refactor(dirvish): extract cj/--html-file-p; match HTML case-insensitively

`cj/dirvish-open-html-in-eww' inlined a `string-match-p' against `\.html?\=' to decide whether to hand a file to eww.  The check was case-sensitive, so `.HTML' fell through to the "Not an HTML file" message even though every browser treats it as HTML.  Lift the predicate into `cj/--html-file-p' and bind `case-fold-search' to t so uppercase and mixed-case extensions match.  The trailing-`\=' anchor stays so files like `html-thing.org' still don't match.

Seven Normal/Boundary/Error tests cover lowercase `.html', `.htm', uppercase `.HTML', mixed-case `.Html', embedded `html' (no match), non-html extensions (no match), and no-extension files (no match).

1 files changed, 10 insertions, 1 deletions

diff --git a/modules/dirvish-config.el b/modules/dirvish-config.el
index 86ecfd2d..ad2227e8 100644
--- a/modules/dirvish-config.el
+++ b/modules/dirvish-config.el
@@ -161,11 +161,20 @@ Filters for audio files, prompts for the playlist name, and saves the resulting
 
 ;;; --------------------------- Dired Open HTML In EWW --------------------------
 
+(defun cj/--html-file-p (file)
+  "Return non-nil when FILE has a `.html' or `.htm' extension.
+
+Match is case-insensitive (`.HTML' counts) and anchored at end so
+embedded `html' in the middle of a name doesn't match.  Pure helper
+used by `cj/dirvish-open-html-in-eww'."
+  (let ((case-fold-search t))
+    (and (string-match-p "\\.html?\\'" file) t)))
+
 (defun cj/dirvish-open-html-in-eww ()
   "Open HTML file at point in dired/dirvish using eww."
   (interactive)
   (let ((file (dired-get-file-for-visit)))
-    (if (string-match-p "\\.html?\\'" file)
+    (if (cj/--html-file-p file)
         (eww-open-file file)
       (message "Not an HTML file: %s" file))))