add variable-builder methods to snippet string, #4956

src/vs/workbench/api/node/extHostTypes.ts

@@ -561,6 +561,31 @@ export class SnippetString {
 		this.value += value;
 		this.value += '}';
 
+		return this;
+	}
+
+	appendVariable(name: string, defaultValue?: string | ((snippet: SnippetString) => any)): SnippetString {
+
+		if (typeof defaultValue === 'function') {
+			const nested = new SnippetString();
+			nested._tabstop = this._tabstop;
+			defaultValue(nested);
+			this._tabstop = nested._tabstop;
+			defaultValue = nested.value;
+
+		} else if (typeof defaultValue === 'string') {
+			defaultValue = defaultValue.replace(/\$|}/g, '\\$&');
+		}
+
+		this.value += '${';
+		this.value += name;
+		if (defaultValue) {
+			this.value += ':';
+			this.value += defaultValue;
+		}
+		this.value += '}';
+
+
 		return this;
 	}
 }