Merge branch 'clippy-flymake'

3 files changed, 85 insertions, 2 deletions

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..3acc1df
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,7 @@
+.PHONY: build clean
+
+build: clean
+	emacs -batch -L . -f batch-byte-compile clippy-flymake.el
+
+clean:
+	rm -f clippy-flymake.elc
diff --git a/README.md b/README.md
index b799486..504c795 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,23 @@
 # flymake-clippy
 
-A Flymake backend for Clippy.
+A Flymake backend for [Clippy](https://doc.rust-lang.org/stable/clippy/index.html), the Rust linter.
+
+## Instructions
+
+Use with [rust-mode](https://elpa.nongnu.org/nongnu/rust-mode.html):
+
+```elisp
+(add-hook 'rust-mode-hook #'clippy-flymake-setup-backend)
+```
+
+## Eglot users
+
+Eglot [fully manages Flymake](https://github.com/joaotavora/eglot/issues/268) so you'll need some extra code to make it cooperate:
+
+```elisp
+(add-to-list 'eglot-stay-out-of 'flymake)
+
+(add-hook 'eglot--managed-mode-hook
+          (lambda ()
+            (add-hook 'flymake-diagnostic-functions #'eglot-flymake-backend nil t)))
+```
diff --git a/clippy-flymake.el b/clippy-flymake.el
index df5624a..e268c63 100644
--- a/clippy-flymake.el
+++ b/clippy-flymake.el
@@ -1,4 +1,8 @@
+<<<<<<< HEAD
 ;;; flymake-clippy.el --- Flymake backend for Clippy  -*- lexical-binding: t; -*-
+=======
+;;; flymake-clippy.el --- Flymake backend for cargo clippy  -*- lexical-binding: t; -*-
+>>>>>>> @{-1}
 
 ;; Copyright (C) 2023  Graham Marlow
 
@@ -20,9 +24,61 @@
 
 ;;; Commentary:
 
-;; Flymake backend for Clippy.
+;; Flymake backend for Clippy, the Rust linter.
+;; https://doc.rust-lang.org/stable/clippy/index.html
 
 ;;; Code:
 
+(defun clippy-flymake (report-fn &rest _args)
+  "Flymake backend for cargo clippy."
+  (unless (executable-find "cargo")
+    (error "Cannot find cargo"))
+
+  (let* ((source (current-buffer))
+         (filename (file-name-nondirectory (buffer-file-name source))))
+    (save-restriction
+      (widen)
+      (setq clippy--flymake-proc
+            (make-process
+             :name "clippy-flymake" :noquery t :connection-type 'pipe
+             :buffer (generate-new-buffer "*clippy-flymake*")
+             :command '("cargo" "clippy")
+             :sentinel
+             (lambda (proc _event)
+               (when (memq (process-status proc) '(exit signal))
+                 (unwind-protect
+                     (if (with-current-buffer source (eq proc clippy--flymake-proc))
+                         (with-current-buffer (process-buffer proc)
+                           (goto-char (point-min))
+                           ;; Collect output buffer into diagnostic messages/locations,
+                           ;; exposing them via `report-fn'.
+                           (cl-loop
+                            while (search-forward-regexp
+                                   ;; Capture group source example:
+                                   ;; "warning: ..."
+                                   ;;    --> src/filename.rs
+                                   ;; 98 | ...
+                                   (concat "^\\(warning:.*\\)\n\\(.*" filename "\\):\\([0-9]+\\):\\([0-9]+\\)$")
+                                   nil t)
+                            for msg = (match-string 1)
+                            for (beg . end) = (flymake-diag-region
+                                               source
+                                               (string-to-number (match-string 3)))
+                            for type = (if (string-match "^warning" msg)
+                                           :warning
+                                         :error)
+                            collect (flymake-make-diagnostic source beg end type msg)
+                            into diags
+                            finally (funcall report-fn diags)))
+                       (flymake-log :warning "Canceling obsolete check %s" proc))
+                   ;; Cleanup temp buffer.
+                   (kill-buffer (process-buffer proc)))))))
+      (process-send-region clippy--flymake-proc (point-min) (point-max))
+      (process-send-eof clippy--flymake-proc))))
+
+(defun clippy-flymake-setup-backend ()
+  "Add `clippy-flymake' to `flymake-diagnostic-functions' hook."
+  (add-hook 'flymake-diagnostic-functions #'clippy-flymake nil t))
+
 (provide 'flymake-clippy)
 ;;; flymake-clippy.el ends here