Add transpileDeclaration API method

src/compiler/emitter.ts

@@ -533,7 +533,7 @@ function getSourceMapFilePath(jsFilePath: string, options: CompilerOptions) {
 }
 
 /** @internal */
-export function getOutputExtension(fileName: string, options: CompilerOptions): Extension {
+export function getOutputExtension(fileName: string, options: Pick<CompilerOptions, "jsx">): Extension {
     return fileExtensionIs(fileName, Extension.Json) ? Extension.Json :
         options.jsx === JsxEmit.Preserve && fileExtensionIsOneOf(fileName, [Extension.Jsx, Extension.Tsx]) ? Extension.Jsx :
         fileExtensionIsOneOf(fileName, [Extension.Mts, Extension.Mjs]) ? Extension.Mjs :

src/harness/harnessIO.ts

@@ -303,6 +303,7 @@ export namespace Compiler {
         { name: "noTypesAndSymbols", type: "boolean", defaultValueDescription: false },
         // Emitted js baseline will print full paths for every output file
         { name: "fullEmitPaths", type: "boolean", defaultValueDescription: false },
+        { name: "reportDiagnostics", type: "boolean", defaultValueDescription: false }, // used to enable error collection in `transpile` baselines
     ];
 
     let optionsIndex: Map<string, ts.CommandLineOption>;

src/harness/runnerbase.ts

@@ -4,7 +4,7 @@ import {
 } from "./_namespaces/Harness";
 import * as ts from "./_namespaces/ts";
 
-export type TestRunnerKind = CompilerTestKind | FourslashTestKind | "project";
+export type TestRunnerKind = CompilerTestKind | FourslashTestKind | "project" | "transpile";
 export type CompilerTestKind = "conformance" | "compiler";
 export type FourslashTestKind = "fourslash" | "fourslash-server";
 

src/services/transpile.ts

@@ -25,6 +25,7 @@ import {
     normalizePath,
     optionDeclarations,
     parseCustomTypeOption,
+    ScriptTarget,
     toPath,
     transpileOptionValueCompilerOptions,
 } from "./_namespaces/ts";
@@ -51,14 +52,64 @@ const optionsRedundantWithVerbatimModuleSyntax = new Set([
 
 /*
  * This function will compile source text from 'input' argument using specified compiler options.
- * If not options are provided - it will use a set of default compiler options.
+ * If no options are provided - it will use a set of default compiler options.
  * Extra compiler options that will unconditionally be used by this function are:
  * - isolatedModules = true
  * - allowNonTsExtensions = true
  * - noLib = true
  * - noResolve = true
+ * - declaration = false
  */
 export function transpileModule(input: string, transpileOptions: TranspileOptions): TranspileOutput {
+    return transpileWorker(input, transpileOptions, /*declaration*/ false);
+}
+
+/*
+ * This function will create a declaration file from 'input' argument using specified compiler options.
+ * If no options are provided - it will use a set of default compiler options.
+ * Extra compiler options that will unconditionally be used by this function are:
+ * - isolatedDeclarations = true
+ * - isolatedModules = true
+ * - allowNonTsExtensions = true
+ * - noLib = true
+ * - noResolve = true
+ * - declaration = true
+ * - emitDeclarationOnly = true
+ * Note that this declaration file may differ from one produced by a full program typecheck,
+ * in that only types in the single input file are available to be used in the generated declarations.
+ */
+export function transpileDeclaration(input: string, transpileOptions: TranspileOptions): TranspileOutput {
+    return transpileWorker(input, transpileOptions, /*declaration*/ true);
+}
+
+// Declaration emit works without a `lib`, but some local inferences you'd expect to work won't without
+//  at least a minimal `lib` available, since the checker will `any` their types without these defined.
+//  Late bound symbol names, in particular, are impossible to define without `Symbol` at least partially defined.
+// TODO: This should *probably* just load the full, real `lib` for the `target`.
+const barebonesLibContent = `/// <reference no-default-lib="true"/>
+interface Boolean {}
+interface Function {}
+interface CallableFunction {}
+interface NewableFunction {}
+interface IArguments {}
+interface Number {}
+interface Object {}
+interface RegExp {}
+interface String {}
+interface Array<T> { length: number; [n: number]: T; }
+interface SymbolConstructor {
+    (desc?: string | number): symbol;
+    for(name: string): symbol;
+    readonly toStringTag: symbol;
+}
+declare var Symbol: SymbolConstructor;
+interface Symbol {
+    readonly [Symbol.toStringTag]: string;
+}`;
+const barebonesLibName = "lib.d.ts";
+const barebonesLibSourceFile = createSourceFile(barebonesLibName, barebonesLibContent, { languageVersion: ScriptTarget.Latest });
+
+function transpileWorker(input: string, transpileOptions: TranspileOptions, declaration?: boolean): TranspileOutput {
     const diagnostics: Diagnostic[] = [];
 
