From c936ca3ea000e11b37c760f94b26283da81ced3c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marco=20Trevisan=20=28Trevi=C3=B1o=29?= <mail@3v1n0.net>
Date: Mon, 1 Feb 2021 16:42:21 +0100
Subject: [PATCH] gdm: Don't try answering query if the user verifier has been
 deleted

Answering a query may be delayed to the moment in which we've not any
more messages in the queue, however this case can also happen just after
we've cleared the UserVerifier and in such case we'd have nothing to
answer, but we currently throw an error:

    JS ERROR: Exception in callback for signal: no-more-messages:
      TypeError: this._userVerifier is null
    answerQuery/signalId<@resource:///org/gnome/shell/gdm/util.js:249:17
    _emit@resource:///org/gnome/gjs/modules/core/_signals.js:133:47
    finishMessageQueue@resource:///org/gnome/shell/gdm/util.js:266:14
    _clearMessageQueue@resource:///org/gnome/shell/gdm/util.js:301:14
    clear@resource:///org/gnome/shell/gdm/util.js:223:14
    cancel@resource:///org/gnome/shell/gdm/util.js:205:18
    reset@resource:///org/gnome/shell/gdm/authPrompt.js:482:32
    cancel@resource:///org/gnome/shell/gdm/authPrompt.js:569:14
    vfunc_key_press_event@resource:///org/gnome/shell/gdm/authPrompt.js:128

So handle this case more gracefully keeping track of the current
cancellable and checking whether it is still valid before trying to answer
a query or do a delayed action.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1622>
---
 js/gdm/util.js | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/js/gdm/util.js b/js/gdm/util.js
index 54cd34631..048e2bf5e 100644
--- a/js/gdm/util.js
+++ b/js/gdm/util.js
@@ -260,9 +260,11 @@ var ShellUserVerifier = class {
         if (!this.hasPendingMessages) {
             this._userVerifier.call_answer_query(serviceName, answer, this._cancellable, null);
         } else {
+            const cancellable = this._cancellable;
             let signalId = this.connect('no-more-messages', () => {
                 this.disconnect(signalId);
-                this._userVerifier.call_answer_query(serviceName, answer, this._cancellable, null);
+                if (!cancellable.is_cancelled())
+                    this._userVerifier.call_answer_query(serviceName, answer, cancellable, null);
             });
         }
     }
@@ -583,9 +585,10 @@ var ShellUserVerifier = class {
             if (!this.hasPendingMessages) {
                 this._retry();
             } else {
+                const cancellable = this._cancellable;
                 let signalId = this.connect('no-more-messages', () => {
                     this.disconnect(signalId);
-                    if (this._cancellable && !this._cancellable.is_cancelled())
+                    if (!cancellable.is_cancelled())
                         this._retry();
                 });
             }
@@ -594,9 +597,11 @@ var ShellUserVerifier = class {
             if (!this.hasPendingMessages) {
                 this._cancelAndReset();
             } else {
+                const cancellable = this._cancellable;
                 let signalId = this.connect('no-more-messages', () => {
                     this.disconnect(signalId);
-                    this._cancelAndReset();
+                    if (!cancellable.is_cancelled())
+                        this._cancelAndReset();
                 });
             }
         }