feat(config): default configuration with merge support for downstream overrides

pkg/config/config.go

@@ -19,7 +19,7 @@ const (
 type StaticConfig struct {
 	DeniedResources []GroupVersionKind `toml:"denied_resources"`
 
-	LogLevel   int    `toml:"log_level,omitempty"`
+	LogLevel   int    `toml:"log_level,omitzero"`
 	Port       string `toml:"port,omitempty"`
 	SSEBaseURL string `toml:"sse_base_url,omitempty"`
 	KubeConfig string `toml:"kubeconfig,omitempty"`
@@ -70,13 +70,6 @@ type StaticConfig struct {
 	parsedClusterProviderConfigs map[string]ProviderConfig
 }
 
-func Default() *StaticConfig {
-	return &StaticConfig{
-		ListOutput: "table",
-		Toolsets:   []string{"core", "config", "helm"},
-	}
-}
-
 type GroupVersionKind struct {
 	Group   string `toml:"group"`
 	Version string `toml:"version"`

pkg/config/config_default.go

@@ -0,0 +1,43 @@
+package config
+
+import (
+	"bytes"
+
+	"github.com/BurntSushi/toml"
+)
+
+func Default() *StaticConfig {
+	defaultConfig := StaticConfig{
+		ListOutput: "table",
+		Toolsets:   []string{"core", "config", "helm"},
+	}
+	overrides := defaultOverrides()
+	mergedConfig := mergeConfig(defaultConfig, overrides)
+	return &mergedConfig
+}
+
+// HasDefaultOverrides indicates whether the internal defaultOverrides function
+// provides any overrides or an empty StaticConfig.
+func HasDefaultOverrides() bool {
+	overrides := defaultOverrides()
+	var buf bytes.Buffer
+	if err := toml.NewEncoder(&buf).Encode(overrides); err != nil {
+		// If marshaling fails, assume no overrides
+		return false
+	}
+	return len(bytes.TrimSpace(buf.Bytes())) > 0
+}
+
+// mergeConfig applies non-zero values from override to base using TOML serialization
+// and returns the merged StaticConfig.
+// In case of any error during marshalling or unmarshalling, it returns the base config unchanged.
+func mergeConfig(base, override StaticConfig) StaticConfig {
+	var overrideBuffer bytes.Buffer
+	if err := toml.NewEncoder(&overrideBuffer).Encode(override); err != nil {
+		// If marshaling fails, return base unchanged
+		return base
+	}
+
+	_, _ = toml.NewDecoder(&overrideBuffer).Decode(&base)
+	return base
+}

pkg/config/config_default_overrides.go

@@ -0,0 +1,8 @@
+package config
+
+func defaultOverrides() StaticConfig {
+	return StaticConfig{
+		// IMPORTANT: this file is used to override default config values in downstream builds.
+		// This is intentionally left blank.
+	}
+}

pkg/config/config_test.go

@@ -174,6 +174,49 @@ func (s *ConfigSuite) TestReadConfigValidPreservesDefaultsForMissingFields() {
 	})
 }
 
+func (s *ConfigSuite) TestMergeConfig() {
+	base := StaticConfig{
+		ListOutput: "table",
+		Toolsets:   []string{"core", "config", "helm"},
+		Port:       "8080",
+	}
+	s.Run("merges override values on top of base", func() {
+		override := StaticConfig{
+			ListOutput: "json",
+			Port:       "9090",
+		}
+
+		result := mergeConfig(base, override)
+
+		s.Equal("json", result.ListOutput, "ListOutput should be overridden")
+		s.Equal("9090", result.Port, "Port should be overridden")
+	})
+
+	s.Run("preserves base values when override is empty", func() {
+		override := StaticConfig{}
+
+		result := mergeConfig(base, override)
+
+		s.Equal("table", result.ListOutput, "ListOutput should be preserved from base")
+		s.Equal([]string{"core", "config", "helm"}, result.Toolsets, "Toolsets should be preserved from base")
+		s.Equal("8080", result.Port, "Port should be preserved from base")
+	})
+
+	s.Run("handles partial overrides", func() {
+		override := StaticConfig{
+			Toolsets: []string{"custom"},
+			ReadOnly: true,
+		}
+
+		result := mergeConfig(base, override)
+
+		s.Equal("table", result.ListOutput, "ListOutput should be preserved from base")
+		s.Equal([]string{"custom"}, result.Toolsets, "Toolsets should be overridden")
+		s.Equal("8080", result.Port, "Port should be preserved from base since override doesn't specify it")
+		s.True(result.ReadOnly, "ReadOnly should be overridden to true")
+	})
+}
+
 func TestConfig(t *testing.T) {
 	suite.Run(t, new(ConfigSuite))
 }

pkg/mcp/toolsets_test.go

@@ -65,6 +65,9 @@ func (s *ToolsetsSuite) TestNoToolsets() {
 }
 
 func (s *ToolsetsSuite) TestDefaultToolsetsTools() {
+	if configuration.HasDefaultOverrides() {
+		s.T().Skip("Skipping test because default configuration overrides are present (this is a downstream fork)")
+	}
 	s.Run("Default configuration toolsets", func() {
 		s.InitMcpClient()
 		tools, err := s.ListTools(s.T().Context(), mcp.ListToolsRequest{})
@@ -82,6 +85,9 @@ func (s *ToolsetsSuite) TestDefaultToolsetsTools() {
 }
 
 func (s *ToolsetsSuite) TestDefaultToolsetsToolsInOpenShift() {
+	if configuration.HasDefaultOverrides() {
+		s.T().Skip("Skipping test because default configuration overrides are present (this is a downstream fork)")
+	}
 	s.Run("Default configuration toolsets in OpenShift", func() {
 		s.Handle(&test.InOpenShiftHandler{})
 		s.InitMcpClient()
@@ -100,6 +106,9 @@ func (s *ToolsetsSuite) TestDefaultToolsetsToolsInOpenShift() {
 }
 
 func (s *ToolsetsSuite) TestDefaultToolsetsToolsInMultiCluster() {
+	if configuration.HasDefaultOverrides() {
+		s.T().Skip("Skipping test because default configuration overrides are present (this is a downstream fork)")
+	}
 	s.Run("Default configuration toolsets in multi-cluster (with 11 clusters)", func() {
 		kubeconfig := s.Kubeconfig()
 		for i := 0; i < 10; i++ {
@@ -123,6 +132,9 @@ func (s *ToolsetsSuite) TestDefaultToolsetsToolsInMultiCluster() {
 }
 
 func (s *ToolsetsSuite) TestDefaultToolsetsToolsInMultiClusterEnum() {
+	if configuration.HasDefaultOverrides() {
+		s.T().Skip("Skipping test because default configuration overrides are present (this is a downstream fork)")
+	}
 	s.Run("Default configuration toolsets in multi-cluster (with 2 clusters)", func() {
 		kubeconfig := s.Kubeconfig()
 		// Add additional cluster to force multi-cluster behavior with enum parameter