     const options: CompilerOptions = transpileOptions.compilerOptions ? fixupCompilerOptions(transpileOptions.compilerOptions, diagnostics) : {};
@@ -86,10 +137,19 @@ export function transpileModule(input: string, transpileOptions: TranspileOption
     // Filename can be non-ts file.
     options.allowNonTsExtensions = true;
 
+    if (declaration) {
+        options.declaration = true;
+        options.emitDeclarationOnly = true;
+        options.isolatedDeclarations = true;
+    }
+    else {
+        options.declaration = false;
+    }
+
     const newLine = getNewLineCharacter(options);
     // Create a compilerHost object to allow the compiler to read and write files
     const compilerHost: CompilerHost = {
-        getSourceFile: fileName => fileName === normalizePath(inputFileName) ? sourceFile : undefined,
+        getSourceFile: fileName => fileName === normalizePath(inputFileName) ? sourceFile : fileName === normalizePath(barebonesLibName) ? barebonesLibSourceFile : undefined,
         writeFile: (name, text) => {
             if (fileExtensionIs(name, ".map")) {
                 Debug.assertEqual(sourceMapText, undefined, "Unexpected multiple source map outputs, file:", name);
@@ -100,12 +160,12 @@ export function transpileModule(input: string, transpileOptions: TranspileOption
                 outputText = text;
             }
         },
-        getDefaultLibFileName: () => "lib.d.ts",
+        getDefaultLibFileName: () => barebonesLibName,
         useCaseSensitiveFileNames: () => false,
         getCanonicalFileName: fileName => fileName,
         getCurrentDirectory: () => "",
         getNewLine: () => newLine,
-        fileExists: (fileName): boolean => fileName === inputFileName,
+        fileExists: (fileName): boolean => fileName === inputFileName || (!!declaration && fileName === barebonesLibName),
         readFile: () => "",
         directoryExists: () => true,
         getDirectories: () => [],
@@ -135,14 +195,18 @@ export function transpileModule(input: string, transpileOptions: TranspileOption
     let outputText: string | undefined;
     let sourceMapText: string | undefined;
 
-    const program = createProgram([inputFileName], options, compilerHost);
+    const inputs = declaration ? [inputFileName, barebonesLibName] : [inputFileName];
+    const program = createProgram(inputs, options, compilerHost);
 
     if (transpileOptions.reportDiagnostics) {
         addRange(/*to*/ diagnostics, /*from*/ program.getSyntacticDiagnostics(sourceFile));
         addRange(/*to*/ diagnostics, /*from*/ program.getOptionsDiagnostics());
     }
     // Emit
-    program.emit(/*targetSourceFile*/ undefined, /*writeFile*/ undefined, /*cancellationToken*/ undefined, /*emitOnlyDtsFiles*/ undefined, transpileOptions.transformers);
+    const result = program.emit(/*targetSourceFile*/ undefined, /*writeFile*/ undefined, /*cancellationToken*/ undefined, /*emitOnlyDtsFiles*/ declaration, transpileOptions.transformers, /*forceDtsEmit*/ declaration);
+
+    // TODO: Should this require `reportDiagnostics`?
+    addRange(/*to*/ diagnostics, /*from*/ result.diagnostics);
 
     if (outputText === undefined) return Debug.fail("Output generation failed");
 

src/testRunner/_namespaces/Harness.ts

@@ -7,6 +7,7 @@ export { Parallel };
 
 export * from "../fourslashRunner";
 export * from "../compilerRunner";
+export * from "../transpileRunner";
 export * from "../runner";
 
