| // Copyright 2015 The LUCI Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package errors |
| |
| // Walk performs a depth-first traversal of the supplied error, unfolding it and |
| // invoke the supplied callback for each layered error recursively. If the |
| // callback returns true, Walk will continue its traversal. |
| // |
| // - If walk encounters a MultiError, the callback is called once for the |
| // outer MultiError, then once for each inner error. |
| // - If walk encounters a Wrapped error, the callback is called for the outer |
| // and inner error. |
| // - If an inner error is, itself, a container, Walk will recurse into it. |
| // |
| // If err is nil, the callback will not be invoked. |
| func Walk(err error, fn func(error) bool) { |
| _ = walkVisit(err, fn, false) |
| } |
| |
| // WalkLeaves is like Walk, but only calls fn on leaf nodes. |
| func WalkLeaves(err error, fn func(error) bool) { |
| _ = walkVisit(err, fn, true) |
| } |
| |
| func walkVisit(err error, fn func(error) bool, leavesOnly bool) bool { |
| if err == nil { |
| return true |
| } |
| |
| // Call fn if we are not in leavesOnly mode. |
| if !(leavesOnly || fn(err)) { |
| return false |
| } |
| |
| switch t := err.(type) { |
| case MultiError: |
| for _, e := range t { |
| if !walkVisit(e, fn, leavesOnly) { |
| return false |
| } |
| } |
| |
| case Wrapped: |
| return walkVisit(t.Unwrap(), fn, leavesOnly) |
| |
| default: |
| if leavesOnly { |
| return fn(err) |
| } |
| } |
| |
| return true |
| } |
| |
| // Any performs a Walk traversal of an error, returning true (and |
| // short-circuiting) if the supplied filter function returns true for any |
| // visited error. |
| // |
| // If err is nil, Any will return false. |
| func Any(err error, fn func(error) bool) (any bool) { |
| Walk(err, func(err error) bool { |
| any = fn(err) |
| return !any |
| }) |
| return |
| } |
| |
| // Contains performs a Walk traversal of |outer|, returning true if any visited |
| // error is equal to |inner|. |
| func Contains(outer error, inner error) bool { |
| return Any(outer, func(item error) bool { |
| if item == inner { |
| return true |
| } |
| if is, ok := item.(interface{ Is(error) bool }); ok { |
| return is.Is(inner) |
| } |
| return false |
| }) |
| } |