Add `Expression.and` and `.or` (#2642)

docs/pages/docs/Dart API/expressions.md

@@ -49,6 +49,16 @@ select(animals)..where((a) => a.isMammal.not() & a.amountOfLegs.equals(4));
 select(animals)..where((a) => a.isMammal | a.amountOfLegs.equals(2));
 ```
 
+If you have a list of predicates for which one or all need to match, you can use
+`Expression.or` and `Expression.and`, respectively:
+
+```dart
+Expression.and([
+  a.isMammal,
+  a.amountOfLegs().equals(4),
+])
+```
+
 ## Arithmetic
 
 For `int` and `double` expressions, you can use the `+`, `-`, `*` and `/` operators. To

drift/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 2.13.0-dev
+
+- Add `Expression.and` and `Expression.or` to create disjunctions and conjunctions
+  of sub-predicates.
+
 ## 2.12.1
 
 - Fix `readWithConverter` throwing an exception for null values in non-

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

@@ -271,6 +271,38 @@ abstract class Expression<D extends Object> implements FunctionParameter {
 
   /// The supported [DriftSqlType] backing this expression.
   DriftSqlType<D> get driftSqlType => DriftSqlType.forType();
+
+  /// Chains all [predicates] together into a single expression that will
+  /// evaluate to `true` iff any of the [predicates] evaluates to `true`.
+  ///
+  /// The [ifEmpty] value will be used when no predicates have been passed to
+  /// [or]. By default, `false` is returned.
+  static Expression<bool> or(
+    Iterable<Expression<bool>> predicates, {
+    Expression<bool> ifEmpty = const Constant(false),
+  }) {
+    if (predicates.isEmpty) {
+      return ifEmpty;
+    }
+
+    return predicates.reduce((value, element) => value | element);
+  }
+
+  /// Chains all [predicates] together into a single expression that will
+  /// evaluate to `true` iff all of the [predicates] evaluates to `true`.
+  ///
+  /// The [ifEmpty] value will be used when no predicates have been passed to
+  /// [or]. By default, `true` is returned.
+  static Expression<bool> and(
+    Iterable<Expression<bool>> predicates, {
+    Expression<bool> ifEmpty = const Constant(true),
+  }) {
+    if (predicates.isEmpty) {
+      return ifEmpty;
+    }
+
+    return predicates.reduce((value, element) => value & element);
+  }
 }
 
 /// Used to order the precedence of sql expressions so that we can avoid

drift/test/database/expressions/expression_test.dart

@@ -131,4 +131,48 @@ void main() {
     expect(a.isExp(b), generates('a IS b'));
     expect(b.isNotExp(a), generates('b IS NOT a'));
   });
+
+  test('Expression.and', () {
+    expect(
+      Expression.and([
+        for (var i = 0; i < 5; i++)
+          CustomExpression<bool>('e$i', precedence: Precedence.primary)
+      ]),
+      generates('e0 AND e1 AND e2 AND e3 AND e4'),
+    );
+
+    expect(Expression.and(const []), generates('1'));
+    expect(Expression.and(const [], ifEmpty: const Constant(false)),
+        generates('0'));
+  });
+
+  test('Expression.or', () {
+    expect(
+      Expression.or([
+        for (var i = 0; i < 5; i++)
+          CustomExpression<bool>('e$i', precedence: Precedence.primary)
+      ]),
+      generates('e0 OR e1 OR e2 OR e3 OR e4'),
+    );
+
+    expect(Expression.or(const []), generates('0'));
+    expect(
+        Expression.or(const [], ifEmpty: const Constant(true)), generates('1'));
+  });
+
+  test('and and or', () {
+    expect(
+      Expression.and([
+        Expression.or([
+          const CustomExpression<bool>('a', precedence: Precedence.primary),
+          const CustomExpression<bool>('b', precedence: Precedence.primary),
+        ]),
+        Expression.and([
+          const CustomExpression<bool>('c', precedence: Precedence.primary),
+          const CustomExpression<bool>('d', precedence: Precedence.primary),
+        ]),
+      ]),
+      generates('(a OR b) AND c AND d'),
+    );
+  });
 }