ref/name, object: Simplify errors

6 files changed, 39 insertions, 47 deletions

diff --git a/object/parse.go b/object/parse.go
index 9a7b9068..b488eb49 100644
--- a/object/parse.go
+++ b/object/parse.go
@@ -1,6 +1,7 @@
 package object
 
 import (
+	"errors"
 	"fmt"
 
 	"lindenii.org/go/furgit/object/blob"
@@ -10,20 +11,10 @@ import (
 	"lindenii.org/go/furgit/object/typ"
 )
 
-// SizeMismatchError indicates a mismatch
-// between the size expected from the object header
-// and the size of the object.
-type SizeMismatchError struct {
-	Expected uint64
-	Got      uint64
-}
-
-func (sizeMismatchError SizeMismatchError) Error() string {
-	return fmt.Sprintf(
-		"object: size mismatch: header says %d bytes, but got %d from body",
-		sizeMismatchError.Expected, sizeMismatchError.Got,
-	)
-}
+// ErrSizeMismatch indicates a mismatch
+// between the size declared in the object header
+// and the size of the object body.
+var ErrSizeMismatch = errors.New("object: size mismatch")
 
 // ParseWithHeader parses a loose object
 // in "type size\x00body" format.
@@ -37,7 +28,7 @@ func ParseWithHeader(raw []byte, objectFormat id.ObjectFormat) (Object, error) {
 
 	body := raw[headerLen:]
 	if uint64(len(body)) != size {
-		return nil, SizeMismatchError{Expected: size, Got: uint64(len(body))}
+		return nil, fmt.Errorf("%w: header declares %d bytes, body has %d", ErrSizeMismatch, size, len(body))
 	}
 
 	return ParseWithoutHeader(ty, body, objectFormat)
diff --git a/ref/name/component.go b/ref/name/component.go
index 40a736e2..b7d3bbb7 100644
--- a/ref/name/component.go
+++ b/ref/name/component.go
@@ -1,6 +1,9 @@
 package name
 
-import "strings"
+import (
+	"fmt"
+	"strings"
+)
 
 const lockSuffix = ".lock"
 
@@ -23,7 +26,7 @@ func nameDisposition(ch byte) byte {
 	}
 }
 
-func checkRefnameComponent(name string, flags *int, sanitized *strings.Builder, fullName string) (int, error) {
+func checkRefnameComponent(name string, flags *int, sanitized *strings.Builder) (int, error) {
 	var last byte
 
 	var componentStart int
@@ -47,7 +50,7 @@ func checkRefnameComponent(name string, flags *int, sanitized *strings.Builder,
 				if sanitized != nil {
 					truncateBuilder(sanitized, sanitized.Len()-1)
 				} else {
-					return 0, &NameError{Name: fullName, Reason: "name contains '..'"}
+					return 0, fmt.Errorf("%w: name contains '..'", ErrInvalidName)
 				}
 			}
 		case 3:
@@ -55,21 +58,21 @@ func checkRefnameComponent(name string, flags *int, sanitized *strings.Builder,
 				if sanitized != nil {
 					overwriteBuilderAt(sanitized, sanitized.Len()-1)
 				} else {
-					return 0, &NameError{Name: fullName, Reason: "name contains '@{'"}
+					return 0, fmt.Errorf("%w: name contains '@{'", ErrInvalidName)
 				}
 			}
 		case 4:
 			if sanitized != nil {
 				overwriteBuilderAt(sanitized, sanitized.Len()-1)
 			} else {
-				return 0, &NameError{Name: fullName, Reason: "name contains a forbidden character"}
+				return 0, fmt.Errorf("%w: name contains a forbidden character", ErrInvalidName)
 			}
 		case 5:
 			if *flags&nameRefspecPattern == 0 {
 				if sanitized != nil {
 					overwriteBuilderAt(sanitized, sanitized.Len()-1)
 				} else {
-					return 0, &NameError{Name: fullName, Reason: "name contains '*'"}
+					return 0, fmt.Errorf("%w: name contains '*'", ErrInvalidName)
 				}
 			}
 
@@ -94,13 +97,13 @@ out:
 		if sanitized != nil {
 			overwriteBuilderAt(sanitized, componentStart)
 		} else {
-			return 0, &NameError{Name: fullName, Reason: "component starts with '.'"}
+			return 0, fmt.Errorf("%w: component starts with '.'", ErrInvalidName)
 		}
 	}
 
 	if componentLen >= len(lockSuffix) && name[componentLen-len(lockSuffix):componentLen] == lockSuffix {
 		if sanitized == nil {
-			return 0, &NameError{Name: fullName, Reason: "component ends with .lock"}
+			return 0, fmt.Errorf("%w: component ends with .lock", ErrInvalidName)
 		}
 
 		for strings.HasSuffix(sanitized.String(), lockSuffix) {
diff --git a/ref/name/errors.go b/ref/name/errors.go
index 438c60aa..1011d518 100644
--- a/ref/name/errors.go
+++ b/ref/name/errors.go
@@ -1,14 +1,6 @@
 package name
 
-import "fmt"
+import "errors"
 
