module: remove --experimental-transform-types

This PR removes the `--experimental-transform-types` flag and all related code, tests, and documentation.
It also changes the following user facing APIs:
- `stripTypeScriptTypes` now only accepts the code to transform, and not the options object.
   It also does not add a sourceURL comment at the end of the transformed code.
- `process.features.typescript` now only returns a boolean.

Author: marco-ippolito

benchmark/fixtures/transform-types-benchmark.js

@@ -1315,17 +1315,6 @@ Enable module mocking in the test runner.
 
 This feature requires `--allow-worker` if used with the [Permission Model][].
 
-### `--experimental-transform-types`
-
-<!-- YAML
-added: v22.7.0
--->
-
-> Stability: 1.2 - Release candidate
-
-Enables the transformation of TypeScript-only syntax into JavaScript code.
-Implies `--enable-source-maps`.
-
 ### `--experimental-vm-modules`
 
 <!-- YAML
@@ -3611,7 +3600,6 @@ one is included in the list below.
 * `--experimental-specifier-resolution`
 * `--experimental-test-isolation`
 * `--experimental-top-level-await`
-* `--experimental-transform-types`
 * `--experimental-vm-modules`
 * `--experimental-wasi-unstable-preview1`
 * `--force-context-aware`

benchmark/fixtures/transform-types-benchmark.ts

@@ -239,35 +239,28 @@ changes:
 Register [hooks][] that customize Node.js module resolution and loading behavior.
 See [Customization hooks][].
 
-### `module.stripTypeScriptTypes(code[, options])`
+### `module.stripTypeScriptTypes(code)`
 
 <!-- YAML
 added:
   - v23.2.0
   - v22.13.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/9999999999999
+    description: Remove `mode` input argument and support for TypeScript features that require transformation and source map.
 -->
 
 > Stability: 1.2 - Release candidate
 
 * `code` {string} The code to strip type annotations from.
-* `options` {Object}
-  * `mode` {string} **Default:** `'strip'`. Possible values are:
-    * `'strip'` Only strip type annotations without performing the transformation of TypeScript features.
-    * `'transform'` Strip type annotations and transform TypeScript features to JavaScript.
-  * `sourceMap` {boolean} **Default:** `false`. Only when `mode` is `'transform'`, if `true`, a source map
-    will be generated for the transformed code.
-  * `sourceUrl` {string}  Specifies the source url used in the source map.
 * Returns: {string} The code with type annotations stripped.
   `module.stripTypeScriptTypes()` removes type annotations from TypeScript code. It
   can be used to strip type annotations from TypeScript code before running it
   with `vm.runInContext()` or `vm.compileFunction()`.
   By default, it will throw an error if the code contains TypeScript features
   that require transformation such as `Enums`,
   see [type-stripping][] for more information.
-  When mode is `'transform'`, it also transforms TypeScript features to JavaScript,
-  see [transform TypeScript features][] for more information.
-  When mode is `'strip'`, source maps are not generated, because locations are preserved.
-  If `sourceMap` is provided, when mode is `'strip'`, an error will be thrown.
 
