[confmap] confmap honors Unmarshal methods on config embedded structs.

.chloggen/support_embedded_structs_confmap.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# 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: confmap honors `Unmarshal` methods on config embedded structs.
+
+# One or more tracking issues or pull requests related to the change
+issues: [6671]
+
+# (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:
+
+# 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: []

cmd/mdatagen/metricdata.go

@@ -125,7 +125,7 @@ func (d *gauge) Unmarshal(parser *confmap.Conf) error {
 	if err := d.MetricValueType.Unmarshal(parser); err != nil {
 		return err
 	}
-	return parser.Unmarshal(d)
+	return parser.Unmarshal(d, confmap.WithIgnoreUnused())
 }
 
 func (d gauge) Type() string {
@@ -155,7 +155,7 @@ func (d *sum) Unmarshal(parser *confmap.Conf) error {
 	if err := d.MetricValueType.Unmarshal(parser); err != nil {
 		return err
 	}
-	return parser.Unmarshal(d)
+	return parser.Unmarshal(d, confmap.WithIgnoreUnused())
 }
 
 // TODO: Currently, this func will not be called because of https://github.com/open-telemetry/opentelemetry-collector/issues/6671. Uncomment function and

confmap/confmap.go

@@ -157,6 +157,7 @@ func decodeConfig(m *Conf, result any, errorUnused bool) error {
 			mapstructure.StringToTimeDurationHookFunc(),
 			mapstructure.TextUnmarshallerHookFunc(),
 			unmarshalerHookFunc(result),
+			embeddedStructsHookFunc(result),
 			zeroSliceHookFunc(),
 		),
 	}
@@ -261,6 +262,41 @@ func mapKeyStringToMapKeyTextUnmarshalerHookFunc() mapstructure.DecodeHookFuncTy
 	}
 }
 
+func embeddedStructsHookFunc(_ any) mapstructure.DecodeHookFuncValue {
+	return func(from reflect.Value, to reflect.Value) (any, error) {
+		if to.Type().Kind() != reflect.Struct {
+			return from.Interface(), nil
+		}
+
+		finalFrom := from.Interface()
+
+		for i := 0; i < to.Type().NumField(); i++ {
+			if to.Type().Field(i).IsExported() && to.Type().Field(i).Anonymous {
+				f := to.Field(i)
+				if unmarshaler, ok := f.Addr().Interface().(Unmarshaler); ok {
+					fromMap, ok := finalFrom.(map[string]any)
+					if !ok {
+						return from.Interface(), nil
+					}
+					if err := unmarshaler.Unmarshal(NewFromStringMap(fromMap)); err != nil {
+						return nil, err
+					}
+					conf := New()
+					if err := conf.Marshal(unmarshaler); err != nil {
+						return nil, err
+					}
+					resultMap := conf.ToStringMap()
+					for k, v := range resultMap {
+						fromMap[k] = v
+					}
+					finalFrom = fromMap
+				}
+			}
+		}
+		return finalFrom, nil
+	}
+}
+
 // Provides a mechanism for individual structs to define their own unmarshal logic,
 // by implementing the Unmarshaler interface.
 func unmarshalerHookFunc(result any) mapstructure.DecodeHookFuncValue {

confmap/confmap_test.go

@@ -309,8 +309,41 @@ func newConfFromFile(t testing.TB, fileName string) map[string]any {
 }
 
 type testConfig struct {
-	Next    *nextConfig `mapstructure:"next"`
-	Another string      `mapstructure:"another"`
+	Next            *nextConfig `mapstructure:"next"`
+	Another         string      `mapstructure:"another"`
+	EmbeddedConfig  `mapstructure:",squash"`
+	EmbeddedConfig2 `mapstructure:",squash"`
+}
+
+type testConfigWithoutUnmarshaler struct {
+	Next            *nextConfig `mapstructure:"next"`
+	Another         string      `mapstructure:"another"`
+	EmbeddedConfig  `mapstructure:",squash"`
+	EmbeddedConfig2 `mapstructure:",squash"`
+}
+
+type EmbeddedConfig struct {
+	Some string `mapstructure:"some"`
+}
+
+func (ec *EmbeddedConfig) Unmarshal(component *Conf) error {
+	if err := component.Unmarshal(ec, WithIgnoreUnused()); err != nil {
+		return err
+	}
+	ec.Some += " is also called"
+	return nil
+}
+
+type EmbeddedConfig2 struct {
+	Some2 string `mapstructure:"some_2"`
+}
+
+func (ec *EmbeddedConfig2) Unmarshal(component *Conf) error {
+	if err := component.Unmarshal(ec, WithIgnoreUnused()); err != nil {
+		return err
+	}
+	ec.Some2 += " also called2"
+	return nil
 }
 
 func (tc *testConfig) Unmarshal(component *Conf) error {
@@ -340,12 +373,34 @@ func TestUnmarshaler(t *testing.T) {
 			"string": "make sure this",
 		},
 		"another": "make sure this",
+		"some":    "make sure this",
+		"some_2":  "this better be",
 	})
 
 	tc := &testConfig{}
 	assert.NoError(t, cfgMap.Unmarshal(tc))
 	assert.Equal(t, "make sure this", tc.Another)
 	assert.Equal(t, "make sure this is called", tc.Next.String)
+	assert.Equal(t, "make sure this is also called", tc.EmbeddedConfig.Some)
+	assert.Equal(t, "this better be also called2", tc.EmbeddedConfig2.Some2)
+}
+
+func TestEmbeddedUnmarshaler(t *testing.T) {
+	cfgMap := NewFromStringMap(map[string]any{
+		"next": map[string]any{
+			"string": "make sure this",
+		},
+		"another": "make sure this",
+		"some":    "make sure this",
+		"some_2":  "this better be",
+	})
+
+	tc := &testConfigWithoutUnmarshaler{}
+	assert.NoError(t, cfgMap.Unmarshal(tc))
+	assert.Equal(t, "make sure this", tc.Another)
+	assert.Equal(t, "make sure this is called", tc.Next.String)
+	assert.Equal(t, "make sure this is also called", tc.EmbeddedConfig.Some)
+	assert.Equal(t, "this better be also called2", tc.EmbeddedConfig2.Some2)
 }
 
 func TestUnmarshalerKeepAlreadyInitialized(t *testing.T) {