Make Ruby: autocorrect by rubocop work even when Rubocop isn't the default formatter.

package.json

@@ -51,7 +51,8 @@
         "title": "Ruby: lint by rubocop"
       },
       {
-        "command": "editor.action.formatDocument",
+        "command": "ruby.rubocop.autocorrect",
+        "when": "editorLangId == 'ruby' || editorLangId == 'gemfile'",
         "title": "Ruby: autocorrect by rubocop"
       }
     ],

src/extension.ts

@@ -47,4 +47,20 @@ export function activate(context: vscode.ExtensionContext): void {
     'gemfile',
     formattingProvider
   );
+
+  const autocorrectDisposable = vscode.commands.registerCommand('ruby.rubocop.autocorrect', () => {
+    vscode.window.activeTextEditor.edit((editBuilder) => {
+      const document = vscode.window.activeTextEditor.document;
+      const edits = formattingProvider.provideDocumentFormattingEdits(document);
+      // We only expect one edit from our formatting provider.
+      if (edits.length === 1) {
+        const edit = edits[0];
+        editBuilder.replace(edit.range, edit.newText);
+      }
+      if (edits.length > 1) {
+        throw new Error("Unexpected error: Rubocop document formatter returned multiple edits.");
+      }
+    });
+  });
+  context.subscriptions.push(autocorrectDisposable);
 }