Zack Williams | e940c7a | 2019-08-21 14:25:39 -0700 | [diff] [blame] | 1 | /* |
| 2 | Copyright 2015 The Kubernetes Authors. |
| 3 | |
| 4 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | you may not use this file except in compliance with the License. |
| 6 | You may obtain a copy of the License at |
| 7 | |
| 8 | http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | |
| 10 | Unless required by applicable law or agreed to in writing, software |
| 11 | distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | See the License for the specific language governing permissions and |
| 14 | limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package errors |
| 18 | |
| 19 | import ( |
| 20 | "errors" |
| 21 | "fmt" |
| 22 | ) |
| 23 | |
| 24 | // MessageCountMap contains occurrence for each error message. |
| 25 | type MessageCountMap map[string]int |
| 26 | |
| 27 | // Aggregate represents an object that contains multiple errors, but does not |
| 28 | // necessarily have singular semantic meaning. |
| 29 | type Aggregate interface { |
| 30 | error |
| 31 | Errors() []error |
| 32 | } |
| 33 | |
| 34 | // NewAggregate converts a slice of errors into an Aggregate interface, which |
| 35 | // is itself an implementation of the error interface. If the slice is empty, |
| 36 | // this returns nil. |
| 37 | // It will check if any of the element of input error list is nil, to avoid |
| 38 | // nil pointer panic when call Error(). |
| 39 | func NewAggregate(errlist []error) Aggregate { |
| 40 | if len(errlist) == 0 { |
| 41 | return nil |
| 42 | } |
| 43 | // In case of input error list contains nil |
| 44 | var errs []error |
| 45 | for _, e := range errlist { |
| 46 | if e != nil { |
| 47 | errs = append(errs, e) |
| 48 | } |
| 49 | } |
| 50 | if len(errs) == 0 { |
| 51 | return nil |
| 52 | } |
| 53 | return aggregate(errs) |
| 54 | } |
| 55 | |
| 56 | // This helper implements the error and Errors interfaces. Keeping it private |
| 57 | // prevents people from making an aggregate of 0 errors, which is not |
| 58 | // an error, but does satisfy the error interface. |
| 59 | type aggregate []error |
| 60 | |
| 61 | // Error is part of the error interface. |
| 62 | func (agg aggregate) Error() string { |
| 63 | if len(agg) == 0 { |
| 64 | // This should never happen, really. |
| 65 | return "" |
| 66 | } |
| 67 | if len(agg) == 1 { |
| 68 | return agg[0].Error() |
| 69 | } |
| 70 | result := fmt.Sprintf("[%s", agg[0].Error()) |
| 71 | for i := 1; i < len(agg); i++ { |
| 72 | result += fmt.Sprintf(", %s", agg[i].Error()) |
| 73 | } |
| 74 | result += "]" |
| 75 | return result |
| 76 | } |
| 77 | |
| 78 | // Errors is part of the Aggregate interface. |
| 79 | func (agg aggregate) Errors() []error { |
| 80 | return []error(agg) |
| 81 | } |
| 82 | |
| 83 | // Matcher is used to match errors. Returns true if the error matches. |
| 84 | type Matcher func(error) bool |
| 85 | |
| 86 | // FilterOut removes all errors that match any of the matchers from the input |
| 87 | // error. If the input is a singular error, only that error is tested. If the |
| 88 | // input implements the Aggregate interface, the list of errors will be |
| 89 | // processed recursively. |
| 90 | // |
| 91 | // This can be used, for example, to remove known-OK errors (such as io.EOF or |
| 92 | // os.PathNotFound) from a list of errors. |
| 93 | func FilterOut(err error, fns ...Matcher) error { |
| 94 | if err == nil { |
| 95 | return nil |
| 96 | } |
| 97 | if agg, ok := err.(Aggregate); ok { |
| 98 | return NewAggregate(filterErrors(agg.Errors(), fns...)) |
