microsoft · Oct 20, 2016 · Oct 19, 2016 · Oct 20, 2016
diff --git a/src/compiler/core.ts b/src/compiler/core.ts
@@ -869,6 +869,14 @@ namespace ts {
         return Array.isArray ? Array.isArray(value) : value instanceof Array;
     }
 
+    /** Does nothing. */
+    export function noop(): void {}
+
+    /** Throws an error because a function is not implemented. */
+    export function notImplemented(): never {
+        throw new Error("Not implemented");
+    }
+
     export function memoize<T>(callback: () => T): () => T {
         let value: T;
         return () => {

diff --git a/src/compiler/declarationEmitter.ts b/src/compiler/declarationEmitter.ts
@@ -63,7 +63,7 @@ namespace ts {
         let isCurrentFileExternalModule: boolean;
         let reportedDeclarationError = false;
         let errorNameNode: DeclarationName;
-        const emitJsDocComments = compilerOptions.removeComments ? () => {} : writeJsDocComments;
+        const emitJsDocComments = compilerOptions.removeComments ? noop : writeJsDocComments;
         const emit = compilerOptions.stripInternal ? stripInternal : emitNode;
         let noDeclare: boolean;
 

diff --git a/src/compiler/program.ts b/src/compiler/program.ts
@@ -950,8 +950,7 @@ namespace ts {
             return runWithCancellationToken(() => {
                 const resolver = getDiagnosticsProducingTypeChecker().getEmitResolver(sourceFile, cancellationToken);
                 // Don't actually write any files since we're just getting diagnostics.
-                const writeFile: WriteFileCallback = () => { };
-                return ts.getDeclarationDiagnostics(getEmitHost(writeFile), resolver, sourceFile);
+                return ts.getDeclarationDiagnostics(getEmitHost(noop), resolver, sourceFile);
             });
         }
 

diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
@@ -63,11 +63,11 @@ namespace ts {
                 // Completely ignore indentation for string writers.  And map newlines to
                 // a single space.
                 writeLine: () => str += " ",
-                increaseIndent: () => { },
-                decreaseIndent: () => { },
+                increaseIndent: noop,
+                decreaseIndent: noop,
                 clear: () => str = "",
-                trackSymbol: () => { },
-                reportInaccessibleThisError: () => { }
+                trackSymbol: noop,
+                reportInaccessibleThisError: noop
             };
         }
 

diff --git a/src/compiler/visitor.ts b/src/compiler/visitor.ts
@@ -1331,18 +1331,18 @@ namespace ts {
     export namespace Debug {
         export const failNotOptional = shouldAssert(AssertionLevel.Normal)
             ? (message?: string) => assert(false, message || "Node not optional.")
-            : () => {};
+            : noop;
 
         export const failBadSyntaxKind = shouldAssert(AssertionLevel.Normal)
             ? (node: Node, message?: string) => assert(false, message || "Unexpected node.", () => `Node ${formatSyntaxKind(node.kind)} was unexpected.`)
-            : () => {};
+            : noop;
 
         export const assertNode = shouldAssert(AssertionLevel.Normal)
             ? (node: Node, test: (node: Node) => boolean, message?: string) => assert(
                     test === undefined || test(node),
                     message || "Unexpected node.",
                     () => `Node ${formatSyntaxKind(node.kind)} did not pass test '${getFunctionName(test)}'.`)
-            : () => {};
+            : noop;
 
         function getFunctionName(func: Function) {
             if (typeof func !== "function") {

diff --git a/src/harness/harness.ts b/src/harness/harness.ts
@@ -690,7 +690,7 @@ namespace Harness {
             export const getCurrentDirectory = () => "";
             export const args = () => <string[]>[];
             export const getExecutingFilePath = () => "";
-            export const exit = () => { };
+            export const exit = ts.noop;
             export const getDirectories = () => <string[]>[];
 
             export let log = (s: string) => console.log(s);
@@ -1668,7 +1668,7 @@ namespace Harness {
         // This does not need to exist strictly speaking, but many tests will need to be updated if it's removed
         export function compileString(_code: string, _unitName: string, _callback: (result: CompilerResult) => void) {
             // NEWTODO: Re-implement 'compileString'
-            throw new Error("compileString NYI");
+            return ts.notImplemented();
         }
 
