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

From
Atharva Raykar <raykar.ath@gmail.com>
Date
Mar 27, 2021, 17:39 UTC
Message-ID
<20210327173938.59391-1-raykar.ath@gmail.com>

Add a diff driver for Scheme (R5RS and R6RS) which recognizes top level and local `define` forms, whether it is a function definition, binding, syntax definition or a user-defined `define-xyzzy` form.

The rationale for picking `define` forms for the hunk headers is because it is usually the only significant form for defining the structure of the program, and it is a common pattern for schemers to have local function definitions to hide their visibility, so it is not only the top level `define`'s that are of interest. Schemers also extend the language with macros to provide their own define forms (for example, something like a `define-test-suite`) which is also captured in the hunk header.

The word regex is a best-effort attempt to conform to R6RS[1] valid identifiers, symbols and numbers.

[1] http://www.r6rs.org/final/html/r6rs/r6rs-Z-H-7.html#node_chap_4
Signed-off-by: Atharva Raykar <raykar.ath@gmail.com>
---

Hi, first-time contributor here, I wanted to have a go at this as a microproject.

A few things I had to consider:
 - Going through the mailing list, there have already been two other
   patches that are for lispy languages that have taken slightly
   different approaches: Elisp[1] and Clojure[2]. Would it make any
   sense to have a single userdiff driver for lisp that just captures
   all top level forms in the hunk? I personally felt it's better to
   differentiate the drivers for each language, as they have different
   constructs.
 - It was hard to decide exactly which forms should appear on the hunk
   headers. Having programmed in a Scheme before, I went with the forms I
   would have liked to see when looking at git diffs, which would be the
   nearest `define` along with `define-syntax` and other define forms that
   are created as user-defined macros. I am willing to ask around in
   certain active scheme communities for some kind of consensus, but there
   is no single large consolidated group of schemers (the closest is
   probably comp.lang.scheme?).
 - By best-effort attempt at the wordregex, I mean that it is a little
   more permissive than it has to be, as it accepts a few words that are
   technically invalid in Scheme.
   Making it handle all cases like numbers and identifiers with separate
   regexen would be greatly complicated (Eg: #x#e10.2f3 is a valid number
   but #x#f10.2e3 is not; 10t1 is a valid identifier, but 10s1 is a number
   -- my wordregex just clubs all of these into a generic 'word match' which
   trades of granularity for simplicity, and it usually does the right thing).

[1] http://public-inbox.org/git/20210213192447.6114-1-git@adamspiers.org/ [2] http://public-inbox.org/git/pull.902.git.1615667191368.gitgitgadget@gmail.com/

 Documentation/gitattributes.txt    | 2 ++
 t/t4018-diff-funcname.sh           | 1 +
 t/t4018/scheme-define-syntax       | 8 ++++++++
 t/t4018/scheme-local-define        | 4 ++++
 t/t4018/scheme-top-level-define    | 4 ++++
 t/t4018/scheme-user-defined-define | 6 ++++++
 t/t4034-diff-words.sh              | 1 +
 t/t4034/scheme/expect              | 9 +++++++++
 t/t4034/scheme/post                | 4 ++++
 t/t4034/scheme/pre                 | 4 ++++
 userdiff.c                         | 8 ++++++++
 11 files changed, 51 insertions(+)
 create mode 100644 t/t4018/scheme-define-syntax
 create mode 100644 t/t4018/scheme-local-define
 create mode 100644 t/t4018/scheme-top-level-define
 create mode 100644 t/t4018/scheme-user-defined-define
 create mode 100644 t/t4034/scheme/expect
 create mode 100644 t/t4034/scheme/post
 create mode 100644 t/t4034/scheme/pre
diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
index 0a60472bb5..cfcfa800c2 100644
--- a/Documentation/gitattributes.txt
+++ b/Documentation/gitattributes.txt
@@ -845,6 +845,8 @@ patterns are available:
 
 - `rust` suitable for source code in the Rust language.
 
+- `scheme` suitable for source code in the Scheme language.
+
 - `tex` suitable for source code for LaTeX documents.
 
 
diff --git a/t/t4018-diff-funcname.sh b/t/t4018-diff-funcname.sh
index 9675bc17db..823ea96acb 100755
--- a/t/t4018-diff-funcname.sh
+++ b/t/t4018-diff-funcname.sh
@@ -48,6 +48,7 @@ diffpatterns="
 	python
 	ruby
 	rust
+	scheme
 	tex
 	custom1
 	custom2
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
diff --git a/t/t4018/scheme-local-define b/t/t4018/scheme-local-define
new file mode 100644
index 0000000000..90e75dcce8
--- /dev/null
+++ b/t/t4018/scheme-local-define
@@ -0,0 +1,4 @@
+(define (higher-order)
+  (define local-function RIGHT
+    (lambda (x)
+     (car "this is" "ChangeMe"))))
\ No newline at end of file
diff --git a/t/t4018/scheme-top-level-define b/t/t4018/scheme-top-level-define
new file mode 100644
index 0000000000..03acdc628d
--- /dev/null
+++ b/t/t4018/scheme-top-level-define
@@ -0,0 +1,4 @@
+(define (some-func x y z) RIGHT
+  (let ((a x)
+        (b y))
+        (ChangeMe a b)))
\ No newline at end of file
diff --git a/t/t4018/scheme-user-defined-define b/t/t4018/scheme-user-defined-define
new file mode 100644
index 0000000000..401093bac3
--- /dev/null
+++ b/t/t4018/scheme-user-defined-define
@@ -0,0 +1,6 @@
+(define-test-suite record-case-tests RIGHT
+  (record-case-1 (lambda (fail)
+                   (let ((a (make-foo 1 2)))
+                     (record-case a
+                       ((bar x) (ChangeMe))
+                       ((foo a b) (+ a b)))))))
\ No newline at end of file
diff --git a/t/t4034-diff-words.sh b/t/t4034-diff-words.sh
index 56f1e62a97..ee7721ab91 100755
--- a/t/t4034-diff-words.sh
+++ b/t/t4034-diff-words.sh
@@ -325,6 +325,7 @@ test_language_driver perl
 test_language_driver php
 test_language_driver python
 test_language_driver ruby
+test_language_driver scheme
 test_language_driver tex
 
