feat(org): right-align headline tags to the window edge

org-tags-column only right-aligns tags to a fixed column, and it does so by baking literal spaces into the file, so it can't track window width or splits. I set it to 0 (org keeps a single space, no padding) and add a font-lock rule that stretches that space with a display property pinned to the window's right edge via :align-to. That value resolves at redisplay, so the tags follow the window width and adapt to splits live, and nothing alignment-specific is written to disk.

The tags stop one column short of the edge on purpose. A glyph filling the final column wraps a non-truncated line, which dropped every tagged heading's tags onto the next line in the first cut. org-agenda-tags-column gets 'auto, the native equivalent for agenda views. Tests cover the heading regexp and the align-spec helper.

1 files changed, 48 insertions, 0 deletions

diff --git a/tests/test-org-config-tag-alignment.el b/tests/test-org-config-tag-alignment.el
new file mode 100644
index 000000000..e999f2613
--- /dev/null
+++ b/tests/test-org-config-tag-alignment.el
@@ -0,0 +1,48 @@
+;;; test-org-config-tag-alignment.el --- Right-aligned org tags -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; cj/org-tag-line-re and cj/org--tag-align-spec drive the display-property
+;; right-alignment of org headline tags (org-config.el).  The regexp isolates
+;; the gap before the tags (group 1) and the tag string (group 2); the spec
+;; helper turns a tag string into the (space :align-to (- right WIDTH)) display
+;; spec that pins the tags to the window's right edge.  These exercise the pure
+;; logic directly, without driving font-lock.
+
+;;; Code:
+
+(require 'ert)
+(require 'org-config)
+
+(ert-deftest test-org-config-tag-align-spec-single-tag ()
+  "Normal: the spec pins a tag to the right edge less its width plus margin."
+  (should (equal (cj/org--tag-align-spec ":work:")
+                 `(space :align-to (- right ,(+ 6 cj/org-tag-right-margin))))))
+
+(ert-deftest test-org-config-tag-align-spec-widths ()
+  "Boundary: shortest and multi-tag strings carry their width plus the margin."
+  (should (equal (cj/org--tag-align-spec ":a:")
+                 `(space :align-to (- right ,(+ 3 cj/org-tag-right-margin)))))
+  (should (equal (cj/org--tag-align-spec ":a:b:")
+                 `(space :align-to (- right ,(+ 5 cj/org-tag-right-margin))))))
+
+(ert-deftest test-org-config-tag-line-re-matches-tagged-heading ()
+  "Normal: a tagged headline matches with the gap and tags captured."
+  (let ((line "** TODO Something :work:"))
+    (should (string-match cj/org-tag-line-re line))
+    (should (equal (match-string 1 line) " "))
+    (should (equal (match-string 2 line) ":work:"))))
+
+(ert-deftest test-org-config-tag-line-re-captures-last-gap-with-padding ()
+  "Boundary: with baked padding, group 1 is the single space before the tags."
+  (let ((line "*** TODO [#C] Foo      :a:b:"))
+    (should (string-match cj/org-tag-line-re line))
+    (should (equal (match-string 1 line) " "))
+    (should (equal (match-string 2 line) ":a:b:"))))
+
+(ert-deftest test-org-config-tag-line-re-rejects-untagged-and-non-heading ()
+  "Error: an untagged heading and a non-heading line do not match."
+  (should-not (string-match cj/org-tag-line-re "** TODO Foo"))
+  (should-not (string-match cj/org-tag-line-re "not a heading :work:")))
+
+(provide 'test-org-config-tag-alignment)
+;;; test-org-config-tag-alignment.el ends here