Typescript support

Finalize plugin for extracting messages from typescript files. This need somebody with Typescript experience.

Status

Base of plugin is created in typescript-extract-messages package (original version created by @johansigfrids). It uses the same test suite as babel-plugin-extract-messages. Extracting of messages works, but there’re few problems:

• babel plugin also transforms file and removes i18nMark functions, because they are used only to mark strings for extraction. Typescript plugin so far doesn’t modify original file and I don’t know if Typescript works in the same way as Babel.
• babel transform plugins take <Trans> tags and i18n.t calls and transform them into low-level API calls. Since there’re no transform plugins for typescript which would do the same, typescript users have to use low-level API directly.
• plugin doesn’t check imports - Trans component and i18n object might be aliased

Once the plugin is finish, it can be easily hooked to CLI:

import extract from "@lingui/typescript-extract-messages"

const extractor: ExtractorType = {
    ...

    extract(filename, targetDir) {
        extract(filename, { localeDir: targetDir })
    }
}

Goals

1. All tests must pass (should be the same test suit as for babel-extract-messages plugin or at least very similar). Remove typescript plugin from ignored modules in scripts/jest/config.unit.js to run the test suit.
2. Check that plugin works on Test project (provided by @papoola)

[quentez]

@tricoder42 Babel has beta support for TypeScript in version 7. Would it be easier to write the extractor by relying on that instead?

UPDATE: I was able to get something working. I’ll publish an update.

[rssfrncs]

FYI - I’m using Typescript as a Babel (v7) preset and extraction is working fine with .tsx files.