diff options
Diffstat (limited to 'vendor/go.uber.org/multierr/error.go')
| -rw-r--r-- | vendor/go.uber.org/multierr/error.go | 208 |
1 files changed, 199 insertions, 9 deletions
diff --git a/vendor/go.uber.org/multierr/error.go b/vendor/go.uber.org/multierr/error.go index 5c9b67d5..faa0a059 100644 --- a/vendor/go.uber.org/multierr/error.go +++ b/vendor/go.uber.org/multierr/error.go @@ -1,4 +1,4 @@ -// Copyright (c) 2019 Uber Technologies, Inc. +// Copyright (c) 2017-2021 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 @@ -35,8 +35,53 @@ // // err = multierr.Append(reader.Close(), writer.Close()) // -// This makes it possible to record resource cleanup failures from deferred -// blocks with the help of named return values. +// 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:", errors) +// } +// +// Appending from a loop +// +// You sometimes need to append into an error from a loop. +// +// var err error +// for _, item := range items { +// err = multierr.Append(err, process(item)) +// } +// +// Cases like this may require knowledge of whether an individual instance +// failed. This usually requires introduction of a new variable. +// +// var err error +// for _, item := range items { +// if perr := process(item); perr != nil { +// log.Warn("skipping item", item) +// err = multierr.Append(err, perr) +// } +// } +// +// multierr includes AppendInto to simplify cases like this. +// +// var err error +// for _, item := range items { +// if multierr.AppendInto(&err, process(item)) { +// log.Warn("skipping item", item) +// } +// } +// +// This will append the error into the err variable, and return true if that +// individual error was non-nil. +// +// See AppendInto for more information. +// +// Deferred Functions +// +// Go makes it possible to modify the return value of a function in a defer +// block if the function was using named returns. This makes it possible to +// record resource cleanup failures from deferred blocks. // // func sendRequest(req Request) (err error) { // conn, err := openConnection() @@ -49,14 +94,21 @@ // // ... // } // -// The underlying list of errors for a returned error object may be retrieved -// with the Errors function. +// multierr provides the Invoker type and AppendInvoke function to make cases +// like the above simpler and obviate the need for a closure. The following is +// roughly equivalent to the example above. // -// errors := multierr.Errors(err) -// if len(errors) > 0 { -// fmt.Println("The following errors occurred:", errors) +// func sendRequest(req Request) (err error) { +// conn, err := openConnection() +// if err != nil { +// return err +// } +// defer multierr.AppendInvoke(err, multierr.Close(conn)) +// // ... // } // +// See AppendInvoke and Invoker for more information. +// // Advanced Usage // // Errors returned by Combine and Append MAY implement the following @@ -87,6 +139,7 @@ package multierr // import "go.uber.org/multierr" import ( "bytes" + "errors" "fmt" "io" "strings" @@ -186,6 +239,33 @@ func (merr *multiError) Errors() []error { return merr.errors } +// As attempts to find the first error in the error list that matches the type +// of the value that target points to. +// +// This function allows errors.As to traverse the values stored on the +// multierr error. +func (merr *multiError) As(target interface{}) bool { + for _, err := range merr.Errors() { + if errors.As(err, target) { + return true + } + } + return false +} + +// Is attempts to match the provided error against errors in the error list. +// +// This function allows errors.Is to traverse the values stored on the +// multierr error. +func (merr *multiError) Is(target error) bool { + for _, err := range merr.Errors() { + if errors.Is(err, target) { + return true + } + } + return false +} + func (merr *multiError) Error() string { if merr == nil { return "" @@ -421,7 +501,7 @@ func Append(left error, right error) error { // items = append(items, item) // } // -// Compare this with a verison that relies solely on Append: +// Compare this with a version that relies solely on Append: // // var err error // for line := range lines { @@ -447,3 +527,113 @@ func AppendInto(into *error, err error) (errored bool) { *into = Append(*into, err) return true } + +// Invoker is an operation that may fail with an error. Use it with +// AppendInvoke to append the result of calling the function into an error. +// This allows you to conveniently defer capture of failing operations. +// +// See also, Close and Invoke. +type Invoker interface { + Invoke() error +} + +// Invoke wraps a function which may fail with an error to match the Invoker +// interface. Use it to supply functions matching this signature to +// AppendInvoke. +// +// For example, +// +// func processReader(r io.Reader) (err error) { +// scanner := bufio.NewScanner(r) +// defer multierr.AppendInvoke(&err, multierr.Invoke(scanner.Err)) +// for scanner.Scan() { +// // ... +// } +// // ... +// } +// +// In this example, the following line will construct the Invoker right away, +// but defer the invocation of scanner.Err() until the function returns. +// +// defer multierr.AppendInvoke(&err, multierr.Invoke(scanner.Err)) +type Invoke func() error + +// Invoke calls the supplied function and returns its result. +func (i Invoke) Invoke() error { return i() } + +// Close builds an Invoker that closes the provided io.Closer. Use it with +// AppendInvoke to close io.Closers and append their results into an error. +// +// For example, +// +// func processFile(path string) (err error) { +// f, err := os.Open(path) +// if err != nil { +// return err +// } +// defer multierr.AppendInvoke(&err, multierr.Close(f)) +// return processReader(f) +// } +// +// In this example, multierr.Close will construct the Invoker right away, but +// defer the invocation of f.Close until the function returns. +// +// defer multierr.AppendInvoke(&err, multierr.Close(f)) +func Close(closer io.Closer) Invoker { + return Invoke(closer.Close) +} + +// AppendInvoke appends the result of calling the given Invoker into the +// provided error pointer. Use it with named returns to safely defer +// invocation of fallible operations until a function returns, and capture the +// resulting errors. +// +// func doSomething(...) (err error) { +// // ... +// f, err := openFile(..) +// if err != nil { +// return err +// } +// +// // multierr will call f.Close() when this function returns and +// // if the operation fails, its append its error into the +// // returned error. +// defer multierr.AppendInvoke(&err, multierr.Close(f)) +// +// scanner := bufio.NewScanner(f) +// // Similarly, this scheduled scanner.Err to be called and +// // inspected when the function returns and append its error +// // into the returned error. +// defer multierr.AppendInvoke(&err, multierr.Invoke(scanner.Err)) +// +// // ... +// } +// +// Without defer, AppendInvoke behaves exactly like AppendInto. +// +// err := // ... +// multierr.AppendInvoke(&err, mutltierr.Invoke(foo)) +// +// // ...is roughly equivalent to... +// +// err := // ... +// multierr.AppendInto(&err, foo()) +// +// The advantage of the indirection introduced by Invoker is to make it easy +// to defer the invocation of a function. Without this indirection, the +// invoked function will be evaluated at the time of the defer block rather +// than when the function returns. +// +// // BAD: This is likely not what the caller intended. This will evaluate +// // foo() right away and append its result into the error when the +// // function returns. +// defer multierr.AppendInto(&err, foo()) +// +// // GOOD: This will defer invocation of foo unutil the function returns. +// defer multierr.AppendInvoke(&err, multierr.Invoke(foo)) +// +// multierr provides a few Invoker implementations out of the box for +// convenience. See Invoker for more information. +func AppendInvoke(into *error, invoker Invoker) { + AppendInto(into, invoker.Invoke()) +} |