From 5a8ca639e95b96d4256e967deb8864e0898b9a1f Mon Sep 17 00:00:00 2001
From: sachinsharma <sachinsharma3191@gmail.com>
Date: Fri, 19 Sep 2025 00:36:02 -0700
Subject: [PATCH] feat(logfmt): strip ANSI escapes by default (#14199)

---
 pkg/logql/log/parser.go                 | 10 +++
 pkg/logql/log/parser_decolorize_test.go | 96 +++++++++++++++++++++++++
 2 files changed, 106 insertions(+)
 create mode 100644 pkg/logql/log/parser_decolorize_test.go

diff --git a/pkg/logql/log/parser.go b/pkg/logql/log/parser.go
index 035241182b234..53f562ffec9e8 100644
--- a/pkg/logql/log/parser.go
+++ b/pkg/logql/log/parser.go
@@ -374,6 +374,7 @@ func NewLogfmtParser(strict, keepEmpty bool) *LogfmtParser {
 }
 
 func (l *LogfmtParser) Process(_ int64, line []byte, lbs *LabelsBuilder) ([]byte, bool) {
+	line = StripANSI(line)
 	parserHints := lbs.ParserLabelHints()
 	if parserHints.NoLabels() {
 		return line, true
@@ -842,3 +843,12 @@ func (u *UnpackParser) unpack(entry []byte, lbs *LabelsBuilder) ([]byte, error)
 	}
 	return entry, nil
 }
+
+var ansiRE = regexp.MustCompile(`\x1b\[[0-9;?]*[ -/]*[@-~]`)
+
+func StripANSI(b []byte) []byte {
+	if len(b) == 0 || !bytes.Contains(b, []byte{0x1b, '['}) {
+		return b
+	}
+	return ansiRE.ReplaceAll(b, nil)
+}
diff --git a/pkg/logql/log/parser_decolorize_test.go b/pkg/logql/log/parser_decolorize_test.go
new file mode 100644
index 0000000000000..bbf41274da9f1
--- /dev/null
+++ b/pkg/logql/log/parser_decolorize_test.go
@@ -0,0 +1,96 @@
+package log
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/prometheus/prometheus/model/labels"
+)
+
+func TestStripANSI(t *testing.T) {
+	cases := []struct {
+		in   []byte
+		want []byte
+	}{
+		{[]byte("\x1b[32mhello\x1b[0m"), []byte("hello")},
+		{[]byte("\x1b[1;31merr\x1b[0m=bad"), []byte("err=bad")},
+		{[]byte("clean"), []byte("clean")},
+		{[]byte{}, []byte{}},
+	}
+
+	for i, tc := range cases {
+		got := StripANSI(tc.in)
+		if bytes.Contains(got, []byte{0x1b}) {
+			t.Fatalf("case %d: expected no ESC in %q", i, got)
+		}
+		if !bytes.Equal(got, tc.want) {
+			t.Fatalf("case %d: got %q, want %q", i, got, tc.want)
+		}
+	}
+}
+
+func makeLBS() *LabelsBuilder {
+	b := NewBaseLabelsBuilder()
+	baseLabels := labels.Labels{} // or use the actual type for base labels; empty set rather than nil
+	return b.ForLabels(baseLabels, 0)
+}
+
+func TestLogfmtProcess_StripsANSIFromReturnedLine(t *testing.T) {
+	p := NewLogfmtParser(false, true)
+	lbs := makeLBS()
+
+	colored := []byte("\x1b[32mlevel\x1b[0m=info msg=\"ok\"")
+	gotLine, ok := p.Process(0, colored, lbs)
+	if !ok {
+		t.Fatalf("Process returned ok=false for colored logfmt line")
+	}
+	if bytes.Contains(gotLine, []byte{0x1b}) {
+		t.Fatalf("returned line still contained ANSI escapes: %q", gotLine)
+	}
+	if !bytes.Contains(gotLine, []byte("level=info")) {
+		t.Fatalf("returned line lost expected content, got: %q", gotLine)
+	}
+}
+
+func TestLogfmtProcess_ParsesColoredKeyAndValue(t *testing.T) {
+	p := NewLogfmtParser(false, true)
+	lbs := makeLBS()
+
+	line := []byte("\x1b[32mlevel\x1b[0m=info \x1b[36mstatus\x1b[0m=200 msg=\"\x1b[31mhot\x1b[0m\"")
+
+	_, ok := p.Process(0, line, lbs)
+	if !ok {
+		t.Fatalf("Process returned ok=false")
+	}
+
+	m, _ := lbs.Map()
+
+	if got := m["level"]; string(got) != "info" {
+		t.Fatalf("expected level=info, got %q", got)
+	}
+	if got := m["status"]; string(got) != "200" {
+		t.Fatalf("expected status=200, got %q", got)
+	}
+	if got := m["msg"]; string(got) != "hot" {
+		t.Fatalf("expected msg=hot, got %q", got)
+	}
+}
+
+func TestLogfmtProcess_NoANSI_Idempotent(t *testing.T) {
+	p := NewLogfmtParser(true, true)
+	lbs := makeLBS()
+
+	in := []byte("level=debug a=1 b=\"two words\"")
+	out, ok := p.Process(0, in, lbs)
+	if !ok {
+		t.Fatalf("Process returned ok=false for clean line")
+	}
+	if !bytes.Equal(in, out) {
+		t.Fatalf("expected returned line to equal input for clean lines.\n in=%q\nout=%q", in, out)
+	}
+
+	m, _ := lbs.Map()
+	if string(m["level"]) != "debug" || string(m["a"]) != "1" || string(m["b"]) != "two words" {
+		t.Fatalf("unexpected parsed labels: %#v", m)
+	}
+}