From c8a9e88a0e1ac122ef1f35fbb23f96a10f21757e Mon Sep 17 00:00:00 2001
From: Ruben van Staden <ruben.vanstaden@elastic.co>
Date: Sun, 18 Aug 2024 21:21:02 -0400
Subject: [PATCH] set event message to error message if empty

---
 model/modelprocessor/errormessage.go      |  3 +
 model/modelprocessor/errormessage_test.go | 76 +++++++++++++++++++----
 2 files changed, 67 insertions(+), 12 deletions(-)

diff --git a/model/modelprocessor/errormessage.go b/model/modelprocessor/errormessage.go
index 6094bbe9..1d4134e4 100644
--- a/model/modelprocessor/errormessage.go
+++ b/model/modelprocessor/errormessage.go
@@ -33,6 +33,9 @@ func (s SetErrorMessage) ProcessBatch(ctx context.Context, b *modelpb.Batch) err
 		event := (*b)[i]
 		if event.Error != nil {
 			event.Error.Message = s.setErrorMessage(event)
+			if event.GetMessage() == "" {
+				event.Message = event.Error.Message
+			}
 		}
 	}
 	return nil
diff --git a/model/modelprocessor/errormessage_test.go b/model/modelprocessor/errormessage_test.go
index dd94d82e..c03170c4 100644
--- a/model/modelprocessor/errormessage_test.go
+++ b/model/modelprocessor/errormessage_test.go
@@ -27,38 +27,90 @@ import (
 	"github.com/elastic/apm-data/model/modelprocessor"
 )
 
+// Copy the error message to the event message if event message is empty.
 func TestSetErrorMessage(t *testing.T) {
 	tests := []struct {
-		input   *modelpb.Error
-		message string
+		input    *modelpb.Error
+		expected string
 	}{{
-		input:   &modelpb.Error{},
-		message: "",
+		input:    &modelpb.Error{},
+		expected: "",
 	}, {
-		input:   &modelpb.Error{Log: &modelpb.ErrorLog{Message: "log_message"}},
-		message: "log_message",
+		input:    &modelpb.Error{Log: &modelpb.ErrorLog{Message: "log_message"}},
+		expected: "log_message",
 	}, {
-		input:   &modelpb.Error{Exception: &modelpb.Exception{Message: "exception_message"}},
-		message: "exception_message",
+		input:    &modelpb.Error{Exception: &modelpb.Exception{Message: "exception_message"}},
+		expected: "exception_message",
 	}, {
 		input: &modelpb.Error{
 			Log:       &modelpb.ErrorLog{},
 			Exception: &modelpb.Exception{Message: "exception_message"},
 		},
-		message: "exception_message",
+		expected: "exception_message",
 	}, {
 		input: &modelpb.Error{
 			Log:       &modelpb.ErrorLog{Message: "log_message"},
 			Exception: &modelpb.Exception{Message: "exception_message"},
 		},
-		message: "log_message",
+		expected: "log_message",
 	}}
-
 	for _, test := range tests {
 		batch := modelpb.Batch{{Error: test.input}}
 		processor := modelprocessor.SetErrorMessage{}
 		err := processor.ProcessBatch(context.Background(), &batch)
 		assert.NoError(t, err)
-		assert.Equal(t, test.message, batch[0].Error.Message)
+		assert.Equal(t, test.expected, batch[0].Message)
+		assert.Equal(t, test.expected, batch[0].Error.Message)
+	}
+}
+
+// If event message is non-empty, do not override with error message.
+func TestSetEventMessage(t *testing.T) {
+	tests := []struct {
+		input    *modelpb.APMEvent
+		expected string
+	}{{
+		input: &modelpb.APMEvent{
+			Message: "message",
+		},
+		expected: "message",
+	}, {
+		input: &modelpb.APMEvent{
+			Error:   &modelpb.Error{Log: &modelpb.ErrorLog{Message: "log_message"}},
+			Message: "message",
+		},
+		expected: "message",
+	}, {
+		input: &modelpb.APMEvent{
+			Error:   &modelpb.Error{Exception: &modelpb.Exception{Message: "exception_message"}},
+			Message: "message",
+		},
+		expected: "message",
+	}, {
+		input: &modelpb.APMEvent{
+			Error: &modelpb.Error{
+				Log:       &modelpb.ErrorLog{},
+				Exception: &modelpb.Exception{Message: "exception_message"},
+			},
+			Message: "message",
+		},
+		expected: "message",
+	}, {
+		input: &modelpb.APMEvent{
+			Error: &modelpb.Error{
+				Log:       &modelpb.ErrorLog{Message: "log_message"},
+				Exception: &modelpb.Exception{Message: "exception_message"},
+			},
+			Message: "message",
+		},
+		expected: "message",
+	}}
+
+	for _, test := range tests {
+		batch := modelpb.Batch{test.input}
+		processor := modelprocessor.SetErrorMessage{}
+		err := processor.ProcessBatch(context.Background(), &batch)
+		assert.NoError(t, err)
+		assert.Equal(t, test.expected, batch[0].Message)
 	}
 }