lib/errors: add support for unwrapping go1.20 multi errors

lib/errors/errors.go

@@ -17,8 +17,10 @@ type WalkFunc func(error) bool
 // The next error in the chain is determined by the following rules:
 //
 //		the return value of this method is used.
-//	  - If the current error has a `Unwrap() error` method (golang.org/x/xerrors),
+//	  - If the current error has a `Unwrap() error` method
 //	    the return value of this method is used.
+//	  - If the current error has a `Unwrap() []error` method
+//	    the return values of this method is used.
 //	  - Common errors in the Go runtime that contain an Err field will use this value.
 func Walk(err error, f WalkFunc) {
 	for prev := err; err != nil; prev = err {
@@ -27,6 +29,11 @@ func Walk(err error, f WalkFunc) {
 		}
 
 		switch e := err.(type) {
+		case multiWrapper:
+			for _, err = range e.Unwrap() {
+				Walk(err, f)
+			}
+			return
 		case causer:
 			err = e.Cause()
 		case wrapper:
@@ -62,3 +69,6 @@ type causer interface {
 type wrapper interface {
 	Unwrap() error
 }
+type multiWrapper interface {
+	Unwrap() []error
+}

lib/errors/errors_test.go

@@ -1,4 +1,4 @@
-package errors_test
+package errors
 
 import (
 	"errors"
@@ -6,86 +6,244 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
-
-	liberrors "github.com/rclone/rclone/lib/errors"
 )
 
 func TestWalk(t *testing.T) {
-	origin := errors.New("origin")
+	var (
+		e1 = errors.New("e1")
+		e2 = errors.New("e2")
+		e3 = errors.New("e3")
+	)
 
 	for _, test := range []struct {
 		err  error
-		calls int
-		last  error
+		want []error
 	}{
-		{causerError{nil}, 1, causerError{nil}},
-		{wrapperError{nil}, 1, wrapperError{nil}},
-		{reflectError{nil}, 1, reflectError{nil}},
-		{causerError{origin}, 2, origin},
-		{wrapperError{origin}, 2, origin},
-		{reflectError{origin}, 2, origin},
-		{causerError{reflectError{origin}}, 3, origin},
-		{wrapperError{causerError{origin}}, 3, origin},
-		{reflectError{wrapperError{origin}}, 3, origin},
-		{causerError{reflectError{causerError{origin}}}, 4, origin},
-		{wrapperError{causerError{wrapperError{origin}}}, 4, origin},
-		{reflectError{wrapperError{reflectError{origin}}}, 4, origin},
-
-		{stopError{nil}, 1, stopError{nil}},
-		{stopError{causerError{nil}}, 1, stopError{causerError{nil}}},
-		{stopError{wrapperError{nil}}, 1, stopError{wrapperError{nil}}},
-		{stopError{reflectError{nil}}, 1, stopError{reflectError{nil}}},
-		{causerError{stopError{origin}}, 2, stopError{origin}},
-		{wrapperError{stopError{origin}}, 2, stopError{origin}},
-		{reflectError{stopError{origin}}, 2, stopError{origin}},
-		{causerError{reflectError{stopError{nil}}}, 3, stopError{nil}},
-		{wrapperError{causerError{stopError{nil}}}, 3, stopError{nil}},
-		{reflectError{wrapperError{stopError{nil}}}, 3, stopError{nil}},
+		{
+			causerError{nil}, []error{
+				causerError{nil},
+			},
+		}, {
+			wrapperError{nil}, []error{
+				wrapperError{nil},
+			},
+		}, {
+			reflectError{nil}, []error{
+				reflectError{nil},
+			},
+		}, {
+			causerError{e1}, []error{
+				causerError{e1}, e1,
+			},
+		}, {
+			wrapperError{e1}, []error{
+				wrapperError{e1}, e1,
+			},
+		}, {
+			reflectError{e1}, []error{
+				reflectError{e1}, e1,
+			},
+		}, {
+			causerError{reflectError{e1}}, []error{
+				causerError{reflectError{e1}},
+				reflectError{e1},
+				e1,
+			},
+		}, {
+			wrapperError{causerError{e1}}, []error{
+				wrapperError{causerError{e1}},
+				causerError{e1},
+				e1,
+			},
+		}, {
+			reflectError{wrapperError{e1}}, []error{
+				reflectError{wrapperError{e1}},
+				wrapperError{e1},
+				e1,
+			},
+		}, {
+			causerError{reflectError{causerError{e1}}}, []error{
+				causerError{reflectError{causerError{e1}}},
+				reflectError{causerError{e1}},
+				causerError{e1},
+				e1,
+			},
+		}, {
+			wrapperError{causerError{wrapperError{e1}}}, []error{
+				wrapperError{causerError{wrapperError{e1}}},
+				causerError{wrapperError{e1}},
+				wrapperError{e1},
+				e1,
+			},
+		}, {
+			reflectError{wrapperError{reflectError{e1}}}, []error{
+				reflectError{wrapperError{reflectError{e1}}},
+				wrapperError{reflectError{e1}},
+				reflectError{e1},
+				e1,
+			},
+		}, {
+			stopError{nil}, []error{
+				stopError{nil},
+			},
+		}, {
+			stopError{causerError{nil}}, []error{
+				stopError{causerError{nil}},
+			},
+		}, {
+			stopError{wrapperError{nil}}, []error{
+				stopError{wrapperError{nil}},
+			},
+		}, {
+			stopError{reflectError{nil}}, []error{
+				stopError{reflectError{nil}},
+			},
+		}, {
+			causerError{stopError{e1}}, []error{
+				causerError{stopError{e1}},
+				stopError{e1},
+			},
+		}, {
+			wrapperError{stopError{e1}}, []error{
+				wrapperError{stopError{e1}},
+				stopError{e1},
+			},
+		}, {
+			reflectError{stopError{e1}}, []error{
+				reflectError{stopError{e1}},
+				stopError{e1},
+			},
+		}, {
+			causerError{reflectError{stopError{nil}}}, []error{
+				causerError{reflectError{stopError{nil}}},
+				reflectError{stopError{nil}},
+				stopError{nil},
+			},
+		}, {
+			wrapperError{causerError{stopError{nil}}}, []error{
+				wrapperError{causerError{stopError{nil}}},
+				causerError{stopError{nil}},
+				stopError{nil},
+			},
+		}, {
+			reflectError{wrapperError{stopError{nil}}}, []error{
+				reflectError{wrapperError{stopError{nil}}},
+				wrapperError{stopError{nil}},
+				stopError{nil},
+			},
+		}, {
+			multiWrapperError{[]error{e1}}, []error{
+				multiWrapperError{[]error{e1}},
+				e1,
+			},
+		}, {
+			multiWrapperError{[]error{}}, []error{
+				multiWrapperError{[]error{}},
+			},
+		}, {
+			multiWrapperError{[]error{e1, e2, e3}}, []error{
+				multiWrapperError{[]error{e1, e2, e3}},
+				e1,
+				e2,
+				e3,
+			},
+		}, {
+			multiWrapperError{[]error{reflectError{e1}, wrapperError{e2}, stopError{e3}}}, []error{
+				multiWrapperError{[]error{reflectError{e1}, wrapperError{e2}, stopError{e3}}},
+				reflectError{e1},
+				e1,
+				wrapperError{e2},
+				e2,
+				stopError{e3},
+			},
+		},
 	} {
-		var last error
-		calls := 0
-		liberrors.Walk(test.err, func(err error) bool {
-			calls++
-			last = err
+		var got []error
+		Walk(test.err, func(err error) bool {
+			got = append(got, err)
 			_, stop := err.(stopError)
 			return stop
 		})
-		assert.Equal(t, test.calls, calls)
-		assert.Equal(t, test.last, last)
+		assert.Equal(t, test.want, got, test.err)
 	}
 }
 
