Revise handling of paths between Emacs and Racket

Two goals:

- Avoid adjusting paths from Racket to Emacs style (on Windows) down
  in the Racket back end. Do any such adjustment up in Emacs. This
  adjustment is to do the thing where c:\path\to\foo.rkt is regarded
  by Enacs as c:/path/to/foo.rkt.

- Support the scenario where someone is running Emacs on Windows
  Subystem for Linux, but instead of running Racket for Linux wants to
  run Windows Racket.exe. In that case, a Windows path like
  c:\path\to\foo.rkt is a Linux path /mnt/c/path/to/foo.rkt. In this
  scenario, we want to adjust paths in both directions. When we tell
  the Windows Racket.exe to run a .rkt file, we want to translate it
  from /mnt/c* to c:\*. In the other direction, we want to translate
  c:\* paths in the response from the `path+md5` command, as well as
  when using compilation-mode to make error messages and #<path>
  structs navigable. Fortunately this is easy to do using the WSL
  command-line utility `wslpath`.

- While reviewing compilation-mode, fix and simplify the regexps. They
  were failing to handle Windows paths starting with drive letters.

Reference.md

@@ -45,13 +45,14 @@ See also [`racket-run-and-switch-to-repl`](#racket-run-and-switch-to-repl), whic
 DrRacket's Run because it selects the REPL window (gives it the
 focus), too.
 
-If your source file has a syntax or runtime error, a "skeleton"
-of your file is evaluated to get identifiers from module
-languages, `require`s, and definitions. That way, things like
-completion and [`racket-describe`](#racket-describe) are more likely to work while
-you edit the file to fix the error. If not even the "skeleton"
-evaluation succeeds, you'll have only identifiers provided by
-racket/base, until you fix the error and run again.
+When [`racket-retry-as-skeleton`](#racket-retry-as-skeleton) is true, if your source file has
+an error, a "skeleton" of your file is evaluated to get
+identifiers from module languages, `require`s, and definitions.
+That way, things like completion and [`racket-describe`](#racket-describe) are more
+likely to work while you edit the file to fix the error. If not
+even the "skeleton" evaluation succeeds, you'll have only
+identifiers provided by racket/base, until you fix the error and
+run again.
 
 Output in the `*Racket REPL*` buffer that describes a file and
 position is automatically "linkified". Examples of such text
@@ -109,7 +110,7 @@ z		racket--profile-show-zero
 
 
 In addition to any hooks its parent mode `special-mode` might have run,
-this mode runs the hook [`racket-profile-mode-hook`](#racket-profile-mode-hook), as the final or penultimate step
+this mode runs the hook [`racket-profile-mode-hook`](#racket-profile-mode-hook), as the final step
 during initialization.
 
 ### racket-logger
@@ -153,7 +154,7 @@ C-c C-z		racket-repl
 
 
 In addition to any hooks its parent mode `special-mode` might have run,
-this mode runs the hook [`racket-logger-mode-hook`](#racket-logger-mode-hook), as the final or penultimate step
+this mode runs the hook [`racket-logger-mode-hook`](#racket-logger-mode-hook), as the final step
 during initialization.
 
 ### racket-debug-mode
@@ -669,7 +670,7 @@ other examples:
 To see a table of all key sequences use `M-x
 describe-input-method <RET> racket-unicode`.
 
-If you don’t like the highlighting of partially matching tokens you
+If you don't like the highlighting of partially matching tokens you
 can turn it off by setting `input-method-highlight-flag` to nil via
 `M-x customize-variable`.
 
@@ -783,7 +784,7 @@ p		racket-stepper-previous-item
 
 
 In addition to any hooks its parent mode `special-mode` might have run,
-this mode runs the hook [`racket-stepper-mode-hook`](#racket-stepper-mode-hook), as the final or penultimate step
+this mode runs the hook [`racket-stepper-mode-hook`](#racket-stepper-mode-hook), as the final step
 during initialization.
 
 ### racket-expand-file
@@ -841,7 +842,7 @@ installing it does _not_ do the `raco setup` that is normally
 done for Racket packages.
 
 This command will do a `raco make` of racket-mode's .rkt files,
-creating bytecode files in a `compiled/` subdirectory. As a
+creating bytecode files in `compiled/` subdirectories. As a
 result, when a [`racket-run`](#racket-run) or [`racket-repl`](#racket-repl) command must start
 the Racket process, it will start faster.
 
@@ -900,6 +901,22 @@ for a specific [`racket-run`](#racket-run) using a C-u prefix. This lets you
 normally run with a faster setting, and temporarily re-run to get
 a more-helpful error message.
 
