Re: [PATCH v3 2/2] userdiff: extend Scheme support to cover other Lisp dialects

> From: "Scott L. Burson" <Scott@sympoiesis.com>
> 
> Common Lisp has top-level forms, such as 'defun' and 'defmacro', that
> are not matched by the current Scheme pattern.  Also, it is more
> common in CL, when defining user macros intended as top-level forms,
> to prefix their names with "def" instead of "define"; such forms are
> also not matched.  And some top-level forms don't even begin with
> "def".
> 
> On the other hand, it is an established formatting convention in the
> Lisp community that only top-level forms start at the left margin.  So
> matching any unindented line starting with an open parenthesis is an
> acceptable heuristic; false positives will be rare.
> 
> However, there are also cases where notionally top-level forms are
> grouped together within some containing form.  At least in the Common
> Lisp community, it is conventional to indent these by two spaces, or
> sometimes one.  But matching just an open parenthesis indented by two
> spaces would be too broad; so the pattern added by this commit
> requires an indented form to start with "(def".  It is believed that
> this strikes a good balance between potential false positives and
> false negatives.

> diff --git a/Documentation/gitattributes.adoc b/Documentation/gitattributes.adoc
> index f20041a323..a9ce5adef9 100644
> --- a/Documentation/gitattributes.adoc
> +++ b/Documentation/gitattributes.adoc
> @@ -912,6 +912,7 @@ patterns are available:
>  - `rust` suitable for source code in the Rust language.
>  
>  - `scheme` suitable for source code in the Scheme language.
> +Also handles Emacs Lisp, Common Lisp, and most other dialects.

>  
>  - `tex` suitable for source code for LaTeX documents.
>  
> diff --git a/t/t4018/scheme-lisp-defun-a b/t/t4018/scheme-lisp-defun-a
> new file mode 100644
> index 0000000000..c3c750f76d
> --- /dev/null
> +++ b/t/t4018/scheme-lisp-defun-a
> @@ -0,0 +1,4 @@
> +(defun some-func (x y z) RIGHT
> +  (let ((a x)
> +        (b y))
> +        (ChangeMe a b)))

> diff --git a/t/t4018/scheme-lisp-defun-b b/t/t4018/scheme-lisp-defun-b
> new file mode 100644
> index 0000000000..21be305968
> --- /dev/null
> +++ b/t/t4018/scheme-lisp-defun-b
> @@ -0,0 +1,4 @@
> +(macrolet ((foo (x) `(bar ,x)))
> +  (defun mumble (x) ; RIGHT
> +    (when (> x 0)
> +      (foo x)))) ; ChangeMe

> diff --git a/t/t4018/scheme-lisp-eval-when b/t/t4018/scheme-lisp-eval-when
> new file mode 100644
> index 0000000000..5d941d7e0e
> --- /dev/null
> +++ b/t/t4018/scheme-lisp-eval-when
> @@ -0,0 +1,4 @@
> +(eval-when (:compile-toplevel :load-toplevel :execute)  ; RIGHT
> +  (set-macro-character #\?
> +		       (lambda (stream char)
> +			 `(make-pattern-variable ,(read stream)))))  ; ChangeMe

> diff --git a/t/t4018/scheme-module b/t/t4018/scheme-module-a
> similarity index 100%
> rename from t/t4018/scheme-module
> rename to t/t4018/scheme-module-a
> diff --git a/t/t4018/scheme-module-b b/t/t4018/scheme-module-b
> new file mode 100644
> index 0000000000..77bc0c5eff
> --- /dev/null
> +++ b/t/t4018/scheme-module-b
> @@ -0,0 +1,6 @@
> +(module A
> +  (export with-display-exception)
> +  (extern (display-exception display-exception))
> +  (def (with-display-exception thunk) RIGHT
> +    (with-catch (lambda (e) (display-exception e (current-error-port)) e)
> +      thunk ChangeMe)))

