Handle raw strings with r and R in action helper

[isidentical]

This is hopefully the last fix we are going to need. Testing this (and the previous PRs) on top of PyPI now.

[isidentical]

Verified on the PyPI dataset, full behavioral roundtrip 👍🏻 (there are still empty "" string constants in joined str parts we can fix, but not a big problem).

[isidentical]

By the way @lysnikolaou, just to confirm, fstring-grammar-rebased-after-sprint is the latest branch right? (I've been merging my code there but now that I was looking into the branch list, there are a couple different rebase branches 🤔)

[lysnikolaou]

Yup, fstring-grammar-rebased-after-sprint was the latest one.

[pablogsal]

Verified on the PyPI dataset, full behavioral roundtrip 👍🏻 (there are still empty "" string constants in joined str parts we can fix, but not a big problem).

Where the empty strings are coming from?

[isidentical]

Where the empty strings are coming from?

Example:

f"""\
{1}
"""

Tree difference:

Module(
   body=[
      Expr(
         value=JoinedStr(
            values=[
               FormattedValue(
                  value=Constant(value=1),
                  conversion=-1),
               Constant(value='\n')]))],
   type_ignores=[])

Module(
   body=[
      Expr(
         value=JoinedStr(
            values=[
               Constant(value=''), # <========================
               FormattedValue(
                  value=Constant(value=1),
                  conversion=-1),
               Constant(value='\n')]))],