 // If running as emitted CJS, don't start executing the tests here; instead start in runner.ts.

src/testRunner/runner.ts

@@ -11,6 +11,7 @@ import {
     setShardId,
     setShards,
     TestRunnerKind,
+    TranspileRunner,
 } from "./_namespaces/Harness";
 import * as project from "./_namespaces/project";
 import * as ts from "./_namespaces/ts";
@@ -66,6 +67,8 @@ export function createRunner(kind: TestRunnerKind): RunnerBase {
             return new FourSlashRunner(FourSlash.FourSlashTestType.Server);
         case "project":
             return new project.ProjectRunner();
+        case "transpile":
+            return new TranspileRunner();
     }
     return ts.Debug.fail(`Unknown runner kind ${kind}`);
 }
@@ -190,6 +193,9 @@ function handleTestConfig() {
                     case "fourslash-generated":
                         runners.push(new GeneratedFourslashRunner(FourSlash.FourSlashTestType.Native));
                         break;
+                    case "transpile":
+                        runners.push(new TranspileRunner());
+                        break;
                 }
             }
         }
@@ -206,6 +212,9 @@ function handleTestConfig() {
         runners.push(new FourSlashRunner(FourSlash.FourSlashTestType.Native));
         runners.push(new FourSlashRunner(FourSlash.FourSlashTestType.Server));
         // runners.push(new GeneratedFourslashRunner());
+
+        // transpile
+        runners.push(new TranspileRunner());
     }
     if (runUnitTests === undefined) {
         runUnitTests = runners.length !== 1; // Don't run unit tests when running only one runner if unit tests were not explicitly asked for