+### racket-retry-as-skeleton
+Retry a "skeleton" of files with errors, for identifier names?
+
+When true: If your source file has an error, a "skeleton" of
+your file is evaluated to get identifiers from module languages,
+`require`s, and definitions. That way, things like completion and
+[`racket-describe`](#racket-describe) are more likely to work while you edit the file
+to fix the error.
+
+Otherwise, you'll have only identifiers provided by racket/base,
+until you fix the error and run again.
+
+You might want to disable this if you work with files that take a
+very long time to expand -- because this feature needs to expand
+again when there is an error.
+
 ### racket-user-command-line-arguments
 List of command-line arguments to supply to your Racket program.
 
@@ -924,6 +941,27 @@ but NOT:
     (list "-f" "bar")
 
 
+### racket-path-from-emacs-to-racket-function
+A function used to transform Emacs Lisp pathnames before supplying to the Racket back end.
+
+If you run Emacs on Windows Subsystem for Linux, and want to run
+Racket programs using Windows Racket.exe rather than Linux
+racket, you can set this to [`racket-wsl-to-windows`](#racket-wsl-to-windows). In that case
+you probably also want to customize the "reverse":
+[`racket-path-from-racket-to-emacs-function`](#racket-path-from-racket-to-emacs-function).
+
+### racket-path-from-racket-to-emacs-function
+A function used to transform pathnames supplied by the Racket back end before using them in Emacs.
+
+The default on Windows replaces back with forward slashes. The
+default elsewhere is `identity`.
+
+If you run Emacs on Windows Subsystem for Linux, and want to run
+Racket programs using Windows Racket.exe rather than Linux
+racket, you can set this to [`racket-windows-to-wsl`](#racket-windows-to-wsl). In that case
+you probably also want to customize the "reverse":
+[`racket-path-from-emacs-to-racket-function`](#racket-path-from-emacs-to-racket-function).
+
 ## REPL
 
 ### racket-history-filter-regexp

makefile

@@ -15,7 +15,7 @@ help:
 	@echo "Targets: clean, compile, deps, doc, test, test-racket, test-elisp"
 
 show-versions:
-	racket --version
+	- racket --version
 	echo `which $(EMACSBIN)`
 	$(EMACSBIN) --version
 
@@ -26,7 +26,7 @@ clean:
 	$(BYTECOMP) $<
 
 compile: clean \
-	show-versions\
+	show-versions \
 	racket-bug-report.elc \
 	racket-common.elc \
 	racket-collection.elc \
@@ -46,7 +46,8 @@ compile: clean \
 	racket-stepper.elc \
 	racket-tests.elc \
 	racket-unicode-input-method.elc \
-	racket-util.elc
+	racket-util.elc \
+	racket-wsl.elc
 
 # Install packages we depend on. Intended for one-time use by
 # developers and for Travis CI. (Normal users of the package get these

racket-common.el

@@ -681,7 +681,8 @@ Allows #; to be followed by zero or more space or newline chars."
 ;;; racket--what-to-run
 
 (defun racket--what-to-run ()
-  (cons (racket--buffer-file-name) (racket--submod-path)))
+  (cons (racket--buffer-file-name)
+        (racket--submod-path)))
 
 (defun racket--submod-path ()
   (and (racket--lang-p)

racket-custom.el

@@ -124,14 +124,44 @@ until you fix the error and run again.
 
 You might want to disable this if you work with files that take a
 very long time to expand -- because this feature needs to expand
-again when there is an error.
-
-Note: The retry "
+again when there is an error."
   :tag "Retry as Skeleton?"
   :type 'boolean
   :safe #'booleanp
   :group 'racket)
 
+(defcustom racket-path-from-emacs-to-racket-function
+  #'identity
+  "A function used to transform Emacs Lisp pathnames before supplying to the Racket back end.
+
+If you run Emacs on Windows Subsystem for Linux, and want to run
+Racket programs using Windows Racket.exe rather than Linux
+racket, you can set this to `racket-wsl-to-windows'. In that case
+you probably also want to customize the \"reverse\":
+`racket-path-from-racket-to-emacs-function'."
+  :tag "Path from Emacs to Racket Function"
+  :type 'function
+  :safe 'functionp
+  :group 'racket)
+
+(defcustom racket-path-from-racket-to-emacs-function
+  (if racket--winp
+      (lambda (path) (subst-char-in-string ?\\ ?/ path))
+      #'identity)
+  "A function used to transform pathnames supplied by the Racket back end before using them in Emacs.
+
+The default on Windows replaces back with forward slashes. The
+default elsewhere is `identity'.
+
+If you run Emacs on Windows Subsystem for Linux, and want to run
+Racket programs using Windows Racket.exe rather than Linux
+racket, you can set this to `racket-windows-to-wsl'. In that case
+you probably also want to customize the \"reverse\":
+`racket-path-from-emacs-to-racket-function'."
+  :tag "Path from Racket to Emacs Function"
+  :type 'function
+  :safe #'functionp)
+
 ;;; REPL
 
