Merge lp:~laney/lightdm/no-prompt-upgrade into lp:lightdm

[Iain Lane]

gdm3 is fixed for this issue, but lightdm causes the same prompt to be shown. Something like this happens-

  - user does a dist-upgrade (or release upgrade)
  - after downloading the packages, they are preconfigured (.config scripts are run)
    + ...
    + gdm3.config is run, sets gdm3 as the default
    + ...
    + lightdm.config is run, sees gdm3 is the default and prompts the user

I think at the last step there we should intercept and not show the prompt.

I didn't think of a really good way to do this. You can't tell from the script if you're being called as part of preconfiguring or configuring (postinst). So after some head scratching I just decided to do this: if you're upgrading from an old version, don't show the prompt. The rationale is that it's not very likely that an upgrader wants to change their display manager - that is normally going to come from a new install.

But I think this is worth a review instead of me just uploading. Opinions welcomed.

[lp:~laney/lightdm/no-prompt-upgrade]

2493. By Iain Lane on 2017-07-18

Don't mangle db_fset ...

2494. By Iain Lane on 2017-07-18

Add a ~

[Didier Roche-Tolomelli (didrocks)]

As discussed on IRC, and with your additional manual testing, +1 from my side

review: Approve

[Iain Lane (laney)]

Thanks!

For the record, the valid concern was that we might suppress the prompt for the initial upgrade but then trigger it for the next update of lightdm. I tested and this doesn't happen. I think this is because gdm3.config is setting "shared/default-x-display-manager seen true".

[lp:~laney/lightdm/no-prompt-upgrade]

2495. By Iain Lane on 2017-07-18

releasing package lightdm version 1.22.0-0ubuntu6

=== modified file 'debian/changelog'
--- debian/changelog	2017-06-21 09:51:55 +0000
+++ debian/changelog	2017-07-18 09:22:13 +0000
@@ -1,3 +1,15 @@
+lightdm (1.22.0-0ubuntu6) artful; urgency=medium
+
+  * debian/lightdm.config: When upgrading to this version, don't show the DM
+    selection prompt. We're trying to suppress the prompt and switch Ubuntu
+    desktop users to gdm3 smoothly, but lightdm's prompt is showing up as gdm3
+    is on the system when lightdm.config is executed. This means that if there
+    is a situation when upgraders to this version *should* be shown the
+    prompt, they won't be. If that is the case, we'll need to think again
+    about how to implement this.
+
+ -- Iain Lane <[e-mail]>  Tue, 18 Jul 2017 10:21:45 +0100
+
 lightdm (1.22.0-0ubuntu5) artful; urgency=medium
 
   * Change back the default session to 'ubuntu', as it now corresponds to

=== modified file 'debian/lightdm.config'
--- debian/lightdm.config	2013-07-16 23:36:16 +0000
+++ debian/lightdm.config	2017-07-18 09:22:13 +0000
@@ -46,10 +46,12 @@
 
 # when installing from scratch as part of a release upgrade, default to
 # lightdm, otherwise ask
+
+# GDM transition: When upgrading from an old version, don't ask the question.
 if [ -z "$2" -a -n "$RELEASE_UPGRADE_IN_PROGRESS" ]; then
     db_set shared/default-x-display-manager lightdm
     db_fset shared/default-x-display-manager seen true
-else
+elif ! dpkg --compare-versions "$2" lt-nl "1.22.0-0ubuntu6~"; then
     db_input high shared/default-x-display-manager || :
     db_go || :
 fi