Make every not exist error unwrappable to a fs.ErrNotExist

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>

models/asymkey/error.go

@@ -4,7 +4,10 @@
 
 package asymkey
 
-import "fmt"
+import (
+	"fmt"
+	"io/fs"
+)
 
 // ErrKeyUnableVerify represents a "KeyUnableVerify" kind of error.
 type ErrKeyUnableVerify struct {
@@ -36,6 +39,10 @@ func (err ErrKeyNotExist) Error() string {
 	return fmt.Sprintf("public key does not exist [id: %d]", err.ID)
 }
 
+func (err ErrKeyNotExist) Unwrap() error {
+	return fs.ErrNotExist
+}
+
 // ErrKeyAlreadyExist represents a "KeyAlreadyExist" kind of error.
 type ErrKeyAlreadyExist struct {
 	OwnerID     int64
@@ -54,6 +61,10 @@ func (err ErrKeyAlreadyExist) Error() string {
 		err.OwnerID, err.Fingerprint, err.Content)
 }
 
+func (err ErrKeyAlreadyExist) Unwrap() error {
+	return fs.ErrExist
+}
+
 // ErrKeyNameAlreadyUsed represents a "KeyNameAlreadyUsed" kind of error.
 type ErrKeyNameAlreadyUsed struct {
 	OwnerID int64
@@ -70,6 +81,10 @@ func (err ErrKeyNameAlreadyUsed) Error() string {
 	return fmt.Sprintf("public key already exists [owner_id: %d, name: %s]", err.OwnerID, err.Name)
 }
 
+func (err ErrKeyNameAlreadyUsed) Unwrap() error {
+	return fs.ErrExist
+}
+
 // ErrGPGNoEmailFound represents a "ErrGPGNoEmailFound" kind of error.
 type ErrGPGNoEmailFound struct {
 	FailedEmails []string
@@ -132,6 +147,10 @@ func (err ErrGPGKeyNotExist) Error() string {
 	return fmt.Sprintf("public gpg key does not exist [id: %d]", err.ID)
 }
 
+func (err ErrGPGKeyNotExist) Unwrap() error {
+	return fs.ErrNotExist
+}
+
 // ErrGPGKeyImportNotExist represents a "GPGKeyImportNotExist" kind of error.
 type ErrGPGKeyImportNotExist struct {
 	ID string
@@ -147,6 +166,10 @@ func (err ErrGPGKeyImportNotExist) Error() string {
 	return fmt.Sprintf("public gpg key import does not exist [id: %s]", err.ID)
 }
 
+func (err ErrGPGKeyImportNotExist) Unwrap() error {
+	return fs.ErrNotExist
+}
+
 // ErrGPGKeyIDAlreadyUsed represents a "GPGKeyIDAlreadyUsed" kind of error.
 type ErrGPGKeyIDAlreadyUsed struct {
 	KeyID string
@@ -162,6 +185,10 @@ func (err ErrGPGKeyIDAlreadyUsed) Error() string {
 	return fmt.Sprintf("public key already exists [key_id: %s]", err.KeyID)
 }
 
+func (err ErrGPGKeyIDAlreadyUsed) Unwrap() error {
+	return fs.ErrExist
+}
+
 // ErrGPGKeyAccessDenied represents a "GPGKeyAccessDenied" kind of Error.
 type ErrGPGKeyAccessDenied struct {
 	UserID int64
@@ -180,6 +207,10 @@ func (err ErrGPGKeyAccessDenied) Error() string {
 		err.UserID, err.KeyID)
 }
 
+func (err ErrGPGKeyAccessDenied) Unwrap() error {
+	return fs.ErrPermission
+}
+
 // ErrKeyAccessDenied represents a "KeyAccessDenied" kind of error.
 type ErrKeyAccessDenied struct {
 	UserID int64
@@ -198,6 +229,10 @@ func (err ErrKeyAccessDenied) Error() string {
 		err.UserID, err.KeyID, err.Note)
 }
 
+func (err ErrKeyAccessDenied) Unwrap() error {
+	return fs.ErrPermission
+}
+
 // ErrDeployKeyNotExist represents a "DeployKeyNotExist" kind of error.
 type ErrDeployKeyNotExist struct {
 	ID     int64
@@ -215,6 +250,10 @@ func (err ErrDeployKeyNotExist) Error() string {
 	return fmt.Sprintf("Deploy key does not exist [id: %d, key_id: %d, repo_id: %d]", err.ID, err.KeyID, err.RepoID)
 }
 
+func (err ErrDeployKeyNotExist) Unwrap() error {
+	return fs.ErrNotExist
+}
+
 // ErrDeployKeyAlreadyExist represents a "DeployKeyAlreadyExist" kind of error.
 type ErrDeployKeyAlreadyExist struct {
 	KeyID  int64
@@ -231,6 +270,10 @@ func (err ErrDeployKeyAlreadyExist) Error() string {
 	return fmt.Sprintf("public key already exists [key_id: %d, repo_id: %d]", err.KeyID, err.RepoID)
 }
 