| 99 | } |
| 100 | if !matchesError(err, fns...) { |
| 101 | return err |
| 102 | } |
| 103 | return nil |
| 104 | } |
| 105 | |
| 106 | // matchesError returns true if any Matcher returns true |
| 107 | func matchesError(err error, fns ...Matcher) bool { |
| 108 | for _, fn := range fns { |
| 109 | if fn(err) { |
| 110 | return true |
| 111 | } |
| 112 | } |
| 113 | return false |
| 114 | } |
| 115 | |
| 116 | // filterErrors returns any errors (or nested errors, if the list contains |
| 117 | // nested Errors) for which all fns return false. If no errors |
| 118 | // remain a nil list is returned. The resulting silec will have all |
| 119 | // nested slices flattened as a side effect. |
| 120 | func filterErrors(list []error, fns ...Matcher) []error { |
| 121 | result := []error{} |
| 122 | for _, err := range list { |
| 123 | r := FilterOut(err, fns...) |
| 124 | if r != nil { |
| 125 | result = append(result, r) |
| 126 | } |
| 127 | } |
| 128 | return result |
| 129 | } |
| 130 | |
| 131 | // Flatten takes an Aggregate, which may hold other Aggregates in arbitrary |
| 132 | // nesting, and flattens them all into a single Aggregate, recursively. |
| 133 | func Flatten(agg Aggregate) Aggregate { |
| 134 | result := []error{} |
| 135 | if agg == nil { |
| 136 | return nil |
| 137 | } |
| 138 | for _, err := range agg.Errors() { |
| 139 | if a, ok := err.(Aggregate); ok { |
| 140 | r := Flatten(a) |
| 141 | if r != nil { |
| 142 | result = append(result, r.Errors()...) |
| 143 | } |
| 144 | } else { |
| 145 | if err != nil { |
| 146 | result = append(result, err) |
| 147 | } |
| 148 | } |
| 149 | } |
| 150 | return NewAggregate(result) |
| 151 | } |
| 152 | |
| 153 | // CreateAggregateFromMessageCountMap converts MessageCountMap Aggregate |
| 154 | func CreateAggregateFromMessageCountMap(m MessageCountMap) Aggregate { |
| 155 | if m == nil { |
| 156 | return nil |
| 157 | } |
| 158 | result := make([]error, 0, len(m)) |
| 159 | for errStr, count := range m { |
| 160 | var countStr string |
| 161 | if count > 1 { |
| 162 | countStr = fmt.Sprintf(" (repeated %v times)", count) |
| 163 | } |
| 164 | result = append(result, fmt.Errorf("%v%v", errStr, countStr)) |
| 165 | } |
| 166 | return NewAggregate(result) |
| 167 | } |
| 168 | |
| 169 | // Reduce will return err or, if err is an Aggregate and only has one item, |
| 170 | // the first item in the aggregate. |
| 171 | func Reduce(err error) error { |
| 172 | if agg, ok := err.(Aggregate); ok && err != nil { |
| 173 | switch len(agg.Errors()) { |
| 174 | case 1: |
| 175 | return agg.Errors()[0] |
| 176 | case 0: |
| 177 | return nil |
| 178 | } |
| 179 | } |
| 180 | return err |
| 181 | } |
| 182 | |
| 183 | // AggregateGoroutines runs the provided functions in parallel, stuffing all |
| 184 | // non-nil errors into the returned Aggregate. |
| 185 | // Returns nil if all the functions complete successfully. |
| 186 | func AggregateGoroutines(funcs ...func() error) Aggregate { |
| 187 | errChan := make(chan error, len(funcs)) |
| 188 | for _, f := range funcs { |
| 189 | go func(f func() error) { errChan <- f() }(f) |
| 190 | } |
| 191 | errs := make([]error, 0) |
| 192 | for i := 0; i < cap(errChan); i++ { |
| 193 | if err := <-errChan; err != nil { |
| 194 | errs = append(errs, err) |
| 195 | } |
| 196 | } |
| 197 | return NewAggregate(errs) |
| 198 | } |
| 199 | |
| 200 | // ErrPreconditionViolated is returned when the precondition is violated |
| 201 | var ErrPreconditionViolated = errors.New("precondition is violated") |