internal: move HTTPError to common file

This is used by both clients and servers now.

internal/internal.go

@@ -3,6 +3,7 @@ package internal
 
 import (
 	"fmt"
+	"net/http"
 )
 
 // Depth indicates whether a request applies to the resource's members. It's
@@ -65,3 +66,36 @@ func FormatOverwrite(overwrite bool) string {
 		return "F"
 	}
 }
+
+type HTTPError struct {
+	Code int
+	Err  error
+}
+
+func HTTPErrorFromError(err error) *HTTPError {
+	if err == nil {
+		return nil
+	}
+	if httpErr, ok := err.(*HTTPError); ok {
+		return httpErr
+	} else {
+		return &HTTPError{http.StatusInternalServerError, err}
+	}
+}
+
+func IsNotFound(err error) bool {
+	return HTTPErrorFromError(err).Code == http.StatusNotFound
+}
+
+func HTTPErrorf(code int, format string, a ...interface{}) *HTTPError {
+	return &HTTPError{code, fmt.Errorf(format, a...)}
+}
+
+func (err *HTTPError) Error() string {
+	s := fmt.Sprintf("%v %v", err.Code, http.StatusText(err.Code))
+	if err.Err != nil {
+		return fmt.Sprintf("%v: %v", s, err.Err)
+	} else {
+		return s
+	}
+}

internal/server.go

@@ -9,39 +9,6 @@ import (
 	"strings"
 )
 
-type HTTPError struct {
-	Code int
-	Err  error
-}
-
-func HTTPErrorFromError(err error) *HTTPError {
-	if err == nil {
-		return nil
-	}
-	if httpErr, ok := err.(*HTTPError); ok {
-		return httpErr
-	} else {
-		return &HTTPError{http.StatusInternalServerError, err}
-	}
-}
-
-func IsNotFound(err error) bool {
-	return HTTPErrorFromError(err).Code == http.StatusNotFound
-}
-
-func HTTPErrorf(code int, format string, a ...interface{}) *HTTPError {
-	return &HTTPError{code, fmt.Errorf(format, a...)}
-}
-
-func (err *HTTPError) Error() string {
-	s := fmt.Sprintf("%v %v", err.Code, http.StatusText(err.Code))
-	if err.Err != nil {
-		return fmt.Sprintf("%v: %v", s, err.Err)
-	} else {
-		return s
-	}
-}
-
 func ServeError(w http.ResponseWriter, err error) {
 	code := http.StatusInternalServerError
 	if httpErr, ok := err.(*HTTPError); ok {