Fix source mapping in react-native 0.52

[ds300]

following discussion from from #37

[dluksza]

Configuration for running jest tests described in #21 (comment) also doesn't work with 0.52

It is failing with error:

  ● Test suite failed to run

    TypeError: Jest: a transform's `process` function must return a string, or an object with `code` key containing this string.
      
      at ScriptTransformer.transformSource (node_modules/jest-runtime/build/script_transformer.js:238:15)

[ds300]

Ah yes, that makes sense. Thanks for the heads-up! I'm going to try duplicating the old upstream transformer locally.

[ds300]

Another thing I'm trying is traversing the ast and updating its mappings in place. Seems doable so far.

[dluksza]

Jest tests are still failing with the same error as mentioned in my previous comment :|

[ds300]

Ah yes. I should have made another issue for that

[ds300]

@dluksza you can do this for now:

var tsTransformer = require('react-native-typescript-transformer')
var rnTransformer = require('react-native/jest/preprocessor')
var generate = require('babel-generator')

var preprocessor = Object.assign({}, rnTransformer, {
  process (src, file) {
    const {ast} = tsTransformer.transform({
      filename: file,
      localPath: file,
      options: {
        dev: true,
        platform: '',
        projectRoot: '',
      },
      src,
    })

    return generate.default(ast, {
      filename: file,
      retainLines: true
    }, src)
  },
})

module.exports = preprocessor

It doesn't do source mapping, but then neither did the original version.

[dluksza]

@ds300 thank you that works! :D