         export interface GeneratedFile {

diff --git a/src/harness/harnessLanguageService.ts b/src/harness/harnessLanguageService.ts
@@ -313,14 +313,10 @@ namespace Harness.LanguageService {
         getLocalizedDiagnosticMessages(): string { return JSON.stringify({}); }
 
         readDirectory(_rootDir: string, _extension: string): string {
-            throw new Error("NYI");
-        }
-        readDirectoryNames(_path: string): string {
-            throw new Error("Not implemented.");
-        }
-        readFileNames(_path: string): string {
-            throw new Error("Not implemented.");
+            return ts.notImplemented();
         }
+        readDirectoryNames = ts.notImplemented;
+        readFileNames = ts.notImplemented;
         fileExists(fileName: string) { return this.getScriptInfo(fileName) !== undefined; }
         readFile(fileName: string) {
             const snapshot = this.nativeHost.getScriptSnapshot(fileName);
@@ -339,7 +335,7 @@ namespace Harness.LanguageService {
         constructor(private shim: ts.ClassifierShim) {
         }
         getEncodedLexicalClassifications(_text: string, _lexState: ts.EndOfLineState, _classifyKeywordsInGenerics?: boolean): ts.Classifications {
-            throw new Error("NYI");
+            return ts.notImplemented();
         }
         getClassificationsForLine(text: string, lexState: ts.EndOfLineState, classifyKeywordsInGenerics?: boolean): ts.ClassificationResult {
             const result = this.shim.getClassificationsForLine(text, lexState, classifyKeywordsInGenerics).split("\n");
@@ -648,7 +644,7 @@ namespace Harness.LanguageService {
         }
 
         createDirectory(_directoryName: string): void {
-            throw new Error("Not Implemented Yet.");
+            return ts.notImplemented();
         }
 
         getCurrentDirectory(): string {
@@ -664,15 +660,15 @@ namespace Harness.LanguageService {
         }
 
         readDirectory(_path: string, _extension?: string[], _exclude?: string[], _include?: string[]): string[] {
-            throw new Error("Not implemented Yet.");
+            return ts.notImplemented();
         }
 
         watchFile(): ts.FileWatcher {
-            return { close() { } };
+            return { close: ts.noop };
         }
 
         watchDirectory(): ts.FileWatcher {
-            return { close() { } };
+            return { close: ts.noop };
         }
 
         close(): void {

diff --git a/src/harness/runner.ts b/src/harness/runner.ts
@@ -222,5 +222,5 @@ else {
 }
 if (!runUnitTests) {
     // patch `describe` to skip unit tests
-    describe = <any>(function () { });
+    describe = ts.noop as any;
 }
diff --git a/src/harness/unittests/cachingInServerLSHost.ts b/src/harness/unittests/cachingInServerLSHost.ts
@@ -21,23 +21,23 @@ namespace ts {
             args: <string[]>[],
             newLine: "\r\n",
             useCaseSensitiveFileNames: false,
-            write: () => { },
+            write: noop,
             readFile: (path: string): string => {
                 return path in fileMap ? fileMap[path].content : undefined;
             },
             writeFile: (_path: string, _data: string, _writeByteOrderMark?: boolean) => {
-                throw new Error("NYI");
+                return ts.notImplemented();
             },
             resolvePath: (_path: string): string => {
-                throw new Error("NYI");
+                return ts.notImplemented();
             },
             fileExists: (path: string): boolean => {
                 return path in fileMap;
             },
             directoryExists: (path: string): boolean => {
                 return existingDirectories[path] || false;
             },
-            createDirectory: () => { },
+            createDirectory: noop,
             getExecutingFilePath: (): string => {
                 return "";
             },
@@ -47,14 +47,14 @@ namespace ts {
             getDirectories: () => [],
             getEnvironmentVariable: () => "",
             readDirectory: (_path: string, _extension?: string[], _exclude?: string[], _include?: string[]): string[] => {
-                throw new Error("NYI");
+                return ts.notImplemented();
             },
-            exit: () => { },
+            exit: noop,
             watchFile: () => ({
-                close: () => { }
+                close: noop
             }),
             watchDirectory: () => ({
-                close: () => { }
+                close: noop
             }),
             setTimeout,
             clearTimeout,
@@ -65,14 +65,14 @@ namespace ts {
 
