Update: Register both '.ts/.tsx' extensions for babel

[wKich]

Fix #61

[phated]

Does this also need a new test?

[wKich]

I think it would be good. I'll add.

[phated]

@wKich I've been digging into this some more and it seems that babel actually supports .ts files being compiled with JSX compilation by setting the options on "@babel/preset-typescript", like so:

{
  "presets": [
    "@babel/preset-env",
    "@babel/preset-react",
    [
      "@babel/preset-typescript",
      {
        "isTSX": true,
        "allExtensions": true
      }
    ]
  ]
}

Is there a use case for registering both extensions?

[phated]

This is also an issue with @babel/register itself. I noticed that it "deregisters" if you try to register another extension. See https://github.com/babel/babel/blob/master/packages/babel-register/src/node.js#L98

I think the proper solution here would be to get an option upstreamed to babel. Want to give that a shot?

[phated]

I'm going to pull in the workaround into the tests but I think we need to upstream the fix into @babel/register by adding an option to avoid de-registering.

[wKich]

But, why not simply register both extensions? I mean, ts-node register ts/tsx extension hooks under the hood and if someone use babel instead of ts-node, it will be good to provide the same behavior.

I agree that babel de-registering is a problem in this scenario, but we can't be sure that behavior is used by somebody. Disable de-registering by default is a breaking change, adding an option increase complexity. For what?

Is there a use case for registering both extensions?

No. These options are not enable .tsx extension for babel. They are used for different purpose. From docs:

• isTSX - Forcibly enables jsx parsing. This mean, that all regular .ts files should be parsed as .tsx
• allExtensions - Indicates that every file should be parsed as TS or TSX And this is used for enable parse '.js' or .jsx files as .ts. Maybe it needed if your project contains .ts along side with .js files.

[wKich]

I'll try to create issue in babel about de-registering option.

[phated]

Disable de-registering by default is a breaking change, adding an option increase complexity. For what?

Because this would also break the promise for .babel.js and .jsx, which I don't want to change due to this bug/problem in babel.

These options are not enable .tsx extension for babel. They are used for different purpose.

Your interpretation of the options is incorrect (they are named very poorly). I've dug into the code to understand what they actually do:

• isTSX disables a deprecated feature of TypeScript that parsed < > brackets for a different purpose than JSX. This shouldn't be used anymore, but babel seemed to err on the side of caution.
• allExtensions just skips a RegExp test that is done because of the isTSX decision. These should probably be on by default but I understand their caution. So it is actually more performant than splitting between .ts and .tsx files.

I'll try to create issue in babel about de-registering option.

Thank you for opening an issue. I believe that is the best way to solve the issue.