Add test for cyclic connector use.

Author: sudiptob2

otelcol/collector_test.go

@@ -511,6 +511,14 @@ func TestCollectorDryRun(t *testing.T) {
 			},
 			expectedErr: `failed to build pipelines: connector "nop/connector1" used as exporter in [logs/in2] pipeline but not used in any supported receiver pipeline`,
 		},
+		"cyclic_connector": {
+			settings: CollectorSettings{
+				BuildInfo:              component.NewDefaultBuildInfo(),
+				Factories:              nopFactories,
+				ConfigProviderSettings: newDefaultConfigProviderSettings(t, []string{filepath.Join("testdata", "otelcol-cyclic-connector.yaml")}),
+			},
+			expectedErr: `failed to build pipelines: cycle detected: connector "nop/forward" (traces to traces) -> connector "nop/forward" (traces to traces)`,
+		},
 	}
 
 	for name, test := range tests {

otelcol/testdata/otelcol-cyclic-connector.yaml

@@ -0,0 +1,19 @@
+receivers:
+  nop:
+
+exporters:
+  nop:
+
+connectors:
+  nop/forward:
+
+service:
+  pipelines:
+    traces/in:
+      receivers: [nop/forward]
+      processors: [ ]
+      exporters: [nop/forward]
+    traces/out:
+      receivers: [nop/forward]
+      processors: [ ]
+      exporters: [nop/forward]