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Add a resolve error function to return first error
When an error object is returned and must be resolved to a single return error, the first error matching one defined by this package should be returned. Signed-off-by: Derek McGowan <[email protected]>
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‎resolve.go‎

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/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package errdefs
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import "context"
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// Resolve returns the first error found in the error chain which matches an
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// error defined in this package or context error. A raw, unwrapped error is
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// returned or ErrUnknown if no matching error is found.
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//
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// This is useful for determining a response code based on the outermost wrapped
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// error rather than the original cause. For example, a not found error deep
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// in the code may be wrapped as an invalid argument. When determining status
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// code from Is* functions, the depth or ordering of the error is not
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// considered.
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//
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// The search order is depth first, a wrapped error returned from any part of
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// the chain from `Unwrap() error` will be returned before any joined errors
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// as returned by `Unwrap() []error`.
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func Resolve(err error) error {
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if err == nil {
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return nil
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}
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err = firstError(err)
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if err == nil {
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err = ErrUnknown
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}
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return err
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}
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func firstError(err error) error {
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for {
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switch err {
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case ErrUnknown,
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ErrInvalidArgument,
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ErrNotFound,
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ErrAlreadyExists,
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ErrPermissionDenied,
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ErrResourceExhausted,
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ErrFailedPrecondition,
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ErrConflict,
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ErrNotModified,
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ErrAborted,
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ErrOutOfRange,
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ErrNotImplemented,
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ErrInternal,
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ErrUnavailable,
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ErrDataLoss,
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ErrUnauthenticated,
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context.DeadlineExceeded,
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context.Canceled:
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return err
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}
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switch e := err.(type) {
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case unknown:
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return ErrUnknown
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case invalidParameter:
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return ErrInvalidArgument
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case notFound:
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return ErrNotFound
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// Skip ErrAlreadyExists, no interface defined
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case forbidden:
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return ErrPermissionDenied
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// Skip ErrResourceExhasuted, no interface defined
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// Skip ErrFailedPrecondition, no interface defined
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case conflict:
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return ErrConflict
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case notModified:
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return ErrNotModified
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// Skip ErrAborted, no interface defined
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// Skip ErrOutOfRange, no interface defined
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case notImplemented:
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return ErrNotImplemented
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case system:
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return ErrInternal
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case unavailable:
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return ErrUnavailable
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case dataLoss:
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return ErrDataLoss
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case unauthorized:
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return ErrUnauthenticated
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case deadlineExceeded:
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return context.DeadlineExceeded
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case cancelled:
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return context.Canceled
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case interface{ Unwrap() error }:
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err = e.Unwrap()
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if err == nil {
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return nil
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}
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case interface{ Unwrap() []error }:
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for _, ue := range e.Unwrap() {
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if fe := firstError(ue); fe != nil {
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return fe
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}
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}
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return nil
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default:
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return nil
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}
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}
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}

‎resolve_test.go‎

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/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package errdefs
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import (
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"context"
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"errors"
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"fmt"
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"testing"
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)
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func TestResolve(t *testing.T) {
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for i, tc := range []struct {
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err error
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resolved error
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}{
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{nil, nil},
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{wrap(ErrUnknown), ErrUnknown},
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{wrap(ErrNotFound), ErrNotFound},
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{wrap(ErrInvalidArgument), ErrInvalidArgument},
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{wrap(ErrNotFound), ErrNotFound},
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{wrap(ErrAlreadyExists), ErrAlreadyExists},
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{wrap(ErrPermissionDenied), ErrPermissionDenied},
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{wrap(ErrResourceExhausted), ErrResourceExhausted},
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{wrap(ErrFailedPrecondition), ErrFailedPrecondition},
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{wrap(ErrConflict), ErrConflict},
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{wrap(ErrNotModified), ErrNotModified},
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{wrap(ErrAborted), ErrAborted},
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{wrap(ErrOutOfRange), ErrOutOfRange},
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{wrap(ErrNotImplemented), ErrNotImplemented},
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{wrap(ErrInternal), ErrInternal},
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{wrap(ErrUnavailable), ErrUnavailable},
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{wrap(ErrDataLoss), ErrDataLoss},
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{wrap(ErrUnauthenticated), ErrUnauthenticated},
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{wrap(context.DeadlineExceeded), context.DeadlineExceeded},
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{wrap(context.Canceled), context.Canceled},
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{errors.Join(errors.New("untyped"), wrap(ErrInvalidArgument)), ErrInvalidArgument},
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{errors.Join(ErrConflict, ErrNotFound), ErrConflict},
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{errors.New("untyped"), ErrUnknown},
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{errors.Join(wrap(ErrUnauthenticated), ErrNotModified), ErrUnauthenticated},
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{ErrDataLoss, ErrDataLoss},
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{errors.Join(ErrOutOfRange), ErrOutOfRange},
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{errors.Join(ErrNotImplemented, ErrInternal), ErrNotImplemented},
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{context.Canceled, context.Canceled},
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{testUnavailable{}, ErrUnavailable},
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{wrap(testUnavailable{}), ErrUnavailable},
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{errors.Join(testUnavailable{}, ErrPermissionDenied), ErrUnavailable},
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{errors.Join(errors.New("untyped join")), ErrUnknown},
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{errors.Join(errors.New("untyped1"), errors.New("untyped2")), ErrUnknown},
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} {
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name := fmt.Sprintf("%d-%s", i, errorString(tc.resolved))
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tc := tc
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t.Run(name, func(t *testing.T) {
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resolved := Resolve(tc.err)
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if resolved != tc.resolved {
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t.Errorf("Expected %s, got %s", tc.resolved, resolved)
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}
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})
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}
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}
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func wrap(err error) error {
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err = fmt.Errorf("wrapped error: %w", err)
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return fmt.Errorf("%w and also %w", err, ErrUnknown)
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}
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func errorString(err error) string {
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if err == nil {
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return "nil"
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}
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return err.Error()
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}
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type testUnavailable struct{}
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func (testUnavailable) Error() string { return "" }
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func (testUnavailable) Unavailable() {}

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