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Diffstat (limited to 'vendor/go.uber.org/multierr/error.go')
| -rw-r--r-- | vendor/go.uber.org/multierr/error.go | 401 |
1 files changed, 401 insertions, 0 deletions
diff --git a/vendor/go.uber.org/multierr/error.go b/vendor/go.uber.org/multierr/error.go new file mode 100644 index 000000000..de6ce4736 --- /dev/null +++ b/vendor/go.uber.org/multierr/error.go @@ -0,0 +1,401 @@ +// Copyright (c) 2017 Uber Technologies, Inc. +// +// Permission is hereby granted, free of charge, to any person obtaining a copy +// of this software and associated documentation files (the "Software"), to deal +// in the Software without restriction, including without limitation the rights +// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell +// copies of the Software, and to permit persons to whom the Software is +// furnished to do so, subject to the following conditions: +// +// The above copyright notice and this permission notice shall be included in +// all copies or substantial portions of the Software. +// +// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN +// THE SOFTWARE. + +// Package multierr allows combining one or more errors together. +// +// Overview +// +// Errors can be combined with the use of the Combine function. +// +// multierr.Combine( +// reader.Close(), +// writer.Close(), +// conn.Close(), +// ) +// +// If only two errors are being combined, the Append function may be used +// instead. +// +// err = multierr.Combine(reader.Close(), writer.Close()) +// +// This makes it possible to record resource cleanup failures from deferred +// blocks with the help of named return values. +// +// func sendRequest(req Request) (err error) { +// conn, err := openConnection() +// if err != nil { +// return err +// } +// defer func() { +// err = multierr.Append(err, conn.Close()) +// }() +// // ... +// } +// +// The underlying list of errors for a returned error object may be retrieved +// with the Errors function. +// +// errors := multierr.Errors(err) +// if len(errors) > 0 { +// fmt.Println("The following errors occurred:") +// } +// +// Advanced Usage +// +// Errors returned by Combine and Append MAY implement the following +// interface. +// +// type errorGroup interface { +// // Returns a slice containing the underlying list of errors. +// // +// // This slice MUST NOT be modified by the caller. +// Errors() []error +// } +// +// Note that if you need access to list of errors behind a multierr error, you +// should prefer using the Errors function. That said, if you need cheap +// read-only access to the underlying errors slice, you can attempt to cast +// the error to this interface. You MUST handle the failure case gracefully +// because errors returned by Combine and Append are not guaranteed to +// implement this interface. +// +// var errors []error +// group, ok := err.(errorGroup) +// if ok { +// errors = group.Errors() +// } else { +// errors = []error{err} +// } +package multierr // import "go.uber.org/multierr" + +import ( + "bytes" + "fmt" + "io" + "strings" + "sync" + + "go.uber.org/atomic" +) + +var ( + // Separator for single-line error messages. + _singlelineSeparator = []byte("; ") + + _newline = []byte("\n") + + // Prefix for multi-line messages + _multilinePrefix = []byte("the following errors occurred:") + + // Prefix for the first and following lines of an item in a list of + // multi-line error messages. + // + // For example, if a single item is: + // + // foo + // bar + // + // It will become, + // + // - foo + // bar + _multilineSeparator = []byte("\n - ") + _multilineIndent = []byte(" ") +) + +// _bufferPool is a pool of bytes.Buffers. +var _bufferPool = sync.Pool{ + New: func() interface{} { + return &bytes.Buffer{} + }, +} + +type errorGroup interface { + Errors() []error +} + +// Errors returns a slice containing zero or more errors that the supplied +// error is composed of. If the error is nil, the returned slice is empty. +// +// err := multierr.Append(r.Close(), w.Close()) +// errors := multierr.Errors(err) +// +// If the error is not composed of other errors, the returned slice contains +// just the error that was passed in. +// +// Callers of this function are free to modify the returned slice. +func Errors(err error) []error { + if err == nil { + return nil + } + + // Note that we're casting to multiError, not errorGroup. Our contract is + // that returned errors MAY implement errorGroup. Errors, however, only + // has special behavior for multierr-specific error objects. + // + // This behavior can be expanded in the future but I think it's prudent to + // start with as little as possible in terms of contract and possibility + // of misuse. + eg, ok := err.(*multiError) + if !ok { + return []error{err} + } + + errors := eg.Errors() + result := make([]error, len(errors)) + copy(result, errors) + return result +} + +// multiError is an error that holds one or more errors. +// +// An instance of this is guaranteed to be non-empty and flattened. That is, +// none of the errors inside multiError are other multiErrors. +// +// multiError formats to a semi-colon delimited list of error messages with +// %v and with a more readable multi-line format with %+v. +type multiError struct { + copyNeeded atomic.Bool + errors []error +} + +var _ errorGroup = (*multiError)(nil) + +// Errors returns the list of underlying errors. +// +// This slice MUST NOT be modified. +func (merr *multiError) Errors() []error { + if merr == nil { + return nil + } + return merr.errors +} + +func (merr *multiError) Error() string { + if merr == nil { + return "" + } + + buff := _bufferPool.Get().