RE: [PATCH] config: add an includeIf.env{Exists,Bool,Is,Match}

["Randall S. Becker" <rsbecker@nexbridge.com>]

On September 27, 2021 4:16 PM, Jeff King wrote:
>Subject: Re: [PATCH] config: add an includeIf.env{Exists,Bool,Is,Match}
>
>On Mon, Sep 27, 2021 at 09:30:41AM -0700, Junio C Hamano wrote:
>
>> >> This asserts what? FOO=" bar"?
>> >
>> > Whoops, that should have been "envIs", asserting that $FOO contains
>> > "bar".
>>
>> Oh, "can we check with a literal with leading whitespace?" was what my
>> question was about ;-)
>
>My assumption was that nobody would really care about doing so. It is true that it's less flexible, though (and is a decision we can't easily
>take back later).
>
>> > As I said, I think it matters more with the infix operators, as:
>> >
>> >   [includeIf "env:FOO == bar"]
>> >
>> > is more readable than:
>> >
>> >   [includeIf "env:FOO==bar"]
>>
>> Sure, but at that point, we'd probably want some quoting mechanism for
>> the literal to be compared, e.g.
>>
>> 	[includeIf "env:PATH ~= \"(:|^)/usr/bin(:|$)\""]
>
>Ick. The extra quoting of the internal double-quotes is pretty horrid to look at. Also, how does one match a double-quote in the value? \\\"?
>
>If it were optional, that would make the common cases easy (no dq, no whitespace), and the hard ones possible.
>
>I think this is getting into a bit of a digression, though. I'm willing to defer to Ævar, who is doing the actual work, and I don't know if he has
>found any of this compelling. ;)

What about something like:

	[includeIf "env:PATH ~= '^(.*😊)/usr/bin(:.*)*$' "]

Using single quotes and a full regex pattern instead of trying to provide a syntax to extract a pattern and then match. One call to regexec() would be easier. Then escaping is regcomp's problem (mostly). Potentially, you could even remove the outer ", but that would be wonky. You could omit the ^ and $ by default assuming a full match.
-Randall