[Python-ideas] Let’s make escaping in f-literals impossible

[Paul Moore]

On 19 August 2016 at 21:50, C Anthony Risinger <anthony at xtfx.me> wrote:
> The only real point I'm trying to make is that expressions within an
> f-string are an *escape*. They escape the normal semantics of a string
> literal and instead do something else for a while. Therefore, the escaped
> sections should not look like (or need to conform to) the rest of the string
> and they should not require quoting as if it were still within the string,
> because I escaped it already!

So, to me

 f'{x.partition(' + ')[0]}'

reads as a string concatenation. I'm not sure how you'd expect a
syntax highlighter to make it look like anything else, to be honest
(given that you're arguing *not* to highlight the whole of the content
of the f-string the same way).

The *real* solution is not to write something like this, instead write

 f"{x.partition(' + ')[0]}"

That makes it easy for *humans* to read. Computers parsing it is
irrelevant. Once you do that, the proposal here (that unescaped quotes
can be used in an f-string) also becomes irrelevant - this expression
parses exactly the same way under both the current code and the
proposed approach. And that's generally true - code that is clearly
written should, in my mind, work the same way regardless. So the
proposal ends up being merely "choose your preference as to which form
of badly-written code is a syntax error".

So the only relevance of syntax highlighting is how badly it fails
when handling badly-written or syntactically incorrect code. And
detecting an f-string just like you detect any other string, is *much*
better behaved in that situation. Detecting a closing quote is simple,
and isn't thrown off by incorrect nesting. If you want the *content*
of an f-string to be highlighted as an expression, Vim can do that, it
can apply specific syntax when in another syntax group such as an
f-string, and I'm sure other editors can do this as well - but you
should do that once you've determined where the f-string starts and
ends.

Paul