 (defgroup racket-repl nil

racket-edit.el

@@ -202,8 +202,8 @@ Please keep in mind the following limitations:
   (pcase (racket--symbol-at-point-or-prompt prefix "Visit definition of: ")
     (`nil nil)
     (str (if (and (eq major-mode 'racket-mode)
-                  (not (equal (racket--cmd/await `(path+md5))
-                              (cons (racket--buffer-file-name) (md5 (current-buffer)))))
+                  (not (equal (racket--repl-file-name+md5)
+                              (cons (racket--buffer-file-name t) (md5 (current-buffer)))))
                   (y-or-n-p "Run current buffer first? "))
              (racket--repl-run nil nil
                                (lambda (_what)

racket-make-doc.el

@@ -151,6 +151,8 @@
     racket-error-context
     racket-retry-as-skeleton
     racket-user-command-line-arguments
+    racket-path-from-emacs-to-racket-function
+    racket-path-from-racket-to-emacs-function
     "REPL"
     racket-history-filter-regexp
     racket-images-inline

racket-repl.el

@@ -24,6 +24,7 @@
 (require 'compile)
 (require 'easymenu)
 (require 'cl-lib)
+(require 'rx)
 
 ;; Don't (require 'racket-debug). Mutual dependency. Instead:
 (declare-function  racket--debug-send-definition "racket-debug" (beg end))
@@ -125,7 +126,17 @@ fallbacks. The version number here is a baseline for run.rkt to
 be able to load at all.")
 
 (defvar racket--run.rkt (expand-file-name "run.rkt" racket--rkt-source-dir)
-  "Pathname of run.rkt")
+  "Pathname of run.rkt.")
+
+(defvar racket-adjust-run-rkt #'identity
+  "A function used to transform the variable `racket--run.rkt'.
+
+You probably don't need to change this unless you are developing
+racket-mode, AND run Emacs on Windows Subsystem for Linux, AND
+want to run your programs using Windows Racket.exe, AND have the
+racket-mode source code under \"/mnt\". Whew. In that case you
+can set this `racket-wsl-to-windows' so that racket-mode can find
+its own run.rkt file.")
 
 (defvar-local racket-user-command-line-arguments
   nil
@@ -223,33 +234,38 @@ Non-nil RUN-COMMAND is supplied as the second command-line
 argument to `racket--run.rkt' so the process can start by
 immediately running a desired file.
 
-Never changes selected window."
+Never changes selected window.
+
+Note that the value of the variable `racket--run.rkt' is applied
+to the function variable `racket-adjust-run-rkt' before being
+used. See the latter for more information."
   (if (racket--repl-live-p)
       (when display
         (display-buffer racket--repl-buffer-name))
     (racket--require-version racket--minimum-required-version)
-    (with-current-buffer
-        (make-comint racket--repl-buffer-name/raw ;w/o *stars*
-                     racket-program
-                     nil
-                     racket--run.rkt
-                     (number-to-string racket-command-port)
-                     (setq racket--cmd-auth (format "%S" `(auth ,(random))))
-                     (format "%S" (or run-command
-                                      (racket--repl-make-run-command nil))))
-      (let ((proc (get-buffer-process racket--repl-buffer-name)))
-        ;; Display now so users see startup and banner sooner.
-        (when display
-          (display-buffer (current-buffer)))
-        (message "Starting %s to run %s ..." racket-program racket--run.rkt)
-        ;; Ensure command server connection closed when racket process dies.
-        (set-process-sentinel proc
-                              (lambda (_proc event)
-                                (with-racket-repl-buffer
-                                  (insert (concat "Process Racket REPL " event)))
-                                (racket--cmd-disconnect)))
-        (set-process-coding-system proc 'utf-8 'utf-8) ;for e.g. λ
-        (racket-repl-mode))))
+    (let ((run.rkt (funcall racket-adjust-run-rkt racket--run.rkt)))
+      (with-current-buffer
+          (make-comint racket--repl-buffer-name/raw ;w/o *stars*
+                       racket-program
+                       nil
+                       run.rkt
+                       (number-to-string racket-command-port)
+                       (setq racket--cmd-auth (format "%S" `(auth ,(random))))
+                       (format "%S" (or run-command
+                                        (racket--repl-make-run-command nil))))
+        (let ((proc (get-buffer-process racket--repl-buffer-name)))
+          ;; Display now so users see startup and banner sooner.
+          (when display
+            (display-buffer (current-buffer)))
+          (message "Starting %s to run %s ..." racket-program run.rkt)
+          ;; Ensure command server connection closed when racket process dies.
+          (set-process-sentinel proc
+                                (lambda (_proc event)
+                                  (with-racket-repl-buffer
+                                    (insert (concat "Process Racket REPL " event)))
+                                  (racket--cmd-disconnect)))
+          (set-process-coding-system proc 'utf-8 'utf-8) ;for e.g. λ
+          (racket-repl-mode)))))
   (unless (racket--cmd-connected-or-connecting-p)
     (racket--cmd-connect-start)))
 
