72 lines
2.3 KiB
Go
72 lines
2.3 KiB
Go
// Copyright 2019 The Cockroach Authors.
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//
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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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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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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
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// implied. See the License for the specific language governing
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// permissions and limitations under the License.
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package errbase
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// Sadly the go 2/1.13 design for errors has promoted the name
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// `Unwrap()` for the method that accesses the cause, whilst the
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// ecosystem has already chosen `Cause()`. In order to unwrap
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// reliably, we must thus support both.
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//
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// See: https://github.com/golang/go/issues/31778
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// UnwrapOnce accesses the direct cause of the error if any, otherwise
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// returns nil.
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//
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// It supports both errors implementing causer (`Cause()` method, from
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// github.com/pkg/errors) and `Wrapper` (`Unwrap()` method, from the
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// Go 2 error proposal).
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//
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// UnwrapOnce treats multi-errors (those implementing the
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// `Unwrap() []error` interface as leaf-nodes since they cannot
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// reasonably be iterated through to a single cause. These errors
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// are typically constructed as a result of `fmt.Errorf` which results
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// in a `wrapErrors` instance that contains an interpolated error
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// string along with a list of causes.
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//
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// The go stdlib does not define output on `Unwrap()` for a multi-cause
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// error, so we default to nil here.
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func UnwrapOnce(err error) (cause error) {
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switch e := err.(type) {
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case interface{ Cause() error }:
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return e.Cause()
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case interface{ Unwrap() error }:
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return e.Unwrap()
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}
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return nil
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}
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// UnwrapAll accesses the root cause object of the error.
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// If the error has no cause (leaf error), it is returned directly.
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// UnwrapAll treats multi-errors as leaf nodes.
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func UnwrapAll(err error) error {
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for {
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if cause := UnwrapOnce(err); cause != nil {
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err = cause
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continue
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}
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break
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}
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return err
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}
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// UnwrapMulti access the slice of causes that an error contains, if it is a
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// multi-error.
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func UnwrapMulti(err error) []error {
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if me, ok := err.(interface{ Unwrap() []error }); ok {
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return me.Unwrap()
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}
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return nil
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}
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