Daemon support (#91)

* Surface errors from prettier daemons

* Add test for daemon error reporting

* Add note about executable dependencies

* Document how to run Prettier as a daemon

* Try to fix "Permission denied" error on Windows

* Add a test for error display using the normal prettier executable

Author: jacksonrayhamilton

.github/workflows/test.yml

@@ -51,8 +51,8 @@ jobs:
       with:
         node-version: '22.x'
 
-    - name: Install prettier
-      run: npm install -g prettier
+    - name: Install prettier executables
+      run: npm install -g prettier @fsouza/prettierd
 
     - name: Build
       run: |

README.md

@@ -130,6 +130,16 @@ And then hook into `web-mode` like this:
                              '("\\.jsx?\\'" . prettier-js-mode))))
 ```
 
+### Usage with prettierd
+
+If you want to mostly eliminate the overhead of running the `prettier` command on every file save (improving performance slightly), you could try using [`prettierd`](https://github.com/fsouza/prettierd) to run Prettier as a daemon.
+
+```elisp
+(setq prettier-js-command "prettierd")
+```
+
+Note that this may come at the expense of a bit more complexity in terms of configuring/managing the daemon.
+
 ## Customization
 
 This package is customizable via Emacs' easy customization interface:

fixtures/syntax-error.js

@@ -0,0 +1,4 @@
+// This file contains a JavaScript syntax error
+function brokenFunction(a, b {  // Missing closing parenthesis
+  return a + b;
+}

prettier-js-test.el

@@ -5,6 +5,11 @@
 ;;; Commentary:
 ;; Tests for prettier-js.el
 
+;; These tests will fail unless node/npm are installed, as well as prettier and
+;; prettierd.  Run the following command to install those latter dependencies:
+
+;; npm install -g prettier @fsouza/prettierd
+
 ;;; Code:
 
 (require 'ert)
@@ -241,5 +246,77 @@
       (when (file-exists-p temp-file)
         (delete-file temp-file)))))
 
+(ert-deftest prettier-js-test-error-display ()
+  "Test that errors from prettier are displayed in the error buffer."
+  (let* ((syntax-error-file (expand-file-name "fixtures/syntax-error.js"))
+         (temp-dir (make-temp-file "prettier-test-dir-" t))
+         (temp-file (expand-file-name "syntax-error.js" temp-dir))
+         (prettier-js-command "prettier")
+         (prettier-js-show-errors 'buffer)
+         (default-directory temp-dir))
+    (unwind-protect
+        (progn
+          ;; Copy syntax error file to temp directory
+          (copy-file syntax-error-file temp-file t)
+
+          ;; Visit the temp file
+          (with-current-buffer (find-file-noselect temp-file)
+            ;; Run prettier-js which should display the error
+            (prettier-js)
+
+            ;; Check that the error buffer exists and contains the error message
+            (let ((error-buffer (get-buffer "*prettier errors*")))
+              (should error-buffer)
+              (with-current-buffer error-buffer
+                (should (string-match-p "SyntaxError: Unexpected token" (buffer-string)))))
+
+            (kill-buffer)
+            ;; Clean up error buffer
+            (when-let ((buf (get-buffer "*prettier errors*")))
+              (kill-buffer buf))))
+
+      ;; Clean up temp directory
+      (when (file-exists-p temp-dir)
+        (delete-directory temp-dir t)))))
+
+(ert-deftest prettier-js-test-prettierd-error-display ()
+  "Test that errors from prettierd are displayed in the error buffer."
+  (let* ((syntax-error-file (expand-file-name "fixtures/syntax-error.js"))
+         (temp-dir (make-temp-file "prettier-test-dir-" t))
+         (temp-file (expand-file-name "syntax-error.js" temp-dir))
+         (prettier-js-command "prettierd")
+         (prettier-js-show-errors 'buffer)
+         (default-directory temp-dir))
+    (unwind-protect
+        (progn
+          ;; Copy syntax error file to temp directory
+          (copy-file syntax-error-file temp-file t)
+
+          ;; Visit the temp file
+          (with-current-buffer (find-file-noselect temp-file)
+            ;; Run prettier-js which should display the error
+            (prettier-js)
+
+            ;; Check that the error buffer exists and contains the error message
+            (let ((error-buffer (get-buffer "*prettier errors*")))
+              (should error-buffer)
+              (with-current-buffer error-buffer
+                (should (string-match-p "SyntaxError: Unexpected token" (buffer-string)))))
+
+            (kill-buffer)
+            ;; Clean up error buffer
+            (when-let ((buf (get-buffer "*prettier errors*")))
+              (kill-buffer buf))))
+
+      ;; Stop prettierd daemon to ensure the temp directory can be deleted on
+      ;; Windows; I think prettierd "locks" the directory where it's started
+      (when (executable-find "prettierd")
+        (message "Stopping prettierd daemon...")
+        (call-process "prettierd" nil nil nil "stop"))
+
+      ;; Clean up temp directory
+      (when (file-exists-p temp-dir)
+        (delete-directory temp-dir t)))))
+
 (provide 'prettier-js-test)
 ;;; prettier-js-test.el ends here

prettier-js.el

@@ -91,6 +91,9 @@ a `before-save-hook'."
           (const :tag "None" nil))
   :group 'prettier-js)
 
+(defvar prettier-js-daemon-commands '("prettier_d" "prettierd")
+  "List of prettier daemon commands that put errors in stdout rather than stderr.")
+
 (defvar-local prettier-js-error-state nil
   "Indicates if there's an error with the prettier executable.
 When non-nil, contains the error message to display.")
@@ -264,6 +267,10 @@ PATCHBUF is the buffer where the diff output will be written."
           (bufferfile (make-temp-file "prettier" nil ext))
           (outputfile (make-temp-file "prettier" nil ext))
           (errorfile (make-temp-file "prettier" nil ext))
+          ;; Some prettier daemons put errors in stdout rather than stderr
+          (program-errorfile (if (member prettier-js-command prettier-js-daemon-commands)
+                                 outputfile
+                               errorfile))
           (errbuf (if prettier-js-show-errors (get-buffer-create "*prettier errors*")))
           (patchbuf (get-buffer-create "*prettier patch*"))
           (coding-system-for-read 'utf-8)
@@ -295,9 +302,8 @@ PATCHBUF is the buffer where the diff output will be written."
                    (setq prettier-js-error-state "Diff command had an issue")
                    (user-error "Error calling diff; is GNU diff on your path?")))
              (message "Could not apply prettier")
-             (if errbuf
-                 (prettier-js--process-errors file-path errorfile errbuf))
-             ))
+             (when errbuf
+               (prettier-js--process-errors file-path program-errorfile errbuf))))
        (kill-buffer patchbuf)
        (delete-file errorfile)
        (delete-file bufferfile)