From 9d9658248b36d92c65d11cdd0b2e4db7f6f724b9 Mon Sep 17 00:00:00 2001
From: Simon Binder <oss@simonbinder.eu>
Date: Sun, 11 Oct 2020 11:14:02 +0200
Subject: [PATCH] Add renameColumn method to migrator

---
 .../en/docs/Advanced Features/migrations.md   |  7 +++++
 moor/CHANGELOG.md                             |  1 +
 moor/lib/sqlite_keywords.dart                 |  4 ++-
 .../src/runtime/query_builder/migration.dart  | 28 +++++++++++++++++++
 moor/test/schema_test.dart                    |  9 ++++++
 5 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/docs/content/en/docs/Advanced Features/migrations.md b/docs/content/en/docs/Advanced Features/migrations.md
index 852de094..70de0454 100644
--- a/docs/content/en/docs/Advanced Features/migrations.md	
+++ b/docs/content/en/docs/Advanced Features/migrations.md	
@@ -136,6 +136,13 @@ If you're renaming a column in Dart, note that the easiest way is to just rename
 `named`: `TextColumn newName => text().named('old_name')()`. That is fully backwards compatible and
 doesn't require a migration.
 
+If you know your app runs on sqlite 3.25.0 or later (it does if you're using `sqlite3_flutter_libs`),
+you can also use the `renameColumn` api in `Migrator`:
+
+```dart
+m.renameColumn(yourTable, 'old_column_name', yourTable.newColumn);
+```
+
 If you do want to change the actual column name in a table, you can write a `columnTransformer` to
 use an old column with a different name:
 
diff --git a/moor/CHANGELOG.md b/moor/CHANGELOG.md
index 10afea45..c4e358f4 100644
--- a/moor/CHANGELOG.md
+++ b/moor/CHANGELOG.md
@@ -12,6 +12,7 @@
 - New `generate_values_in_copy_with` [build option](https://moor.simonbinder.eu/docs/advanced-features/builder_options/).
   It wraps nullable columns in a `Value` in `copyWith` methods so that they can be set to `null`.
 - Added `groupConcat`, `cast` and `coalesce` functions to the Dart query builder.
+- Added `renameColumn` to `Migrator` to generate `ALTER TABLE RENAME COLUMN` statement.
 - Added `VmDatabase.closeExistingInstances()` to close zombie database connections after hot restarts.
 
 ## 3.3.1
diff --git a/moor/lib/sqlite_keywords.dart b/moor/lib/sqlite_keywords.dart
index 060388ca..491e6586 100644
--- a/moor/lib/sqlite_keywords.dart
+++ b/moor/lib/sqlite_keywords.dart
@@ -147,8 +147,10 @@ const sqliteKeywords = {
 /// [sqliteKeywords].
 bool isSqliteKeyword(String s) => sqliteKeywords.contains(s.toUpperCase());
 
+final _whitespace = RegExp(r'\s');
+
 /// Escapes [s] by wrapping it in backticks if it's an sqlite keyword.
 String escapeIfNeeded(String s) {
-  if (isSqliteKeyword(s)) return '`$s`';
+  if (isSqliteKeyword(s) || s.contains(_whitespace)) return '`$s`';
   return s;
 }
diff --git a/moor/lib/src/runtime/query_builder/migration.dart b/moor/lib/src/runtime/query_builder/migration.dart
index f50a5756..be6f336c 100644
--- a/moor/lib/src/runtime/query_builder/migration.dart
+++ b/moor/lib/src/runtime/query_builder/migration.dart
@@ -322,6 +322,34 @@ class Migrator {
     return _issueCustomQuery(context.sql);
   }
 
+  /// Changes the name of a column in a [table].
+  ///
+  /// After renaming a column in a Dart table or a moor file and re-running the
+  /// generator, you can use [renameColumn] in a migration step to rename the
+  /// column for existing databases.
+  ///
+  /// The [table] argument must be set to the table enclosing the changed
+  /// column. The [oldName] must be set to the old name of the [column] in SQL.
+  /// For Dart tables, note that moor will transform `camelCase` column names in
+  /// Dart to `snake_case` column names in SQL.
+  ///
+  /// __Important compatibility information__: [renameColumn] uses an
+  /// `ALTER TABLE RENAME COLUMN` internally. Support for that syntax was added
+  /// in sqlite version 3.25.0, released on 2018-09-15. When you're using
+  /// Flutter and depend on `sqlite3_flutter_libs`, you're guaranteed to have
+  /// that version. Otherwise, please ensure that you only use [renameColumn] if
+  /// you know you'll run on sqlite 3.20.0 or later.
+  Future<void> renameColumn(
+      TableInfo table, String oldName, GeneratedColumn column) async {
+    final context = _createContext();
+    context.buffer
+      ..write('ALTER TABLE ${escapeIfNeeded(table.$tableName)} ')
+      ..write('RENAME COLUMN ${escapeIfNeeded(oldName)} ')
+      ..write('TO ${column.escapedName};');
+
+    return _issueCustomQuery(context.sql);
+  }
+
   /// Executes the custom query.
   @Deprecated('Use customStatement in the database class')
   Future<void> issueCustomQuery(String sql, [List<dynamic> args]) {
diff --git a/moor/test/schema_test.dart b/moor/test/schema_test.dart
index 3088e5e9..141e8288 100644
--- a/moor/test/schema_test.dart
+++ b/moor/test/schema_test.dart
@@ -101,6 +101,15 @@ void main() {
           'is_awesome INTEGER NOT NULL DEFAULT 1 '
           'CHECK (is_awesome in (0, 1));'));
     });
+
+    test('renames columns', () async {
+      await db
+          .createMigrator()
+          .renameColumn(db.users, 'my name', db.users.name);
+
+      verify(mockExecutor
+          .runCustom('ALTER TABLE users RENAME COLUMN `my name` TO name;'));
+    });
   });
 
   test('custom statements', () async {