(*bytes.Buffer) + buff.Reset() + + merr.writeSingleline(buff) + + result := buff.String() + _bufferPool.Put(buff) + return result +} + +func (merr *multiError) Format(f fmt.State, c rune) { + if c == 'v' && f.Flag('+') { + merr.writeMultiline(f) + } else { + merr.writeSingleline(f) + } +} + +func (merr *multiError) writeSingleline(w io.Writer) { + first := true + for _, item := range merr.errors { + if first { + first = false + } else { + w.Write(_singlelineSeparator) + } + io.WriteString(w, item.Error()) + } +} + +func (merr *multiError) writeMultiline(w io.Writer) { + w.Write(_multilinePrefix) + for _, item := range merr.errors { + w.Write(_multilineSeparator) + writePrefixLine(w, _multilineIndent, fmt.Sprintf("%+v", item)) + } +} + +// Writes s to the writer with the given prefix added before each line after +// the first. +func writePrefixLine(w io.Writer, prefix []byte, s string) { + first := true + for len(s) > 0 { + if first { + first = false + } else { + w.Write(prefix) + } + + idx := strings.IndexByte(s, '\n') + if idx < 0 { + idx = len(s) - 1 + } + + io.WriteString(w, s[:idx+1]) + s = s[idx+1:] + } +} + +type inspectResult struct { + // Number of top-level non-nil errors + Count int + + // Total number of errors including multiErrors + Capacity int + + // Index of the first non-nil error in the list. Value is meaningless if + // Count is zero. + FirstErrorIdx int + + // Whether the list contains at least one multiError + ContainsMultiError bool +} + +// Inspects the given slice of errors so that we can efficiently allocate +// space for it. +func inspect(errors []error) (res inspectResult) { + first := true + for i, err := range errors { + if err == nil { + continue + } + + res.Count++ + if first { + first = false + res.FirstErrorIdx = i + } + + if merr, ok := err.(*multiError); ok { + res.Capacity += len(merr.errors) + res.ContainsMultiError = true + } else { + res.Capacity++ + } + } + return +} + +// fromSlice converts the given list of errors into a single error. +func fromSlice(errors []error) error { + res := inspect(errors) + switch res.Count { + case 0: + return nil + case 1: + // only one non-nil entry + return errors[res.FirstErrorIdx] + case len(errors): + if !res.ContainsMultiError { + // already flat + return &multiError{errors: errors} + } + } + + nonNilErrs := make([]error, 0, res.Capacity) + for _, err := range errors[res.FirstErrorIdx:] { + if err == nil { + continue + } + + if nested, ok := err.(*multiError); ok { + nonNilErrs = append(nonNilErrs, nested.errors...) + } else { + nonNilErrs = append(nonNilErrs, err) + } + } + + return &multiError{errors: nonNilErrs} +} + +// Combine combines the passed errors into a single error. +// +// If zero arguments were passed or if all items are nil, a nil error is +// returned. +// +// Combine(nil, nil) // == nil +// +// If only a single error was passed, it is returned as-is. +// +// Combine(err) // == err +// +// Combine skips over nil arguments so this function may be used to combine +// together errors from operations that fail independently of each other. +// +// multierr.Combine( +// reader.Close(), +// writer.Close(), +// pipe.Close(), +// ) +// +// If any of the passed errors is a multierr error, it will be flattened along +// with the other errors. +// +// multierr.Combine(multierr.Combine(err1, err2), err3) +// // is the same as +// multierr.Combine(err1, err2, err3) +// +// The returned error formats into a readable multi-line error message if +// formatted with %+v. +// +// fmt.Sprintf("%+v", multierr.Combine(err1, err2)) +func Combine(errors ...error) error { + return fromSlice(errors) +} + +// Append appends the given errors together. Either value may be nil. +// +// This function is a specialization of Combine for the common case where +// there are only two errors. +// +// err = multierr.Append(reader.Close(), writer.Close()) +// +// The following pattern may also be used to record failure of deferred +// operations without losing information about the original error. +// +// func doSomething(..) (err error) { +// f := acquireResource() +// defer func() { +// err = multierr.Append(err, f.Close()) +// }() +func Append(left error, right error) error { + switch { + case left == nil: + return right + case right == nil: + return left + } + + if _, ok := right.(*multiError); !ok { + if l, ok := left.(*multiError); ok && !l.copyNeeded.Swap(true) { + // Common case where the error on the left is constantly being + // appended to. + errs := append(l.errors, right) + return &multiError{errors: errs} + } else if !ok { + // Both errors are single errors. + return &multiError{errors: []error{left, right}} + } + } + + // Either right or both, left and right, are multiErrors. Rely on usual + // expensive logic. + errors := [2]error{left, right} + return fromSlice(errors[0:]) +} |