Make every not exist error unwrappable to a fs.ErrNotExist (#20891)

A lot of our code is repeatedly testing if individual errors are
specific types of Not Exist errors. This is repetitative and unnecesary.
`Unwrap() error` provides a common way of labelling an error as a
NotExist error and we can/should use this.

This PR has chosen to use the common `io/fs` errors e.g.
`fs.ErrNotExist` for our errors. This is in some ways not completely
correct as these are not filesystem errors but it seems like a
reasonable thing to do and would allow us to simplify a lot of our code
to `errors.Is(err, fs.ErrNotExist)` instead of
`package.IsErr...NotExist(err)`

I am open to suggestions to use a different base error - perhaps
`models/db.ErrNotExist` if that would be felt to be better.


Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: delvh <dev.lh@web.de>

1 files changed, 8 insertions, 0 deletions

diff --git a/models/repo/release.go b/models/repo/release.go
index 2b484c9b84..2e7bc6d322 100644
--- a/models/repo/release.go
+++ b/models/repo/release.go
@@ -37,6 +37,10 @@ func (err ErrReleaseAlreadyExist) Error() string {
 	return fmt.Sprintf("release tag already exist [tag_name: %s]", err.TagName)
 }
 
+func (err ErrReleaseAlreadyExist) Unwrap() error {
+	return util.ErrAlreadyExist
+}
+
 // ErrReleaseNotExist represents a "ReleaseNotExist" kind of error.
 type ErrReleaseNotExist struct {
 	ID      int64
@@ -53,6 +57,10 @@ func (err ErrReleaseNotExist) Error() string {
 	return fmt.Sprintf("release tag does not exist [id: %d, tag_name: %s]", err.ID, err.TagName)
 }
 
+func (err ErrReleaseNotExist) Unwrap() error {
+	return util.ErrNotExist
+}
+
 // Release represents a release of repository.
 type Release struct {
 	ID               int64            `xorm:"pk autoincr"`