Proposal for codefix commands

[ghost]

This would enable microsoft/TypeScript#14423.
I am mostly describing changes to protocol.ts in the TypeScript repository here.
@mjbvz @egamma @mhegazy we discussed this today.

1

The returned CodeAction in a code action request may include a list of commands.

export interface CodeAction {
    description: string;
    changes: FileCodeEdits[];
    command?: {};
}

A code action may even have an empty changes list and consist of only a command.
We could choose specify that command must an of commands, although I'm not sure if that's worth bothering with.

2

If the code action is accepted, the editor must send the commands back to the language service to actually be carried out. This means needing a new request type, "applyCodeFixCommand". This looks like:

export interface ApplyCodeFixCommandRequest extends Request {
    command: CommandTypes.ApplyCodeFixCommand;
    arguments: ApplyCodeFixCommandRequestArgs;
}

export interface ApplyCodeFixCommandRequestArgs extends FileRequestArgs {
    command: {};
}

The contents of command will just be what was sent to the editor.
(Typically this will include a "type" field so the language service can dispatch on the type of action.)

3

The language service should send a response when the action is complete.

export interface ApplyCodeFixCommandResponse extends Response {
    body: {};
}

I'm thinking we can just reuse the message field for error reporting and for a successful response. (Currently the field is documented to only be used if success is false.) We could put that in the body, but then it seems redundant.

[mjbvz]

This proposed TS API changes seem good to me. I don't see any issues implementing this on our side. We'll just need to figure out how best to surface the success / failure messages to users

Let me know when the TS part lands in a nightly build so that I can try prototyping this

[ghost]

If we put this in a nightly build, people will start seeing codefixes that don't work. Could you check out a branch instead?

[mjbvz]

Sure, sounds good

[ghost]

@mjbvz You can checkout and build the install_types_fix branch from the TypeScript repository.
If you include nonsense; in a file and it is an unused identifier, we'll give you a code fix that comes with a command to write a file nonsense.d.ts. (It also replaces the file content so you can verify that at least that works.)

[mjbvz]

Thanks @andy-ms. I'll open a PR on our side shortly. A few quick notes:

Looks like ApplyCodeFixCommandRequestArgs is currently using action instead of command for the key. The command name makes more sense to me

Also, I get this error when I try to run the command:

[Trace  - 4:01:56 PM] Sending request: applyCodeFixCommand (15). Response expected: yes. Current queue length: 0
Arguments: {
    "file": "/Users/matb/projects/sand/y.ts",
    "action": {
        "type": "nonsense"
    }
}

Error: EISDIR: illegal operation on a directory, open '/Users/matb/projects/san'
    at Object.fs.openSync (fs.js:584:18)
    at Object.module.(anonymous function) [as openSync] (ELECTRON_ASAR.js:173:20)
    at Object.writeFile (/Users/matb/projects/TypeScript/built/local/tsserver.js:3963:30)
    at Object.ts.sys.sys.writeFile (/Users/matb/projects/TypeScript/built/local/tsserver.js:4226:37)
    at LSHost.writeFile (/Users/matb/projects/TypeScript/built/local/tsserver.js:95670:27)
    at Object.applyCodeFixCommand (/Users/matb/projects/TypeScript/built/local/tsserver.js:93685:30)
    at IOSession.Session.applyCodeFixCommand (/Users/matb/projects/TypeScript/built/local/tsserver.js:100557:67)
    at Session.handlers.ts.createMapFromTemplate._a.(anonymous function) (/Users/matb/projects/TypeScript/built/local/tsserver.js:99436:40)
    at /Users/matb/projects/TypeScript/built/local/tsserver.js:100701:88
    at IOSession.Session.executeWithRequestId (/Users/matb/projects/TypeScript/built/local/tsserver.js:100692:28)
    at IOSession.Session.executeCommand (/Users/matb/projects/TypeScript/built/local/tsserver.js:100701:33)
    at IOSession.Session.onMessage (/Users/matb/projects/TypeScript/built/local/tsserver.js:100721:35)
    at Interface.<anonymous> (/Users/matb/projects/TypeScript/built/local/tsserver.js:101943:27)
    at emitOne (events.js:96:13)
    at Interface.emit (events.js:191:7)
    at Interface._onLine (readline.js:241:10)
    at Interface._normalWrite (readline.js:384:12)
    at Socket.ondata (readline.js:101:10)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at readableAddChunk (_stream_readable.js:178:18)
    at Socket.Readable.push (_stream_readable.js:136:10)
    at Pipe.onread (net.js:560:20)

[mjbvz]

Here's the PR: #35002

[ghost]

@mjbvz I pushed a quick fix of those two issues -- changed the name from "action" to "command" and remembered to write to a file rather than to a directory.

[mjbvz]

Ok, the fix looks good. I see the d.ts file being created now

[ghost]

Any reason this couldn't land in nightly so I can experiment with it? Regular users won't see anything until we actually add something in TypeScript master that uses this.

[mjbvz]

We're getting ready for release currently but I can check this in once we branch off for the September release. This code in its current state won't compile until we pick up a new *.d.ts file from TypeScript, but we can sprinkle in some any casts to work around this until then