Rework the caching logic

The main changes from before are:

- Each project has its own cache file
- Cache files are consulted only when you request the files of some project

This makes caching both more robust and faster, as before the cache file
for all projects was loaded when projectile-mode was enabled.

1 files changed, 26 insertions, 25 deletions

diff --git a/projectile.el b/projectile.el
index ed8ec38..b7ed7a5 100644
--- a/projectile.el
+++ b/projectile.el
@@ -224,9 +224,9 @@ When nil Projectile will consider the current directory the project root."
   :group 'projectile
   :type 'string)
 
-(defcustom projectile-cache-file
-  (expand-file-name "projectile.cache" user-emacs-directory)
-  "The name of Projectile's cache file."
+(defcustom projectile-cache-file  ".projectile.cache"
+  "The name of Projectile's cache.
+It's relative to the project root."
   :group 'projectile
   :type 'string)
 
@@ -599,10 +599,10 @@ project."
                                             (run-hooks 'projectile-idle-timer-hook)))))))
   :type 'boolean)
 
-(defvar projectile-projects-cache nil
+(defvar projectile-projects-cache (make-hash-table :test 'equal)
   "A hashmap used to cache project file names to speed up related operations.")
 
-(defvar projectile-projects-cache-time nil
+(defvar projectile-projects-cache-time (make-hash-table :test 'equal)
   "A hashmap used to record when we populated `projectile-projects-cache'.")
 
 (defvar projectile-project-root-cache (make-hash-table :test 'equal)
@@ -1066,7 +1066,7 @@ to invalidate."
     (remhash project-root projectile-project-type-cache)
     (remhash project-root projectile-projects-cache)
     (remhash project-root projectile-projects-cache-time)
-    (projectile-serialize-cache)
+    (projectile-serialize nil (projectile-project-cache-file project-root))
     (when projectile-verbose
       (message "Invalidated Projectile cache for %s."
                (propertize project-root 'face 'font-lock-keyword-face))))
@@ -1086,7 +1086,13 @@ The cache is created both in memory and on the hard drive."
   (when projectile-enable-caching
     (puthash project files projectile-projects-cache)
     (puthash project (projectile-time-seconds) projectile-projects-cache-time)
-    (projectile-serialize-cache)))
+    (projectile-serialize files (projectile-project-cache-file project))))
+
+(defun projectile-load-project-cache (project-root)
+  "Load the cache file for PROJECT-ROOT in memory."
+  (when-let* ((cache-file (projectile-project-cache-file project-root)))
+    (when (file-exists-p cache-file)
+      (puthash project-root (projectile-unserialize cache-file) projectile-projects-cache))))
 
 ;;;###autoload
 (defun projectile-purge-file-from-cache (file)
@@ -1100,7 +1106,7 @@ The cache is created both in memory and on the hard drive."
     (if (projectile-file-cached-p file project-root)
         (progn
           (puthash project-root (remove file project-cache) projectile-projects-cache)
-          (projectile-serialize-cache)
+          (projectile-serialize project-cache (projectile-project-cache-file project-root))
           (when projectile-verbose
             (message "%s removed from cache" file)))
       (error "%s is not in the cache" file))))
@@ -1133,10 +1139,9 @@ The cache is created both in memory and on the hard drive."
         (unless (or (projectile-file-cached-p current-file current-project)
                     (projectile-ignored-directory-p (file-name-directory abs-current-file))
                     (projectile-ignored-file-p abs-current-file))
-          (puthash current-project
-                   (cons current-file (gethash current-project projectile-projects-cache))
-                   projectile-projects-cache)
-          (projectile-serialize-cache)
+          (let ((project-files (cons current-file (gethash current-project projectile-projects-cache))))
+            (puthash current-project project-files projectile-projects-cache)
+            (projectile-serialize project-files (projectile-project-cache-file current-project)))
           (message "File %s added to project %s cache."
                    (propertize current-file 'face 'font-lock-keyword-face)
                    (propertize current-project 'face 'font-lock-keyword-face)))))))
@@ -1158,7 +1163,7 @@ The cache is created both in memory and on the hard drive."
 (defun projectile-maybe-invalidate-cache (force)
   "Invalidate if FORCE or project's dirconfig newer than cache."
   (when (or force (file-newer-than-file-p (projectile-dirconfig-file)
-                                          projectile-cache-file))
+                                          (projectile-project-cache-file)))
     (projectile-invalidate-cache nil)))
 
 ;;;###autoload
@@ -2131,7 +2136,8 @@ project-root for every file."
 
     ;; Use the cache, if requested and available.
     (when projectile-enable-caching
-      (setq files (gethash project-root projectile-projects-cache)))
+      (setq files (or (gethash project-root projectile-projects-cache)
+                      (projectile-load-project-cache project-root))))
 
     ;; Calculate the list of files.
     (when (null files)
@@ -4979,9 +4985,12 @@ directory to open."
            (lambda (f) (string-prefix-p project-root (expand-file-name f)))
            recentf-list)))))
 
-(defun projectile-serialize-cache ()
-  "Serializes the memory cache to the hard drive."
-  (projectile-serialize projectile-projects-cache projectile-cache-file))
+(defun projectile-project-cache-file (&optional project-root)
+  "The path to a project's cache file for PROJECT-ROOT.
+Acts on the current project is not specified explicitly."
+  (if project-root
+      (expand-file-name projectile-cache-file project-root)
+    (projectile-expand-root projectile-cache-file)))
 
 (defvar projectile-configure-cmd-map
   (make-hash-table :test 'equal)
@@ -6301,14 +6310,6 @@ Otherwise behave as if called interactively.
    (projectile-mode
     ;; setup the commander bindings
     (projectile-commander-bindings)
-    ;; initialize the projects cache if needed
-    (unless projectile-projects-cache
-      (setq projectile-projects-cache
-            (or (projectile-unserialize projectile-cache-file)
-                (make-hash-table :test 'equal))))
-    (unless projectile-projects-cache-time
-      (setq projectile-projects-cache-time
-            (make-hash-table :test 'equal)))
     ;; load the known projects
     (projectile-load-known-projects)
     ;; update the list of known projects