 type causerError struct {
 	err error
 }
-type wrapperError struct {
-	err error
-}
-type reflectError struct {
-	Err error
-}
-type stopError struct {
-	err error
-}
 
 func (e causerError) Error() string {
 	return fmt.Sprintf("causerError(%s)", e.err)
 }
+
 func (e causerError) Cause() error {
 	return e.err
 }
+
+var (
+	_ error  = causerError{nil}
+	_ causer = causerError{nil}
+)
+
+type wrapperError struct {
+	err error
+}
+
 func (e wrapperError) Unwrap() error {
 	return e.err
 }
+
 func (e wrapperError) Error() string {
 	return fmt.Sprintf("wrapperError(%s)", e.err)
 }
+
+var (
+	_ error   = wrapperError{nil}
+	_ wrapper = wrapperError{nil}
+)
+
+type multiWrapperError struct {
+	errs []error
+}
+
+func (e multiWrapperError) Unwrap() []error {
+	return e.errs
+}
+
+func (e multiWrapperError) Error() string {
+	return fmt.Sprintf("multiWrapperError(%s)", e.errs)
+}
+
+var (
+	_ error        = multiWrapperError{nil}
+	_ multiWrapper = multiWrapperError{nil}
+)
+
+type reflectError struct {
+	Err error
+}
+
 func (e reflectError) Error() string {
 	return fmt.Sprintf("reflectError(%s)", e.Err)
 }
+
+var (
+	_ error = reflectError{nil}
+)
+
+type stopError struct {
+	err error
+}
+
 func (e stopError) Error() string {
 	return fmt.Sprintf("stopError(%s)", e.err)
 }
+
 func (e stopError) Cause() error {
 	return e.err
 }
+
+var (
+	_ error  = stopError{nil}
+	_ causer = stopError{nil}
+)