On 9/21/2021 3:29 PM, Guido van Rossum wrote:
On Tue, Sep 21, 2021 at 11:49 AM Eric V. Smith <e...@trueblade.com
<mailto:e...@trueblade.com>> wrote:
[Pablo]
* The parser will allow nesting quote characters. This means that
we **could** allow reusing the same quote type in nested expressions
like this:
f"some text { my_dict["string1"] } more text"
I'm okay with this, with the caveat that I raised in another email:
the effect on non-Python tools and alternate Python implementations.
To restate that here: as long as we survey some (most?) of the
affected parties and they're okay with it (or at least it doesn't
cause them a gigantic amount of work), then I'm okay with it. This
will of course be subjective. My big concern is tools that today use
regex's (or similar) to recognize f-strings, and then completely
ignore what's inside them. They just want to "skip over" f-strings
in the source code, maybe because they're doing some sort of
source-to-source transpiling, and they're just going to output the
f-strings as-is. It seems to me we're creating a lot of work for
such tools. Are there a lot of such tools? I don't know: maybe there
are none.
I assume this is primarily an issue for syntax highlighters, which must
work under adverse conditions: the code may contain syntax errors nearby
and they must update fast when the user is typing. (I recall these were
the challenges when I implemented the first syntax coloring for IDLE
several decades ago.)
If same-quote nesting were limited to 1 deep, REs could handle it.
Since nesting is not, and same-quote nesting would not be, they cannot
in general.
f'''length is {len(3*f"{f'{a}'}")}'''
'length is 3'
Still, if this arrives, I would consider a patch to handle the first
nesting level.
If the syntax highlighter shows the wrong colors in an edge case, users
can usually live with that.
Since IDLE is a gift, not a product, I've decided a feature falling
short of perfection is OK.
Something that just colors the entire
f-string, including the interpolations, with the "string" color is not
optimal anyways;
To me, there is a tradeoff. Thunderbird bird displays the gmane version
of the example below highlighted. I find the broken chunks to jarring.
the editor I currently use, VS Code, knows about
f-strings and colorizes (and otherwise analyzes) the interpolations as
expressions.
The red underline on the original display is a nice touch. It would
definitely help to tie the whole string together. Assuming VS Code
handles the double nesting, does it give two underlines for the example
above, for the outer and middle strings?
I imagine if you have a simple-minded highlighter that just uses a regex
that matches string quotes, it will take something like my example and
color it "string" until the first nested quote, then be confused for a
bit, and then start coloring "string" after the second
nested quote, until the end of the f-string. So the confusion is local.
This is what IDLE does now.
I created a gist with my example. This uses some well-known colorizer
written in JavaScript (I presume). It seems to actually already support
nested quotes?!
https://gist.github.com/gvanrossum/b8ca09175a0d1399a8999f13c7bfa616
<https://gist.github.com/gvanrossum/b8ca09175a0d1399a8999f13c7bfa616>
And here's a copy-paste from VS Code (it also shows a red underline
under the entire f-string, but the copy doesn't show it):
def generate(source):
print("# What comes before")
print(f"{source.removesuffix(".py")}.c: $(srcdir)/{source}")
print("\t$(COMMAND)")
So these two tools, at least, seem to be doing all right (maybe because
they both come from the JavaScript culture, where nested interpolations
are well-known).
With only 1 or even 2 types of quotes, reusing them would be more
necessary than it is in Python.
--
Terry Jan Reedy
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