Trim relative portions from the paths

[toadzky]

If a file that has message descriptors resolves to a relative path starting with .., it will create the json files right next to the js files, instead of in the messagesDir. This fixes that, and I think will fix #23.

[ericf]

I think it would be best to use

p.normalize(p.sep + relativePath);

[ericf]

@toadzky have you run into this issue? If so, I'm curious to know why it came up in your project.

[toadzky]

The project I'm working on is structured like this:

./
  i18n/
    messages/   <------ where i want the messages extracted to
  services/
    serviceA/
      code
    serviceB/
      code
  shared/
     common-components/
       code

We use a node module to resolve sibling directories without relative paths, so files in serviceA can just import things from 'shared/common-components'. Each service has it's own package.json and it's own build script. When the build script runs the babel plugin, the messages extracted from the service directory show up in i18n/messages correctly, but the messages extracted from shared are written to json files in the same directory as the original javascript it was extracted from.

Here's my plugin config:

plugins: [
            [require.resolve('babel-plugin-react-intl'), {
              "messagesDir": '../../i18n/messages',
              "enforceDescriptions": true
            }]
          ]

When I was debugging it, I hacked on a bunch of console.log into the plugin in my node_modules folder and saw that the result of the p.join(...) was ending up as just the relative path to the original file. So p.join('../../i18n/messages', '../../shared/common...', filename + '.json') ends up ../../shared/common.../filename.json. I'm not thoroughly familiar with the path module, so I'm not sure why.

[toadzky]

@ericf is there anything else on this PR or can this be merged? I prefer not to depend on personal forks of projects for too long if I can avoid it.

[ericf]

I rebased this into one commit and merged it. Thanks!