noImplicitAny on single file

[OliverJAsh]

Is it possible to enable noImplicitAny for a single file? This would help us as we are gradually migrating and, when a file is complete, we can begin to use noImplicitAny.

[basarat]

Is it possible to enable noImplicitAny for a single file

Individual file compiler flags aren't supported at the moment. Figuring out how different files compiled with different flags interact would be a problem.

You probably want something like disable certain errors per file. There is an issue request for that somewhere (I'm on a train) 🌹

[Arnavion]

You could patch the existing CompilerHost or create your own that suppresses arbitrary diagnostics from arbitrary files, but I don't believe there's anything in-built.

[timruffles]

@basarat we're incrementally adopting TypeScript - a use-case I imagine is shared by many! In this case opt-in is preferable. We start off files as noImplicitAny and would like to move them out of that state one by one.

[mhegazy]

The issue here is that types could leak into the compilation context. there is no grantee that an implicit any has a local effect. and thus there are no guarantees about refactoring, find all refes, etc..

in general if it is a point-in-time, e.g. migrating to TS or from implicit anys to noImplicitAny, etc, i would recommend doing it all in one shot, or splitting the compilation into two chunks, each with a different flag, and moving files/modules from one chunk to the other.

You can see a similar response for --strictNullChecks in #8405 (comment).

[OliverJAsh]

i would recommend doing it all in one shot, or splitting the compilation into two chunks, each with a different flag, and moving files/modules from one chunk to the other.

This is really difficult for a large code base sadly :-( We did think about maintaining two graphs, one strict and one unstrict, however this means modules can't be shared between the two which makes it hard.

I might have a crack at wrapping tsc and just filter out implicit any errors for a given whitelist.

[Arnavion]

<OliverJAsh> I want to write a wrapper around tsc which allows me to filter out errors for certain files, e.g. I only want `noImplicitAny` to apply for `strict.ts,` not `unstrict.ts`. Any tips how I might go about this? My instinct is to try and parse the error output from tsc (split by new line??) and filter out that way
<OliverJAsh> Should I be using some Node API instead to receive parsed errors instead of trying to parse them myself?

Does #8855 (comment) not work for you?

Edit: i.e. ts.createCompilerHost() + ts.createProgram(host) + program.get*Diagnostics() - each Diagnostic has a filename so you can filter on that when emitting them.

[OliverJAsh]

@Arnavion

Great, that works! See below. Now I am wondering how I could wrap/configure IDE plugins so they give they filter errors in the same way. Any ideas on how I might do that? Seems ambitious…

// main.ts
// ts-node --project main.ts
// https://github.com/Microsoft/TypeScript/wiki/Using-the-Compiler-API

import ts = require('typescript');

const options: ts.CompilerOptions = {
    // TODO: Consume project config somehow
    // project: `server/tsconfig.json`,
    outDir: 'tmp',
    // Strict only
    noImplicitAny: true
};
const program = ts.createProgram([`main.ts`]);
const emitResult = program.emit();

const allDiagnostics = ts.getPreEmitDiagnostics(program).concat(emitResult.diagnostics);

// We only care about no implicit any errors on "strict files"
const strictFiles = [
    'strict-file.ts'
].map(str => `${__dirname}/${str}`)

const errors = allDiagnostics
    .filter(diagnostic => {
        const isStrictFile = strictFiles.indexOf(diagnostic.file.fileName) !== -1;
        const message = ts.flattenDiagnosticMessageText(diagnostic.messageText, '\n');
        const isImplicitAnyError = / implicitly has an 'any(\[\])?' type.$/.test(message);
                return isStrictFile ? true : !isImplicitAnyError;
    });

const errorStr = errors
    .map(diagnostic => {
        const { line, character } = diagnostic.file.getLineAndCharacterOfPosition(diagnostic.start);
        const message = ts.flattenDiagnosticMessageText(diagnostic.messageText, '\n');
        return `${diagnostic.file.fileName} (${line + 1},${character + 1}): ${message}`;
    })
    .join('\n');

if (errorStr) {
    process.stderr.write(errorStr);
    process.stderr.write('\n\r');
    process.exit(1);
}

[robin-anil]

How about doing it on a per-type basis See #18540. It avoids the need to create two graphs, and now the check becomes a property of the type. A potential suggestion is to use comments to indicate strictness.

/* @strict */
interface MyType {
....
}

At any point during compilation, the use of type implicitly converts to any or vice versa, throw a compiler error.