Expose emitter with visitors and transforms by ivogabe · Pull Request #11561 · microsoft/TypeScript

Ivo Gabe de Wolff (ivogabe) · 2016-10-12T15:36:18Z

I hope that the emitter could be exposed, like requested in #10786. I played a bit with the API, and it appeared that it could be used easily, so I made this PR. With this change, people can write tools that emit or modify JavaScript or TypeScript code. I made the following changes:

Added a new function emit(file: SourceFile, transformers: Transformer[] = nullTransformers, newLine = "\n")
Move code of emitFiles to createPrinter, so it can be used in emit and emitFiles
Expose most of factory.ts, in a new namespace ts.factory.
Expose visitEachChild
Expose transformers api.

Examples:

import * as ts from "typescript";

const file = ts.createSourceFile("test.ts", "function foo(x) { if (x === undefined) x = 2; return x * 3; }", ts.ScriptTarget.Latest, true);

// Visitor
const file1 = visit(file) as ts.SourceFile;

console.log(ts.emit(file1).result);

function visit(node: ts.Node): ts.Node {
    if (node.kind === ts.SyntaxKind.Identifier && (node as ts.Identifier).text === "undefined") {
        return ts.factory.createVoidZero();
    }
    return ts.visitEachChild(node, visit);
}

// Transforms
const transform: ts.Transformer = context => file => {
    context.enableSubstitution(ts.SyntaxKind.Identifier);
    context.onSubstituteNode = (emitContext, node) => {
        if (node.kind === ts.SyntaxKind.Identifier && (node as ts.Identifier).text === "undefined") {
            return ts.factory.createVoidZero();
        }
    };
    return file;
}

console.log(ts.emit(file, [transform]).result);

The result of both examples is: function foo(x) { if (x === void 0)\n x = 2; return x * 3; }

Fixes #10786

Conflicts: src/compiler/checker.ts src/compiler/emitter.ts src/compiler/transformers/module/module.ts src/compiler/transformers/module/system.ts src/compiler/transformers/ts.ts src/compiler/visitor.ts

Before this change, this would be rewritten to `namespace "typescript".factory {` by the build process, resulting in an invalid definition file.

Herrington Darkholme (HerringtonDarkholme) · 2016-10-12T16:44:56Z

Alex Eagle (@alexeagle) Angular team may find this useful.

Alex Eagle (alexeagle) · 2016-10-12T16:47:29Z

Yes! We would love to use this. cc Evan Martin (@evmar) for angular/tsickle and Jason Killian (@jkillian) for tslint.
Also cc Chuck Jazdzewski (@chuckjaz) for Angular language services

Mohamed Hegazy (mhegazy) · 2016-10-12T19:40:37Z

Thanks Ivo Gabe de Wolff (@ivogabe). We intend to expose the API in future releases, but we have some cleanup work that needs to be done first. We are doing this right now, so hopefully we should have more details on the time line for this change in the next few weeks.

Ivo Gabe de Wolff (ivogabe) · 2016-10-12T20:33:34Z

Thanks for the reply, Mohamed Hegazy (@mhegazy). Would it be possible to merge the PR before the cleanup, by temporarily marking all functions as internal? I guess that the problem is that the API will change during of the cleanup, but if all functions are marked as internal that wouldn't be a problem. Merging it earlier would prevent some merge conflicts and would allow me to use a custom build, that exposes everything, to experiment with the API, as I can't wait to use it.. Then I do need to accept the risk of future changes of course. Can you tell which parts will be refactored?

Mohamed Hegazy (mhegazy) · 2016-10-12T20:58:10Z

Would it be possible to merge the PR before the cleanup, by temporarily marking all functions as internal?

I would rather we clean it up first before any one uses it. i would assuming using your local copy now would be an alternative.

Can you tell which parts will be refactored?

We need to change the order of the transforms, and push some transforms out. we need to update the helper logic, and how they are handled, and we need to clean up the factory and emit interfaces.

