fix: mark projectile-globally-ignored-files as safe local variable

- Add :safe predicate to projectile-globally-ignored-files custom variable
- Update tests to verify safe local variable predicate behavior
- Document change in CHANGELOG.md

Author: takeokunn

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## master (unreleased)
 
 ### Changes
+* [#1958](https://github.com/bbatsov/projectile/issues/1958): Exclude `.projectile-cache.eld` from search results (ripgrep/ag/grep) by default.
 * [#1954](https://github.com/bbatsov/projectile/issues/1954): update ELisp for usage.html / "Removal of missing projects"
 * [#1947](https://github.com/bbatsov/projectile/issues/1947): `projectile-project-name` should be marked as safe
 * Set `projectile-auto-discover` to `nil` by default.

projectile.el

@@ -402,10 +402,11 @@ Similar to '#' in .gitignore files."
   :package-version '(projectile . "2.2.0"))
 
 (defcustom projectile-globally-ignored-files
-  (list projectile-tags-file-name)
+  (list projectile-tags-file-name projectile-cache-file)
   "A list of files globally ignored by projectile.
 Note that files aren't filtered if `projectile-indexing-method'
 is set to `alien'."
+  :safe (lambda (x) (not (remq t (mapcar #'stringp x))))
   :group 'projectile
   :type '(repeat string))
 

test/projectile-test.el

@@ -352,6 +352,32 @@ Just delegates OPERATION and ARGS for all operations except for`shell-command`'.
     (expect (projectile-ignored-file-p "/path/to/project/TAGS") :to-be-truthy)
     (expect (projectile-ignored-file-p "/path/to/project/foo.el") :not :to-be-truthy)))
 
+(describe "projectile-globally-ignored-files"
+  (it "includes TAGS file by default"
+    (expect (member projectile-tags-file-name projectile-globally-ignored-files) :to-be-truthy))
+  (it "includes cache file by default"
+    (expect (member projectile-cache-file projectile-globally-ignored-files) :to-be-truthy))
+  (it "causes cache file to be ignored via projectile-ignored-file-p"
+    (spy-on 'projectile-ignored-files :and-return-value
+            (list (concat "/path/to/project/" projectile-cache-file)
+                  (concat "/path/to/project/" projectile-tags-file-name)))
+    (expect (projectile-ignored-file-p (concat "/path/to/project/" projectile-cache-file)) :to-be-truthy)
+    (expect (projectile-ignored-file-p "/path/to/project/source.el") :not :to-be-truthy)))
+
+(describe "projectile-globally-ignored-files :safe predicate"
+  (it "accepts list of strings as safe"
+    (let ((pred (get 'projectile-globally-ignored-files 'safe-local-variable)))
+      (expect (funcall pred '("file1" "file2")) :to-be-truthy)))
+  (it "rejects list containing non-strings as unsafe"
+    (let ((pred (get 'projectile-globally-ignored-files 'safe-local-variable)))
+      (expect (funcall pred '("file1" 123)) :not :to-be-truthy)))
+  (it "accepts empty list as safe"
+    (let ((pred (get 'projectile-globally-ignored-files 'safe-local-variable)))
+      (expect (funcall pred '()) :to-be-truthy)))
+  (it "rejects non-list as unsafe"
+    (let ((pred (get 'projectile-globally-ignored-files 'safe-local-variable)))
+      (expect (funcall pred "not-a-list") :not :to-be-truthy))))
+
 (describe "projectile-ignored-files"
   (it "returns list of ignored files"
     (spy-on 'projectile-project-root :and-return-value "/path/to/project")