';
 
 /// Expression that is true if the inner expression resolves to a null value.
-@Deprecated('Use isNull through the SqlIsNull extension')
+@Deprecated('Use isNull on the Expression class')
-Expression<bool> isNull(Expression inner) => _NullCheck(inner, true);
+Expression<bool> isNull(Expression inner) => inner.isNull();
 
 /// Expression that is true if the inner expression resolves to a non-null
 /// value.
-@Deprecated('Use isNotNull through the SqlIsNull extension')
+@Deprecated('Use isNotNull on the Expression class')
-Expression<bool> isNotNull(Expression inner) => _NullCheck(inner, false);
+Expression<bool> isNotNull(Expression inner) => inner.isNotNull();
-
-/// Extension defines the `isNull` and `isNotNull` members to check whether the
-/// expression evaluates to null or not.
-extension SqlIsNull on Expression {
-  /// Expression that is true if the inner expression resolves to a null value.
-  Expression<bool> isNull() => _NullCheck(this, true);
-
-  /// Expression that is true if the inner expression resolves to a non-null
-  /// value.
-  Expression<bool> isNotNull() => _NullCheck(this, false);
-}
 
 /// Evaluates to the first expression in [expressions] that's not null, or
 /// null if all [expressions] evaluate to null.
@@ -35,34 +24,3 @@ Expression<T> ifNull<T extends Object>(
     Expression<T> first, Expression<T> second) {
   return FunctionCallExpression<T>('IFNULL', [first, second]);
 }
-
-class _NullCheck extends Expression<bool> {
-  final Expression _inner;
-  final bool _isNull;
-
-  @override
-  final Precedence precedence = Precedence.comparisonEq;
-
-  _NullCheck(this._inner, this._isNull);
-
-  @override
-  void writeInto(GenerationContext context) {
-    writeInner(context, _inner);
-
-    context.buffer.write(' IS ');
-    if (!_isNull) {
-      context.buffer.write('NOT ');
-    }
-    context.buffer.write('NULL');
-  }
-
-  @override
-  int get hashCode => Object.hash(_inner, _isNull);
-
-  @override
-  bool operator ==(Object other) {
-    return other is _NullCheck &&
-        other._inner == _inner &&
-        other._isNull == _isNull;
-  }
-}

drift/pubspec.yaml

@@ -1,6 +1,6 @@
 name: drift
 description: Drift is a reactive library to store relational data in Dart and Flutter applications.
-version: 2.4.2
+version: 2.5.0-dev
 repository: https://github.com/simolus3/drift
 homepage: https://drift.simonbinder.eu/
 issue_tracker: https://github.com/simolus3/drift/issues

drift/test/database/expressions/expression_test.dart

@@ -120,4 +120,15 @@ void main() {
     expect(a.equalsNullable(null), generates('a IS NULL'));
     expect(a.equalsExp(b), generates('a = b'));
   });
+
+  test('is', () {
+    const a = CustomExpression<int>('a', precedence: Precedence.primary);
+    const b = CustomExpression<int>('b', precedence: Precedence.primary);
+
+    expect(a.isValue(3), generates('a IS ?', [3]));
+    expect(a.isNotValue(3), generates('a IS NOT ?', [3]));
+
+    expect(a.isExp(b), generates('a IS b'));
+    expect(b.isNotExp(a), generates('b IS NOT a'));
+  });
 }

drift_dev/pubspec.yaml

@@ -25,7 +25,7 @@ dependencies:
   io: ^1.0.3
 
   # Drift-specific analysis and apis
-  drift: '>=2.4.0 <2.5.0'
+  drift: '>=2.5.0 <2.6.0'
   sqlite3: '>=0.1.6 <2.0.0'
   sqlparser: '^2.27.0-dev'