From 437abf27fb45efbccf182b537cc9b9b2290e35e8 Mon Sep 17 00:00:00 2001
From: Sebastiaan van Stijn <github@gone.nl>
Date: Mon, 21 Sep 2026 17:12:55 +0200
Subject: [PATCH] otel: add WithSpanIDField option to Logrus hook

Add WithSpanIDField to allow callers to include the active span ID in
Logrus entries, independently of the existing trace ID option.

Extend the span-context field tests to cover trace ID, span ID, both
fields, disabled options, and entries without a span or context.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
---
 otel/log.go      | 12 ++++++++++
 otel/log_test.go | 60 +++++++++++++++++++++++++++++++++++++-----------
 2 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/otel/log.go b/otel/log.go
index 3233eff..25fca2b 100644
--- a/otel/log.go
+++ b/otel/log.go
@@ -62,6 +62,14 @@ func WithTraceIDField(enabled bool) HookOpt {
 	}
 }
 
+// WithSpanIDField configures the hook to add the span ID of the active span
+// to log entries.
+func WithSpanIDField(enabled bool) HookOpt {
+	return func(h *LogrusHook) {
+		h.enableSpanIDField = enabled
+	}
+}
+
 // WithLevel configures the minimum log level handled by the hook.
 // Entries below this level are ignored.
 func WithLevel(level log.Level) HookOpt {
@@ -90,6 +98,7 @@ func WithErrorStatusLevel(level log.Level) HookOpt {
 // [logrus.Hook]: https://github.com/sirupsen/logrus/blob/v1.9.3/hooks.go#L3-L11
 type LogrusHook struct {
 	enableTraceIDField bool
+	enableSpanIDField  bool
 	errorStatusLevel   *log.Level
 	levels             []log.Level
 }
@@ -117,6 +126,9 @@ func (h *LogrusHook) Fire(entry *log.Entry) error {
 	if h.enableTraceIDField {
 		entry.Data["trace_id"] = spanCtx.TraceID().String()
 	}
+	if h.enableSpanIDField {
+		entry.Data["span_id"] = spanCtx.SpanID().String()
+	}
 
 	if !span.IsRecording() {
 		return nil
diff --git a/otel/log_test.go b/otel/log_test.go
index d3755b5..c4f61cc 100644
--- a/otel/log_test.go
+++ b/otel/log_test.go
@@ -32,7 +32,10 @@ import (
 	"go.opentelemetry.io/otel/trace"
 )
 
-const expectedTraceIDStr = "0102030405060708090a0b0c0d0e0f10"
+const (
+	expectedTraceIDStr = "0102030405060708090a0b0c0d0e0f10"
+	expectedSpanIDStr  = "0102030405060708"
+)
 
 var (
 	testTraceID = trace.TraceID{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}
@@ -54,33 +57,49 @@ func (s *testSpan) IsRecording() bool                     { return true }
 func (s *testSpan) AddEvent(string, ...trace.EventOption) {}
 func (s *testSpan) SetStatus(code codes.Code, _ string)   { s.status = code }
 
-func TestLogrusHookTraceID(t *testing.T) {
+func TestLogrusHookSpanContextFields(t *testing.T) {
 	tests := []struct {
 		name        string
-		enableOpt   bool
+		traceID     bool
+		spanID      bool
 		nilContext  bool
 		withSpan    bool
 		expectedTID string
+		expectedSID string
 	}{
 		{
 			name:        "TraceIDInjected",
-			enableOpt:   true,
+			traceID:     true,
+			withSpan:    true,
+			expectedTID: expectedTraceIDStr,
+		},
+		{
+			name:        "SpanIDInjected",
+			spanID:      true,
+			withSpan:    true,
+			expectedSID: expectedSpanIDStr,
+		},
+		{
+			name:        "TraceAndSpanIDInjected",
+			traceID:     true,
+			spanID:      true,
 			withSpan:    true,
 			expectedTID: expectedTraceIDStr,
+			expectedSID: expectedSpanIDStr,
 		},
 		{
-			name:      "TraceIDNotInjected_OptionDisabled",
-			enableOpt: false,
-			withSpan:  true,
+			name:     "FieldsNotInjected_OptionsDisabled",
+			withSpan: true,
 		},
 		{
-			name:      "TraceIDNotInjected_NoSpan",
-			enableOpt: true,
-			withSpan:  false,
+			name:    "FieldsNotInjected_NoSpan",
+			traceID: true,
+			spanID:  true,
 		},
 		{
-			name:       "TraceIDNotInjected_NoContext",
-			enableOpt:  true,
+			name:       "FieldsNotInjected_NoContext",
+			traceID:    true,
+			spanID:     true,
 			nilContext: true,
 		},
 	}
@@ -89,7 +108,10 @@ func TestLogrusHookTraceID(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			logger := logrus.New()
 			logger.SetOutput(io.Discard)
-			logger.AddHook(otel.NewLogrusHook(otel.WithTraceIDField(tc.enableOpt)))
+			logger.AddHook(otel.NewLogrusHook(
+				otel.WithTraceIDField(tc.traceID),
+				otel.WithSpanIDField(tc.spanID),
+			))
 			testHook := test.NewLocal(logger)
 
 			switch {
@@ -123,6 +145,18 @@ func TestLogrusHookTraceID(t *testing.T) {
 			} else if ok {
 				t.Errorf(`unexpected "trace_id" field: %v`, traceID)
 			}
+
+			spanID, ok := entry.Data["span_id"]
+			if tc.expectedSID != "" {
+				if !ok {
+					t.Fatal(`expected "span_id" field`)
+				}
+				if spanID != tc.expectedSID {
+					t.Errorf(`"span_id" = %v; want %q`, spanID, tc.expectedSID)
+				}
+			} else if ok {
+				t.Errorf(`unexpected "span_id" field: %v`, spanID)
+			}
 		})
 	}
 }