500 on /profile after disabling LDAP

Summary

After migrating users from LDAP to Google OAuth2 (adding google_oauth2 identity and removing the ldapmain one on all of our users) we have disabled LDAP and that is when we started to notice this issue.

Steps to reproduce

Sign in using LDAP and let GitLab to create the account automatically. After that, add another auth provider (eg., google_oauth2), connect an account using the provider, remove LDAP identity, disable LDAP and remove or comment out all LDAP-related settings in GitLab configuration.

What is the current bug behavior?

Whoops, something went wrong on our end. message is shown when trying to access /profile, accompanied by 500 HTTP status code.

What is the expected correct behavior?

Profile settings are shown.

Relevant logs and/or screenshots

ActionView::Template::Error (Missing setting 'servers' in 'ldap' section in /opt/gitlab/embedded/service/gitlab-rails/config/gitlab.yml):
    50:         = f.text_field :id, readonly: true, label: 'User ID', wrapper: { class: 'col-md-3' }
    51: 
    52:       - if @user.external_email?
    53:         = f.text_field :email, required: true, readonly: true, help: "Your email address was automatically set based on your #{email_provider_label} account."
    54:       - else
    55:         = f.text_field :email, required: true, value: (@user.email unless @user.temp_oauth_email?),
    56:           help: user_email_help_text(@user)
  lib/gitlab/ldap/config.rb:18:in `servers'
  lib/gitlab/ldap/config.rb:28:in `providers'
  lib/gitlab/ldap/config.rb:32:in `valid_provider?'
  lib/gitlab/o_auth/provider.rb:25:in `config_for'
  lib/gitlab/o_auth/provider.rb:37:in `label_for'
  app/helpers/profiles_helper.rb:5:in `email_provider_label'
  app/views/profiles/show.html.haml:53:in `block in _app_views_profiles_show_html_haml__649189244153273714_69978741509920'
  app/views/profiles/show.html.haml:5:in `_app_views_profiles_show_html_haml__649189244153273714_69978741509920'
  lib/gitlab/i18n.rb:46:in `with_locale'
  lib/gitlab/i18n.rb:52:in `with_user_locale'
  app/controllers/application_controller.rb:326:in `set_locale'
  lib/gitlab/middleware/multipart.rb:93:in `call'
  lib/gitlab/request_profiler/middleware.rb:14:in `call'
  lib/gitlab/middleware/go.rb:16:in `call'
  lib/gitlab/etag_caching/middleware.rb:11:in `call'
  lib/gitlab/request_context.rb:18:in `call'
  lib/gitlab/metrics/requests_rack_middleware.rb:27:in `call'

Output of checks

This issue may share the root cause with #19787 (closed).

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:
Current User:	git
Using RVM:	no
Ruby Version:	2.3.3p222
Gem Version:	2.6.6
Bundler Version:1.13.7
Rake Version:	12.0.0
Redis Version:	3.2.5
Git Version:	2.13.5
Sidekiq Version:5.0.4
Go Version:	unknown
GitLab information
Version:	9.5.3
Revision:	789cc67
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
URL:		Private information stripped
HTTP Clone URL:	Private information stripped
SSH Clone URL:	Private information stripped
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers: google_oauth2
GitLab Shell
Version:	5.8.0
Repository storage paths:

• default: /var/opt/gitlab/git-data/repositories Hooks: /opt/gitlab/embedded/service/gitlab-shell/hooks Git: /opt/gitlab/embedded/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check

Checking GitLab Shell ...
GitLab Shell version >= 5.8.0 ? ... OK (5.8.0)
Repo base directory exists?
default... yes
Repo storage directories are symlinks?
default... no
Repo paths owned by git:root, or git:git?
default... yes
Repo paths access is drwxrws---?
default... yes
hooks directories in repos are links: ...
4/1 ... ok
4/2 ... ok
4/3 ... ok
7/4 ... ok
9/5 ... ok
5/6 ... ok
4/8 ... ok
4/9 ... ok
12/18 ... ok
12/19 ... ok
12/20 ... ok
12/21 ... ok
4/22 ... ok
4/23 ... ok
4/24 ... ok
4/26 ... ok
4/27 ... ok
12/28 ... ok
4/30 ... ok
4/31 ... ok
12/32 ... ok
12/36 ... ok
12/38 ... ok
4/40 ... ok
12/41 ... ok
4/43 ... ok
12/47 ... ok
12/50 ... ok
12/51 ... ok
12/52 ... ok
4/53 ... ok
4/56 ... ok
12/57 ... ok
12/58 ... ok
4/59 ... ok
12/60 ... ok
4/61 ... ok
12/62 ... ok
12/63 ... ok
4/66 ... ok
12/67 ... ok
12/68 ... ok
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Access to /var/opt/gitlab/.ssh/authorized_keys: OK
Send ping to redis server: OK
gitlab-shell self-check successful
Checking GitLab Shell ... Finished
Checking Sidekiq ...
Running? ... yes
Number of Sidekiq processes ... 1
Checking Sidekiq ... Finished
Checking Reply by email ...
Reply by email is disabled in config/gitlab.yml
Checking Reply by email ... Finished
Checking LDAP ...
LDAP is disabled in config/gitlab.yml
Checking LDAP ... Finished
Checking GitLab ...
Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... yes
Uploads directory tmp has correct permissions? ... yes
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ...
4/1 ... yes
4/2 ... yes
4/3 ... yes
7/4 ... yes
9/5 ... yes
5/6 ... yes
4/8 ... yes
4/9 ... yes
12/18 ... yes
12/19 ... yes
12/20 ... yes
12/21 ... yes
4/22 ... yes
4/23 ... yes
4/24 ... yes
4/26 ... yes
4/27 ... yes
12/28 ... yes
4/30 ... yes
4/31 ... yes
12/32 ... yes
12/36 ... yes
12/38 ... yes
4/40 ... yes
12/41 ... yes
4/43 ... yes
12/47 ... yes
12/50 ... yes
12/51 ... yes
12/52 ... yes
4/53 ... yes
4/56 ... yes
12/57 ... yes
12/58 ... yes
4/59 ... yes
12/60 ... yes
4/61 ... yes
12/62 ... yes
12/63 ... yes
4/66 ... yes
12/67 ... yes
12/68 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.3 ? ... yes (2.3.3)
Git version >= 2.7.3 ? ... yes (2.13.5)
Active users: ... 16
Checking GitLab ... Finished

Possible fixes

To work around this issue, make sure to leave your ldap_servers settings present and uncommented even though ldap_enabled is false or commented out.