go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/common/errors/annotate_example_test.go (about)

     1  // Copyright 2016 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package errors
    16  
    17  import (
    18  	"fmt"
    19  )
    20  
    21  func someProcessingFunction(val int) error {
    22  	if val == 1 {
    23  		// New and Reason automatically include stack information.
    24  		return Reason("bad number: %d", val).Err()
    25  	}
    26  	if err := someProcessingFunction(val - 1); err != nil {
    27  		// correctly handles recursion
    28  		return Annotate(err, "").InternalReason("val(%d)", val).Err()
    29  	}
    30  	return nil
    31  }
    32  
    33  func someLibFunc(vals ...int) error {
    34  	for i, v := range vals {
    35  		if err := someProcessingFunction(v); err != nil {
    36  			return Annotate(err, "processing %d", v).
    37  				InternalReason("secret(%s)/i(%d)", "value", i).Err()
    38  		}
    39  	}
    40  	return nil
    41  }
    42  
    43  type MiscWrappedError struct{ error }
    44  
    45  func (e *MiscWrappedError) Error() string { return fmt.Sprintf("super wrapper(%s)", e.error.Error()) }
    46  func (e *MiscWrappedError) Unwrap() error { return e.error }
    47  
    48  func errorWrapper(err error) error {
    49  	if err != nil {
    50  		err = &MiscWrappedError{err}
    51  	}
    52  	return err
    53  }
    54  
    55  func someIntermediateFunc(vals ...int) error {
    56  	errch := make(chan error)
    57  	go func() {
    58  		defer close(errch)
    59  		errch <- Annotate(errorWrapper(someLibFunc(vals...)), "could not process").Err()
    60  	}()
    61  	me := MultiError(nil)
    62  	for err := range errch {
    63  		if err != nil {
    64  			me = append(me, err)
    65  		}
    66  	}
    67  	if me != nil {
    68  		return Annotate(me, "while processing %v", vals).Err()
    69  	}
    70  	return nil
    71  }
    72  
    73  func ExampleAnnotate() {
    74  	if err := someIntermediateFunc(3); err != nil {
    75  		err = Annotate(err, "top level").Err()
    76  		fmt.Println("Public-facing error:\n ", err)
    77  		fmt.Println("\nfull error:")
    78  		for _, l := range FixForTest(RenderStack(err, "runtime", "_test")) {
    79  			fmt.Println(l)
    80  		}
    81  	}
    82  
    83  	// Output:
    84  	// Public-facing error:
    85  	//   top level: while processing [3]: could not process: super wrapper(processing 3: bad number: 1)
    86  	//
    87  	// full error:
    88  	// original error: bad number: 1
    89  	//
    90  	// GOROUTINE LINE
    91  	// #? go.chromium.org/luci/common/errors/annotate_example_test.go:24 - errors.someProcessingFunction()
    92  	//   reason: bad number: 1
    93  	//
    94  	// #? go.chromium.org/luci/common/errors/annotate_example_test.go:26 - errors.someProcessingFunction()
    95  	//   internal reason: val(2)
    96  	//
    97  	// #? go.chromium.org/luci/common/errors/annotate_example_test.go:26 - errors.someProcessingFunction()
    98  	//   internal reason: val(3)
    99  	//
   100  	// From frame 2 to 3, the following wrappers were found:
   101  	//   unknown wrapper *errors.MiscWrappedError
   102  	//
   103  	// #? go.chromium.org/luci/common/errors/annotate_example_test.go:35 - errors.someLibFunc()
   104  	//   reason: processing 3
   105  	//   internal reason: secret(value)/i(0)
   106  	//
   107  	// From frame 3 to 4, the following wrappers were found:
   108  	//   internal reason: MultiError 1/1: following first non-nil error.
   109  	//
   110  	// #? go.chromium.org/luci/common/errors/annotate_example_test.go:59 - errors.someIntermediateFunc.func1()
   111  	//   reason: could not process
   112  	//
   113  	// ... skipped SOME frames in pkg "runtime"...
   114  	//
   115  	// GOROUTINE LINE
   116  	// #? go.chromium.org/luci/common/errors/annotate_example_test.go:68 - errors.someIntermediateFunc()
   117  	//   reason: while processing [3]
   118  	//
   119  	// #? go.chromium.org/luci/common/errors/annotate_example_test.go:74 - errors.ExampleAnnotate()
   120  	//   reason: top level
   121  	//
   122  	// #? testing/run_example.go:XXX - testing.runExample()
   123  	// #? testing/example.go:XXX - testing.runExamples()
   124  	// #? testing/testing.go:XXX - testing.(*M).Run()
   125  	// #? ./_testmain.go:XXX - main.main()
   126  	// ... skipped SOME frames in pkg "runtime"...
   127  }