| // Copyright 2020 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 |
| |
| import ( |
| "fmt" |
| "runtime/debug" |
| "strings" |
| ) |
| |
| func CrashingFunction() { |
| panic("boom") |
| } |
| |
| func ExampleIsPanicking() { |
| A := func(crash bool) { |
| defer func() { |
| if IsPanicking(0) { |
| fmt.Println("PANIK!") |
| } else { |
| fmt.Println("kalm") |
| } |
| }() |
| if crash { |
| fmt.Println("about to boom") |
| CrashingFunction() |
| } else { |
| fmt.Println("smooth sailing") |
| } |
| } |
| |
| defer func() { |
| // Make sure IsPanicking didn't do a `recover()`, which would goof up the |
| // stack. |
| stack := string(debug.Stack()) |
| if !strings.Contains(stack, "CrashingFunction") { |
| fmt.Println("stack trace doesn't originate from CrashingFunction") |
| } else { |
| fmt.Println("stack trace originates from CrashingFunction") |
| } |
| // But recover ourselves to make sure ExampleIsPanicking actually passes |
| // instead of crashing with an unrecovered panic. |
| recover() |
| }() |
| |
| if IsPanicking(0) { |
| fmt.Println("cannot be panicing when not in defer'd function.") |
| } |
| |
| A(false) |
| fmt.Println("first pass success") |
| A(true) |
| |
| // Output: |
| // smooth sailing |
| // kalm |
| // first pass success |
| // about to boom |
| // PANIK! |
| // stack trace originates from CrashingFunction |
| } |