>From b373d749d85addd82d17fe4b6c6ec92a0c52e12b Mon Sep 17 00:00:00 2001
From: Alex Branham <address@hidden>
Date: Fri, 16 Feb 2018 10:55:52 -0600
Subject: [PATCH] Support flymake in Emacs 26+ using chktex

---
 latex-flymake.el | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 latex.el         |  3 ++
 2 files changed, 89 insertions(+)
 create mode 100644 latex-flymake.el

diff --git a/latex-flymake.el b/latex-flymake.el
new file mode 100644
index 00000000..e77e0591
--- /dev/null
+++ b/latex-flymake.el
@@ -0,0 +1,86 @@
+;;; latex-flymake.el --- Flymake integration  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; This file provides flymake integration for latex documents using
+;; "chktex" as a backend.  You must be running Emacs 26 or newer.
+;; Enable it by adding the following to your init file:
+
+;; (add-hook 'LaTeX-mode-hook flymake-mode)
+
+;;; Code:
+
+(eval-when-compile
+  (require 'cl-lib))
+(require 'flymake)
+
+(defvar-local LaTeX--flymake-proc nil)
+
+(defun LaTeX-flymake (report-fn &rest _args)
+  "Setup flymake integration.
+
+REPORT-FN is flymake's callback function."
+  (unless (executable-find "chktex")
+    (error "Cannot find chktex"))
+  (when (process-live-p LaTeX--flymake-proc)
+    (kill-process LaTeX--flymake-proc))
+  (let ((source (current-buffer)))
+    (save-restriction
+      (widen)
+      (setq
+       LaTeX--flymake-proc
+       (make-process
+        :name "LaTeX-flymake" :noquery t :connection-type 'pipe
+        :buffer (generate-new-buffer " *LaTeX-flymake*")
+        :command '("chktex" "--verbosity=0" "--quiet" "--inputfiles")
+        :sentinel
+        (lambda (proc _event)
+          (when (eq 'exit (process-status proc))
+            (unwind-protect
+                (if (with-current-buffer source (eq proc LaTeX--flymake-proc))
+                    (with-current-buffer (process-buffer proc)
+                      (goto-char (point-min))
+                      (cl-loop
+                       while (search-forward-regexp
+                              (rx line-start "stdin:"
+                                  ;; line
+                                  (group-n 1 (one-or-more num))
+                                  ":"
+                                  ;; column
+                                  (group-n 2 (one-or-more num))
+                                  ":"
+                                  ;; This is information about the
+                                  ;; number of the warning, which we
+                                  ;; probably don't care about:
+                                  (one-or-more num)
+                                  ":"
+                                  ;; Warning message:
+                                  (group-n 3 (one-or-more not-newline)) line-end)
+                              nil t)
+                       for msg = (match-string 3)
+                       for (beg . end) = (flymake-diag-region
+                                          source
+                                          (string-to-number (match-string 1))
+                                          (string-to-number (match-string 2)))
+                       for type = :warning
+                       collect (flymake-make-diagnostic source
+                                                        beg
+                                                        end
+                                                        type
+                                                        msg)
+                       into diags
+                       finally (funcall report-fn diags)))
+                  (flymake-log :warning "Canceling obsolete check %s"
+                               proc))
+              (kill-buffer (process-buffer proc)))))))
+      (process-send-region LaTeX--flymake-proc (point-min) (point-max))
+      (process-send-eof LaTeX--flymake-proc))))
+
+(defun LaTeX-setup-flymake-backend ()
+  "Setup flymake backend for LaTeX."
+  (add-hook 'flymake-diagnostic-functions 'LaTeX-flymake nil t))
+
+(when (< 25 emacs-major-version)
+  (add-hook 'LaTeX-mode-hook #'LaTeX-setup-flymake-backend))
+
+(provide 'latex-flymake)
+;;; latex-flymake.el ends here
diff --git a/latex.el b/latex.el
index c2d8a4ca..2d7f8223 100644
--- a/latex.el
+++ b/latex.el
@@ -31,6 +31,9 @@
 (require 'tex)
 (require 'tex-style)
 (require 'tex-ispell)
+(when (<= 26 emacs-major-version)
+  ;; latex-flymake requires Emacs 26.
+  (require 'latex-flymake))
 (eval-when-compile (require 'cl))       ;FIXME: Use cl-lib.
 
 ;;; Syntax
-- 
2.16.1