Re: [GSOC][PATCH] userdiff: add support for Scheme

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 27, 2021, 22:50 UTC
Message-ID: <xmqq5z1cqki7.fsf@gitster.g>
In-Reply-To: <20210327173938.59391-1-raykar.ath@gmail.com>

Atharva Raykar <raykar.ath@gmail.com> writes:

Show 15 quoted lines

> diff --git a/t/t4018/scheme-define-syntax b/t/t4018/scheme-define-syntax
> new file mode 100644
> index 0000000000..603b99cea4
> --- /dev/null
> +++ b/t/t4018/scheme-define-syntax
> @@ -0,0 +1,8 @@
> +(define-syntax define-test-suite RIGHT
> +  (syntax-rules ()
> +    ((_ suite-name (name test) ChangeMe ...)
> +     (define suite-name
> +       (let ((tests
> +              `((name . ,test) ...)))
> +         (lambda ()
> +           (ChangeMe 'suite-name tests)))))))
> \ No newline at end of file

Is there a good reason to leave the final line incomplete? If there isn't, complete it (applies to other newly-created files in the patch).

Show 10 quoted lines

> diff --git a/userdiff.c b/userdiff.c
> index 3f81a2261c..c51a8c98ba 100644
> --- a/userdiff.c
> +++ b/userdiff.c
> @@ -191,6 +191,14 @@ PATTERNS("rust",
>  	 "[a-zA-Z_][a-zA-Z0-9_]*"
>  	 "|[0-9][0-9_a-fA-Fiosuxz]*(\\.([0-9]*[eE][+-]?)?[0-9_fF]*)?"
>  	 "|[-+*\\/<>%&^|=!:]=|<<=?|>>=?|&&|\\|\\||->|=>|\\.{2}=|\\.{3}|::"),
> +PATTERNS("scheme",
> +         "^[\t ]*(\\(define-?.*)$",

Didn't "git diff HEAD" before committing (or "git show") highlighted these whitespace errors?

.git/rebase-apply/patch:183: indent with spaces.
         "^[\t ]*(\\(define-?.*)$",
.git/rebase-apply/patch:184: trailing whitespace, indent with spaces.
         /* 
.git/rebase-apply/patch:185: indent with spaces.
          * Scheme allows symbol names to have any character,
.git/rebase-apply/patch:186: indent with spaces.
          * as long as it is not a form of a parenthesis.
.git/rebase-apply/patch:187: indent with spaces.
          * The spaces must be escaped.
warning: squelched 2 whitespace errors
warning: 7 lines applied after fixing whitespace errors.

Show 6 quoted lines

> +         /* 
> +          * Scheme allows symbol names to have any character,
> +          * as long as it is not a form of a parenthesis.
> +          * The spaces must be escaped.
> +          */
> +         "(\\.|[^][)(\\}\\{ ])+"),

One or more "dot or anything other than SP or parentheses"? But a dot "." is neither a space or any {bra-ce} letter, so would the above be equivalent to

	"[^][()\\{\\} \t]+"

I wonder...

I am also trying to figure out what you wanted to achieve by mentioning "The spaces must be escaped.". Did you mean something like (string->symbol "a symbol with SP in it") is a symbol? Even so, I cannot quite guess the significance of that fact wrt the regexp you added here?

As we are trying to catch program identifiers (symbols in scheme) and numeric literals, treating any group of non-whitespace letters that is delimited by one or more whitespaces as a "word" would be a good first-order approximation, but in addition, as can be seen in an example like (a(b(c))), parentheses can also serve as such "word delimiters" in addition to whitespaces. So the regexp given above makes sense to me from that angle, especially if you do not limit the whitespace to only SP, but include HT (\t) as well. But was that how you came up with the regexp?

Thanks.

>  PATTERNS("bibtex", "(@[a-zA-Z]{1,}[ \t]*\\{{0,1}[ \t]*[^ \t\"@',\\#}{~%]*).*$",
>  	 "[={}\"]|[^={}\" \t]+"),
>  PATTERNS("tex", "^(\\\\((sub)*section|chapter|part)\\*{0,1}\\{.*)$",