> On Dec 13, 2020, at 7:15 AM, Damjan Marion via lists.fd.io > <dmarion=me....@lists.fd.io> wrote: > > > Hi, > > I was playing a bit with clang-format as replacement to gnu indent which we > use today[1]. > > While it is impossible to render exact same result like gnu indent, good > thing is that clang-format can be used only on lines which are changed in the > diff so no major reformat is needed. My patch deos exactly that.
I have an emacs function that can be used to do this (reformat only changed
lines) on file save as well. I've included it below.. It does count on
"clang-format.el" already being installed. The first couple of items are for
hooking before-save, and only do the reformat if CLANG is specified in the
standard VPP trailer comment (instead of INDENT or ON).
Thanks,
Chris.
(defun vpp-maybe-format-buffer ()
"Reformat buffer if contains VPP magic"
(when (save-excursion
(goto-char (point-min))
(re-search-forward "coding-style-patch-verification:
\\(ON\\|INDENT\\|CLANG\\)" nil t))
(cond
((string= "CLANG" (match-string 1)) (clang-format-vc-diff) t)
;; ((string= "ON" (match-string 1)) (vpp-format-buffer) t)
;; ((string= "INDENT" (match-string 1)) (vpp-format-buffer) t)
(t t))))
(defun vpp-maybe-format-buffer-on-save ()
(add-hook 'before-save-hook 'vpp-maybe-format-buffer nil t))
(add-hook 'c-mode-hook 'vpp-maybe-format-buffer-on-save)
(add-hook 'c++-mode-hook 'vpp-maybe-format-buffer-on-save)
(defvar diffu-new-lines-re "^@@.*\\+\\([0-9]+\\)\\(,\\([0-9]+\\)\\)?")
(defun clang-format-args-from-diff-buffer (&optional buffer)
(let ((use-buf (or buffer (current-buffer)))
lines)
(with-current-buffer use-buf
(save-excursion
(goto-char (point-max))
(while (re-search-backward diffu-new-lines-re nil 'noerror)
(let ((start (string-to-number (match-string 1)))
(count (string-to-number (or (match-string 3) "1"))))
(unless (= count 0)
(setq lines (cons (format "--lines=%d:%d" start (+ start
count -1)) lines)))))))
lines))
(defun clang-format-vc-diff ()
"Reformat only the changed lines from VC in the buffer"
(interactive)
(let* ((code-buffer (current-buffer))
(cursor (clang-format--bufferpos-to-filepos (point) 'exact
'utf-8-unix))
;; vc-working-revision has some bizarre cache bug, it
;; returns the revision that was HEAD the first time it is
;; checked in a buffer. If that buffer is saved, and checked
;; the next call to vc-working-revision is not updated, one
;; must reload the file. So instead invoke the backend
directly.
(head-revision (vc-call-backend (vc-backend buffer-file-name)
'working-revision
buffer-file-name))
(temp-buffer (generate-new-buffer " *clang-format-temp*"))
(temp-file (make-temp-file "clang-format"))
diff-line-args
head-temp-file)
(unwind-protect
(if (not head-revision)
(progn
(message "(clang-format-vc-diff: %s not revision
controlled, formatting whole buffer"
buffer-file-name)
(clang-format-buffer))
;; Get the HEAD revision into a temp file
(let ((head-temp-buf (vc-find-revision buffer-file-name
head-revision)))
(setq head-temp-file (buffer-file-name head-temp-buf))
(kill-buffer head-temp-buf))
;; Get the diff of buffer from the HEAD revision
(let ((status (call-process-region
nil nil (executable-find "diff")
nil `(,temp-buffer ,temp-file) nil
"-u0"
head-temp-file
"-"))
(stderr (with-temp-buffer
(unless (zerop (cadr (insert-file-contents
temp-file)))
(insert ": "))
(buffer-substring-no-properties
(point-min) (line-end-position)))))
(cond
((stringp status)
(error "(clang-format-vc-diff diff killed by signal
%s%s)" status stderr))
((zerop status)
(message "(clang-format-vc-diff no diff"))
((not (= 1 status))
(error "(clang-format-vc-diff diff failed with code
%d%s)" status stderr))))
(setq diff-line-args (clang-format-args-from-diff-buffer
temp-buffer))
;; empty the temp buffer, and delete the temp file
(with-current-buffer temp-buffer (erase-buffer))
;; Get xml-replacements into now-empty temp-buffer
(if (not diff-line-args)
(message "(clang-format-vc-diff no differences to
format)")
(let ((status (apply #'call-process-region
nil nil clang-format-executable
nil `(,temp-buffer ,temp-file) nil
`("-output-replacements-xml"
"-assume-filename"
,(file-name-nondirectory buffer-file-name)
"-fallback-style"
,clang-format-fallback-style
"-cursor" ,(number-to-string cursor)
,@diff-line-args)))
(stderr (with-temp-buffer
(unless (zerop (cadr (insert-file-contents
temp-file)))
(insert ": "))
(buffer-substring-no-properties
(point-min) (line-end-position)))))
(cond
((stringp status)
(error "(clang-format killed by signal %s%s)" status
stderr))
((not (zerop status))
(error "(clang-format failed with code %d%s)" status
stderr)))
(if (= 0 (buffer-size temp-buffer))
(message "(vpp-clang-diff-format-buffer no formatting
changes")
(cl-destructuring-bind (replacements cursor
incomplete-format)
(with-current-buffer temp-buffer
(clang-format--extract (car (xml-parse-region))))
(save-excursion
(dolist (rpl replacements)
(apply #'clang-format--replace rpl)))
(when cursor
(goto-char (clang-format--filepos-to-bufferpos
cursor 'exact
'utf-8-unix)))
(if incomplete-format
(message "(clang-format: incomplete (syntax
errors)%s)" stderr)
(message "(clang-format: success%s)" stderr)))))))
(ignore-errors (kill-buffer temp-buffer))
(ignore-errors (delete-file temp-file))
(ignore-errors (delete-file head-temp-file)))))
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