     function createProject(rootFile: string, serverHost: server.ServerHost): { project: server.Project, rootScriptInfo: server.ScriptInfo } {
         const logger: server.Logger = {
-            close() { },
+            close: noop,
             hasLevel: () => false,
             loggingEnabled: () => false,
-            perftrc: () => { },
-            info: () => { },
-            startGroup: () => { },
-            endGroup: () => { },
-            msg: () => { },
+            perftrc: noop,
+            info: noop,
+            startGroup: noop,
+            endGroup: noop,
+            msg: noop,
             getLogFileName: (): string => undefined
         };
 
@@ -109,10 +109,7 @@ namespace ts {
             const originalFileExists = serverHost.fileExists;
             {
                 // patch fileExists to make sure that disk is not touched
-                serverHost.fileExists = (): boolean => {
-                    assert.isTrue(false, "fileExists should not be called");
-                    return false;
-                };
+                serverHost.fileExists = notImplemented;
 
                 const newContent = `import {x} from "f1"
                 var x: string = 1;`;

diff --git a/src/harness/unittests/moduleResolution.ts b/src/harness/unittests/moduleResolution.ts
@@ -290,7 +290,7 @@ namespace ts {
                     return path in files ? createSourceFile(fileName, files[path], languageVersion) : undefined;
                 },
                 getDefaultLibFileName: () => "lib.d.ts",
-                writeFile: (): void => { throw new Error("NotImplemented"); },
+                writeFile: notImplemented,
                 getCurrentDirectory: () => currentDirectory,
                 getDirectories: () => [],
                 getCanonicalFileName: fileName => fileName.toLowerCase(),
@@ -300,7 +300,7 @@ namespace ts {
                     const path = normalizePath(combinePaths(currentDirectory, fileName));
                     return path in files;
                 },
-                readFile: (): string => { throw new Error("NotImplemented"); }
+                readFile: notImplemented
             };
 
             const program = createProgram(rootFiles, options, host);
@@ -370,7 +370,7 @@ export = C;
                     return path in files ? createSourceFile(fileName, files[path], languageVersion) : undefined;
                 },
                 getDefaultLibFileName: () => "lib.d.ts",
-                writeFile: (): void => { throw new Error("NotImplemented"); },
+                writeFile: notImplemented,
                 getCurrentDirectory: () => currentDirectory,
                 getDirectories: () => [],
                 getCanonicalFileName,
@@ -380,7 +380,7 @@ export = C;
                     const path = getCanonicalFileName(normalizePath(combinePaths(currentDirectory, fileName)));
                     return path in files;
                 },
-                readFile: (): string => { throw new Error("NotImplemented"); }
+                readFile: notImplemented
             };
             const program = createProgram(rootFiles, options, host);
             const diagnostics = sortAndDeduplicateDiagnostics(program.getSemanticDiagnostics().concat(program.getOptionsDiagnostics()));
@@ -911,15 +911,11 @@ import b = require("./moduleB");
         });
     });
 
-    function notImplemented(name: string): () => any {
-        return () => assert(`${name} is not implemented and should not be called`);
-    }
-
     describe("ModuleResolutionHost.directoryExists", () => {
         it("No 'fileExists' calls if containing directory is missing", () => {
             const host: ModuleResolutionHost = {
-                readFile: notImplemented("readFile"),
-                fileExists: notImplemented("fileExists"),
+                readFile: notImplemented,
+                fileExists: notImplemented,
                 directoryExists: _ => false
             };
 
