Merge commit 'be3e8236086165e5e45a5a10783823874b3f3ebd' as 'lib/vscode'

lib/vscode/extensions/emmet/src/evaluateMathExpression.ts

@@ -0,0 +1,35 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+/* Based on @sergeche's work in his emmet plugin */
+
+import * as vscode from 'vscode';
+import evaluate from '@emmetio/math-expression';
+import { DocumentStreamReader } from './bufferStream';
+
+export function evaluateMathExpression() {
+	if (!vscode.window.activeTextEditor) {
+		vscode.window.showInformationMessage('No editor is active');
+		return;
+	}
+	const editor = vscode.window.activeTextEditor;
+	const stream = new DocumentStreamReader(editor.document);
+	editor.edit(editBuilder => {
+		editor.selections.forEach(selection => {
+			const pos = selection.isReversed ? selection.anchor : selection.active;
+			stream.pos = pos;
+
+			try {
+				const result = String(evaluate(stream, true));
+				editBuilder.replace(new vscode.Range(stream.pos, pos), result);
+			} catch (err) {
+				vscode.window.showErrorMessage('Could not evaluate expression');
+				// Ignore error since most likely it’s because of non-math expression
+				console.warn('Math evaluation error', err);
+			}
+		});
+	});
+
+}