From cffdf3b92a97b1af3aedec624a9fb43db1c60ef8 Mon Sep 17 00:00:00 2001
From: Craig Jennings <c@cjennings.net>
Date: Sun, 10 May 2026 13:42:11 -0500
Subject: 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).
---
 modules/dirvish-config.el                | 11 ++++++-
 tests/test-dirvish-config-html-file-p.el | 53 ++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100644 tests/test-dirvish-config-html-file-p.el

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))))
 
diff --git a/tests/test-dirvish-config-html-file-p.el b/tests/test-dirvish-config-html-file-p.el
new file mode 100644
index 00000000..dd18edaf
--- /dev/null
+++ b/tests/test-dirvish-config-html-file-p.el
@@ -0,0 +1,53 @@
+;;; test-dirvish-config-html-file-p.el --- Tests for the html-file predicate -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; `cj/--html-file-p' is the predicate behind `cj/dirvish-open-html-in-eww'.
+;; The earlier inline regex was case-sensitive (`.html?\='), but most
+;; browsers treat `.HTML' as HTML too, so the helper is case-insensitive.
+;; The predicate also anchors on the trailing extension so files with
+;; "html" embedded in the middle of the name don't match.
+
+;;; Code:
+
+(require 'ert)
+(require 'package)
+
+(setq package-user-dir (expand-file-name "elpa" user-emacs-directory))
+(package-initialize)
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "elpa/dirvish-2.3.0/extensions"
+                                          user-emacs-directory))
+(require 'user-constants)
+(require 'keybindings)
+(require 'dirvish-config)
+
+(ert-deftest test-cj--html-file-p-html-extension-matches ()
+  "Normal: `.html' extension matches."
+  (should (cj/--html-file-p "/tmp/index.html")))
+
+(ert-deftest test-cj--html-file-p-htm-extension-matches ()
+  "Normal: `.htm' extension matches (legacy 8.3 form)."
+  (should (cj/--html-file-p "/tmp/page.htm")))
+
+(ert-deftest test-cj--html-file-p-uppercase-html-matches ()
+  "Boundary: `.HTML' (uppercase) matches -- match is case-insensitive."
+  (should (cj/--html-file-p "/tmp/index.HTML")))
+
+(ert-deftest test-cj--html-file-p-mixed-case-html-matches ()
+  "Boundary: mixed case (`.Html') matches."
+  (should (cj/--html-file-p "/tmp/index.Html")))
+
+(ert-deftest test-cj--html-file-p-embedded-html-does-not-match ()
+  "Boundary: `html' in the middle of the name doesn't match (anchor at end)."
+  (should-not (cj/--html-file-p "/tmp/html-thing.org")))
+
+(ert-deftest test-cj--html-file-p-non-html-extension-does-not-match ()
+  "Error: a non-html file returns nil."
+  (should-not (cj/--html-file-p "/tmp/notes.txt")))
+
+(ert-deftest test-cj--html-file-p-no-extension-does-not-match ()
+  "Boundary: a file without an extension does not match."
+  (should-not (cj/--html-file-p "/tmp/README")))
+
+(provide 'test-dirvish-config-html-file-p)
+;;; test-dirvish-config-html-file-p.el ends here
-- 
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