textlogger: optionally turn off header

textlogger/options.go

@@ -59,6 +59,7 @@ type configOptions struct {
 	verbosityDefault  int
 	fixedTime         *time.Time
 	unwind            func(int) (string, int)
+	withHeader        bool
 	output            io.Writer
 }
 
@@ -106,6 +107,22 @@ func FixedTime(ts time.Time) ConfigOption {
 	}
 }
 
+// WithHeader controls whether the header (time, source code location, etc.)
+// is included in the output. The default is to include it.
+//
+// This can be useful in combination with redirection to a buffer to
+// turn structured log parameters into a string (see example).
+//
+// # Experimental
+//
+// Notice: This function is EXPERIMENTAL and may be changed or removed in a
+// later release.
+func WithHeader(enabled bool) ConfigOption {
+	return func(co *configOptions) {
+		co.withHeader = enabled
+	}
+}
+
 // Backtrace overrides the default mechanism for determining the call site.
 // The callback is invoked with the number of function calls between itself
 // and the call site. It must return the file name and line number. An empty
@@ -131,6 +148,7 @@ func NewConfig(opts ...ConfigOption) *Config {
 			vmoduleFlagName:   "vmodule",
 			verbosityDefault:  0,
 			unwind:            runtimeBacktrace,
+			withHeader:        true,
 			output:            os.Stderr,
 		},
 	}

textlogger/textlogger.go

@@ -92,17 +92,23 @@ func (l *tlogger) Error(err error, msg string, kvList ...interface{}) {
 }
 
 func (l *tlogger) print(err error, s severity.Severity, msg string, kvList []interface{}) {
-	// Determine caller.
-	// +1 for this frame, +1 for Info/Error.
-	skip := l.callDepth + 2
-	file, line := l.config.co.unwind(skip)
-	if file == "" {
-		file = "???"
-		line = 1
-	} else if slash := strings.LastIndex(file, "/"); slash >= 0 {
-		file = file[slash+1:]
+	var file string
+	var line int
+	var now time.Time
+	if l.config.co.withHeader {
+		// Determine caller.
+		// +1 for this frame, +1 for Info/Error.
+		skip := l.callDepth + 2
+		file, line = l.config.co.unwind(skip)
+		if file == "" {
+			file = "???"
+			line = 1
+		} else if slash := strings.LastIndex(file, "/"); slash >= 0 {
+			file = file[slash+1:]
+		}
+		now = time.Now()
 	}
-	l.printWithInfos(file, line, time.Now(), err, s, msg, kvList)
+	l.printWithInfos(file, line, now, err, s, msg, kvList)
 }
 
 func runtimeBacktrace(skip int) (string, int) {
@@ -124,11 +130,13 @@ func (l *tlogger) printWithInfos(file string, line int, now time.Time, err error
 	b := buffer.GetBuffer()
 	defer buffer.PutBuffer(b)
 
-	// Format header.
-	if l.config.co.fixedTime != nil {
-		now = *l.config.co.fixedTime
+	if l.config.co.withHeader {
+		// Format header.
+		if l.config.co.fixedTime != nil {
+			now = *l.config.co.fixedTime
+		}
+		b.FormatHeader(s, file, line, now)
 	}
-	b.FormatHeader(s, file, line, now)
 
 	b.Write(qMsg)
 

textlogger/textlogger_test.go

@@ -17,7 +17,9 @@ limitations under the License.
 package textlogger_test
 
 import (
+	"bytes"
 	"errors"
+	"fmt"
 	"os"
 	"time"
 
@@ -65,11 +67,11 @@ func ExampleNewLogger() {
 	someHelper(logger, "hello world")
 
 	// Output:
-	// I1224 12:30:40.000000     123 textlogger_test.go:54] "A debug message"
-	// I1224 12:30:40.000000     123 textlogger_test.go:56] "An info message"
-	// E1224 12:30:40.000000     123 textlogger_test.go:57] "An error" err="fake error"
-	// I1224 12:30:40.000000     123 textlogger_test.go:58] "With values" int=42 duration="1s" float=3.12 coordinates={"X":100,"Y":200} variables={"A":1,"B":2}
-	// I1224 12:30:40.000000     123 textlogger_test.go:65] "hello world"
+	// I1224 12:30:40.000000     123 textlogger_test.go:56] "A debug message"
+	// I1224 12:30:40.000000     123 textlogger_test.go:58] "An info message"
+	// E1224 12:30:40.000000     123 textlogger_test.go:59] "An error" err="fake error"
+	// I1224 12:30:40.000000     123 textlogger_test.go:60] "With values" int=42 duration="1s" float=3.12 coordinates={"X":100,"Y":200} variables={"A":1,"B":2}
+	// I1224 12:30:40.000000     123 textlogger_test.go:67] "hello world"
 }
 
 func someHelper(logger klog.Logger, msg string) {
@@ -108,3 +110,20 @@ func ExampleBacktrace() {
 	// I1224 12:30:40.000000     123 ???:1] "First message"
 	// I1224 12:30:40.000000     123 fake.go:42] "Second message"
 }
+
+func ExampleWithHeader() {
+	var buffer bytes.Buffer
+	config := textlogger.NewConfig(
+		textlogger.WithHeader(false),
+		textlogger.Output(&buffer),
+	)
+	logger := textlogger.NewLogger(config)
+
+	logger.Error(errors.New("fake error"), "Something broke", "id", 42)
+	logger.WithName("name").WithValues("key", "value").WithCallDepth(0).Info("Still no header")
+	fmt.Println(buffer.String())
+
+	// Output:
+	// "Something broke" err="fake error" id=42
+	// "Still no header" logger="name" key="value"
+}