Avoid mutating default value of erc-server-last-peers

* lisp/erc/erc-backend.el (erc-server-last-peers): Leave default as
nil instead of a quoted constant.
(erc-server-connect): Initialize `erc-server-last-peers' to a new
value local to a server buffer.
(erc-message): Operate on server's local `erc-server-last-peers' value
instead of the global default.  Prefer replacing value instead of
mutating CDR to make for easier testing.
(erc-server-PRIVMSG): Create a new `erc-server-last-peers' for easier
testing. (Bug#56449)

1 files changed, 82 insertions, 0 deletions

diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index 4971d0e194f..0f222edacfa 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -893,4 +893,86 @@
 
           (should-not calls))))))
 
+;; Note: if adding an erc-backend-tests.el, please relocate this there.
+
+(ert-deftest erc-message ()
+  (should-not erc-server-last-peers)
+  (let (server-proc
+        calls
+        erc-kill-channel-hook erc-kill-server-hook erc-kill-buffer-hook)
+    (cl-letf (((symbol-function 'erc-display-message)
+               (lambda (_ _ _ line) (push line calls)))
+              ((symbol-function 'erc-server-send)
+               (lambda (line _) (push line calls)))
+              ((symbol-function 'erc-server-buffer)
+               (lambda () (process-buffer server-proc))))
+      (with-current-buffer (get-buffer-create "ExampleNet")
+        (erc-mode)
+        (setq erc-server-current-nick "tester"
+              server-proc (start-process "sleep" (current-buffer) "sleep" "1")
+              erc-server-process server-proc
+              erc-server-last-peers (cons nil nil)
+              erc-server-users (make-hash-table :test 'equal)
+              erc-network 'ExampleNet)
+        (set-process-query-on-exit-flag erc-server-process nil))
+
+      (with-current-buffer (get-buffer-create "#chan")
+        (erc-mode)
+        (setq erc-server-process (buffer-local-value 'erc-server-process
+                                                     (get-buffer "ExampleNet"))
+              erc-default-recipients '("#chan")
+              erc-channel-users (make-hash-table :test 'equal)
+              erc-network 'ExampleNet)
+        (erc-update-current-channel-member "alice" "alice")
+        (erc-update-current-channel-member "tester" "tester"))
+
+      (with-current-buffer "ExampleNet"
+        (erc-server-PRIVMSG erc-server-process
+                            (make-erc-response
+                             :sender "alice!~u@fsf.org"
+                             :command "PRIVMSG"
+                             :command-args '("#chan" "hi")
+                             :unparsed ":alice!~u@fsf.org PRIVMSG #chan :hi"))
+        (should (equal erc-server-last-peers '("alice")))
+        (should (string-match "<alice>" (pop calls))))
+
+      (with-current-buffer "#chan"
+        (ert-info ("Shortcuts usable in target buffers")
+          (should-not (local-variable-p 'erc-server-last-peers))
+          (should-not erc-server-last-peers)
+          (erc-message "PRIVMSG" ". hi")
+          (should-not erc-server-last-peers)
+          (should (eq 'no-target (pop calls)))
+          (erc-message "PRIVMSG" ", hi")
+          (should-not erc-server-last-peers)
+          (should (string-match "alice :hi" (pop calls)))))
+
+      (with-current-buffer "ExampleNet"
+        (ert-info ("Shortcuts local in server bufs")
+          (should (equal erc-server-last-peers '("alice" . "alice")))
+          (erc-message "PRIVMSG" ", hi")
+          (should (equal erc-server-last-peers '("alice" . "alice")))
+          (should (string-match "PRIVMSG alice :hi" (pop calls)))
+          (setcdr erc-server-last-peers "bob")
+          (erc-message "PRIVMSG" ". hi")
+          (should (equal erc-server-last-peers '("alice" . "bob")))
+          (should (string-match "PRIVMSG bob :hi" (pop calls)))))
+
+      (with-current-buffer "#chan"
+        (ert-info ("Non-shortcuts are local to server buffer")
+          (should-not (local-variable-p 'erc-server-last-peers))
+          (should-not erc-server-last-peers)
+          (erc-message "PRIVMSG" "#chan hola")
+          (should-not erc-server-last-peers)
+          (should-not (default-value 'erc-server-last-peers))
+          (should (equal (buffer-local-value 'erc-server-last-peers
+                                             (get-buffer "ExampleNet"))
+                         '("alice" . "#chan")))
+          (should (string-match "hola" (pop calls))))))
+
+    (should-not erc-server-last-peers)
+    (should-not calls)
+    (kill-buffer "ExampleNet")
+    (kill-buffer "#chan")))
+
 ;;; erc-tests.el ends here