> diff --git a/t/t4034/scheme/expect b/t/t4034/scheme/expect
> index 138abe9f56..72592665f1 100644
> --- a/t/t4034/scheme/expect
> +++ b/t/t4034/scheme/expect
> @@ -6,7 +6,7 @@
>  (define (<RED>myfunc a b<RESET><GREEN>my-func first second<RESET>)
>    ; This is a <RED>really<RESET><GREEN>(moderately)<RESET> cool function.
>    (<RED>this\place<RESET><GREEN>that\place<RESET> (+ 3 4))
> -  (define <RED>|the greeting|<RESET><GREEN>|a greeting|<RESET> "hello")
> +  (define <RED>|the \greeting|<RESET><GREEN>|a \greeting|<RESET> |hello there|)
>    ({<RED>}<RESET>(([<RED>]<RESET>(func-n)<RED>[<RESET>]))<RED>{<RESET>})
>    (let ((c (<RED>+ a b<RESET><GREEN>add1 first<RESET>)))
>      (format "one more than the total is %d" (<RED>add1<RESET><GREEN>+<RESET> c <GREEN>second<RESET>))))

> diff --git a/t/t4034/scheme/post b/t/t4034/scheme/post
> index 0e3bab101d..450cc234f7 100644
> --- a/t/t4034/scheme/post
> +++ b/t/t4034/scheme/post
> @@ -1,7 +1,7 @@
>  (define (my-func first second)
>    ; This is a (moderately) cool function.
>    (that\place (+ 3 4))
> -  (define |a greeting| "hello")
> +  (define |a \greeting| |hello there|)
>    ({(([(func-n)]))})
>    (let ((c (add1 first)))
>      (format "one more than the total is %d" (+ c second))))
> diff --git a/t/t4034/scheme/pre b/t/t4034/scheme/pre
> index 03d77c7c43..ba8b8ac0a4 100644
> --- a/t/t4034/scheme/pre
> +++ b/t/t4034/scheme/pre
> @@ -1,7 +1,7 @@
>  (define (myfunc a b)
>    ; This is a really cool function.
>    (this\place (+ 3 4))
> -  (define |the greeting| "hello")
> +  (define |the \greeting| |hello there|)
>    ({}(([](func-n)[])){})
>    (let ((c (+ a b)))
>      (format "one more than the total is %d" (add1 c))))
> diff --git a/userdiff.c b/userdiff.c
> index fe710a68bf..b5412e6bc3 100644
> --- a/userdiff.c
> +++ b/userdiff.c
> @@ -344,14 +344,24 @@ PATTERNS("rust",
>  	 "|[0-9][0-9_a-fA-Fiosuxz]*(\\.([0-9]*[eE][+-]?)?[0-9_fF]*)?"
>  	 "|[-+*\\/<>%&^|=!:]=|<<=?|>>=?|&&|\\|\\||->|=>|\\.{2}=|\\.{3}|::"),
>  PATTERNS("scheme",
> -	 "^[\t ]*(\\(((define|def(struct|syntax|class|method|rules|record|proto|alias)?)[-*/ \t]|(library|module|struct|class)[*+ \t]).*)$",
>  	 /*
> -	  * R7RS valid identifiers include any sequence enclosed
> -	  * within vertical lines having no backslashes
> +	  * An unindented opening parenthesis identifies a top-level
> +	  * expression in all Lisp dialects.
>  	  */
> -	 "\\|([^\\\\]*)\\|"
> -	 /* All other words should be delimited by spaces or parentheses */
> -	 "|([^][)(}{[ \t])+"),
> +	 "^(\\(.*)$\n"
> +	 /* For Scheme: a possibly indented left paren followed by a keyword. */
> +	 "^[\t ]*(\\(((define|def(struct|syntax|class|method|rules|record|proto|alias)?)[-*/ \t]|(library|module|struct|class)[*+ \t]).*)$\n"
> +	 /*
> +	  * For all Lisp dialects: a slightly indented line starting with "(def".
> +	  */
> +	 "^  ?(\\([Dd][Ee][Ff].*)$",
> +	 /*
> +	  * The union of R7RS and Common Lisp symbol syntax: allows arbitrary
> +	  * strings between vertical bars, including any escaped characters.
> +	  */
> +	 "\\|([^|\\\\]|\\\\.)*\\|"
> +	 /* All other words should be delimited by spaces or parentheses. */
> +	 "|([^][)(}{ \t])+"),
>  PATTERNS("tex", "^(\\\\((sub)*section|chapter|part)\\*{0,1}\\{.*)$",
>  	 "\\\\[a-zA-Z@]+|\\\\.|([a-zA-Z0-9]|[^\x01-\x7f])+"),
>  { .name = "default", .binary = -1 },