Tether query rolls to channel membership in ERC

* lisp/erc/erc-backend.el (erc-server-JOIN): Update query membership
via `erc--ensure-query-member' when someone else joins a channel.
(erc-server-NICK): Update query membership via
`erc--ensure-query-member' after someone else changes their nick.
(erc-server-PRIVMSG): After printing a query message from some other
person, remove their nick's data from the query buffer's user table if
they're "untracked," i.e., not a member of a channel.
(erc-server-263, erc-server-263-functions): New function and variable,
a default response handler and hook for "RPL_TRYAGAIN", which servers
send for things like rejecting "WHO" and "WHOX" responses due to rate
limiting.
(erc-server-311): Fix call to `erc-update-user-nick' so the userhost
login component is no longer supplied as the `info' parameter but
rather, correctly, as the `login'.
(erc--extract-352-full-name): Factor out trailing hop-count and GECOS
parsing for use by overriding handlers or those for adjacent numerics.
(erc-server-352): Refactor to handle asterisk as `channel' parameter,
which indicates a nick rather than a channel target.
(erc-server-366): Update membership in all query buffers via
`erc--ensure-query-members' after all names have been received.
(erc-server-401): Forget a known user completely when the server
reports them as nonexistent.
* lisp/erc/erc-common.el (erc--get-server-user): New function, a thin
wrapper around `erc-get-server-user' for cases were inlining would
require declaring symbols not defined in erc-common.
* lisp/erc/erc.el (erc-channel-members): Mention that instances are
used for query-participant tables as well.
(erc--decouple-query-and-channel-membership-p): New variable, a
compatibility flag to access pre-5.6 query bookkeeping behavior.
(erc--ensure-query-member, erc--ensure-query-members): New functions.
(erc-cmd-QUERY): Ensure parties are present in the query buffer's
membership table if they're known to be on the server by simple virtue
of being present in some joined channel.
(erc-message-english-s352-you): New variable.
* test/lisp/erc/erc-scenarios-base-query-participants.el
(erc-scenarios-base-query-participants)
(erc-scenarios-base-query-participants/legacy): Rename former to
latter.  Enable compat flag to activate legacy query behavior in which
channel membership does not impact query membership.
(erc-scenarios-base-query-participants/coupled): New test asserting
new behavior in which channel membership dictates query
membership.  (Bug#70928)

test/lisp/erc/erc-scenarios-base-query-participants.el

@@ -24,7 +24,7 @@
   (let ((load-path (cons (ert-resource-directory) load-path)))
     (require 'erc-scenarios-common)))
 
-(ert-deftest erc-scenarios-base-query-participants ()
+(ert-deftest erc-scenarios-base-query-participants/legacy ()
   :tags '(:expensive-test)
 
   (erc-scenarios-common-with-cleanup
@@ -32,6 +32,7 @@
        (erc-server-flood-penalty 0.1)
        (dumb-server (erc-d-run "localhost" t 'legacy))
        (expect (erc-d-t-make-expecter))
+       (erc--decouple-query-and-channel-membership-p t)
        (port (process-contact dumb-server :service)))
 
     (ert-info ("Connect to foonet")
@@ -113,5 +114,95 @@
         (should-not (erc-get-server-user "bob")) ; missing from query
         (should (erc-get-server-user "dummy"))))))
 
+(ert-deftest erc-scenarios-base-query-participants/coupled ()
+  :tags '(:expensive-test)
+
+  (erc-scenarios-common-with-cleanup
+      ((erc-scenarios-common-dialog "base/query-participants")
+       (erc-server-flood-penalty 0.1)
+       (dumb-server (erc-d-run "localhost" t 'legacy))
+       (expect (erc-d-t-make-expecter))
+       (port (process-contact dumb-server :service)))
+
+    (ert-info ("Connect to foonet")
+      (with-current-buffer (erc :server "127.0.0.1"
+                                :port port
+                                :nick "tester"
+                                :user "tester"
+                                :full-name "tester")
+        (funcall expect 10 "This server is in debug mode")
+        (erc-scenarios-common-say "/query bob")))
+
+    (ert-info ("Opening query on untracked user bob doesn't create entry.")
+      (with-current-buffer "bob"
+        (should-not (erc-get-channel-member "bob"))))
+
+    (ert-info ("DM from untracked user also doesn't create a query entry.")
+      (with-current-buffer (erc-d-t-wait-for 10 (get-buffer "dummy"))
+        (funcall expect 10 "<dummy> hi")
+        (should-not (erc-get-channel-member "dummy"))
+        (should-not (erc-get-server-user "dummy"))))
+
+    (with-current-buffer "foonet"
+      (erc-scenarios-common-say "/join #chan"))
+
+    (ert-info ("Members in new chan added to existing query buffers")
+      (with-current-buffer (erc-d-t-wait-for 10 (get-buffer "#chan"))
+        (funcall expect 10 "bob ")) ; bob is present in #chan (353)
+      (with-current-buffer "bob"
+        (should (erc-get-server-user "bob"))
+        ;; Can't assert immediately: must wait until 366 arrives.
+        (erc-d-t-wait-for 10 (erc-get-channel-member "bob"))))
+
+    (ert-info ("Opening query on tracked user creates entry")
+      (with-current-buffer "#chan"
+        (funcall expect 10 " alice") ;; alice is present
+        (erc-scenarios-common-say "hi channel") ; gate
+        (funcall expect 10 "<tester> hi channel")
+        (erc-scenarios-common-say "/query alice"))
+      (with-current-buffer "alice"
+        (should (erc-get-channel-member "alice"))))
+
+    ;; Bob says something.
+    (with-current-buffer "bob"
+      (funcall expect 10 "<bob> hi")
+      (should (erc-get-channel-member "bob")))
+
+    (ert-info ("Query pal parting channel removes them from query")
+      ;; Identical result if they're kicked: they're removed from the
+      ;; server AND their target buffers
+      (with-current-buffer "#chan"
+        (funcall expect 10 "has left")
+        (should-not (erc-get-channel-member "dummy"))
+        (should-not (erc-get-server-user "dummy")))
+      (with-current-buffer "dummy"
+        (should-not (erc-get-channel-member "dummy"))))
+
+    ;; This is unchanged from legacy behavior.
+    (ert-info ("Query pal quitting channel removes them everywhere")
+      (with-current-buffer "#chan"
+        (funcall expect 10 "has quit")
+        (should-not (erc-get-channel-member "bob"))
+        (should-not (erc-get-server-user "bob")))
+      (with-current-buffer "bob"
+        (should-not (erc-get-channel-member "bob"))))
+
+    (ert-info ("Query pal re-joining repopulates query")
+      (with-current-buffer "#chan"
+        (erc-scenarios-common-say "bob gone")
+        (funcall expect 10 "<alice> bob, welcome back!")
+        (should (erc-get-server-user "bob")))
+      (with-current-buffer "bob"
+        (should (erc-get-channel-member "bob"))))
+
+    (ert-info ("Parting removes chan members from server and queries")
+      (with-current-buffer "#chan"
+        (erc-scenarios-common-say "/part")
+        (funcall expect 10 "you have left")
+        (should-not (erc-get-server-user "fsbot"))
+        (should-not (erc-get-server-user "alice")) ; she never said anything
+        (should-not (erc-get-server-user "bob")) ; missing from query
+        (should-not (erc-get-server-user "dummy"))))))
+
 
 ;;; erc-scenarios-base-query-participants.el ends here