Make fill functions respect Pandoc pipe blocks

Closes GH-144.

CHANGES.md

@@ -110,6 +110,7 @@
     -   Add font lock support for Pandoc inline footnotes. ([GH-81][])
     -   Raise footnote markers and inline footnote text, and
         optionally hide markup.
+    -   Filling with now respects Pandoc line blocks.  ([GH-144][])
 
 *   Improvements:
 
@@ -152,6 +153,7 @@
   [gh-123]: https://github.com/jrblevin/markdown-mode/issues/123
   [gh-130]: https://github.com/jrblevin/markdown-mode/issues/130
   [gh-134]: https://github.com/jrblevin/markdown-mode/issues/134
+  [gh-144]: https://github.com/jrblevin/markdown-mode/issues/144
   [gh-172]: https://github.com/jrblevin/markdown-mode/issues/172
   [gh-176]: https://github.com/jrblevin/markdown-mode/issues/176
   [gh-185]: https://github.com/jrblevin/markdown-mode/issues/185

markdown-mode.el

@@ -3333,6 +3333,11 @@ Set match data for `markdown-regex-header'."
       (set-match-data match-data)
       t)))
 
+(defun markdown-pipe-at-bol-p ()
+  "Return non-nil if the line begins with a pipe symbol.
+This may be useful for tables and Pandoc's line_blocks extension."
+  (char-equal (char-after (point-at-bol)) ?|))
+
 
 ;;; Markdown Font Lock Matching Functions =====================================
 
@@ -7891,6 +7896,10 @@ return the number of paragraphs left to move."
        ;; Move point past whitespace following list marker.
        ((looking-at markdown-regex-list)
         (goto-char (match-end 0)))
+       ;; Move point past whitespace following pipe at beginning of line
+       ;; to handle Pandoc line blocks.
+       ((looking-at "^|\\s-*")
+        (goto-char (match-end 0)))
        ;; Return point if the paragraph passed was a code block.
        ((markdown-code-block-at-pos (point-at-bol 2))
         (goto-char start)))))
@@ -8356,6 +8365,7 @@ position."
                     "[ \t]*\\(?:[0-9]+\\|#\\)\\.[ \t]+" ; ordered list item
                     "[ \t]*\\[\\S-*\\]:[ \t]+" ; link ref def
                     "[ \t]*:[ \t]+" ; definition
+                    "^|" ; table or Pandoc line block
                     )
                   "\\|"))
   (set
@@ -8394,6 +8404,8 @@ position."
             'markdown-inside-link-p nil t)
   (add-hook 'fill-nobreak-predicate
             'markdown-line-is-reference-definition-p nil t)
+  (add-hook 'fill-nobreak-predicate
+            'markdown-pipe-at-bol-p nil t)
 
   ;; Indentation
   (setq indent-line-function markdown-indent-function)

tests/markdown-test.el

@@ -4494,6 +4494,21 @@ paragraph 2")))))
    (fill-paragraph)
    (should (string-equal (buffer-string) "aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa\naaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa\naaa aaa [aaa aaa aaa aaa](aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) aaa aaa aaa aaa aaa."))))
 
+(ert-deftest test-markdown-filling/pandoc-line-blocks ()
+  "Filling should leave Pandoc line blocks undisturbed.
+This includes preserving whitespace after the pipe."
+  (let ((text "| The limerick packs laughs anatomical
+| In space that is quite economical.
+|    But the good ones I've seen
+|    So seldom are clean
+| And the clean ones so seldom are comical
+
+| 200 Main St.
+| Berkeley, CA 94718"))
+    (markdown-test-string text
+      (fill-region (point-min) (point-max))
+      (should (string-equal (buffer-string) text)))))
+
 ;;; Export tests:
 
 (ert-deftest test-markdown-hook/xhtml-standalone ()