Implement custom column constraints

README.md

@@ -316,7 +316,6 @@ let me know by creating an issue!
   - Validation
 - Table joins
 - Bulk inserts
-- Custom column constraints
 - When inserts / updates fail, explain why that happened
 ### Interesting stuff that would be nice to have
 Implementing this will very likely result in backwards-incompatible changes.

moor/lib/src/dsl/columns.dart

@@ -1,8 +1,7 @@
 import 'dart:typed_data';
 
+import 'package:moor/moor.dart';
 import 'package:moor/src/runtime/expressions/expression.dart';
-import 'package:moor/src/runtime/expressions/comparable.dart';
-import 'package:moor/src/types/sql_types.dart';
 
 abstract class Column<T, S extends SqlType<T>> extends Expression<T, S> {}
 
@@ -47,6 +46,33 @@ class ColumnBuilder<Builder, ResultColumn> {
   /// primary key. Columns are non-null by default.
   Builder nullable() => null;
 
+  /// Tells moor to write a custom constraint after this column definition when
+  /// writing this column, for instance in a CREATE TABLE statement.
+  ///
+  /// When no custom constraint is set, columns will be written like this:
+  /// `name TYPE NULLABILITY NATIVE_CONSTRAINTS`. Native constraints are used to
+  /// enforce that booleans are either 0 or 1 (e.g.
+  /// `field BOOLEAN NOT NULL CHECK (field in (0, 1)`). Auto-Increment
+  /// columns also make use of the native constraints.
+  /// If [customConstraint] has been called, the nullability information and
+  /// native constraints will never be written. Instead, they will be replaced
+  /// with the [constraint]. For example, if you call
+  /// `customConstraint('UNIQUE')` on an [IntColumn] named "votes", the
+  /// generated column definition will be `votes INTEGER UNIQUE`. Notice how the
+  /// nullability information is lost - you'll have to include it in
+  /// [constraint] if that is desired.
+  ///
+  /// This can be used to implement constraints that moor does not (yet)
+  /// support (e.g. unique keys, etc.). If you've found a common use-case for
+  /// this, it should be considered a limitation of moor itself. Please feel
+  /// free to open an issue at https://github.com/simolus3/moor/issues/new to
+  /// report that.
+  ///
+  /// See also:
+  /// - https://www.sqlite.org/syntax/column-constraint.html
+  /// - [GeneratedColumn.writeCustomConstraints]
+  Builder customConstraint(String constraint) => null;
+
   /// Turns this column builder into a column. This method won't actually be
   /// called in your code. Instead, moor_generator will take a look at your
   /// source code to figure out your table structure.

moor/lib/src/runtime/statements/query.dart

@@ -79,6 +79,19 @@ abstract class Query<Table, DataClass> {
   /// Applies a [where] statement so that the row with the same primary key as
   /// [d] will be matched.
   void whereSamePrimaryKey(DataClass d) {
+    assert(
+        table.$primaryKey != null && table.$primaryKey.isNotEmpty,
+        'When using Query.whereSamePrimaryKey, which is also called from '
+        'DeleteStatement.delete and UpdateStatement.replace, the affected table'
+        'must have a primary key. You can either specify a primary implicitly '
+        'by making an integer() column autoIncrement(), or by explictly '
+        'overriding the primaryKey getter in your table class. You\'ll also '
+        'have to re-run the code generation step.\n'
+        'Alternatively, if you\'re using DeleteStatement.delete or '
+        'UpdateStatement.replace, consider using DeleteStatement.go or '
+        'UpdateStatement.write respectively. In that case, you need to use a '
+        'custom where statement.');
+
     final primaryKeys = table.$primaryKey.map((c) => c.$name);
 
     final updatedFields = table.entityToSql(d, includeNulls: true);

moor/lib/src/runtime/structure/columns.dart

@@ -16,7 +16,12 @@ abstract class GeneratedColumn<T, S extends SqlType<T>> extends Column<T, S> {
   /// Whether null values are allowed for this column.
   final bool $nullable;
 
