feat(coverage): report modules missing from SimpleCov + project-module score

=make coverage= used to print a line-weighted percentage that only saw
files SimpleCov instrumented.  104 modules existed on disk but only 49
appeared in =.coverage/simplecov.json=, so the headline number was
flattering: untouched modules counted for nothing.

The summary script now adds two things on top of the existing report:

- A =Not in SimpleCov report= section listing modules present under
  =modules/*.el= but absent from the SimpleCov output.  Missing-module
  detection is exactly direct =modules/*.el=; subdirectories and =.elc=
  files are ignored.
- A =Project module coverage= line that is module-weighted across every
  direct =modules/*.el= file.  Tracked modules contribute their per-file
  coverage percentage; missing modules contribute 0%.

The original line-weighted SimpleCov percentage stays as the
=instrumented coverage= number.  The new module-weighted score is the
honest project-level reading: missing modules count as 0% without
inventing a fake executable-line denominator for them.

Tests assert the missing-module section, the new percentage, and the
ignore rules for .elc / nested files.

1 files changed, 79 insertions, 12 deletions

diff --git a/tests/test-coverage-summary.el b/tests/test-coverage-summary.el
index 01c9efa0..2dc9d517 100644
--- a/tests/test-coverage-summary.el
+++ b/tests/test-coverage-summary.el
@@ -18,6 +18,12 @@
 	  (insert content))
 	file))
 
+(defun test-coverage-summary--touch (file)
+  "Create FILE and its parent directory."
+  (make-directory (file-name-directory file) t)
+  (with-temp-file file
+    (insert ";;; fixture\n")))
+
 (ert-deftest test-coverage-summary-modules-only ()
   "Normal: summary includes modules files and ignores non-module files."
   (let* ((root (file-name-as-directory (make-temp-file "coverage-root-" t)))
@@ -29,14 +35,20 @@
 				   module-a module-b other))
 		 (file (test-coverage-summary--write-json content)))
 	(unwind-protect
-		(let ((output (cj/coverage-summary-text
-					   file
-					   (expand-file-name "modules" root)
-					   root)))
+		(progn
+          (test-coverage-summary--touch module-a)
+          (test-coverage-summary--touch module-b)
+          (test-coverage-summary--touch other)
+          (let ((output (cj/coverage-summary-text
+					     file
+					     (expand-file-name "modules" root)
+					     root)))
 		  (should (string-match-p "modules/a\\.el" output))
 		  (should (string-match-p "modules/b\\.el" output))
 		  (should-not (string-match-p "tests/test-a\\.el" output))
-		  (should (string-match-p "2 of 5" output)))
+		  (should (string-match-p "2 of 5" output))
+          (should (string-match-p "Project module coverage: 33\\.3%" output))
+          (should (string-match-p "Not in SimpleCov report: 0 modules" output))))
 	  (delete-file file)
 	  (delete-directory root t))))
 
@@ -50,17 +62,72 @@
 				   low high))
 		 (file (test-coverage-summary--write-json content)))
 	(unwind-protect
-		(let* ((output (cj/coverage-summary-text
-						file
-						(expand-file-name "modules" root)
-						root))
-			   (pos-low (string-match "modules/low\\.el" output))
-			   (pos-high (string-match "modules/high\\.el" output)))
+		(progn
+          (test-coverage-summary--touch low)
+          (test-coverage-summary--touch high)
+          (let* ((output (cj/coverage-summary-text
+						  file
+						  (expand-file-name "modules" root)
+						  root))
+			     (pos-low (string-match "modules/low\\.el" output))
+			     (pos-high (string-match "modules/high\\.el" output)))
 		  (should pos-low)
 		  (should pos-high)
-		  (should (< pos-low pos-high)))
+		  (should (< pos-low pos-high))))
 	  (delete-file file)
 	  (delete-directory root t))))
 
+(ert-deftest test-coverage-summary-lists-modules-missing-from-simplecov ()
+  "Normal: modules on disk but absent from SimpleCov are listed separately."
+  (let* ((root (file-name-as-directory (make-temp-file "coverage-root-" t)))
+         (tracked (expand-file-name "modules/tracked.el" root))
+         (missing-a (expand-file-name "modules/missing-a.el" root))
+         (missing-b (expand-file-name "modules/missing-b.el" root))
+         (content (format
+                   "{\"run\":{\"coverage\":{\"%s\":[1,0,null,1]}}}"
+                   tracked))
+         (file (test-coverage-summary--write-json content)))
+    (unwind-protect
+        (progn
+          (test-coverage-summary--touch tracked)
+          (test-coverage-summary--touch missing-a)
+          (test-coverage-summary--touch missing-b)
+          (let ((output (cj/coverage-summary-text
+                         file
+                         (expand-file-name "modules" root)
+                         root)))
+            (should (string-match-p "Total: 2 of 3 lines covered" output))
+            (should (string-match-p
+                     "Project module coverage: 22\\.2% (1 tracked, 2 missing, 3 total; missing modules count as 0%)"
+                     output))
+            (should (string-match-p "Not in SimpleCov report: 2 modules" output))
+            (should (string-match-p "modules/missing-a\\.el" output))
+            (should (string-match-p "modules/missing-b\\.el" output))
+            (should (string-match-p "count as 0% in project module coverage" output))))
+      (delete-file file)
+      (delete-directory root t))))
+
+(ert-deftest test-coverage-summary-missing-module-helper-ignores-elc-and-subdirs ()
+  "Boundary: untracked module detection is exactly direct modules/*.el files."
+  (let* ((root (file-name-as-directory (make-temp-file "coverage-root-" t)))
+         (module-dir (expand-file-name "modules" root))
+         (tracked-file (expand-file-name "modules/tracked.el" root))
+         (missing-file (expand-file-name "modules/missing.el" root))
+         (compiled-file (expand-file-name "modules/compiled.elc" root))
+         (nested-file (expand-file-name "modules/nested/not-a-module.el" root))
+         (tracked-table (make-hash-table :test 'equal)))
+    (unwind-protect
+        (progn
+          (test-coverage-summary--touch tracked-file)
+          (test-coverage-summary--touch missing-file)
+          (make-directory (file-name-directory compiled-file) t)
+          (with-temp-file compiled-file (insert "compiled"))
+          (test-coverage-summary--touch nested-file)
+          (puthash "modules/tracked.el" t tracked-table)
+          (should (equal (cj/coverage-summary--missing-module-files
+                          tracked-table module-dir root)
+                         '("modules/missing.el"))))
+      (delete-directory root t))))
+
 (provide 'test-coverage-summary)
 ;;; test-coverage-summary.el ends here