Optimize compilation-find-file-projectile-find-compilation-buffer (#1874)

If the target file already exists, navigate to it directly instead of running the expensive extra logic.

Author: sonictk

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### New features
 
+* [#1874](https://github.com/bbatsov/projectile/pull/1874): Changes `compilation-find-file-projectile-find-compilation-buffer` to navigate directly to the file if already present on disk to help improve performance in scenarios where there are a large number of project directories.
 * [#1870](https://github.com/bbatsov/projectile/pull/1870): Add package command for CMake projects.
 * [#1875](https://github.com/bbatsov/projectile/pull/1875): Add support for Sapling VCS.
 * [#1876](https://github.com/bbatsov/projectile/pull/1876): Add support for Jujutsu VCS.

projectile.el

@@ -5406,14 +5406,18 @@ We enhance its functionality by appending the current project's directories
 to its search path. This way when filenames in compilation buffers can't be
 found by compilation's normal logic they are searched for in project
 directories."
-  (let* ((root (projectile-project-root))
-         (compilation-search-path
-          (if (projectile-project-p)
-              (append compilation-search-path (list root)
-                      (mapcar (lambda (f) (expand-file-name f root))
-                              (projectile-current-project-dirs)))
-            compilation-search-path)))
-    (apply orig-fun `(,marker ,filename ,directory ,@formats))))
+  ; If the file already exists, don't bother running the extra logic as the project directories might be massive (i.e. Unreal-sized).
+  (if (file-exists-p filename)
+      (apply orig-fun `(,marker ,filename ,directory ,@formats))
+
+    (let* ((root (projectile-project-root))
+           (compilation-search-path
+            (if (projectile-project-p)
+                (append compilation-search-path (list root)
+                        (mapcar (lambda (f) (expand-file-name f root))
+                                (projectile-current-project-dirs)))
+              compilation-search-path)))
+      (apply orig-fun `(,marker ,filename ,directory ,@formats)))))
 
 (defun projectile-open-projects ()
   "Return a list of all open projects.