-  GeneratedColumn(this.$name, this.$nullable);
+  /// If custom constraints have been specified for this column via
+  /// [ColumnBuilder.customConstraint], these are kept here. Otherwise, this
+  /// field is going to be null.
+  final String $customConstraints;
+
+  GeneratedColumn(this.$name, this.$nullable, {this.$customConstraints});
 
   /// Writes the definition of this column, as defined
   /// [here](https://www.sqlite.org/syntax/column-def.html), into the given
@@ -56,8 +61,8 @@ class GeneratedTextColumn extends GeneratedColumn<String, StringType>
   final int maxTextLength;
 
   GeneratedTextColumn(String name, bool nullable,
-      {this.minTextLength, this.maxTextLength})
-      : super(name, nullable);
+      {this.minTextLength, this.maxTextLength, String $customConstraints})
+      : super(name, nullable, $customConstraints: $customConstraints);
 
   @override
   Expression<bool, BoolType> like(String pattern) =>
@@ -81,7 +86,8 @@ class GeneratedTextColumn extends GeneratedColumn<String, StringType>
 
 class GeneratedBoolColumn extends GeneratedColumn<bool, BoolType>
     implements BoolColumn {
-  GeneratedBoolColumn(String name, bool nullable) : super(name, nullable);
+  GeneratedBoolColumn(String name, bool nullable, {String $customConstraints})
+      : super(name, nullable, $customConstraints: $customConstraints);
 
   @override
   final String typeName = 'BOOLEAN';
@@ -108,8 +114,8 @@ class GeneratedIntColumn extends GeneratedColumn<int, IntType>
   final String typeName = 'INTEGER';
 
   GeneratedIntColumn(String name, bool nullable,
-      {this.hasAutoIncrement = false})
-      : super(name, nullable);
+      {this.hasAutoIncrement = false, String $customConstraints})
+      : super(name, nullable, $customConstraints: $customConstraints);
 
   @override
   void writeColumnDefinition(StringBuffer into) {
@@ -127,8 +133,9 @@ class GeneratedIntColumn extends GeneratedColumn<int, IntType>
 
 class GeneratedDateTimeColumn extends GeneratedColumn<DateTime, DateTimeType>
     implements DateTimeColumn {
-  GeneratedDateTimeColumn(String $name, bool $nullable)
-      : super($name, $nullable);
+  GeneratedDateTimeColumn(String $name, bool $nullable,
+      {String $customConstraints})
+      : super($name, $nullable, $customConstraints: $customConstraints);
 
   @override
   String get typeName => 'INTEGER'; // date-times are stored as unix-timestamps
@@ -136,7 +143,8 @@ class GeneratedDateTimeColumn extends GeneratedColumn<DateTime, DateTimeType>
 
 class GeneratedBlobColumn extends GeneratedColumn<Uint8List, BlobType>
     implements BlobColumn {
-  GeneratedBlobColumn(String $name, bool $nullable) : super($name, $nullable);
+  GeneratedBlobColumn(String $name, bool $nullable, {String $customConstraints})
+      : super($name, $nullable, $customConstraints: $customConstraints);
 
   @override
   final String typeName = 'BLOB';

moor_flutter/README.md

@@ -316,7 +316,6 @@ let me know by creating an issue!
   - Validation
 - Table joins
 - Bulk inserts
-- Custom column constraints
 - When inserts / updates fail, explain why that happened
 ### Interesting stuff that would be nice to have
 Implementing this will very likely result in backwards-incompatible changes.

moor_generator/lib/src/model/specified_column.dart

@@ -63,6 +63,10 @@ class SpecifiedColumn {
   final bool declaredAsPrimaryKey;
   final List<ColumnFeature> features;
 
+  /// If this columns has custom constraints that should be used instead of the
+  /// default ones.
+  final String customConstraints;
+
   /// The dart type that matches the values of this column. For instance, if a
   /// table has declared an `IntColumn`, the matching dart type name would be [int].
   String get dartTypeName => {
@@ -105,13 +109,15 @@ class SpecifiedColumn {
         ColumnType.blob: 'BlobType',
       }[type];
 