Long Ho (longlho) · 2016-11-13T19:25:01Z

Mohamed Hegazy (@mhegazy) just wanna ping you on any update for this :)

Mohamed Hegazy (mhegazy) · 2016-11-13T21:41:55Z

We have made a whole set of changes recently. including move stuff around into ES2017 and esNext transforms, moved module transformation to the correct place, etc... A few issues still remain, namely handling of helpers (Ron Buckton (@rbuckton) has a PR for this), and handling of --out transformation which will require changing the API.

We also need to clean up the printer to be able to print any subtree, though this does not gate exposing the transformation api.

Hopefully we should be able to do this soon.

Claudia Meadows (dead-claudia) · 2016-11-19T20:01:48Z

I could see this as also very useful for implementing constant folding as a third-party module.

Cameron Taggart (ctaggart) · 2017-01-20T03:49:21Z

Any update on this Mohamed Hegazy (@mhegazy)?

Mohamed Hegazy (mhegazy) · 2017-01-20T05:59:10Z

Handling --out is the last remaining issue. we should have this enabled soon. sorry for the delay.

Fabian Leutgeb (fabiandev) · 2017-01-27T20:00:37Z

Mohamed Hegazy (@mhegazy) Is there a way to already play around with it? Or would it be an option to clone this PR and then transition to the final implementation once exposed, as I would really need this to get further in a project.

Edit:
I'm temporarily using Ivo Gabe de Wolff (@ivogabe)'s PR, which works fine for now. Thanks for that!
Looking forward to the official release :)

Cameron Taggart (ctaggart) · 2017-02-11T01:00:51Z

Can this be put on the roadmap for 2.3? May be this is somewhat related to the #1564 Generator support for ES3/ES5.

Mohamed Hegazy (mhegazy) · 2017-02-11T01:35:15Z

Closing in favor of #13940

Ivo Gabe de Wolff (ivogabe) added 9 commits October 8, 2016 12:28

Expose emit function

5422446

Expose src/compiler/factory.ts as ts.factory.

5fe1042

Move @internal annotations

9101a14

Expose visitEachChild instead of visitNode

2b37926

Make last argument of visitEachChild optional

dde2dc7

Merge remote-tracking branch 'Microsoft/master' into emit

8c49db9

Conflicts: src/compiler/checker.ts src/compiler/emitter.ts src/compiler/transformers/module/module.ts src/compiler/transformers/module/system.ts src/compiler/transformers/ts.ts src/compiler/visitor.ts

Merge remote-tracking branch 'Microsoft/master' into emit

e85bda5

Fix source map generation

fd441fa

Nested namespace for ts.factory

4b10786

Before this change, this would be rewritten to `namespace "typescript".factory {` by the build process, resulting in an invalid definition file.

Microsoft Contribution License Agreements (msftclas) added the cla-already-signed label Oct 12, 2016

Ivo Gabe de Wolff (ivogabe) mentioned this pull request Oct 12, 2016

Ability to emit TypeScript from syntax tree #10786

Closed

Fix linting errors

6c122bc

This was referenced Jan 26, 2017

Rewrite Tsickle to use TypeScript v2.1 transforms angular/tsickle#285

Closed

Proposal: AOT Compiler instructions angular/angular#14128

Closed

Fabian Leutgeb (fabiandev) mentioned this pull request Jan 29, 2017

Transformations with unofficial TypeScript API fabiandev/ts-runtime#1

Merged

4 tasks done

Mohamed Hegazy (mhegazy) mentioned this pull request Feb 7, 2017

Expose public API for transformation. #13940

Merged

Mohamed Hegazy (mhegazy) closed this Feb 11, 2017

Fabian Leutgeb (fabiandev) mentioned this pull request Mar 24, 2017

Transformation API (official TypeScript nightly build) fabiandev/ts-runtime#2

Merged

Microsoft (microsoft) locked and limited conversation to collaborators Jun 19, 2018

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Expose emitter with visitors and transforms - #11561

Expose emitter with visitors and transforms#11561
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