[receiver/podman] remove config Validate call on start (open-telemetr…

…y#33555)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->

Configuration validation is done during collector's startup, making it
redundant when being called inside component's logic. This PR removes
the Validate call done during Podman's receiver start function.

**Link to tracking Issue:** <Issue number if applicable>

open-telemetry#33498

Context:
https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/32981/files#r1621849257

**Testing:** <Describe what testing was performed and which tests were
added.>
Tests moved to the `config_test.go` file following the testdata
strategy.

**Documentation:** <Describe the documentation added.>

---------

Co-authored-by: Andrzej Stencel <[email protected]>

receiver/podmanreceiver/config_test.go

@@ -24,9 +24,9 @@ func TestLoadConfig(t *testing.T) {
 	require.NoError(t, err)
 
 	tests := []struct {
-		id          component.ID
-		expected    component.Config
-		expectedErr error
+		id             component.ID
+		expected       component.Config
+		expectedErrMsg string
 	}{
 		{
 			id: component.NewIDWithName(metadata.Type, ""),
@@ -54,6 +54,14 @@ func TestLoadConfig(t *testing.T) {
 				MetricsBuilderConfig: metadata.DefaultMetricsBuilderConfig(),
 			},
 		},
+		{
+			id:             component.NewIDWithName(metadata.Type, "empty_endpoint"),
+			expectedErrMsg: "config.Endpoint must be specified",
+		},
+		{
+			id:             component.NewIDWithName(metadata.Type, "invalid_collection_interval"),
+			expectedErrMsg: `config.CollectionInterval must be specified; "collection_interval": requires positive value`,
+		},
 	}
 
 	for _, tt := range tests {
@@ -65,6 +73,11 @@ func TestLoadConfig(t *testing.T) {
 			require.NoError(t, err)
 			require.NoError(t, sub.Unmarshal(cfg))
 
+			if tt.expectedErrMsg != "" {
+				assert.EqualError(t, component.ValidateConfig(cfg), tt.expectedErrMsg)
+				return
+			}
+
 			assert.NoError(t, component.ValidateConfig(cfg))
 			assert.Equal(t, tt.expected, cfg)
 		})

receiver/podmanreceiver/receiver.go

@@ -66,11 +66,6 @@ func createMetricsReceiver(
 }
 
 func (r *metricsReceiver) start(ctx context.Context, _ component.Host) error {
-	err := r.config.Validate()
-	if err != nil {
-		return err
-	}
-
 	podmanClient, err := r.clientFactory(r.set.Logger, r.config)
 	if err != nil {
 		return err

receiver/podmanreceiver/receiver_test.go

@@ -37,13 +37,7 @@ func TestErrorsInStart(t *testing.T) {
 	assert.NotNil(t, recv)
 	err := recv.start(context.Background(), componenttest.NewNopHost())
 	require.Error(t, err)
-	assert.Equal(t, "config.Endpoint must be specified", err.Error())
-
-	recv = newMetricsReceiver(receivertest.NewNopSettings(), &Config{Endpoint: "someEndpoint"}, nil)
-	assert.NotNil(t, recv)
-	err = recv.start(context.Background(), componenttest.NewNopHost())
-	require.Error(t, err)
-	assert.Equal(t, "config.CollectionInterval must be specified", err.Error())
+	assert.Equal(t, `unable to create connection. "" is not a supported schema`, err.Error())
 }
 
 func TestScraperLoop(t *testing.T) {

receiver/podmanreceiver/testdata/config.yaml

@@ -3,3 +3,7 @@ podman_stats/all:
   endpoint: http://example.com/
   collection_interval: 2s
   timeout: 20s
+podman_stats/empty_endpoint:
+  endpoint: ""
+podman_stats/invalid_collection_interval:
+  collection_interval: 0s