slogsink.go

Documentation: github.com/go-logr/logr/funcr

     1  //go:build go1.21
     2  // +build go1.21
     3  
     4  /*
     5  Copyright 2023 The logr Authors.
     6  
     7  Licensed under the Apache License, Version 2.0 (the "License");
     8  you may not use this file except in compliance with the License.
     9  You may obtain a copy of the License at
    10  
    11      http://www.apache.org/licenses/LICENSE-2.0
    12  
    13  Unless required by applicable law or agreed to in writing, software
    14  distributed under the License is distributed on an "AS IS" BASIS,
    15  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    16  See the License for the specific language governing permissions and
    17  limitations under the License.
    18  */
    19  
    20  package funcr
    21  
    22  import (
    23  	"context"
    24  	"log/slog"
    25  
    26  	"github.com/go-logr/logr"
    27  )
    28  
    29  var _ logr.SlogSink = &fnlogger{}
    30  
    31  const extraSlogSinkDepth = 3 // 2 for slog, 1 for SlogSink
    32  
    33  func (l fnlogger) Handle(_ context.Context, record slog.Record) error {
    34  	kvList := make([]any, 0, 2*record.NumAttrs())
    35  	record.Attrs(func(attr slog.Attr) bool {
    36  		kvList = attrToKVs(attr, kvList)
    37  		return true
    38  	})
    39  
    40  	if record.Level >= slog.LevelError {
    41  		l.WithCallDepth(extraSlogSinkDepth).Error(nil, record.Message, kvList...)
    42  	} else {
    43  		level := l.levelFromSlog(record.Level)
    44  		l.WithCallDepth(extraSlogSinkDepth).Info(level, record.Message, kvList...)
    45  	}
    46  	return nil
    47  }
    48  
    49  func (l fnlogger) WithAttrs(attrs []slog.Attr) logr.SlogSink {
    50  	kvList := make([]any, 0, 2*len(attrs))
    51  	for _, attr := range attrs {
    52  		kvList = attrToKVs(attr, kvList)
    53  	}
    54  	l.AddValues(kvList)
    55  	return &l
    56  }
    57  
    58  func (l fnlogger) WithGroup(name string) logr.SlogSink {
    59  	l.startGroup(name)
    60  	return &l
    61  }
    62  
    63  // attrToKVs appends a slog.Attr to a logr-style kvList.  It handle slog Groups
    64  // and other details of slog.
    65  func attrToKVs(attr slog.Attr, kvList []any) []any {
    66  	attrVal := attr.Value.Resolve()
    67  	if attrVal.Kind() == slog.KindGroup {
    68  		groupVal := attrVal.Group()
    69  		grpKVs := make([]any, 0, 2*len(groupVal))
    70  		for _, attr := range groupVal {
    71  			grpKVs = attrToKVs(attr, grpKVs)
    72  		}
    73  		if attr.Key == "" {
    74  			// slog says we have to inline these
    75  			kvList = append(kvList, grpKVs...)
    76  		} else {
    77  			kvList = append(kvList, attr.Key, PseudoStruct(grpKVs))
    78  		}
    79  	} else if attr.Key != "" {
    80  		kvList = append(kvList, attr.Key, attrVal.Any())
    81  	}
    82  
    83  	return kvList
    84  }
    85  
    86  // levelFromSlog adjusts the level by the logger's verbosity and negates it.
    87  // It ensures that the result is >= 0. This is necessary because the result is
    88  // passed to a LogSink and that API did not historically document whether
    89  // levels could be negative or what that meant.
    90  //
    91  // Some example usage:
    92  //
    93  //	logrV0 := getMyLogger()
    94  //	logrV2 := logrV0.V(2)
    95  //	slogV2 := slog.New(logr.ToSlogHandler(logrV2))
    96  //	slogV2.Debug("msg") // =~ logrV2.V(4) =~ logrV0.V(6)
    97  //	slogV2.Info("msg")  // =~  logrV2.V(0) =~ logrV0.V(2)
    98  //	slogv2.Warn("msg")  // =~ logrV2.V(-4) =~ logrV0.V(0)
    99  func (l fnlogger) levelFromSlog(level slog.Level) int {
   100  	result := -level
   101  	if result < 0 {
   102  		result = 0 // because LogSink doesn't expect negative V levels
   103  	}
   104  	return int(result)
   105  }
   106
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