+func (err ErrDeployKeyAlreadyExist) Unwrap() error {
+	return fs.ErrExist
+}
+
 // ErrDeployKeyNameAlreadyUsed represents a "DeployKeyNameAlreadyUsed" kind of error.
 type ErrDeployKeyNameAlreadyUsed struct {
 	RepoID int64
@@ -247,6 +290,10 @@ func (err ErrDeployKeyNameAlreadyUsed) Error() string {
 	return fmt.Sprintf("public key with name already exists [repo_id: %d, name: %s]", err.RepoID, err.Name)
 }
 
+func (err ErrDeployKeyNameAlreadyUsed) Unwrap() error {
+	return fs.ErrNotExist
+}
+
 // ErrSSHInvalidTokenSignature represents a "ErrSSHInvalidTokenSignature" kind of error.
 type ErrSSHInvalidTokenSignature struct {
 	Wrapped     error
@@ -262,3 +309,7 @@ func IsErrSSHInvalidTokenSignature(err error) bool {
 func (err ErrSSHInvalidTokenSignature) Error() string {
 	return "the provided signature does not sign the token with the provided key"
 }
+
+func (err ErrSSHInvalidTokenSignature) Unwrap() error {
+	return fs.ErrInvalid
+}

models/auth/oauth2.go

@@ -10,6 +10,7 @@ import (
 	"encoding/base32"
 	"encoding/base64"
 	"fmt"
+	"io/fs"
 	"net/url"
 	"strings"
 
@@ -483,6 +484,11 @@ func (err ErrOAuthClientIDInvalid) Error() string {
 	return fmt.Sprintf("Client ID invalid [Client ID: %s]", err.ClientID)
 }
 
+// Unwrap unwraps this as a ErrNotExist err
+func (err ErrOAuthClientIDInvalid) Unwrap() error {
+	return fs.ErrNotExist
+}
+
 // ErrOAuthApplicationNotFound will be thrown if id cannot be found
 type ErrOAuthApplicationNotFound struct {
 	ID int64
@@ -499,6 +505,11 @@ func (err ErrOAuthApplicationNotFound) Error() string {
 	return fmt.Sprintf("OAuth application not found [ID: %d]", err.ID)
 }
 
+// Unwrap unwraps this as a ErrNotExist err
+func (err ErrOAuthApplicationNotFound) Unwrap() error {
+	return fs.ErrNotExist
+}
+
 // GetActiveOAuth2ProviderSources returns all actived LoginOAuth2 sources
 func GetActiveOAuth2ProviderSources() ([]*Source, error) {
 	sources := make([]*Source, 0, 1)

models/auth/source.go

@@ -7,6 +7,7 @@ package auth
 
 import (
 	"fmt"
+	"io/fs"
 	"reflect"
 
 	"code.gitea.io/gitea/models/db"
@@ -366,6 +367,11 @@ func (err ErrSourceNotExist) Error() string {
 	return fmt.Sprintf("login source does not exist [id: %d]", err.ID)
 }
 
+// Unwrap unwraps this as a ErrNotExist err
+func (err ErrSourceNotExist) Unwrap() error {
+	return fs.ErrNotExist
+}
+
 // ErrSourceAlreadyExist represents a "SourceAlreadyExist" kind of error.
 type ErrSourceAlreadyExist struct {
 	Name string
@@ -381,6 +387,11 @@ func (err ErrSourceAlreadyExist) Error() string {
 	return fmt.Sprintf("login source already exists [name: %s]", err.Name)
 }
 
+// Unwrap unwraps this as a ErrExist err
+func (err ErrSourceAlreadyExist) Unwrap() error {
+	return fs.ErrExist
+}
+
 // ErrSourceInUse represents a "SourceInUse" kind of error.
 type ErrSourceInUse struct {
 	ID int64

models/auth/twofactor.go

@@ -11,6 +11,7 @@ import (
 	"encoding/base32"
 	"encoding/base64"
 	"fmt"
+	"io/fs"
 
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/modules/secret"
@@ -41,6 +42,11 @@ func (err ErrTwoFactorNotEnrolled) Error() string {
 	return fmt.Sprintf("user not enrolled in 2FA [uid: %d]", err.UID)
 }
 
+// Unwrap unwraps this as a ErrNotExist err
+func (err ErrTwoFactorNotEnrolled) Unwrap() error {
+	return fs.ErrNotExist
+}
+
 // TwoFactor represents a two-factor authentication token.
 type TwoFactor struct {
 	ID               int64 `xorm:"pk autoincr"`

models/auth/webauthn.go

@@ -7,6 +7,7 @@ package auth
 import (
 	"context"
 	"fmt"
+	"io/fs"
 	"strings"
 
