Add #'projectile-track-known-projects-find-file-hook to 'buffer-list-update-hook

CHANGELOG.md

@@ -11,6 +11,7 @@
 * [#1877](https://github.com/bbatsov/projectile/pull/1877): Add custom variable `projectile-cmd-hist-ignoredups`.
 * Add support for Eask projects.
 * [#1892](https://github.com/bbatsov/projectile/pull/1892): Add category metadata to `completing-read`. (it's used by packages like `marginalia` and `embark`)
+* [#1895](https://github.com/bbatsov/projectile/pull/1895): Modify projectile-mode to add a hook to `buffer-list-update-hook` such that any change in the buffer list will update the selected project.
 
 ### Bugs fixed
 

projectile.el

@@ -6284,14 +6284,24 @@ Otherwise behave as if called interactively.
       (projectile-discover-projects-in-search-path))
     (add-hook 'project-find-functions #'project-projectile)
     (add-hook 'find-file-hook 'projectile-find-file-hook-function)
-    (add-hook 'projectile-find-dir-hook #'projectile-track-known-projects-find-file-hook t)
-    (add-hook 'dired-before-readin-hook #'projectile-track-known-projects-find-file-hook t t)
+    ;; Add hooks to track which buffer is currently active.
+    ;; Note - In Emacs 28.1 `buffer-list-update-hook' was modified to no
+    ;; longer run on temporary buffers, this allows us to use it to track
+    ;; changes to the active buffer instead of relying on more specific hooks
+    ;; such as `dired-before-readin-hook'.
+    (if (version<= "28.1" emacs-version)
+        (add-hook 'buffer-list-update-hook #'projectile-track-known-projects-find-file-hook t)
+      (add-hook 'projectile-find-dir-hook #'projectile-track-known-projects-find-file-hook t)
+      (add-hook 'dired-before-readin-hook #'projectile-track-known-projects-find-file-hook t t))
+
     (advice-add 'compilation-find-file :around #'compilation-find-file-projectile-find-compilation-buffer)
     (advice-add 'delete-file :before #'delete-file-projectile-remove-from-cache))
    (t
     (remove-hook 'project-find-functions #'project-projectile)
     (remove-hook 'find-file-hook #'projectile-find-file-hook-function)
-    (remove-hook 'dired-before-readin-hook #'projectile-track-known-projects-find-file-hook t)
+    (if (version<= "28.1" emacs-version)
+        (remove-hook 'buffer-list-update-hook #'projectile-track-known-projects-find-file-hook)
+      (remove-hook 'dired-before-readin-hook #'projectile-track-known-projects-find-file-hook t))
     (advice-remove 'compilation-find-file #'compilation-find-file-projectile-find-compilation-buffer)
     (advice-remove 'delete-file #'delete-file-projectile-remove-from-cache))))
 

test/projectile-test.el

@@ -1957,6 +1957,40 @@ projectile-process-current-project-buffers-current to have similar behaviour"
                 (with-current-buffer (find-file-noselect "foo" t))
                 (expect (length (projectile-project-buffers)) :to-equal 1)))))
 
+(describe "projectile-mode buffer-list-update-hook"
+          (it "check that the hooks properly update the known projects when changing files or windows"
+              (projectile-test-with-sandbox
+               (projectile-test-with-files
+                ("project1/"
+                 "project1/.projectile"
+                 "project1/foo"
+                 "project2/"
+                 "project2/.projectile"
+                 "project2/bar")
+                (find-file "project1/")
+                (projectile-mode 1)
+
+                ;; Check that opening a file leads to the known-projects being updated
+                (find-file "project1/foo")
+                (expect (mapcar (lambda (x) (file-name-base (directory-file-name x)))  projectile-known-projects)
+                        :to-equal '("project1"))
+
+                ;; Check that opening a file in a different project leads to the known-projects being updated
+                (find-file-other-window "../../project2/bar")
+                (expect (mapcar (lambda (x) (file-name-base (directory-file-name x)))  projectile-known-projects)
+                        :to-equal '("project2" "project1"))
+
+                ;; Check that selecting a different buffer also updates the known-projects
+                (other-window 1)
+                (expect (mapcar (lambda (x) (file-name-base (directory-file-name x)))  projectile-known-projects)
+                        ;; Sadly this behavior is contigent on the existance of
+                        ;; `buffer-list-update-hook' so it will behave
+                        ;; differently on older versions of Emacs that do not
+                        ;; have this variable.
+                        :to-equal (if (version<= "28.1" emacs-version)
+                                      '("project1" "project2")
+                                    '("project2" "project1")))))))
+
 (describe "projectile--impl-name-for-test-name"
   :var ((mock-projectile-project-types
          '((foo test-suffix "Test")