add variable-builder methods to snippet string, #4956

src/vs/vscode.d.ts

@@ -2048,6 +2048,7 @@ declare module 'vscode' {
 		 * the [`value`](#SnippetString.value) of this snippet string.
 		 *
 		 * @param string A value to append 'as given'. The string will be escaped.
+		 * @return This snippet string.
 		 */
 		appendText(string: string): SnippetString;
 
@@ -2057,6 +2058,7 @@ declare module 'vscode' {
 		 *
 		 * @param number The number of this tabstop, defaults to an auto-incremet
 		 * value starting at 1.
+		 * @return This snippet string.
 		 */
 		appendTabstop(number?: number): SnippetString;
 
@@ -2068,8 +2070,29 @@ declare module 'vscode' {
 		 * with which a nested snippet can be created.
 		 * @param number The number of this tabstop, defaults to an auto-incremet
 		 * value starting at 1.
+		 * @return This snippet string.
 		 */
 		appendPlaceholder(value: string | ((snippet: SnippetString) => any), number?: number): SnippetString;
+
+		/**
+		 * Builder-function that appends a variable (`$VAR`) to
+		 * the [`value`](#SnippetString.value) of this snippet string.
+		 *
+		 * @param name The name of the variable - excluding the `$`.
+		 * @return This snippet string.
+		 */
+		appendVariable(name: string): SnippetString;
+
+		/**
+		 * Builder-function that appends a variable and default value (`${VAR:fallback}`) to
+		 * the [`value`](#SnippetString.value) of this snippet string.
+		 *
+		 * @param name The name of the variable (excluding the `$`)
+		 * @param defaultValue The default value which is used when the variable name cannot
+		 * be resolved - either a string or a function with which a nested snippet can be created.
+		 * @return This snippet string.
+		 */
+		appendVariable(name: string, defaultValue: string | ((snippet: SnippetString) => any)): SnippetString;
 	}
 
 	/**

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;
 	}
 }

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

@@ -452,5 +452,21 @@ suite('ExtHostTypes', function () {
 		string.appendText('foo').appendPlaceholder(b => b.appendText('abc').appendPlaceholder('nested')).appendText('bar');
 		assert.equal(string.value, 'foo${1:abc${2:nested}}bar');
 
+		string = new types.SnippetString();
+		string.appendVariable('foo');
+		assert.equal(string.value, '${foo}');
+
+		string = new types.SnippetString();
+		string.appendText('foo').appendVariable('TM_SELECTED_TEXT').appendText('bar');
+		assert.equal(string.value, 'foo${TM_SELECTED_TEXT}bar');
+
+		string = new types.SnippetString();
+		string.appendVariable('BAR', b => b.appendPlaceholder('ops'));
+		assert.equal(string.value, '${BAR:${1:ops}}');
+
+		string = new types.SnippetString();
+		string.appendVariable('BAR', b => { });
+		assert.equal(string.value, '${BAR}');
+
 	});
 });