@@ -1022,9 +1018,7 @@ import b = require("./moduleB");
                 fileExists : fileName => fileName in sourceFiles,
                 getSourceFile: fileName => sourceFiles[fileName],
                 getDefaultLibFileName: () => "lib.d.ts",
-                writeFile(_file, _text) {
-                    throw new Error("NYI");
-                },
+                writeFile: notImplemented,
                 getCurrentDirectory: () => "/",
                 getDirectories: () => [],
                 getCanonicalFileName: f => f.toLowerCase(),

diff --git a/src/harness/unittests/reuseProgramStructure.ts b/src/harness/unittests/reuseProgramStructure.ts
@@ -111,9 +111,7 @@ namespace ts {
             getDefaultLibFileName(): string {
                 return "lib.d.ts";
             },
-            writeFile() {
-                throw new Error("NYI");
-            },
+            writeFile: notImplemented,
             getCurrentDirectory(): string {
                 return "";
             },
@@ -244,13 +242,13 @@ namespace ts {
 
         it("fails if change affects type references", () => {
             const program_1 = newProgram(files, ["a.ts"], { types: ["a"] });
-            updateProgram(program_1, ["a.ts"], { types: ["b"] }, () => { });
+            updateProgram(program_1, ["a.ts"], { types: ["b"] }, noop);
             assert.isTrue(!program_1.structureIsReused);
         });
 
         it("succeeds if change doesn't affect type references", () => {
             const program_1 = newProgram(files, ["a.ts"], { types: ["a"] });
-            updateProgram(program_1, ["a.ts"], { types: ["a"] }, () => { });
+            updateProgram(program_1, ["a.ts"], { types: ["a"] }, noop);
             assert.isTrue(program_1.structureIsReused);
         });
 
@@ -276,19 +274,19 @@ namespace ts {
 
         it("fails if module kind changes", () => {
             const program_1 = newProgram(files, ["a.ts"], { target, module: ModuleKind.CommonJS });
-            updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.AMD }, () => { });
+            updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.AMD }, noop);
             assert.isTrue(!program_1.structureIsReused);
         });
 
         it("fails if rootdir changes", () => {
             const program_1 = newProgram(files, ["a.ts"], { target, module: ModuleKind.CommonJS, rootDir: "/a/b" });
-            updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.CommonJS, rootDir: "/a/c" }, () => { });
+            updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.CommonJS, rootDir: "/a/c" }, noop);
             assert.isTrue(!program_1.structureIsReused);
         });
 
         it("fails if config path changes", () => {
             const program_1 = newProgram(files, ["a.ts"], { target, module: ModuleKind.CommonJS, configFilePath: "/a/b/tsconfig.json" });
-            updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.CommonJS, configFilePath: "/a/c/tsconfig.json" }, () => { });
+            updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.CommonJS, configFilePath: "/a/c/tsconfig.json" }, noop);
             assert.isTrue(!program_1.structureIsReused);
         });
 

diff --git a/src/harness/unittests/session.ts b/src/harness/unittests/session.ts
@@ -10,32 +10,32 @@ namespace ts.server {
         useCaseSensitiveFileNames: true,
         write(s): void { lastWrittenToHost = s; },
         readFile(): string { return void 0; },
-        writeFile(): void {},
+        writeFile: noop,
         resolvePath(): string { return void 0; },
         fileExists: () => false,
         directoryExists: () => false,
         getDirectories: () => [],
-        createDirectory(): void {},
+        createDirectory: noop,
         getExecutingFilePath(): string { return void 0; },
         getCurrentDirectory(): string { return void 0; },
         getEnvironmentVariable(): string { return ""; },
         readDirectory(): string[] { return []; },
-        exit(): void { },
+        exit: noop,
         setTimeout() { return 0; },
-        clearTimeout() { },
+        clearTimeout: noop,
         setImmediate: () => 0,
-        clearImmediate() {}
+        clearImmediate: noop
     };
     const nullCancellationToken: HostCancellationToken = { isCancellationRequested: () => false };
     const mockLogger: Logger = {
-        close(): void {},
+        close: noop,
         hasLevel(): boolean { return false; },
         loggingEnabled(): boolean { return false; },
-        perftrc(): void {},
-        info(): void {},
-        startGroup(): void {},
-        endGroup(): void {},
-        msg(): void {},
+        perftrc: noop,
+        info: noop,
+        startGroup: noop,
+        endGroup: noop,
+        msg: noop,
         getLogFileName: (): string => undefined
     };