MergeFleetPolicy implementation using readConfigurationContent

pkg/config/nodetreemodel/config.go

@@ -634,7 +634,7 @@ func (c *ntmConfig) MergeConfig(in io.Reader) error {
 	}
 
 	other := newInnerNode(nil)
-	if err = c.readConfigurationContent(other, content); err != nil {
+	if err = c.readConfigurationContent(other, model.SourceFile, content); err != nil {
 		return err
 	}
 
@@ -663,8 +663,17 @@ func (c *ntmConfig) MergeFleetPolicy(configPath string) error {
 	}
 	defer in.Close()
 
-	// TODO: Implement merging, merge in the policy that was read
-	return c.logErrorNotImplemented("MergeFleetPolicy")
+	content, err := io.ReadAll(in)
+	if err != nil {
+		return err
+	}
+
+	other := newInnerNode(nil)
+	if err = c.readConfigurationContent(other, model.SourceFleetPolicies, content); err != nil {
+		return err
+	}
+
+	return c.root.Merge(other)
 }
 
 // AllSettings returns all settings from the config

pkg/config/nodetreemodel/config_test.go

@@ -575,3 +575,18 @@ func TestUnsetForSource(t *testing.T) {
       val:4, source:default`
 	assert.Equal(t, expect, txt)
 }
+
+func TestMergeFleetPolicy(t *testing.T) {
+	config := NewConfig("test", "TEST", strings.NewReplacer(".", "_")) // nolint: forbidigo
+	config.SetConfigType("yaml")
+	config.Set("foo", "bar", model.SourceFile)
+
+	file, err := os.CreateTemp("", "datadog.yaml")
+	assert.NoError(t, err, "failed to create temporary file: %w", err)
+	file.Write([]byte("foo: baz"))
+	err = config.MergeFleetPolicy(file.Name())
+	assert.NoError(t, err)
+
+	assert.Equal(t, "baz", config.Get("foo"))
+	assert.Equal(t, model.SourceFleetPolicies, config.GetSource("foo"))
+}

pkg/config/nodetreemodel/read_config_file.go

@@ -67,7 +67,7 @@ func (c *ntmConfig) ReadConfig(in io.Reader) error {
 	if err != nil {
 		return err
 	}
-	if err := c.readConfigurationContent(c.file, content); err != nil {
+	if err := c.readConfigurationContent(c.file, model.SourceFile, content); err != nil {
 		return err
 	}
 	return c.mergeAllLayers()
@@ -78,10 +78,10 @@ func (c *ntmConfig) readInConfig(filePath string) error {
 	if err != nil {
 		return err
 	}
-	return c.readConfigurationContent(c.file, content)
+	return c.readConfigurationContent(c.file, model.SourceFile, content)
 }
 
-func (c *ntmConfig) readConfigurationContent(target InnerNode, content []byte) error {
+func (c *ntmConfig) readConfigurationContent(target InnerNode, source model.Source, content []byte) error {
 	var inData map[string]interface{}
 
 	if strictErr := yaml.UnmarshalStrict(content, &inData); strictErr != nil {
@@ -90,7 +90,7 @@ func (c *ntmConfig) readConfigurationContent(target InnerNode, content []byte) e
 			return err
 		}
 	}
-	c.warnings = append(c.warnings, loadYamlInto(target, model.SourceFile, inData, "", c.schema)...)
+	c.warnings = append(c.warnings, loadYamlInto(target, source, inData, "", c.schema)...)
 	return nil
 }
 
@@ -142,7 +142,7 @@ func loadYamlInto(dest InnerNode, source model.Source, inData map[string]interfa
 				// Both default and dest have a child but they conflict in type. This should never happen.
 				warnings = append(warnings, "invalid tree: default and dest tree don't have the same layout")
 			} else {
-				dest.InsertChildNode(key, newLeafNode(value, model.SourceFile))
+				dest.InsertChildNode(key, newLeafNode(value, source))
 			}
 			continue
 		}