#282 Add strict po loader

[jonasraoni]

Hi @oscarotero!

I did some initial updates to cover my needs.

• I saw it was missing support for the "previous translation comment", so I've added the needed parts to the translator, generator and the StrictPoLoader.
• About the strictness, I've tried to follow the rules of msgfmt -c (e.g. line break/whitespace is optional almost everywhere) 🫠
• I was going to enhance the PoLoader, but it became too polluted with my checks and I decided to write a new parser...
• I barely changed code to handle the comments and the headers.
• I've tried to avoid using regexps, as the performance drops severely with large texts

[jonasraoni]

I've tested some weird combinations, but forgot to move them to the unit test 🤦 Well, I'll wait for some comments (e.g. if it's ok to keep a new class or if you prefer to replace the existing one, etc), then I might add some tests.

[oscarotero]

Hi. Thanks for this work!! I'm not familiarized with the strict mode. What's the difference between strict mode and regular po? This will help me to understand the need to create a new different Po loader.

[jonasraoni]

Hi!

There's no "strict" syntax, I just mimicked the behavior of the GNU tools, which I think is a good guide (given the documentation is missing details) :)

For example, the msgfmt works fine with this syntax (the new lines are required just to break comments):

msgctxt"context"msgid"message"msgstr"translation"

But it fails if you try to parse things in the wrong order, with an invalid msgstr index (out of order/out of bounds), bad escaping, etc.

So in theory this could replace the current PoLoader class, but it can introduce surprises (exceptions) for your users if their files have a bad syntax (I've tested this code against 1274 files of my project and all the exceptions I had were genuine).

So I'll wait for your feedback. In order to decrease the pain, I could just add a flag, to swallow the exceptions by default, and continue to the next translation... But the input vs output of a defective file won't be the same as the current class.

[jonasraoni]

Ok @oscarotero, I'm done with the performance fixes (more than that will require me to uglify the code even more or drop features). In a small dataset with 22 files (564KB) the time went from 4s to .47s, while the PoLoader is taking .25s.

I thought about doing a memory optimization (parse the file by chunks), but that will damage the speed (and my use case doesn't need it: locale files with a max of 170KB) 🤔

If you think it's helpful, I could rebase the commits to mark the tests/BasePoLoaderTestCase.php as a file rename from tests/PoLoaderTest.php, just to improve the code history.

[oscarotero]

Thanks @jonasraoni

If you think it's helpful, I could rebase the commits to mark the tests/BasePoLoaderTestCase.php as a file rename from tests/PoLoaderTest.php, just to improve the code history.

Yeah, it makes sense. But I think it's not so important, so whatever you want :)

One think that I would like is update the README.md file to include this new loader and explain the differences between both PO loaders (including also the difference in performance). As this info is more in your head, could you please add this latest change before merging?

Thanks so much!

[jonasraoni]

@oscarotero I've updated the README and the CHANGELOG 👌

[oscarotero]

Thank you! 👍