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The wrapper function solves two problems: - Types which inherit a String implementation from some embedded type and then don't overwrite it get logged as JSON dump (text output) and struct (JSON). Example: KubeletConfig. - Types which have a generated String implementation and no MarshalLog get differently (JSON + struct) depending on the logger, instead of always using a string. Example: all of the Kubernetes API types. Ideally, types should get fixed to handle both cases. klog.Format is the fallback for cases where that is not possible or not desirable.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,65 @@ | ||
| /* | ||
| Copyright 2023 The Kubernetes 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 klog | ||
|
|
||
| import ( | ||
| "encoding/json" | ||
| "fmt" | ||
| "strings" | ||
|
|
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| "github.com/go-logr/logr" | ||
| ) | ||
|
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| // Format wraps a value of an arbitrary type and implement fmt.Stringer and | ||
| // logr.Marshaler for them. Stringer returns pretty-printed JSON. MarshalLog | ||
| // returns the original value with a type that has no special methods, in | ||
| // particular no MarshalLog or MarshalJSON. | ||
| // | ||
| // Wrapping values like that is useful when the value has a broken | ||
| // implementation of these special functions (for example, a type which | ||
| // inherits String from TypeMeta, but then doesn't re-implement String) or the | ||
| // implementation produces output that is less readable or unstructured (for | ||
| // example, the generated String functions for Kubernetes API types). | ||
| func Format(obj interface{}) formatAny { | ||
| return formatAny{Object: obj} | ||
| } | ||
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| type formatAny struct { | ||
| Object interface{} | ||
| } | ||
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| func (f formatAny) String() string { | ||
| var buffer strings.Builder | ||
| encoder := json.NewEncoder(&buffer) | ||
| encoder.SetIndent("", " ") | ||
| if err := encoder.Encode(&f.Object); err != nil { | ||
| return fmt.Sprintf("error marshaling %T to JSON: %v", f, err) | ||
| } | ||
| return buffer.String() | ||
| } | ||
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| func (f formatAny) MarshalLog() interface{} { | ||
| // Returning a pointer to a pointer ensures that zapr doesn't find a | ||
| // fmt.Stringer or logr.Marshaler when it checks the type of the | ||
| // value. It then falls back to reflection, which dumps the value being | ||
| // pointed to (JSON doesn't have pointers). | ||
| ptr := &f.Object | ||
| return &ptr | ||
| } | ||
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| var _ fmt.Stringer = formatAny{} | ||
| var _ logr.Marshaler = formatAny{} |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,78 @@ | ||
| /* | ||
| Copyright 2023 The Kubernetes 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. | ||
| */ | ||
|
|
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| package klog_test | ||
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|
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| import ( | ||
| "encoding/json" | ||
| "fmt" | ||
| "strings" | ||
| "testing" | ||
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| "k8s.io/klog/v2" | ||
| ) | ||
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| func TestFormat(t *testing.T) { | ||
| obj := config{ | ||
| TypeMeta: TypeMeta{ | ||
| Kind: "config", | ||
| }, | ||
| RealField: 42, | ||
| } | ||
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| assertEqual(t, "kind is config", obj.String(), "config.String()") | ||
| assertEqual(t, `{ | ||
| "Kind": "config", | ||
| "RealField": 42 | ||
| } | ||
| `, klog.Format(obj).String(), "Format(config).String()") | ||
| // fmt.Sprintf would call String if it was available. | ||
| str := fmt.Sprintf("%s", klog.Format(obj).MarshalLog()) | ||
| if strings.Index(str, "kind is config") >= 0 { | ||
| t.Errorf("fmt.Sprintf called TypeMeta.String for klog.Format(obj).MarshalLog():\n%s", str) | ||
| } | ||
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| structured, err := json.Marshal(klog.Format(obj).MarshalLog()) | ||
| if err != nil { | ||
| t.Errorf("JSON Marshal: %v", err) | ||
| } else { | ||
| assertEqual(t, `{"Kind":"config","RealField":42}`, string(structured), "json.Marshal(klog.Format(obj).MarshalLog())") | ||
| } | ||
| } | ||
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| func assertEqual(t *testing.T, expected, actual, what string) { | ||
| if expected != actual { | ||
| t.Errorf("%s:\nExpected\n%s\nActual\n%s\n", what, expected, actual) | ||
| } | ||
| } | ||
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| type TypeMeta struct { | ||
| Kind string | ||
| } | ||
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| func (t TypeMeta) String() string { | ||
| return "kind is " + t.Kind | ||
| } | ||
|
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| func (t TypeMeta) MarshalLog() interface{} { | ||
| return t.Kind | ||
| } | ||
|
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| type config struct { | ||
| TypeMeta | ||
|
|
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| RealField int | ||
| } |
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