 	"code.gitea.io/gitea/models/db"
@@ -29,6 +30,11 @@ func (err ErrWebAuthnCredentialNotExist) Error() string {
 	return fmt.Sprintf("WebAuthn credential does not exist [credential_id: %x]", err.CredentialID)
 }
 
+// Unwrap unwraps this as a ErrNotExist err
+func (err ErrWebAuthnCredentialNotExist) Unwrap() error {
+	return fs.ErrNotExist
+}
+
 // IsErrWebAuthnCredentialNotExist checks if an error is a ErrWebAuthnCredentialNotExist.
 func IsErrWebAuthnCredentialNotExist(err error) bool {
 	_, ok := err.(ErrWebAuthnCredentialNotExist)

models/db/engine.go

@@ -225,7 +225,7 @@ func NamesToBean(names ...string) ([]interface{}, error) {
 	for _, name := range names {
 		bean, ok := beanMap[strings.ToLower(strings.TrimSpace(name))]
 		if !ok {
-			return nil, fmt.Errorf("No table found that matches: %s", name)
+			return nil, fmt.Errorf("no table found that matches: %s", name)
 		}
 		if !gotBean[bean] {
 			beans = append(beans, bean)

models/db/error.go

@@ -6,6 +6,7 @@ package db
 
 import (
 	"fmt"
+	"io/fs"
 )
 
 // ErrCancelled represents an error due to context cancellation
@@ -45,7 +46,8 @@ func (err ErrSSHDisabled) Error() string {
 
 // ErrNotExist represents a non-exist error.
 type ErrNotExist struct {
-	ID int64
+	Resource string
+	ID       int64
 }
 
 // IsErrNotExist checks if an error is an ErrNotExist
@@ -55,5 +57,18 @@ func IsErrNotExist(err error) bool {
 }
 
 func (err ErrNotExist) Error() string {
-	return fmt.Sprintf("record does not exist [id: %d]", err.ID)
+	name := "record"
+	if err.Resource != "" {
+		name = err.Resource
+	}
+
+	if err.ID != 0 {
+		return fmt.Sprintf("%s does not exist [id: %d]", name, err.ID)
+	}
+	return fmt.Sprintf("%s does not exist", name)
+}
+
+// Unwrap unwraps this as a ErrNotExist err
+func (err ErrNotExist) Unwrap() error {
+	return fs.ErrNotExist
 }

models/db/name.go

@@ -5,21 +5,31 @@
 package db
 
 import (
-	"errors"
 	"fmt"
+	"io/fs"
 	"regexp"
 	"strings"
 	"unicode/utf8"
 )
 
 var (
 	// ErrNameEmpty name is empty error
-	ErrNameEmpty = errors.New("Name is empty")
+	ErrNameEmpty = errNameEmpty{}
 
 	// AlphaDashDotPattern characters prohibited in a user name (anything except A-Za-z0-9_.-)
 	AlphaDashDotPattern = regexp.MustCompile(`[^\w-\.]`)
 )
 
+type errNameEmpty struct{}
+
+func (err errNameEmpty) Error() string {
+	return "name is empty"
+}
+
+func (err errNameEmpty) Unwrap() error {
+	return fs.ErrInvalid
+}
+
 // ErrNameReserved represents a "reserved name" error.
 type ErrNameReserved struct {
 	Name string
@@ -35,6 +45,11 @@ func (err ErrNameReserved) Error() string {
 	return fmt.Sprintf("name is reserved [name: %s]", err.Name)
 }
 
+// Unwrap unwraps this as a ErrInvalid err
+func (err ErrNameReserved) Unwrap() error {
+	return fs.ErrInvalid
+}
+
 // ErrNamePatternNotAllowed represents a "pattern not allowed" error.
 type ErrNamePatternNotAllowed struct {
 	Pattern string
@@ -50,6 +65,11 @@ func (err ErrNamePatternNotAllowed) Error() string {
 	return fmt.Sprintf("name pattern is not allowed [pattern: %s]", err.Pattern)
 }
 
+// Unwrap unwraps this as a ErrInvalid err
+func (err ErrNamePatternNotAllowed) Unwrap() error {
+	return fs.ErrInvalid
+}
+
 // ErrNameCharsNotAllowed represents a "character not allowed in name" error.
 type ErrNameCharsNotAllowed struct {
 	Name string
@@ -62,7 +82,12 @@ func IsErrNameCharsNotAllowed(err error) bool {
 }
 
 func (err ErrNameCharsNotAllowed) Error() string {
-	return fmt.Sprintf("User name is invalid [%s]: must be valid alpha or numeric or dash(-_) or dot characters", err.Name)
+	return fmt.Sprintf("name is invalid [%s]: must be valid alpha or numeric or dash(-_) or dot characters", err.Name)
+}
+
+// Unwrap unwraps this as a ErrInvalid err
+func (err ErrNameCharsNotAllowed) Unwrap() error {
+	return fs.ErrInvalid
 }
 
 // IsUsableName checks if name is reserved or pattern of name is not allowed