Fix bug in Config.Update

Incoming config updates with slices smaller than the current slice
didn't resize the current slice, resulting in undesirable values
in the tail of the slice.

config/config.go

@@ -64,10 +64,23 @@ func New(cfg *common.Config) (Config, error) {
 }
 
 func (c *Config) Update(cfg *common.Config) error {
+	// Overwrite the parts of the config received in the update body.
 	if err := cfg.Unpack(&c); err != nil {
 		return err
 	}
 
+	// Shorter slices in the incoming config won't resize the corresponding slice
+	// in the current config, leaving undesirable values in the tail of the slice.
+	// This needs to be handled.
+	uc, err := New(cfg)
+	if err != nil {
+		return err
+	}
+
+	for i := range c.Streams {
+		c.Streams[i].DataYaml.ActivatedRules.CISK8S = uc.Streams[i].DataYaml.ActivatedRules.CISK8S
+	}
+
 	return nil
 }
 

config/config_test.go

@@ -41,8 +41,8 @@ func (s *ConfigTestSuite) SetupTest() {
 
 func (s *ConfigTestSuite) TestNew() {
 	var tests = []struct {
-		config           string
-		expectedPatterns []string
+		config   string
+		expected []string
 	}{
 		{
 			`
@@ -54,8 +54,9 @@ func (s *ConfigTestSuite) TestNew() {
             - b
             - c
             - d
+            - e
 `,
-			[]string{"a", "b", "c", "d"},
+			[]string{"a", "b", "c", "d", "e"},
 		},
 	}
 
@@ -66,7 +67,92 @@ func (s *ConfigTestSuite) TestNew() {
 		c, err := New(cfg)
 		s.NoError(err)
 
-		s.Equal(test.expectedPatterns, c.Streams[0].DataYaml.ActivatedRules.CISK8S)
+		s.Equal(test.expected, c.Streams[0].DataYaml.ActivatedRules.CISK8S)
+	}
+}
+
+func (s *ConfigTestSuite) TestUpdate() {
+	config := `
+    streams:
+      - data_yaml:
+          activated_rules:
+            cis_k8s:
+              - a
+              - b
+              - c
+              - d
+              - e`
+
+	var tests = []struct {
+		update   string
+		expected []string
+	}{
+		{
+			`
+          streams:
+            - data_yaml:
+                activated_rules:
+                  cis_k8s:
+                    - a
+                    - b
+                    - c
+                    - d
+        `,
+			[]string{"a", "b", "c", "d"},
+		},
+		{
+			`
+          streams:
+            - data_yaml:
+                activated_rules:
+                  cis_k8s:
+                    - b
+                    - c
+                    - d
+                    - e
+                    - f
+        `,
+			[]string{"b", "c", "d", "e", "f"},
+		},
+		{
+			`
+          streams:
+            - data_yaml:
+                activated_rules:
+                  cis_k8s: []
+        `,
+			[]string{},
+		},
+		{
+			`
+          streams:
+            - data_yaml:
+                activated_rules:
+                  cis_k8s:
+                    - a
+                    - b
+                    - c
+                    - d
+                    - e
+        `,
+			[]string{"a", "b", "c", "d", "e"},
+		},
+	}
+
+	cfg, err := common.NewConfigFrom(config)
+	s.NoError(err)
+
+	c, err := New(cfg)
+	s.NoError(err)
+
+	for _, test := range tests {
+		cfg, err := common.NewConfigFrom(test.update)
+		s.NoError(err)
+
+		err = c.Update(cfg)
+		s.NoError(err)
+
+		s.Equal(test.expected, c.Streams[0].DataYaml.ActivatedRules.CISK8S)
 	}
 }