Add --ts flag to properly support projects with mixed .js and .ts files.

[kyegupov]

Properly addresses issues #549 and #526

[isaacs]

I'm curious why we can't just detect the double-instrumentation and prevent it? The problem seems like it arises when you have something like this:

// load-ts.js
require('./ok.ts')

// ok.ts
import * as t from './'
t.pass('this is fine')

node -r ts-node/register -r ts-node/register load-ts.js

But when I run that, it seems like it works fine, so I'm a little bit confused about whether I understand the problem this is trying to address. Do you have an example where I can reproduce the problem you're experiencing?

Also: note that this PR is to the master branch, which is version 13. To address the issue in a v12 legacy release, it'll have to be done (a little bit differently) in the v12 branch. Maybe not an issue you care about if you want to upgrade anyway, but worth mentioning.

[isaacs]

This seems unrelated?

[isaacs]

Oh! Maybe what you're describing only happens when there are two different instances of ts-node in play? I copied ts-node to another folder, and ran it this way. This is an interesting problem:

$ node -r ts-node-duplicate/register -r ts-node/register load-ts.js

/Users/isaacs/dev/js/tap/node_modules/ts-node/src/index.ts:240
    return new TSError(diagnosticText, diagnosticCodes)
           ^
TSError: ⨯ Unable to compile TypeScript:
ok.ts:2:23 - error TS2304: Cannot find name 'exports'.

2 Object.defineProperty(exports, "__esModule", { value: true });
                        ~~~~~~~
ok.ts:3:9 - error TS2580: Cannot find name 'require'. Do you need to install type definitions for node? Try `npm i @types/node`.

3 var t = require("./");
          ~~~~~~~

    at createTSError (/Users/isaacs/dev/js/tap/node_modules/ts-node/src/index.ts:240:12)
    at reportTSError (/Users/isaacs/dev/js/tap/node_modules/ts-node/src/index.ts:244:19)
    at getOutput (/Users/isaacs/dev/js/tap/node_modules/ts-node/src/index.ts:360:34)
    at Object.compile (/Users/isaacs/dev/js/tap/node_modules/ts-node/src/index.ts:393:11)
    at Module.m._compile (/Users/isaacs/dev/js/tap/node_modules/ts-node/src/index.ts:439:43)
    at Module.m._compile (/Users/isaacs/dev/js/tap/node_modules/ts-node-duplicate/src/index.ts:439:23)
    at Module._extensions..js (internal/modules/cjs/loader.js:770:10)
    at require.extensions.<computed> (/Users/isaacs/dev/js/tap/node_modules/ts-node-duplicate/src/index.ts:442:12)
    at Object.require.extensions.<computed> [as .ts] (/Users/isaacs/dev/js/tap/node_modules/ts-node/src/index.ts:442:12)
    at Module.load (internal/modules/cjs/loader.js:628:32)

[isaacs]

Interestingly, if I do what the error message says, and npm i @types/node, it fixes the problem in that case as well. Of course, not as efficient to double-transpile it since the second one has nothing to do, but still, not a crash.

[isaacs]

It seems like a cleaner way to address this would be to treat --ts or --no-ts in the same way as the --esm flag. Ie, it's a flag that just means "do -r ts-node/register for any /\.tsx?$/ files". If you want to provide your own mechanism, you'd do tap --test-arg=--require=my-ts-node/register --no-ts test/foo.ts. To make it even easier, you could put this in your package.json:

{
  "tap": {
    "ts": false,
    "test-arg": [
      "-r",
      "my-ts-node/register"
    ]
  }
}

Would that address the problem?

[isaacs]

@kyegupov Can you check out 9fd8a12 and see if that would give you what you need?