Parse shebangs on Windows (#293)

Parses the shebang from formatter scripts on Windows, and inserts the
binary in to the command. This fixes
#285.
Please let me know if there is still something that need more work,
thanks.

One minor issue I noticed is that errors will now get logged to
`*aphleia-bash-log*` instead of `*apheleia-npx-log*`.

CHANGELOG.md

@@ -9,8 +9,11 @@ The format is based on [Keep a Changelog].
 ### Bugs fixed
 * `apheleia-indent-lisp-buffer` updated to apply local variables after
   calling major-mode. Also includes setting for `indent-tabs-mode` ([#286]).
+* [Formatter scripts](scripts/formatters) will now work on Windows if Emacs
+  can find the executable defined in the shebang.
 
 [#286]: https://github.com/radian-software/apheleia/pull/286
+[#285]: https://github.com/radian-software/apheleia/issues/285
 
 ## 4.1 (released 2024-02-25)
 ### Enhancements

apheleia-formatters.el

@@ -992,6 +992,26 @@ machine from the machine file is available on"))
              collect val
              else do (error "Result of command evaluation must be a string \
 or list of strings: %S" arg)))
+
+      ;; Windows fails to run formatter scripts. Check whether the
+      ;; command executable is a script that contains a shebang. Parse
+      ;; the shebang and insert the binary into the command.
+      (when (member system-type '(ms-dos windows-nt))
+        (when-let ((arg1-file (locate-file (car command) exec-path)))
+          (with-temp-buffer
+            (insert-file-contents arg1-file nil 0 2)
+            (when (string= (buffer-string) "#!")
+              ;; Assumes that the full shebang is max 200 characters
+              (insert-file-contents arg1-file nil 2 200 t)
+              (let* ((shebang-components (split-string (thing-at-point 'line)))
+                     (shebang-binary
+                      (if (string= (car shebang-components) "/usr/bin/env")
+                          (cdr shebang-components)
+                        (last (split-string (car shebang-components) "/")))))
+                (setq command (append shebang-binary
+                                      (list arg1-file)
+                                      (cdr command))))))))
+
       (setf (apheleia-formatter--arg1 context) (car command)
             (apheleia-formatter--argv context) (cdr command))
       context)))
@@ -1009,17 +1029,17 @@ purposes."
   ;; resolve for the whole formatting process (for example
   ;; `apheleia--current-process').
   (with-current-buffer buffer
-    (when-let ((ctx
-                (apheleia--formatter-context formatter command remote stdin))
-               (exec-path
+    (when-let ((exec-path
                 (append `(,(expand-file-name
                             "scripts/formatters"
                             (file-name-directory
                              (file-truename
                               ;; Borrowed with love from Magit
                               (let ((load-suffixes '(".el")))
                                 (locate-library "apheleia"))))))
-                        exec-path)))
+                        exec-path))
+               (ctx
+                (apheleia--formatter-context formatter command remote stdin)))
       (if (executable-find (apheleia-formatter--arg1 ctx)
                            (eq apheleia-remote-algorithm 'remote))
           (apheleia--execute-formatter-process