Flymake's flymake-proc.el backend slightly easier to debug

Misc cleanup in flymake-proc.el

Improve description of what this file contains.

Better name for the backend function.  Fix the case where it is run
interactively.

Keep the output buffer alive iff the external process panics.

* lisp/progmodes/flymake-proc.el
(flymake-proc-legacy-flymake): Rename from
flymake-proc-start-syntax-check.  Allow running interactively.
(flymake-start-syntax-check): Obsolete alias for
flymake-proc-legacy-flymake.
(flymake-proc-start-syntax-check): Delete.
(flymake-diagnostic-functions): Include flymake-proc-legacy-flymake
(flymake-proc--process-sentinel): Keep output buffer alive.
Clarify with comments.
(flymake-proc--diagnostics-for-pattern)
(flymake-proc--process-sentinel)
(flymake-proc--safe-delete-directory)
(flymake-proc--start-syntax-check-process): Use condition-case-unless-debug.

1 files changed, 44 insertions, 24 deletions

diff --git a/lisp/progmodes/flymake-proc.el b/lisp/progmodes/flymake-proc.el
index 1028d9ae40c..37b7e49dea4 100644
--- a/lisp/progmodes/flymake-proc.el
+++ b/lisp/progmodes/flymake-proc.el
@@ -1,4 +1,4 @@
-;;; flymake-proc.el --- Flymake for external syntax checker processes  -*- lexical-binding: t; -*-
+;;; flymake-proc.el --- Flymake backend for external tools  -*- lexical-binding: t; -*-
 
 ;; Copyright (C) 2003-2017 Free Software Foundation, Inc.
 
@@ -26,9 +26,13 @@
 ;;
 ;; Flymake is a minor Emacs mode performing on-the-fly syntax checks.
 ;;
-;; This file contains the most original implementation of flymake's
-;; main source of on-the-fly diagnostic info, the external syntax
-;; checker backend.
+;; This file contains a significant part of the original flymake's
+;; implementation, a buffer-checking mechanism that parses the output
+;; of an external syntax check tool with regular expressions.
+;;
+;; That work has been adapted into a flymake "backend" function,
+;; `flymake-proc-legacy-flymake' suitable for adding to the
+;; `flymake-diagnostic-functions' variable.
 ;;
 ;;; Bugs/todo:
 
@@ -412,7 +416,7 @@ Create parent directories as needed."
                              :warning)
                             (t
                              :error)))))))
-    (condition-case err
+    (condition-case-unless-debug err
         (cl-loop
          with (regexp file-idx line-idx col-idx message-idx) = pattern
          while (search-forward-regexp regexp nil t)
@@ -497,11 +501,13 @@ Create parent directories as needed."
            (diagnostics (process-get
                          proc
                          'flymake-proc--collected-diagnostics))
-           (interrupted (process-get proc 'flymake-proc--interrupted)))
+           (interrupted (process-get proc 'flymake-proc--interrupted))
+           (panic nil)
+           (output-buffer (process-get proc 'flymake-proc--output-buffer)))
       (flymake-log 2 "process %d exited with code %d"
                    (process-id proc) exit-status)
-      (unwind-protect
-          (when (buffer-live-p source-buffer)
+      (condition-case-unless-debug err
+          (progn
             (flymake-log 3 "cleaning up using %s" cleanup-f)
             (with-current-buffer source-buffer
               (funcall cleanup-f)
@@ -509,19 +515,24 @@ Create parent directories as needed."
                      (funcall flymake-proc--report-fn diagnostics))
                     (interrupted
                      (flymake-proc--panic :stopped interrupted))
+                    (diagnostics
+                     ;; non-zero exit but some diagnostics is quite
+                     ;; normal...
+                     (funcall flymake-proc--report-fn diagnostics))
                     ((null diagnostics)
-                     ;; non-zero exit but no errors is strange
+                     ;; ...but no diagnostics is strange, so panic.
+                     (setq panic t)
                      (flymake-proc--panic
                       :configuration-error
                       (format "Command %s errored, but no diagnostics"
-                              command)))
-                    (diagnostics
-                     (funcall flymake-proc--report-fn diagnostics)))))
+                              command))))))
         (delete-process proc)
         (setq flymake-proc--processes
               (delq proc flymake-proc--processes))
-        (unless (> flymake-log-level 2)
-          (kill-buffer (process-get proc 'flymake-proc--output-buffer)))))))
+        (if panic
+            (flymake-log 1 "Output buffer %s kept alive for debugging"
+                         output-buffer)
+          (kill-buffer output-buffer))))))
 
 (defun flymake-proc--panic (problem explanation)
   "Tell flymake UI about a fatal PROBLEM with this backend.
@@ -679,7 +690,7 @@ expression. A match indicates `:warning' type, otherwise
     (flymake-log 2 "deleted file %s" file-name)))
 
 (defun flymake-proc--safe-delete-directory (dir-name)
-  (condition-case nil
+  (condition-case-unless-debug nil
       (progn
         (delete-directory dir-name)
         (flymake-log 2 "deleted dir %s" dir-name))
@@ -687,13 +698,21 @@ expression. A match indicates `:warning' type, otherwise
      (flymake-log 1 "Failed to delete dir %s, error ignored" dir-name))))
 
 
-(defun flymake-proc-start-syntax-check (report-fn &optional interactive)
-  "Start syntax checking for current buffer."
+(defun flymake-proc-legacy-flymake (report-fn &optional interactive)
+  "Flymake backend based on the original flymake implementation.
+This function is suitable for inclusion in
+`flymake-dianostic-types-alist'. For backward compatibility, it
+can also be executed interactively independently of
+`flymake-mode'."
   ;; Interactively, behave as if flymake had invoked us through its
   ;; `flymake-diagnostic-functions' with a suitable ID so flymake can
   ;; clean up consistently
-  (interactive (list (flymake-make-report-fn 'flymake-proc-start-syntax-check)
-                     t))
+  (interactive (list
+                (lambda (diags &rest args)
+                  (apply (flymake-make-report-fn 'flymake-proc-legacy-flymake)
+                         diags
+                         (append args '(:force t))))
+                t))
   (cond
    ((process-live-p flymake-proc--process)
     (when interactive
@@ -728,9 +747,13 @@ expression. A match indicates `:warning' type, otherwise
                                                          dir)
                t)))))))
 
+(define-obsolete-function-alias 'flymake-start-syntax-check
+  'flymake-proc-legacy-flymake "26.1"
+  "Flymake backend based on the original flymake implementation.")
+
 (defun flymake-proc--start-syntax-check-process (cmd args dir)
   "Start syntax check process."
-  (condition-case err
+  (condition-case-unless-debug err
       (let* ((process
               (let ((default-directory (or dir default-directory)))
                 (when dir
@@ -1070,7 +1093,7 @@ Use CREATE-TEMP-F for creating temp copy."
 
 ;;;; Hook onto flymake-ui
 (add-to-list 'flymake-diagnostic-functions
-             'flymake-proc-start-syntax-check)
+             'flymake-proc-legacy-flymake)
 
 
 ;;;;
@@ -1254,9 +1277,6 @@ Return its components if so, nil otherwise.")
   (define-obsolete-function-alias 'flymake-safe-delete-directory
     'flymake-proc--safe-delete-directory "26.1"
     nil)
-  (define-obsolete-function-alias 'flymake-start-syntax-check
-    'flymake-proc-start-syntax-check "26.1"
-    "Start syntax checking for current buffer.")
   (define-obsolete-function-alias 'flymake-stop-all-syntax-checks
     'flymake-proc-stop-all-syntax-checks "26.1"
     "Kill all syntax check processes.")