test: regression lock for nil :foreground in --make-emoji-icon

When wttrin-mode-line-emoji-font is set and the cache is fresh, --make-emoji-icon was emitting a face plist of the form (:family ... :height 1.0 :foreground nil). Emacs validates faces on every redisplay, so a single fresh-cache state produced hundreds of "Invalid face attribute :foreground nil" warnings in *Messages*.

The new boundary test asserts the face plist omits :foreground entirely when the caller passes nil. The assertion uses plist-member, not plist-get. plist-get returns nil for both a missing key and a present key bound to nil. That's the exact distinction Emacs's redisplay validator cares about.

1 files changed, 11 insertions, 0 deletions

diff --git a/tests/test-wttrin--mode-line-helpers.el b/tests/test-wttrin--mode-line-helpers.el
index d6811ba..34523a8 100644
--- a/tests/test-wttrin--mode-line-helpers.el
+++ b/tests/test-wttrin--mode-line-helpers.el
@@ -70,6 +70,17 @@
       ;; Without font or foreground, should be plain string
       (should (equal result "☀")))))
 
+(ert-deftest test-wttrin--make-emoji-icon-boundary-nil-foreground-with-font ()
+  "With font set and nil foreground, the face plist must omit :foreground entirely.
+A literal `:foreground nil' entry triggers \"Invalid face attribute\" warnings on
+every redisplay.  `plist-member' (not `plist-get') is required: `plist-get' can't
+distinguish a missing key from a present key bound to nil."
+  (let ((wttrin-mode-line-emoji-font "Noto Color Emoji"))
+    (let* ((result (wttrin--make-emoji-icon "☀" nil))
+           (face (get-text-property 0 'face result)))
+      (should (equal (plist-get face :family) "Noto Color Emoji"))
+      (should-not (plist-member face :foreground)))))
+
 ;;; --------------------------------------------------------------------------
 ;;; wttrin--set-mode-line-string
 ;;; --------------------------------------------------------------------------