 _WARNING_: The output of this function should not be considered stable across Node.js versions,
 due to changes in the TypeScript parser.
@@ -288,58 +281,6 @@ console.log(strippedCode);
 // Prints: const a         = 1;
 ```
 
-If `sourceUrl` is provided, it will be used appended as a comment at the end of the output:
-
-```mjs
-import { stripTypeScriptTypes } from 'node:module';
-const code = 'const a: number = 1;';
-const strippedCode = stripTypeScriptTypes(code, { mode: 'strip', sourceUrl: 'source.ts' });
-console.log(strippedCode);
-// Prints: const a         = 1\n\n//# sourceURL=source.ts;
-```
-
-```cjs
-const { stripTypeScriptTypes } = require('node:module');
-const code = 'const a: number = 1;';
-const strippedCode = stripTypeScriptTypes(code, { mode: 'strip', sourceUrl: 'source.ts' });
-console.log(strippedCode);
-// Prints: const a         = 1\n\n//# sourceURL=source.ts;
-```
-
-When `mode` is `'transform'`, the code is transformed to JavaScript:
-
-```mjs
-import { stripTypeScriptTypes } from 'node:module';
-const code = `
-  namespace MathUtil {
-    export const add = (a: number, b: number) => a + b;
-  }`;
-const strippedCode = stripTypeScriptTypes(code, { mode: 'transform', sourceMap: true });
-console.log(strippedCode);
-// Prints:
-// var MathUtil;
-// (function(MathUtil) {
-//     MathUtil.add = (a, b)=>a + b;
-// })(MathUtil || (MathUtil = {}));
-// # sourceMappingURL=data:application/json;base64, ...
-```
-
-```cjs
-const { stripTypeScriptTypes } = require('node:module');
-const code = `
-  namespace MathUtil {
-    export const add = (a: number, b: number) => a + b;
-  }`;
-const strippedCode = stripTypeScriptTypes(code, { mode: 'transform', sourceMap: true });
-console.log(strippedCode);
-// Prints:
-// var MathUtil;
-// (function(MathUtil) {
-//     MathUtil.add = (a, b)=>a + b;
-// })(MathUtil || (MathUtil = {}));
-// # sourceMappingURL=data:application/json;base64, ...
-```
-
 ### `module.syncBuiltinESMExports()`
 
 <!-- YAML
@@ -2041,5 +1982,4 @@ returned object contains the following keys:
 [synchronous hook functions]: #hook-functions-accepted-by-moduleregisterhooks
 [the documentation of `Worker`]: worker_threads.md#new-workerfilename-options
 [transferable objects]: worker_threads.md#portpostmessagevalue-transferlist
-[transform TypeScript features]: typescript.md#typescript-features
 [type-stripping]: typescript.md#type-stripping

benchmark/ts/transform-typescript.js

@@ -2011,10 +2011,9 @@ changes:
 
 > Stability: 1.2 - Release candidate
 
-* Type: {boolean|string}
+* Type: {boolean}
 
-A value that is `"strip"` by default,
-`"transform"` if Node.js is run with `--experimental-transform-types`, and `false` if
+A value that is `true` by default, and `false` if
 Node.js is run with `--no-strip-types`.
 
 ## `process.features.uv`

doc/api/cli.md

@@ -2,6 +2,9 @@
 
 <!-- YAML
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/9999999999999
+    description: Removed `--experimental-transform-types` flag.
   - version:
       - v25.2.0
       - v24.12.0
@@ -77,8 +80,6 @@ By default Node.js will execute TypeScript files that contains only
 erasable TypeScript syntax.
 Node.js will replace TypeScript syntax with whitespace,
 and no type checking is performed.
-To enable the transformation of non erasable TypeScript syntax, which requires JavaScript code generation,
-such as `enum` declarations, parameter properties use the flag [`--experimental-transform-types`][].
 To disable this feature, use the flag [`--no-strip-types`][].
 
 Node.js ignores `tsconfig.json` files and therefore
@@ -139,8 +140,7 @@ include the `.ts` extension.
 ### TypeScript features
 
 Since Node.js is only removing inline types, any TypeScript features that
-involve _replacing_ TypeScript syntax with new JavaScript syntax will error,
-unless the flag [`--experimental-transform-types`][] is passed.
+involve _replacing_ TypeScript syntax with new JavaScript syntax will error.
 
 The most prominent features that require transformation are:
 
@@ -211,8 +211,6 @@ TypeScript syntax is unsupported in the REPL, `--check`, and
 
 Since inline types are replaced by whitespace, source maps are unnecessary for
 correct line numbers in stack traces; and Node.js does not generate them.
-When [`--experimental-transform-types`][] is enabled, source-maps
-are enabled by default.
 
 ### Type stripping in dependencies
 
@@ -229,7 +227,6 @@ with `#`.
 [CommonJS]: modules.md
 [ES Modules]: esm.md
 [Full TypeScript support]: #full-typescript-support
-[`--experimental-transform-types`]: cli.md#--experimental-transform-types
 [`--no-strip-types`]: cli.md#--no-strip-types
 [`ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX`]: errors.md#err_unsupported_typescript_syntax
 [`tsconfig` "paths"]: https://www.typescriptlang.org/tsconfig/#paths

doc/api/module.md

@@ -677,8 +677,7 @@ anotherFunction();
 
 It is possible to reconstruct the original locations by setting the option `sourceMap` to `true`.
 If the source map is not available, the original location will be the same as the current location.
-When the `--enable-source-maps` flag is enabled, for example when using `--experimental-transform-types`,
-`sourceMap` will be true by default.
+When the `--enable-source-maps` flag is enabled,`sourceMap` will be true by default.
 
 ```ts
 import { getCallSites } from 'node:util';

doc/api/process.md

@@ -213,10 +213,6 @@
           "type": "boolean",
           "description": "experimental node:sqlite module"
         },
-        "experimental-transform-types": {
-          "type": "boolean",
-          "description": "enable transformation of TypeScript-onlysyntax into JavaScript code"
-        },
         "experimental-vm-modules": {
           "type": "boolean",
           "description": "experimental ES Module support in vm module"

doc/api/typescript.md

@@ -741,10 +741,6 @@ collecting code coverage from tests for more details.
 Enable module mocking in the test runner.
 This feature requires \fB--allow-worker\fR if used with the Permission Model.
 .
-.It Fl -experimental-transform-types
-Enables the transformation of TypeScript-only syntax into JavaScript code.
-Implies \fB--enable-source-maps\fR.
-.
 .It Fl -experimental-vm-modules
 Enable experimental ES Module support in the \fBnode:vm\fR module.
 .
@@ -1878,8 +1874,6 @@ one is included in the list below.
 .It
 \fB--experimental-top-level-await\fR
 .It
-\fB--experimental-transform-types\fR
-.It
 \fB--experimental-vm-modules\fR
 .It
 \fB--experimental-wasi-unstable-preview1\fR