front: extract i18n keys with TypeScript

[emersion]

i18next-parser uses the TypeScript compiler only for lexing. In
other words, it has no contextual information about the translation
calls. This makes extracting translation keys more fragile and
error-prone. For instance, when TFunctions are passed around, the
namespace is lost. As another example, "i18n.t" is not recognized
as a translation function. In general, this is a fool's errand:
operating on tokens without type information will always result in
a lot of unhandled corner cases.

Instead, use the TypeScript compiler API to extract type information
and iterate over all calls to the translation function.

(This should probably be extracted into a re-usable NPM package.)

See individual commits.

Typescript compiler API debugging notes

  //console.log(node.expression.escapedText);
  //console.log(checker.typeToString(type));
  //console.log(type.symbol?.escapedName);

  //if (node.expression.escapedText !== 't') {
  //  console.log('A', file.fileName, file.getLineAndCharacterOfPosition(node.pos));
  //}

    //console.log(checker.typeToString(namespaceType));

      //console.log(namespaceType.resolvedTypeArguments.map(checker.typeToString));
      //console.log(ts.Debug.formatSyntaxKind(symbol.valueDeclaration.kind));

    const symbol = checker.getSymbolAtLocation(keyNode);
    const type = symbol ? checker.getTypeOfSymbol(symbol) : null;
    if (!ts.isTemplateExpression(keyNode)) {
      //console.log('E', file.fileName, file.getLineAndCharacterOfPosition(node.pos));
      //console.log(ts.Debug.formatSyntaxKind(keyNode.kind));
      //console.log(type);
    }

[emersion]

For what it's worth, this has been extracted into https://github.com/emersion/i18next-typescript-parser

[Synar]

Great work! Reviewed all commits but the script one. I still need some time to completely understand that one ^^''.

[Synar]

Should we drop i18next-parser from package.json?

[emersion]

Good point! Done.

[Synar]

I saw you removed t('error') at the profit of t('default') in one commit, is this still used somewhere else?

[emersion]

Indeed, this can be dropped.

[Synar]

Should we remove this comment?

[emersion]

Yup, done!