 test_expect_success 'word-diff with diff.sbe' '
diff --git a/t/t4034/scheme/expect b/t/t4034/scheme/expect
new file mode 100644
index 0000000000..eed21e803c
--- /dev/null
+++ b/t/t4034/scheme/expect
@@ -0,0 +1,9 @@
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index 6a5efba..7c4a6b4 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
+<CYAN>@@ -1,4 +1,4 @@<RESET>
+(define (<RED>myfunc a b<RESET><GREEN>my-func first second<RESET>)
+  ; This is a <RED>really<RESET><GREEN>(moderately)<RESET> cool function.
+  (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
new file mode 100644
index 0000000000..7c4a6b4f3d
--- /dev/null
+++ b/t/t4034/scheme/post
@@ -0,0 +1,4 @@
+(define (my-func first second)
+  ; This is a (moderately) cool function.
+  (let ((c (add1 first)))
+    (format "one more than the total is %d" (+ c second))))
\ No newline at end of file
diff --git a/t/t4034/scheme/pre b/t/t4034/scheme/pre
new file mode 100644
index 0000000000..6a5efbae61
--- /dev/null
+++ b/t/t4034/scheme/pre
@@ -0,0 +1,4 @@
+(define (myfunc a b)
+  ; This is a really cool function.
+  (let ((c (+ a b)))
+    (format "one more than the total is %d" (add1 c))))
\ No newline at end of file
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-?.*)$",
+         /* 
+          * Scheme allows symbol names to have any character,
+          * as long as it is not a form of a parenthesis.
+          * The spaces must be escaped.
+          */
+         "(\\.|[^][)(\\}\\{ ])+"),
 PATTERNS("bibtex", "(@[a-zA-Z]{1,}[ \t]*\\{{0,1}[ \t]*[^ \t\"@',\\#}{~%]*).*$",
 	 "[={}\"]|[^={}\" \t]+"),
 PATTERNS("tex", "^(\\\\((sub)*section|chapter|part)\\*{0,1}\\{.*)$",

-- 
2.31.0
Next: Junio C Hamano
Message 1 of 35 in “userdiff: add support for Scheme”
  1. Atharva RaykarMar 27, 2021
  2. Junio C HamanoMar 27, 2021
  3. Junio C HamanoMar 27, 2021
  4. Ævar Arnfjörð BjarmasonMar 28, 2021
  5. Junio C HamanoMar 28, 2021
  6. Atharva RaykarMar 28, 2021
  7. Phillip WoodMar 29, 2021
  8. Atharva RaykarMar 30, 2021
  9. Ævar Arnfjörð BjarmasonMar 30, 2021
  10. Atharva RaykarMar 30, 2021
  11. Atharva RaykarMar 28, 2021
  12. Atharva RaykarMar 28, 2021
  13. Junio C HamanoMar 28, 2021
  14. Atharva RaykarMar 29, 2021
  15. Junio C HamanoMar 29, 2021
  16. Phillip WoodMar 29, 2021
  17. Johannes SixtMar 27, 2021
  18. Atharva RaykarMar 28, 2021
  19. Phillip WoodMar 29, 2021
  20. Johannes SixtMar 29, 2021
  21. Ævar Arnfjörð BjarmasonMar 29, 2021
  22. Phillip WoodMar 29, 2021
  23. Atharva RaykarMar 30, 2021
  24. Atharva RaykarMar 30, 2021
  25. Phillip WoodApr 5, 2021
  26. Johannes SixtApr 5, 2021
  27. Atharva RaykarApr 6, 2021
  28. Phillip WoodApr 6, 2021
  29. [GSoC][PATCH v2 0/1] userdiff: add support for schemeAtharva Raykar, Apr 3, 2021
  30. [GSoC][PATCH v2 1/1] userdiff: add support for schemeAtharva Raykar, Apr 3, 2021
  31. Phillip WoodApr 5, 2021
  32. Atharva RaykarApr 6, 2021
  33. [GSoC][PATCH v3 0/1] userdiff: add support for schemeAtharva Raykar, Apr 8, 2021
  34. [GSoC][PATCH v3 1/1] userdiff: add support for SchemeAtharva Raykar, Apr 8, 2021
  35. Junio C HamanoApr 12, 2021

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