Cannot fetch project by project path via API

Summary

/api/v4/projects/:id always returns a 404 Not found when using the project path for :id instead of the numeric project id. According to https://docs.gitlab.com/ee/api/projects.html#get-single-project it is possible to use the URL encoded project path to obtain information about a project. Also the WebIDE introduced in Gitlab 10.7 uses this method to access a project via the Gitlab API. That's how I first stumbled on this issue as I cannot get WebIDE to Work in 10.7.1

Steps to reproduce

Fetch the project record using the encoded project path.

e.g. /api/v4/projects/group%2Fproject

Example Project

(If possible, please create an example project here on GitLab.com that exhibits the problematic behaviour, and link to it here in the bug report)

(If you are using an older version of GitLab, this will also determine whether the bug has been fixed in a more recent version)

What is the current bug behavior?

/api/v4/projects/group%2Fproject return a 404 while /api/v4/projects/1 returns the project's information

(all via authenticated client calls)

What is the expected correct behavior?

/api/v4/projects/group%2Fproject return the actual project information

Relevant logs and/or screenshots

Web console output when launching WebIDE (which uses project paths for API calls)

Output of checks

(If you are reporting a bug on GitLab.com, write: This bug happens on GitLab.com)

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:		Ubuntu 14.04
Current User:	git
Using RVM:	no
Ruby Version:	2.3.6p384
Gem Version:	2.6.13
Bundler Version:1.13.7
Rake Version:	12.3.0
Redis Version:	3.2.11
Git Version:	2.14.3
Sidekiq Version:5.0.5
Go Version:	go1.5.1 linux/amd64
GitLab information
Version:	10.7.1
Revision:	0d49bb8
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
URL:		https://gitlab.domain.com
HTTP Clone URL:	https://gitlab.domain.com/some-group/some-project.git
SSH Clone URL:	git@gitlab.domain.com:some-group/some-project.git
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers: github
GitLab Shell
Version:	7.1.2
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

root@prod-1:~# sudo gitlab-rake gitlab:check SANITIZE=true
Checking GitLab Shell ...
GitLab Shell version >= 7.1.2 ? ... OK (7.1.2)
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: ...
3/2 ... ok
3/3 ... ok
3/4 ... ok
3/5 ... repository is empty
3/6 ... repository is empty
5/7 ... ok
5/8 ... ok
5/9 ... ok
5/10 ... ok
5/11 ... ok
5/12 ... ok
3/13 ... ok
3/14 ... ok
8/15 ... ok
9/16 ... ok
8/17 ... ok
8/18 ... ok
8/19 ... ok
8/20 ... ok
8/21 ... ok
8/22 ... ok
8/23 ... ok
8/24 ... ok
13/25 ... repository is empty
8/26 ... repository is empty
8/27 ... ok
8/28 ... ok
8/29 ... ok
8/30 ... ok
8/31 ... ok
16/32 ... ok
16/33 ... ok
8/34 ... ok
8/35 ... ok
8/36 ... ok
16/37 ... ok
2/38 ... ok
8/39 ... ok
8/40 ... ok
18/41 ... ok
18/42 ... ok
8/43 ... ok
8/44 ... ok
20/45 ... ok
8/46 ... ok
8/47 ... ok
8/48 ... ok
21/49 ... ok
21/50 ... ok
8/51 ... ok
8/52 ... ok
21/53 ... ok
21/54 ... ok
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OK
Access to /var/opt/gitlab/.ssh/authorized_keys: OK
gitlab-shell self-check successful
Checking GitLab Shell ... Finished
Checking Sidekiq ...
Running? ... yes
Number of Sidekiq processes ... 1
Checking Sidekiq ... Finished
Reply by email is disabled in config/gitlab.yml
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: ...
3/2 ... yes
3/3 ... yes
3/4 ... yes
3/5 ... yes
3/6 ... yes
5/7 ... yes
5/8 ... yes
5/9 ... yes
5/10 ... yes
5/11 ... yes
5/12 ... yes
3/13 ... yes
3/14 ... yes
8/15 ... yes
9/16 ... yes
8/17 ... yes
8/18 ... yes
8/19 ... yes
8/20 ... yes
8/21 ... yes
8/22 ... yes
8/23 ... yes
8/24 ... yes
13/25 ... yes
8/26 ... yes
8/27 ... yes
8/28 ... yes
8/29 ... yes
8/30 ... yes
8/31 ... yes
16/32 ... yes
16/33 ... yes
8/34 ... yes
8/35 ... yes
8/36 ... yes
16/37 ... yes
2/38 ... yes
8/39 ... yes
8/40 ... yes
18/41 ... yes
18/42 ... yes
8/43 ... yes
8/44 ... yes
20/45 ... yes
8/46 ... yes
8/47 ... yes
8/48 ... yes
21/49 ... yes
21/50 ... yes
8/51 ... yes
8/52 ... yes
21/53 ... yes
21/54 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.5 ? ... yes (2.3.6)
Git version >= 2.9.5 ? ... yes (2.14.3)
Git user has default SSH configuration? ... yes
Active users: ... 5
Checking GitLab ... Finished