-// NameError reports an invalid reference name.
-type NameError struct {
-	Name   string
-	Reason string
-}
-
-// Error implements error.
-func (err *NameError) Error() string {
-	return fmt.Sprintf("ref/name: invalid name %q: %s", err.Name, err.Reason)
-}
+// ErrInvalidName indicates an invalid reference name.
+var ErrInvalidName = errors.New("ref/name: invalid name")
diff --git a/ref/name/shorthand.go b/ref/name/shorthand.go
index 75d4854f..24142edb 100644
--- a/ref/name/shorthand.go
+++ b/ref/name/shorthand.go
@@ -1,6 +1,9 @@
 package name
 
-import "strings"
+import (
+	"fmt"
+	"strings"
+)
 
 // Branch checks a branch shorthand
 // and returns its fully-qualified refs/heads/... name.
@@ -10,7 +13,7 @@ import "strings"
 func Branch(name string) (string, error) {
 	full := "refs/heads/" + name
 	if strings.HasPrefix(name, "-") || full == "refs/heads/HEAD" {
-		return "", &NameError{Name: name, Reason: "invalid branch name"}
+		return "", fmt.Errorf("%w: invalid branch name", ErrInvalidName)
 	}
 
 	err := validate(full, 0)
@@ -29,7 +32,7 @@ func Branch(name string) (string, error) {
 // and returns its fully-qualified refs/tags/... name.
 func Tag(name string) (string, error) {
 	if strings.HasPrefix(name, "-") || name == "HEAD" {
-		return "", &NameError{Name: name, Reason: "invalid tag name"}
+		return "", fmt.Errorf("%w: invalid tag name", ErrInvalidName)
 	}
 
 	full := "refs/tags/" + name
diff --git a/ref/name/update.go b/ref/name/update.go
index d29afe4b..a87165a4 100644
--- a/ref/name/update.go
+++ b/ref/name/update.go
@@ -1,11 +1,14 @@
 package name
 
-import "strings"
+import (
+	"fmt"
+	"strings"
+)
 
 // ValidateUpdateName checks whether name is valid for a direct ref update.
 func ValidateUpdateName(name string, hasNewValue bool) error {
 	if IsPseudo(name) {
-		return &NameError{Name: name, Reason: "pseudoref updates are not allowed"}
+		return fmt.Errorf("%w: pseudoref updates are not allowed", ErrInvalidName)
 	}
 
 	if hasNewValue {
@@ -13,7 +16,7 @@ func ValidateUpdateName(name string, hasNewValue bool) error {
 	}
 
 	if !IsSafe(name) {
-		return &NameError{Name: name, Reason: "unsafe name for update"}
+		return fmt.Errorf("%w: unsafe name for update", ErrInvalidName)
 	}
 
 	return nil
@@ -23,7 +26,7 @@ func ValidateUpdateName(name string, hasNewValue bool) error {
 func ValidateSymbolicTarget(name string, target string) error {
 	parsed := ParseWorktree(name)
 	if parsed.BareRefName == "HEAD" && !strings.HasPrefix(target, "refs/heads/") {
-		return &NameError{Name: target, Reason: name + " must point to refs/heads/..."}
+		return fmt.Errorf("%w: %s must point to refs/heads/...", ErrInvalidName, name)
 	}
 
 	if IsRoot(target) {
@@ -43,5 +46,5 @@ func ValidateSymbolicTarget(name string, target string) error {
 		return nil
 	}
 
-	return &NameError{Name: target, Reason: "symref target is not a ref"}
+	return fmt.Errorf("%w: symref target is not a ref", ErrInvalidName)
 }
diff --git a/ref/name/validate.go b/ref/name/validate.go
index 989858b1..2c524491 100644
--- a/ref/name/validate.go
+++ b/ref/name/validate.go
@@ -20,7 +20,7 @@ func checkOrSanitizeRefname(name string, flags int, sanitized *strings.Builder)
 
 	if name == "@" {
 		if sanitized == nil {
-			return &NameError{Name: name, Reason: "single @ is not allowed"}
+			return fmt.Errorf("%w: single @ is not allowed", ErrInvalidName)
 		}
 
 		sanitized.WriteByte('-')
@@ -31,7 +31,7 @@ func checkOrSanitizeRefname(name string, flags int, sanitized *strings.Builder)
 			sanitized.WriteByte('/')
 		}
 
-		componentLen, err := checkRefnameComponent(remaining, &flags, sanitized, name)
+		componentLen, err := checkRefnameComponent(remaining, &flags, sanitized)
 		switch {
 		case sanitized != nil && componentLen == 0:
 		case componentLen <= 0:
@@ -39,7 +39,7 @@ func checkOrSanitizeRefname(name string, flags int, sanitized *strings.Builder)
 				return err
 			}
 
-			return &NameError{Name: name, Reason: "component has zero length"}
+			return fmt.Errorf("%w: component has zero length", ErrInvalidName)
 		case err != nil:
 			return err
 		}
@@ -56,12 +56,12 @@ func checkOrSanitizeRefname(name string, flags int, sanitized *strings.Builder)
 	componentLen := len(remaining)
 	if componentLen > 0 && remaining[componentLen-1] == '.' {
 		if sanitized == nil {
-			return &NameError{Name: name, Reason: "name ends with '.'"}
+			return fmt.Errorf("%w: name ends with '.'", ErrInvalidName)
 		}
 	}
 
 	if flags&nameAllowOneLevel == 0 && componentCount < 2 {
-		return &NameError{Name: name, Reason: "one-level name is not allowed"}
+		return fmt.Errorf("%w: one-level name is not allowed", ErrInvalidName)
 	}
 
 	return nil