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>

2 files changed, 18 insertions, 0 deletions

diff --git a/models/organization/org.go b/models/organization/org.go
index 044ea06563..fbbf6d04fa 100644
--- a/models/organization/org.go
+++ b/models/organization/org.go
@@ -18,6 +18,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/structs"
+	"code.gitea.io/gitea/modules/util"
 
 	"xorm.io/builder"
 )
@@ -45,6 +46,10 @@ func (err ErrOrgNotExist) Error() string {
 	return fmt.Sprintf("org does not exist [id: %d, name: %s]", err.ID, err.Name)
 }
 
+func (err ErrOrgNotExist) Unwrap() error {
+	return util.ErrNotExist
+}
+
 // ErrLastOrgOwner represents a "LastOrgOwner" kind of error.
 type ErrLastOrgOwner struct {
 	UID int64
@@ -73,6 +78,10 @@ func (err ErrUserNotAllowedCreateOrg) Error() string {
 	return "user is not allowed to create organizations"
 }
 
+func (err ErrUserNotAllowedCreateOrg) Unwrap() error {
+	return util.ErrPermissionDenied
+}
+
 // Organization represents an organization
 type Organization user_model.User
 
diff --git a/models/organization/team.go b/models/organization/team.go
index bd80b1a8c7..83e5bd6fe1 100644
--- a/models/organization/team.go
+++ b/models/organization/team.go
@@ -16,6 +16,7 @@ import (
 	"code.gitea.io/gitea/models/unit"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/util"
 
 	"xorm.io/builder"
 )
@@ -43,6 +44,10 @@ func (err ErrTeamAlreadyExist) Error() string {
 	return fmt.Sprintf("team already exists [org_id: %d, name: %s]", err.OrgID, err.Name)
 }
 
+func (err ErrTeamAlreadyExist) Unwrap() error {
+	return util.ErrAlreadyExist
+}
+
 // ErrTeamNotExist represents a "TeamNotExist" error
 type ErrTeamNotExist struct {
 	OrgID  int64
@@ -60,6 +65,10 @@ func (err ErrTeamNotExist) Error() string {
 	return fmt.Sprintf("team does not exist [org_id %d, team_id %d, name: %s]", err.OrgID, err.TeamID, err.Name)
 }
 
+func (err ErrTeamNotExist) Unwrap() error {
+	return util.ErrNotExist
+}
+
 // OwnerTeamName return the owner team name
 const OwnerTeamName = "Owners"