Python 3.6 f-string literal support

[achimnol]

Python 3.6 f-string literal support

[nfnty]

This has been fixed over at the fork vim-python/python-syntax.

[achimnol]

Trying to make a PR for this, but needs help!
I'm not quite professional in vim syntax writing. 😞

syn region pythonFString   start=+[fF]'+ skip=+\\\\\|\\'\|\\$+ excludenl end=+'+ end=+$+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,@Spell
syn region pythonFString   start=+[fF]"+ skip=+\\\\\|\\"\|\\$+ excludenl end=+"+ end=+$+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,@Spell
syn region pythonFString   start=+[fF]"""+ end=+"""+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,pythonDocTest2,pythonSpaceError,@Spell
syn region pythonFString   start=+[fF]'''+ end=+'''+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,pythonDocTest,pythonSpaceError,@Spell
...
syn match pythonStrFormat "{{\|}}" contained containedin=pythonString,pythonRawString
syn match pythonStrFormat "{\%(\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\d\+\)\=\%(\.\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\[\%(\d\+\|[^!:\}]\+\)\]\)*\%(![rsa]\)\=\%(:\%({\%(\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\d\+\)}\|\%([^}]\=[<>=^]\)\=[ +-]\=#\=0\=\d*,\=\%(\.\d\+\)\=[bcdeEfFgGnosxX%]\=\)\=\)\=}" contained containedin=pythonString,pythonRawString
syn match pythonStrInterpFormat "{{\|}}" contained containedin=pythonFString
syn match pythonStrInterpFormat "{<any python expression>\%(![rsa]\)\=\%(:\%({\%(\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\d\+\)}\|\%([^}]\=[<>=^]\)\=[ +-]\=#\=0\=\d*,\=\%(\.\d\+\)\=[bcdeEfFgGnosxX%]\=\)\=\)\=}" contained containedin=pythonFString
...
HiLink pythonFString            String
HiLink pythonStrInterpFormat    Special

I need to make Vim to treat above <any python expression> part like a just normal Python expression. The only rules for them are:

• It should not contain the string terminating quote (e.g., if the current f-string has begun with a single quote, then the expressions may not contain single quote because it will break the Python parser.
• As the content inside braces are limited to expressions, colon and exclamation mark can be used like previous string formatting mini-language. So I've copy-and-pasted the later part from the existing syntax. Update: colon may be used in parenthesized lambda expression, for example, f"{(lambda: 1)()}"

A nice test case would be something like f"{var} plain {expr1 if True or False else expr2} text {var!r} {dictob['key']:.2f} abc {123_34E+2:g} {(lambda: 1)()}". Somebody please help me to figure out how to do this! 😁