arrow function emit emit error

[basarat]

TypeScript Version: nightly latest

Code

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es5",
        "noImplicitAny": false,
        "sourceMap": false,
        "lib": [
          "es6", "dom"
        ]
    },
    "exclude": [
        "node_modules"
    ]
}

const foo = (x: string) => null;

Expected behavior:

Gives js

var foo = function (x) { return null; };

Actual behavior:

var foo = function (x: string) { return null; };

[mhegazy]

@rbuckton can you take a look.

[rbuckton]

@basarat Is this the entire set of repro steps? I tried this locally and cannot repro this.

[basarat]

Is this the entire set of repro steps?

Sadly no. Seems to be an issue one with language service compile on save, stuff like semicolons etc can be used to trigger it to come in and go out. Same code can give different output depending on how the edits were made :-/

Made a quick video : https://www.youtube.com/watch?v=N4EgtjRnZGE 🌹

[rbuckton]

Thanks, I'll take a look at it.

[rbuckton]

In the video it looks like you're using VSCode. Are you using a .vscode/tasks.json and compiling with tsc in watch mode, or are you using grunt or gulp with a plugin? So far I'm still unable to reproduce this issue.

[rbuckton]

Or rather, is this Atom?

[jesseschalken]

@rbuckton I think it's https://github.com/alm-tools/alm

[basarat]

I think it's https://github.com/alm-tools/alm

Yup.

[basarat]

Basically compileOnSave. This is my build function is simply : https://github.com/alm-tools/alm/blob/c98ffc247078c5f6308548cdcc79f8f8f90c50b0/src/server/workers/lang/modules/building.ts#L35-L43 🌹

[basarat]

I can repro in alm with just const foo = (x: string) => null => const foo = (x) => null;

With a simple tsconfig.json

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es5"
    }
}

That said I ran the same with tsc -w and it doesn't happen, does that use languageService. getEmitOutput? 🌹

[basarat]

Looked at the tsserver and it uses the same function as me getFileEmitOutput : https://github.com/Microsoft/TypeScript/blob/3b0515fd8b8742d1c25c70642e853a9ed4e324c7/src/server/project.ts#L227-L232 and since you haven't been able to repro in vscode (which uses tsserver) I'll look into it a bit more 🌹

[basarat]

Guess compileOnSave isn't supported in tsserver yet : #10838 (comment) so I can't give you repro in vscode :-/

[basarat]

I've attached the project:

ts-emit-error.zip

Opening it in alm is easy npm install alm -g and then alm -o in the project folder.

The repro is simply changing const foo = (x: string) => "hello"; => const foo = (x: string) => "hello" => const foo = (x: string) => "hello"; and the x:string should start appearing in the output.

I added a log to getRawOutput function in alm locally as shown:

export function getRawOutput(proj: project.Project, filePath: string): ts.EmitOutput {
    let services = proj.languageService;
    let output: ts.EmitOutput = services.getEmitOutput(filePath);
    console.log({ input: services.getNonBoundSourceFile(filePath).getFullText(), output: output.outputFiles[0].text });
    return output;
}

You can see the annotation appear and disappear in the output of services.getEmitOutput in the screenshot below as you edit the file to add a ; :

Please let me know if there is still more info required 🌹

[basarat]

PS: thanks for your great work. async / await has already prevented some hacky stuff at work ❤️ 🌹

[basarat]

Update: I've pushed the fix in alm : alm-tools/alm@687c238 that uses the slow but correct ts.transpile to get around the problem. So you need npm install [email protected] -g for the repro on the sample project 🌹

[frankwallis]

I have a similar issue to this where compile on save is not producing valid es5 output, I'm using

• Visual Studio 2015 Professional Update 3
• Microsoft.TypeScript.MSBuild v2.1.0-beta-20161008-1

Steps to reproduce:

1. Build entire project verify that async/await is correctly transpiled to ES5

function loadAgendaItems(meetingId, listid) {
    var _this = this;
    return function (dispatch, getState) { return __awaiter(_this, void 0, void 0, function () {
        var meetingHub, agendaItemsResponse, err_1;
        return __generator(this, function (_a) {
            switch (_a.label) {
                case 0:
                    _a.trys.push([0, 2, , 3]);
                    meetingHub = hubs_1.getMeetingHubServer();
                    return [4 /*yield*/, meetingHub.getAgendaItems(meetingId)];
                case 1:
                    agendaItemsResponse = _a.sent();
                    dispatch(repository_action_creators_1.repositoryPutNormalized(agendaItemsResponse.AgendaItems, data_types_1.DataTypes.AgendaItem, { dataType: data_types_1.DataTypes.Meeting, dataKey: meetingId }));
                    return [3 /*break*/, 3];
                case 2:
                    err_1 = _a.sent();
                    dispatch(notification_action_creators_1.growlError({ message: err_1.message }));
                    return [3 /*break*/, 3];
                case 3: return [2 /*return*/];
            }
        });
    }); };
}

2. Edit function containing async/await

export function loadAgendaItems(meetingId: number, listid: any) {
    return async (dispatch: Dispatch<GlobalState>, getState: () => GlobalState) => {
        /* I added this comment */
        try {
            const meetingHub = getMeetingHubServer();
            const agendaItemsResponse = await meetingHub.getAgendaItems(meetingId);
            dispatch(repositoryPutNormalized(agendaItemsResponse.AgendaItems, DataTypes.AgendaItem, { dataType: DataTypes.Meeting, dataKey: meetingId }));
        } catch (err) {
            dispatch(growlError({ message: err.message }));
        }
    };
}

3. Transpiled output now contains await keyword:

function loadAgendaItems(meetingId, listid) {
    var _this = this;
    return function (dispatch, getState) { return __awaiter(_this, void 0, void 0, function () {
        return __generator(this, function (_a) {
            /* I added this comment */
            try {
                const meetingHub = hubs_1.getMeetingHubServer();
                const agendaItemsResponse = await meetingHub.getAgendaItems(meetingId);
                dispatch(repository_action_creators_1.repositoryPutNormalized(agendaItemsResponse.AgendaItems, data_types_1.DataTypes.AgendaItem, { dataType: data_types_1.DataTypes.Meeting, dataKey: meetingId }));
            }
            catch (err) {
                dispatch(notification_action_creators_1.growlError({ message: err.message }));
            }
            return [2 /*return*/];
        });
    }); };
}

Let me know if you would like any more information, thanks

[mhegazy]

@frankwallis what version of TS are you using for VS? compile on save is not driven from the MSBuild nugget package.

[frankwallis]

@mhegazy I have run the VSDevMode.ps1 script (as per here) and pointed it at my global npm typescript installation (in ...AppData/Roaming/npm/node_modules/typescript/lib) which is:

$ tsc -v
Version 2.1.0-dev.20161014

I reran the VSDevMode.ps1 script today and retried the steps above, and the same issue is present. Is there a way of verifying which version the language service is actually using?

[mhegazy]

Is there a way of verifying which version the language service is actually using?

This is sufficient information. thank you.

[frankwallis]

@mhegazy - can the "Needs More Info" label be removed now?

[mhegazy]

@basarat can you give tonight's build a try.

[mhegazy]

@basarat have you had a chance to try the fix?

[basarat]

In Mexico 🇲🇽 for a conf. Will update once I try 🌹❤️

[mhegazy]

thanks.

[basarat]

I can no longer reproduce it with the latest nightly. Thanks! 🌹

[mhegazy]

thanks for conforming 🌷