@@ -459,16 +475,25 @@ mistake."
 
 ;;; Misc
 
+(defun racket--repl-file-name+md5 ()
+  "Return the file and MD5 running in the REPL, or nil.
+
+The result can be nil if the REPL is not started, or if it is
+running no particular file as with the `,top` command."
+  (when (comint-check-proc racket--repl-buffer-name)
+    (pcase (racket--cmd/await `(path+md5))
+      (`(,(and (pred stringp) path) . ,md5)
+       (cons (funcall racket-path-from-racket-to-emacs-function path)
+             md5))
+      (_ nil))))
+
 (defun racket-repl-file-name ()
   "Return the file running in the REPL, or nil.
 
 The result can be nil if the REPL is not started, or if it is
-running no particular file as with the `,top` command.
-
-On Windows this will replace \ with / in an effort to match the
-Unix style names used by Emacs on Windows."
+running no particular file as with the `,top` command."
   (when (comint-check-proc racket--repl-buffer-name)
-    (pcase (racket--cmd/await `(path+md5))
+    (pcase (racket--repl-file-name+md5)
       (`(,(and (pred stringp) path) . ,_md5) path)
       (_ nil))))
 
@@ -732,16 +757,20 @@ With prefix arg, open the N-th last shown image."
   (compilation-setup t)
   (setq-local
    compilation-error-regexp-alist
-   '(;; error
-     ("^;?[ ]*\\([^ :]+\\):\\([0-9]+\\)[:.]\\([0-9]+\\)" 1 2 3)
-     ;; contract
-     ("^;?[ ]*at:[ ]+\\([^ :]+\\):\\([0-9]+\\)[.]\\([0-9]+\\)$" 1 2 3)
-     ;; rackunit check-xxx
-     ("#<path:\\([^>]+\\)> \\([0-9]+\\) \\([0-9]+\\)" 1 2 3)
-     ;;rackunit/text-ui test-suite
-     ("^location:[ ]+\\(\\([^:]+\\):\\([0-9]+\\):\\([0-9]+\\)\\)" 2 3 4 2 1)
-     ;; path struct
-     ("#<path:\\([^>]+\\)>" 1 nil nil 0))))
+   (list
+    ;; Any apparent file:line:col
+    (list (rx (group-n 1 (+? (not (syntax whitespace))))
+              (any ?\: ?\.)
+              (group-n 2 (+ digit))
+              (any ?\: ?\.)
+              (group-n 3 (+ digit)))
+          #'racket--adjust-group-1 2 3)
+     ;; Any path struct
+     (list (rx "#<path:" (group-n 1 (+? (not (any ?\>)))) ?\>)
+           #'racket--adjust-group-1 nil nil 0))))
+
+(defun racket--adjust-group-1 ()
+  (list (funcall racket-path-from-racket-to-emacs-function (match-string 1))))
 
 (provide 'racket-repl)
 

racket-util.el

@@ -41,10 +41,17 @@ strings."
           spec)
     m))
 
-(defun racket--buffer-file-name ()
-  "Like `buffer-file-name' but always a non-propertized string."
-  (and (buffer-file-name)
-       (substring-no-properties (buffer-file-name))))
+(defun racket--buffer-file-name (&optional no-adjust)
+  "Like `buffer-file-name' but always a non-propertized string.
+
+Unless NO-ADJUST is not nil, applies the name to the function
+variable `racket-path-from-emacs-to-racket-function'."
+  (let ((v (and (buffer-file-name)
+                (substring-no-properties (buffer-file-name)))))
+    (if no-adjust
+        v
+      (funcall racket-path-from-emacs-to-racket-function
+               v))))
 
 (defun racket--save-if-changed ()
   (unless (eq major-mode 'racket-mode)