test: add test cases covering builder options

builder.go

@@ -45,6 +45,8 @@ func WithLabelNameMaxLen(maxLen int) BuilderOption {
 //   - [Builder.LabelStringQuote]
 //   - [Builder.LabelError]
 //   - [Builder.LabelErrorQuote]
+//   - [Builder.LabelNamedError]
+//   - [Builder.LabelNamedErrorQuote]
 //
 // Zero means no length limit.
 //
@@ -139,7 +141,7 @@ func (b *Builder) labelString(name, value string, escapeQuotes bool) *Builder {
 	if !b.isValidLabelName(name) {
 		return b
 	}
-	if !b.isValidLabelValue(value) {
+	if !b.isValidLabelValue(name, value) {
 		return b
 	}
 	b.buf = b.appendCommaOrLeftBracket()
@@ -429,14 +431,14 @@ func (b *Builder) isValidLabelName(name string) bool {
 // label value len must also be less than the provided max len value.
 //
 // In case of an invalid label value, a log line containing the reasons will be output to [os.Stderr].
-func (b *Builder) isValidLabelValue(value string) bool {
+func (b *Builder) isValidLabelValue(name, value string) bool {
 	lv := len(value)
 	if lv == 0 {
-		log.Printf("vimebu: metric %q, label name: %q, received empty label value - skipping", b.buf, value)
+		log.Printf("vimebu: metric %q, label name: %q, received empty label value - skipping", b.buf, name)
 		return false
 	}
 	if b.labelValueMaxLen > 0 && lv > b.labelValueMaxLen {
-		log.Printf("vimebu: metric %q, label name %q, label value %q len exceeds set limit of %d - skipping", b.buf, value, value, b.labelNameMaxLen)
+		log.Printf("vimebu: metric %q, label name %q, label value %q len exceeds set limit of %d - skipping", b.buf, name, value, b.labelNameMaxLen)
 		return false
 	}
 	return true

builder_test.go

@@ -1,7 +1,11 @@
 package vimebu
 
 import (
+	"bytes"
 	"fmt"
+	"log"
+	"os"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -308,6 +312,50 @@ func TestBuilderParallel(t *testing.T) {
 	require.NoError(t, eg.Wait())
 }
 
+func captureLogOutput(f func()) []string {
+	var buf bytes.Buffer
+	log.SetOutput(&buf)
+	f()
+	log.SetOutput(os.Stderr)
+	return strings.FieldsFunc(buf.String(), func(c rune) bool {
+		return c == '\n' || c == '\r'
+	})
+}
+
+func TestBuilderOptionsWithLabelNameMaxLen(t *testing.T) {
+	logLines := captureLogOutput(func() {
+		metric := Metric("test_options", WithLabelNameMaxLen(3)).
+			LabelString("one", "one").
+			LabelString("two", "two").
+			LabelString("three", "three").                         // Will be skipped.
+			LabelStringQuote("four", `fo"ur`).                     // Will be skipped.
+			LabelError(fmt.Errorf("something went wrong")).        // Will be skipped.
+			LabelErrorQuote(fmt.Errorf(`"something" went wrong`)). // Will be skipped.
+			LabelNamedError("err", fmt.Errorf("mayday")).
+			String()
+		require.Equal(t, `test_options{one="one",two="two",err="mayday"}`, metric)
+	})
+
+	require.Len(t, logLines, 4) // One log line for each label name exceeding the limit of 3 bytes, thus getting skipped.
+}
+
+func TestBuilderOptionsWithLabelValueMaxLen(t *testing.T) {
+	logLines := captureLogOutput(func() {
+		metric := Metric("test_options", WithLabelValueMaxLen(5)).
+			LabelString("one", "one").
+			LabelString("two", "two").
+			LabelString("three", "three").
+			LabelStringQuote("four", `fo"ur`).
+			LabelError(fmt.Errorf("something went wrong")).        // Will be skipped.
+			LabelErrorQuote(fmt.Errorf(`"something" went wrong`)). // Will be skipped.
+			LabelNamedError("err", fmt.Errorf("mayday")).          // Will be skipped.
+			String()
+		require.Equal(t, `test_options{one="one",two="two",three="three",four="fo\"ur"}`, metric)
+	})
+
+	require.Len(t, logLines, 3) // One log line for each label value exceeding the limit of 5 bytes, thus getting skipped.
+}
+
 func BenchmarkBuilderTestCasesParallel(b *testing.B) {
 	b.ReportAllocs()
 
@@ -341,7 +389,7 @@ func BenchmarkBuilderTestCasesSequential(b *testing.B) {
 }
 
 func doBenchmarkCase(in input) {
-	builder := Metric(in.name)
+	builder := Metric(in.name, WithLabelNameMaxLen(100), WithLabelValueMaxLen(100))
 	for _, label := range in.labels {
 		addLabelAnyToBuilder(builder, label)
 	}