Enhance ns form caching

Now we cache the ns form in a hash table, which makes it possible
to have separate value for each connection. After this change
the caching will work properly no matter how many connections we're
using to work with the same source file.

Author: bbatsov

cider-interaction.el

@@ -1571,8 +1571,22 @@ otherwise fall back to \"user\"."
     #'identity)
   "Function to translate Emacs filenames to nREPL namestrings.")
 
-(defvar-local cider--cached-ns-form nil
-  "Cached ns form in the current buffer.")
+(defvar-local cider--ns-form-cache (make-hash-table :test 'equal)
+  "ns form cache for the current buffer.
+
+The cache is a hash where the keys are connection names and the values
+are ns forms. This allows every connection to keep track of the ns
+form independently.")
+
+(defun cider--cache-ns-form ()
+  "Cache the form in the current buffer for the current connection."
+  (puthash (nrepl-current-connection-buffer)
+           (cider-ns-form)
+           cider--ns-form-cache))
+
+(defun cider--cached-ns-form ()
+  "Retrieve the cached ns form for the current buffer & connection."
+  (gethash (nrepl-current-connection-buffer) cider--ns-form-cache))
 
 (defun cider--prep-interactive-eval (form)
   "Prepares the environment for an interactive eval of FORM.
@@ -1586,12 +1600,12 @@ Clears any compilation highlights and kills the error window."
   (cider--quit-error-window)
   (let ((cur-ns-form (cider-ns-form)))
     (when (and cur-ns-form
-               (not (string= cur-ns-form cider--cached-ns-form))
+               (not (string= cur-ns-form (cider--cached-ns-form)))
                (not (cider-ns-form-p form)))
       ;; this should probably be done synchronously
       ;; otherwise an errors in the ns form will go unnoticed
       (cider-eval-ns-form)
-      (setq cider--cached-ns-form cur-ns-form))))
+      (cider--cache-ns-form))))
 
 (defun cider-interactive-eval (form &optional callback)
   "Evaluate FORM and dispatch the response to CALLBACK.
@@ -1937,7 +1951,7 @@ unconditionally."
                                      (buffer-file-name))))))
   (cider--clear-compilation-highlights)
   (cider--quit-error-window)
-  (setq cider--cached-ns-form (cider-ns-form))
+  (cider--cache-ns-form)
   (cider-request:load-file
    (cider-file-string filename)
    (funcall cider-to-nrepl-filename-function (cider--server-filename filename))
@@ -2102,7 +2116,7 @@ Quitting closes all active nREPL connections and kills all CIDER buffers."
     ;; which connection we simply clean the cache for all buffers
     (dolist (clojure-buffer (cider-util--clojure-buffers))
       (with-current-buffer clojure-buffer
-        (setq cider--cached-ns-form nil)))))
+        (setq cider--ns-form-cache (make-hash-table :test 'equal))))))
 
 (defun cider-restart (&optional prompt-project)
   "Quit CIDER and restart it.