Replace PO parse / compose with Expo library

[maennchen]

Partial implementation of #215

Blocked by elixir-gettext/expo#30

This is only an initial draft and not the finished implementation. I'll be on vacation until 25th and will probably not work on this until then.

[maennchen]

@whatyouhide I would really like to finish up this PR. Will you be able to have a look at the outstanding parser issue or should I try to find some help somewhere else?

[whatyouhide]

@maennchen hey, sorry for the wait. I was spending my OSS cycles mostly on Xandra the past few weeks, and I have just a little more to go. I would be able to take a look at this in something like a couple of weeks, would that works? If I'll get to it sooner, I'll get to it sooner 😄

[maennchen]

@whatyouhide Thanks for the feedback. Xandra sounds interesting, I'll have to look at that one a bit closer :)

I think I'm going to attempt it once more on my own in the meantime and if that doesn't work I'll wait for you.

[maennchen]

@whatyouhide I tried in a new way and I nearly got it working.

To get to this point, I added a $end token and tried to get rid of as many $empty states as possible.

There are now only 2 errors left. It seems like the previous and obsolete tokens are somehow consumed prematurely.

Details: elixir-gettext/expo#30

[maennchen]

@josevalim FYI: I quickly rebased & fixed the tests.

I will have to do one more pass over the PR and make sure all the naming etc. is correct.

[maennchen]

@josevalim / @whatyouhide I've completed the integration.

A few points to note:

• Look at the commits separately
  • commit 1 is the actual integration
  • commit 2 renames translations to messages (except public function names etc.; as discussed with @josevalim via slack)
  • commit 2 has no actual code changes, it's all just names
• Even though expo already supports previous / obsolete, that has no noticeable impact to the user of gettext
  • previous translations are kept on merge. no new ones are added
  • obsolete translations are discarded on compile -
  • obsolete translations are kept on merge. no new ones are added
  • since neither were supported and would've been broken by merge previously, I think it's a safe assumption that our users do not have any of those anyways
• flags MapSet => nested lists
  • needed so that the file formatting does not change when merging po files (order & line separation)

Thank you both for your time :)

[josevalim]

Suggested change

	defmodule GettextMergerTest do
	defmodule Gettext.MergerTest do

[josevalim]

💚 💙 💜 💛 ❤️

[maennchen]

@josevalim Oh wow, I was not expecting for this to get through that easy. Thanks ❤️

[josevalim]

We just need an expo release and we can start working on the other issues. :)