Merge from vscode 31e03b8ffbb218a87e3941f2b63a249f061fe0e4 (#4986)

src/vs/workbench/api/common/extHostLanguages.ts

@@ -0,0 +1,33 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { MainContext, MainThreadLanguagesShape, IMainContext } from './extHost.protocol';
+import * as vscode from 'vscode';
+import { ExtHostDocuments } from 'vs/workbench/api/common/extHostDocuments';
+
+export class ExtHostLanguages {
+
+	private readonly _proxy: MainThreadLanguagesShape;
+	private readonly _documents: ExtHostDocuments;
+
+	constructor(
+		mainContext: IMainContext,
+		documents: ExtHostDocuments
+	) {
+		this._proxy = mainContext.getProxy(MainContext.MainThreadLanguages);
+		this._documents = documents;
+	}
+
+	getLanguages(): Promise<string[]> {
+		return this._proxy.$getLanguages();
+	}
+
+	changeLanguage(uri: vscode.Uri, languageId: string): Promise<vscode.TextDocument | undefined> {
+		return this._proxy.$changeLanguage(uri, languageId).then(() => {
+			const data = this._documents.getDocumentData(uri);
+			return data ? data.document : undefined;
+		});
+	}
+}