Add the Placeable node

[stasm]

WIP. Implement projectfluent/fluent#52.

This doesn't pass structure tests because the AST changes, obviously. All but one behavior tests pass. I'm trying to find the bug.

[stasm]

I'd like to open this up for your feedback, @zbraniecki, before I fix the tests and port this to fluent.js. Thanks!

[zbraniecki]

I like it a lot!

[stasm]

@zbraniecki This fixed the parsing of the following FTL:

key =
    { foo }
    Bar

Before this change, get_pattern would break after the closing }. Does this look right to you?

There's a bit of repetition between this code and get_text_element. I wonder if that's OK? An alternative would be to make get_text_element return None in some cases so that we can break in get_pattern. However that would be inconsistent with the return values of other get_ methods, I think?

[zbraniecki]

I think returning None as an option is fine. If you really want to avoid that, it seems that returning a TextElement with an empty buffer and then testing against the length of the buffer on the last element also works.
I think I prefer that over double is_peek_next_line_pattern, but quite honestly, not by that much. If you find the duplication easier, I'm ok with it.

[stasm]

Thanks. After some more thought I decided to leave the second is_peek_next_line_pattern in, with a comment explaining the end-condition of get_pattern's loop.

Checking for length of the value of the last TextElement would mean that we create the element, add spans to it in with_span and then discard it. Returning None would in turn create a precedent where we need to check the truthiness of nodes returned from get_ methods, at least in with_span.

Another reason to not optimize this code wrt. duplication right now is that a lot of it might change when we fix #15. If it then turns out it's easier to return None after all, we can add it.

[stasm]

Let's move the review of this to projectfluent/fluent.js#64. Once it lands I'll port it to python.

[stasm]

@zbraniecki Would you mind taking another look? It's an almost one-to-one port of the JS implementation, with the exception of the lineOffset and columnOffset functions which are not available in python-fluent yet.

[stasm]

Hey @zbraniecki, can I assume this is good for landing since it's a close port of the JS implementation?

[zbraniecki]

yes, sorry!