-  const SpecifiedColumn(
-      {this.type,
-      this.dartGetterName,
-      this.name,
-      this.declaredAsPrimaryKey = false,
-      this.nullable = false,
-      this.features = const []});
+  const SpecifiedColumn({
+    this.type,
+    this.dartGetterName,
+    this.name,
+    this.customConstraints,
+    this.declaredAsPrimaryKey = false,
+    this.nullable = false,
+    this.features = const [],
+  });
 }
 
 abstract class ColumnFeature {

moor_generator/lib/src/parser/column_parser.dart

@@ -20,6 +20,7 @@ const String functionReferences = 'references';
 const String functionAutoIncrement = 'autoIncrement';
 const String functionWithLength = 'withLength';
 const String functionNullable = 'nullable';
+const String functionCustomConstraint = 'customConstraint';
 
 const String errorMessage = 'This getter does not create a valid column that '
     'can be parsed by moor. Please refer to the readme from moor to see how '
@@ -55,6 +56,7 @@ class ColumnParser extends ParserBase {
 
     String foundStartMethod;
     String foundExplicitName;
+    String foundCustomConstraint;
     var wasDeclaredAsPrimaryKey = false;
     var nullable = false;
     // todo parse reference
@@ -71,22 +73,28 @@ class ColumnParser extends ParserBase {
       switch (methodName) {
         case functionNamed:
           if (foundExplicitName != null) {
-            generator.errors.add(MoorError(
+            generator.errors.add(
+              MoorError(
                 critical: false,
                 affectedElement: getter.declaredElement,
                 message:
                     "You're setting more than one name here, the first will "
-                    'be used'));
+                    'be used',
+              ),
+            );
           }
 
           foundExplicitName =
               readStringLiteral(remainingExpr.argumentList.arguments.first, () {
-            generator.errors.add(MoorError(
+            generator.errors.add(
+              MoorError(
                 critical: false,
                 affectedElement: getter.declaredElement,
                 message:
                     'This table name is cannot be resolved! Please only use '
-                    'a constant string as parameter for .named().'));
+                    'a constant string as parameter for .named().',
+              ),
+            );
           });
           break;
         case functionPrimaryKey:
@@ -110,6 +118,21 @@ class ColumnParser extends ParserBase {
           break;
         case functionNullable:
           nullable = true;
+          break;
+        case functionCustomConstraint:
+          foundCustomConstraint =
+              readStringLiteral(remainingExpr.argumentList.arguments.first, () {
+            generator.errors.add(
+              MoorError(
+                critical: false,
+                affectedElement: getter.declaredElement,
+                message:
+                    'This constraint is cannot be resolved! Please only use '
+                    'a constant string as parameter for .customConstraint().',
+              ),
+            );
+          });
+          break;
       }
 
       // We're not at a starting method yet, so we need to go deeper!
@@ -129,6 +152,7 @@ class ColumnParser extends ParserBase {
         dartGetterName: getter.name.name,
         name: name.escapeIfSqlKeyword(),
         declaredAsPrimaryKey: wasDeclaredAsPrimaryKey,
+        customConstraints: foundCustomConstraint,
         nullable: nullable,
         features: foundFeatures);
   }

moor_generator/test/parser/parser_test.dart

@@ -29,7 +29,7 @@ void main() async {
      
      class CustomPrimaryKey extends Table {
         IntColumn get partA => integer()();
-        IntColumn get partB => integer()();
+        IntColumn get partB => integer().customConstraint('custom')();
         
         @override
         Set<Column> get primaryKey => {partA, partB};
@@ -109,6 +109,19 @@ void main() async {
       expect(
           idColumn.features, contains(LimitingTextLength.withLength(max: 100)));
     });
+
+    test('parses custom constraints', () {
+      final table =
+          TableParser(generator).parse(testLib.getType('CustomPrimaryKey'));
+
+      final partA =
+          table.columns.singleWhere((c) => c.dartGetterName == 'partA');
+      final partB =
+          table.columns.singleWhere((c) => c.dartGetterName == 'partB');
+
+      expect(partB.customConstraints, 'custom');
+      expect(partA.customConstraints, isNull);
+    });
   });
 
   test('parses custom primary keys', () {