Error viewing issue, http 500

[jeppech]

I'm getting a 500 when accessing an issue. This happens apparently because of a missing label.
I'm using v/ 1.0.0+244-ga6751cec

It seem's, that this issue had a label, which has been deleted later on, but not it's relation to the issue.

2017/02/10 19:03:22 [...outers/repo/issue.go:612 ViewIssue()] [E] LoadLabel: label does not exist [label_id: 20, repo_id: 0]
2017/02/10 19:03:22 [D] Template: status/500

[jeppech]

Here's some data from my db:

sqlite> select count(*) from label where id = 20;
count(*)
----------
0

sqlite> select count(*) from repository where id = 0;
count(*)
----------
0

So something is definitely up, I just noticed that the repo_id is supposedly 0.
I realised repo_id is 0, because it's not parsed to the error model, https://github.com/go-gitea/gitea/blob/master/models/issue_comment.go#L215-L219

This is the concerned issues, with their labels

sqlite> SELECT
   ...>     iss.id, iss.repo_id, iss.`index`,
   ...>     isl.label_id,
   ...>     lab.name, lab.num_issues
   ...> FROM issue iss
   ...> LEFT JOIN issue_label isl
   ...>     ON isl.issue_id = iss.id
   ...> LEFT JOIN label lab
   ...>     ON lab.id = isl.label_id
   ...> WHERE iss.`index`
   ...>     IN (102,101,98);
id          repo_id     index       label_id    name             num_issues
----------  ----------  ----------  ----------  ---------------  ----------
167         15          98          75          priority/medium  8
170         15          101         75          priority/medium  8
171         15          102         75          priority/medium  8

I cannot fint any label_id = 20, anywhere in the database.

[jeppech]

Okay, so the problem seems to be with the feature, of tracking labels by @lunny. If a label that has been used in an issue, is deleted afterwards. It throws.

And I'm guessing it's due to this
https://github.com/go-gitea/gitea/blob/master/routers/repo/issue.go#L610-L614

Though, I'm still struggling to find out where label_id=20 originates.

Never the less, to replicate this:
Create an issue, and add a label to it.
Delete the label, from the label management page.
Viewing issue, throws 500

[jeppech]

I've found the sinner!

sqlite> SELECT
   ...>     iss.id,
   ...>     iss.`index`,
   ...>     cmt.label_id
   ...> FROM issue iss
   ...> LEFT JOIN comment cmt
   ...>     ON cmt.issue_id = iss.id
   ...> WHERE iss.`index`
   ...>     IN (102,101,98)
   ...> AND cmt.label_id = 20;
id          index       label_id
----------  ----------  ----------
167         98          20
170         101         20
171         102         20

The label_id is still in the comment table. So, when deleting labels, the related records in the comment should be deleted as well.

Also note, this error also occurs for milestones!

[lunny]

I will send a PR to fix this.