src/testRunner/transpileRunner.ts

@@ -0,0 +1,128 @@
+import {
+    Baseline,
+    Compiler,
+    getFileBasedTestConfigurations,
+    IO,
+    RunnerBase,
+    TestCaseParser,
+    TestRunnerKind,
+} from "./_namespaces/Harness";
+import * as ts from "./_namespaces/ts";
+import * as vpath from "./_namespaces/vpath";
+
+export class TranspileRunner extends RunnerBase {
+    protected basePath = "tests/cases/transpile";
+    protected testSuiteName: TestRunnerKind = "transpile";
+
+    public enumerateTestFiles() {
+        // see also: `enumerateTestFiles` in tests/webTestServer.ts
+        return this.enumerateFiles(this.basePath, /\.[cm]?[tj]sx?/i, { recursive: true });
+    }
+
+    public kind() {
+        return this.testSuiteName;
+    }
+
+    public initializeTests() {
+        if (this.tests.length === 0) {
+            this.tests = IO.enumerateTestFiles(this);
+        }
+
+        describe(this.testSuiteName + " tests", () => {
+            this.tests.forEach(file => {
+                file = vpath.normalizeSeparators(file);
+                describe(file, () => {
+                    const tests = TranspileTestCase.getConfigurations(file);
+                    for (const test of tests) {
+                        test.run();
+                    }
+                });
+            });
+        });
+    }
+}
+
+enum TranspileKind {
+    Module,
+    Declaration,
+}
+
+class TranspileTestCase {
+    static varyBy = [];
+
+    static getConfigurations(file: string): TranspileTestCase[] {
+        const ext = vpath.extname(file);
+        const baseName = vpath.basename(file);
+        const justName = baseName.slice(0, baseName.length - ext.length);
+        const content = IO.readFile(file)!;
+        const settings = TestCaseParser.extractCompilerSettings(content);
+        const settingConfigurations = getFileBasedTestConfigurations(settings, TranspileTestCase.varyBy);
+        return settingConfigurations?.map(c => {
+            const desc = Object.entries(c).map(([key, value]) => `${key}=${value}`).join(",");
+            return new TranspileTestCase(`${justName}(${desc})`, ext, content, { ...settings, ...c });
+        }) ?? [new TranspileTestCase(justName, ext, content, settings)];
+    }
+
+    private jsOutName;
+    private dtsOutName;
+    private units;
+    constructor(
+        private justName: string,
+        private ext: string,
+        private content: string,
+        private settings: TestCaseParser.CompilerSettings,
+    ) {
+        this.jsOutName = justName + this.getJsOutputExtension(`${justName}${ext}`);
+        this.dtsOutName = justName + ts.getDeclarationEmitExtensionForPath(`${justName}${ext}`);
+        this.units = TestCaseParser.makeUnitsFromTest(content, `${justName}${ext}`, settings);
+    }
+
+    getJsOutputExtension(name: string) {
+        return ts.getOutputExtension(name, { jsx: this.settings.jsx === "preserve" ? ts.JsxEmit.Preserve : undefined });
+    }
+
+    runKind(kind: TranspileKind) {
+        it(`transpile test ${this.justName} has expected ${kind === TranspileKind.Module ? "js" : "declaration"} output`, () => {
+            let baselineText = "";
+
+            // include inputs in output so how the test is parsed and broken down is more obvious
+            this.units.testUnitData.forEach(unit => {
+                baselineText += `//// [${unit.name}] ////\r\n`;
+                baselineText += unit.content;
+                if (!unit.content.endsWith("\n")) {
+                    baselineText += "\r\n";
+                }
+            });
+
+            this.units.testUnitData.forEach(unit => {
+                const opts: ts.CompilerOptions = {};
+                Compiler.setCompilerOptionsFromHarnessSetting(this.settings, opts);
+                const result = (kind === TranspileKind.Module ? ts.transpileModule : ts.transpileDeclaration)(unit.content, { compilerOptions: opts, fileName: unit.name, reportDiagnostics: this.settings.reportDiagnostics === "true" });
+
+                baselineText += `//// [${ts.changeExtension(unit.name, kind === TranspileKind.Module ? this.getJsOutputExtension(unit.name) : ts.getDeclarationEmitExtensionForPath(unit.name))}] ////\r\n`;
+                baselineText += result.outputText;
+                if (!result.outputText.endsWith("\n")) {
+                    baselineText += "\r\n";
+                }
+                if (result.diagnostics && result.diagnostics.length) {
+                    baselineText += "\r\n\r\n//// [Diagnostics reported]\r\n";
+                    baselineText += Compiler.getErrorBaseline([{ content: unit.content, unitName: unit.name }], result.diagnostics, !!opts.pretty);
+                    if (!baselineText.endsWith("\n")) {
+                        baselineText += "\r\n";
+                    }
+                }
+            });
+
+            Baseline.runBaseline(`transpile/${kind === TranspileKind.Module ? this.jsOutName : this.dtsOutName}`, baselineText);
+        });
+    }
+
+    run() {
+        if (!this.settings.emitDeclarationOnly) {
+            this.runKind(TranspileKind.Module);
+        }
+        if (this.settings.declaration) {
+            this.runKind(TranspileKind.Declaration);
+        }
+    }
+}

tests/baselines/reference/api/typescript.d.ts

@@ -11190,6 +11190,7 @@ declare namespace ts {
     };
     function preProcessFile(sourceText: string, readImportFiles?: boolean, detectJavaScriptImports?: boolean): PreProcessedFileInfo;
     function transpileModule(input: string, transpileOptions: TranspileOptions): TranspileOutput;
+    function transpileDeclaration(input: string, transpileOptions: TranspileOptions): TranspileOutput;
     function transpile(input: string, compilerOptions?: CompilerOptions, fileName?: string, diagnostics?: Diagnostic[], moduleName?: string): string;
     interface TranspileOptions {
         compilerOptions?: CompilerOptions;