improvement: svc1zap: Add WithEntryMutatorFunc for dynamically modifying or skipping entries

adapters/svc1zap/svc1zap.go

@@ -26,6 +26,7 @@ import (
 
 type svc1zapCore struct {
 	log                svc1log.Logger
+	mutator            func(entry zapcore.Entry) (zapcore.Entry, bool)
 	originFromCallLine bool
 	newParamFunc       func(key string, value interface{}) svc1log.Param
 }
@@ -64,6 +65,12 @@ func WithNewParamFunc(newParam func(key string, value interface{}) svc1log.Param
 	return func(core *svc1zapCore) { core.newParamFunc = newParam }
 }
 
+// WithEntryMutatorFunc provides a function for modifying or skipping entries dynamically.
+// If mutator is set, ok must return true for the message to be logged.
+func WithEntryMutatorFunc(mutator func(entry zapcore.Entry) (out zapcore.Entry, ok bool)) Option {
+	return func(core *svc1zapCore) { core.mutator = mutator }
+}
+
 func (c svc1zapCore) Enabled(level zapcore.Level) bool {
 	if checker, ok := c.log.(wlog.LevelChecker); ok {
 		switch level {
@@ -85,6 +92,13 @@ func (c svc1zapCore) With(fields []zapcore.Field) zapcore.Core {
 }
 
 func (c svc1zapCore) Check(entry zapcore.Entry, ce *zapcore.CheckedEntry) *zapcore.CheckedEntry {
+	if c.mutator != nil {
+		var ok bool
+		entry, ok = c.mutator(entry)
+		if !ok {
+			return ce
+		}
+	}
 	return ce.AddCore(entry, c)
 }
 

adapters/svc1zap/svc1zap_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/palantir/witchcraft-go-logging/wlog/svclog/svc1log"
 	"github.com/stretchr/testify/assert"
 	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
 
 	// Use zap as logger implementation
 	_ "github.com/palantir/witchcraft-go-logging/wlog-zap"
@@ -106,6 +107,39 @@ func TestSvc1ZapWrapper(t *testing.T) {
 		logr4.Debug("logr 4")
 		assert.Empty(t, buf.String())
 	})
+
+	t.Run("logger with mutator", func(t *testing.T) {
+		buf := new(bytes.Buffer)
+		logger := svc1log.New(buf, wlog.DebugLevel)
+		logr5 := New(logger, WithEntryMutatorFunc(func(entry zapcore.Entry) (out zapcore.Entry, ok bool) {
+			if entry.Message == "skip me" {
+				return entry, false
+			}
+			if entry.Message == "drop to debug" {
+				entry.Level = zapcore.DebugLevel
+			}
+			return entry, true
+		}))
+		logr5.Info("logr 5")
+		logr5.Warn("skip me")
+		logr5.Warn("drop to debug")
+
+		lines := bytes.Split(bytes.TrimSpace(buf.Bytes()), []byte("\n"))
+		if assert.Len(t, lines, 2) {
+			assertLogLine(t, lines[0], objmatcher.MapMatcher{
+				"type":    objmatcher.NewEqualsMatcher(svc1log.TypeValue),
+				"time":    objmatcher.NewRegExpMatcher(".+"),
+				"level":   objmatcher.NewEqualsMatcher("INFO"),
+				"message": objmatcher.NewEqualsMatcher("logr 5"),
+			})
+			assertLogLine(t, lines[1], objmatcher.MapMatcher{
+				"type":    objmatcher.NewEqualsMatcher(svc1log.TypeValue),
+				"time":    objmatcher.NewRegExpMatcher(".+"),
+				"level":   objmatcher.NewEqualsMatcher("DEBUG"),
+				"message": objmatcher.NewEqualsMatcher("drop to debug"),
+			})
+		}
+	})
 }
 
 func assertLogLine(t *testing.T, logLine []byte, matcher objmatcher.MapMatcher) {

changelog/@unreleased/pr-199.v2.yml

@@ -0,0 +1,5 @@
+type: improvement
+improvement:
+  description: 'svc1zap: Add WithEntryMutatorFunc for dynamically modifying or skipping entries'
+  links:
+  - https://github.com/palantir/witchcraft-go-logging/pull/199