Match error in tests and add changelog

Author: mx-psi

.chloggen/mx-psi_error-map.yaml

@@ -0,0 +1,26 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: confmap
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Surface YAML parsing errors when they happen at the top-level.
+
+# One or more tracking issues or pull requests related to the change
+issues: [12180]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  This adds context to some instances of the error "retrieved value (type=string) cannot be used as a Conf", which typically happens because of invalid YAML documents
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

confmap/provider_test.go

@@ -135,6 +135,9 @@ func TestNewRetrievedFromYAMLInvalidYAMLBytes(t *testing.T) {
 
 	_, err = ret.AsConf()
 	require.Error(t, err)
+	assert.EqualError(t, err,
+		"retrieved value (type=string) cannot be used as a Conf: assuming string type since contents are not valid YAML: yaml: line 1: did not find expected node content",
+	)
 
 	str, err := ret.AsString()
 	require.NoError(t, err)
@@ -151,6 +154,7 @@ func TestNewRetrievedFromYAMLInvalidAsMap(t *testing.T) {
 
 	_, err = ret.AsConf()
 	require.Error(t, err)
+	assert.EqualError(t, err, "retrieved value (type=string) cannot be used as a Conf")
 
 	str, err := ret.AsString()
 	require.NoError(t, err)

otelcol/collector_test.go

@@ -312,7 +312,7 @@ func TestCollectorStartInvalidConfig(t *testing.T) {
 		ConfigProviderSettings: newDefaultConfigProviderSettings(t, []string{filepath.Join("testdata", "otelcol-invalid.yaml")}),
 	})
 	require.NoError(t, err)
-	assert.Error(t, col.Run(context.Background()))
+	assert.EqualError(t, col.Run(context.Background()), "invalid configuration: service::pipelines::traces: references processor \"invalid\" which is not configured")
 }
 
 func TestNewCollectorInvalidConfigProviderSettings(t *testing.T) {