Fix AMQP09 panic when exchangeDeclareArgs is nil - issue #3576

internal/impl/amqp09/output.go

@@ -251,8 +251,11 @@ func amqp09WriterFromParsed(conf *service.ParsedConfig, mgr *service.Resources)
 			if err != nil {
 				return nil, err
 			}
-			for key, value := range args {
-				a.exchangeDeclareArgs[key] = value
+			if len(args) > 0 {
+				a.exchangeDeclareArgs = make(amqp.Table)
+				for key, value := range args {
+					a.exchangeDeclareArgs[key] = value
+				}
 			}
 		}
 	}

internal/impl/amqp09/output_test.go

@@ -0,0 +1,80 @@
+// Copyright 2024 Redpanda Data, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package amqp09
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/redpanda-data/benthos/v4/public/service"
+)
+
+func TestAMQP09WriterFromParsedWithExchangeDeclareArgs(t *testing.T) {
+	// This test reproduces issue #3576 - panic when exchangeDeclareArgs is nil
+	// but we try to assign to it when exchange_declare.arguments is configured
+
+	configYAML := `
+urls:
+  - amqp://guest:guest@localhost:5672/
+exchange: test-exchange
+exchange_declare:
+  enabled: true
+  type: direct
+  durable: true
+  arguments:
+    alternate-exchange: my-ae
+    x-message-ttl: 60000
+`
+
+	spec := amqp09OutputSpec()
+	config, err := spec.ParseYAML(configYAML, nil)
+	require.NoError(t, err)
+
+	// This should not panic
+	writer, err := amqp09WriterFromParsed(config, service.MockResources())
+	require.NoError(t, err)
+	require.NotNil(t, writer)
+
+	// Verify that the arguments were properly set
+	require.NotNil(t, writer.exchangeDeclareArgs)
+	require.Equal(t, "my-ae", writer.exchangeDeclareArgs["alternate-exchange"])
+	require.Equal(t, "60000", writer.exchangeDeclareArgs["x-message-ttl"])
+}
+
+func TestAMQP09WriterFromParsedWithoutExchangeDeclareArgs(t *testing.T) {
+	// Test that configuration without arguments still works
+
+	configYAML := `
+urls:
+  - amqp://guest:guest@localhost:5672/
+exchange: test-exchange
+exchange_declare:
+  enabled: true
+  type: direct
+  durable: true
+`
+
+	spec := amqp09OutputSpec()
+	config, err := spec.ParseYAML(configYAML, nil)
+	require.NoError(t, err)
+
+	writer, err := amqp09WriterFromParsed(config, service.MockResources())
+	require.NoError(t, err)
+	require.NotNil(t, writer)
+
+	// exchangeDeclareArgs should remain nil when no arguments are configured
+	require.Nil(t, writer.exchangeDeclareArgs)
+}