py: Implement partial PEP-498 (f-string) support (v3) #7649
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tests/cpydiff/core_fstring_repr.py
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| categories: Core | |||
| description: f-strings don't the !r, !s, and !a conversions | |||
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missing a word after "don't"?
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I'm detached from the world of Micro and CircuitPythons these days quite a bit, and frankly went through enough bouts of FOSS burnout in 2019+2020 (plus, ya know... gestures at everything going on in the world and specifically the US where I live) that I mostly backed out of contributing to open-source entirely until this summer rolled around (in a bit different of a space now). I want to just give @jimmo a huge thanks for adopting this and shepherding it across the line, cleaning up the few messes I left behind, and also for the personal emails you sent last spring offering support. You're a great human. Thanks for that. |
This implements (most of) the PEP-498 spec for f-strings and is based on micropython#4998 by @klardotsh. It is implemented in the lexer as a syntax translation to `str.format`: f"{a}" --> "{}".format(a) It also supports: f"{a=}" --> "a={}".format(a) This is done by extracting the arguments into a temporary vstr buffer, then after the string has been tokenized, the lexer input queue is saved and the contents of the temporary vstr buffer are injected ito the lexer instead. There are four main limitations: - raw f-strings (`fr` or `rf` prefixes) are not supported and will raise `SyntaxError: raw f-strings are not supported`. - literal concatenation of f-strings with adjacent strings will fail "{}" f"{a}" --> "{}{}".format(a) (str.format will incorrectly use the braces from the non-f-string) f"{a}" f"{a}" --> "{}".format(a) "{}".format(a) (cannot concatenate) - PEP-498 requires the full parser to understand the interpolated argument, however because this entirely runs in the lexer it cannot resolve nested braces in expressions like f"{'}'}" - The !r, !s, and !a conversions are not supported. Includes tests and cpydiffs. Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
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Rebased and merged in 692d36d and 5733c49 with the following minor changes:
A big thanks to @klardotsh for the initial idea and work on this feature, the implementation is quite simple conceptually, for what is a very hairy feature. Also big thanks to @jimmo for taking it the last mile. |
…tation Improve pwmio documentation
Extends on #6247 which was originally based on #4998 by @klardotsh
This is a slightly more extensive re-work with the aim of reducing code size and also now supporting the
=operator which I find quite useful (a=1; f'{a=}'-->'a=1'. I've also split the tests into regular tests (that now run on CPython too) and cpydiff tests for the deviations from PEP498.The limitations are the same as the previous approach (due to it being implemented in the lexer not the parser) and the quirks with literal concatenation. I think this is a reasonable trade-off (in the spirit of #6247 (comment)) and has been working for CircuitPython for a while now.
This is +380 bytes on PYBV11 (compared to +432 previously for #6247).