cmd: change how default configuration values are built

For the orchestrator, we need to build default values for slice of
configurations. We introduce a Reset() method that will be called by
mapstructure.

cmd/config.go

@@ -11,6 +11,7 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"reflect"
 	"sort"
 	"strconv"
 	"strings"
@@ -77,6 +78,7 @@ func (c ConfigRelatedOptions) Parse(out io.Writer, component string, config inte
 	}
 
 	// Parse provided configuration
+	defaultHook, disableDefaultHook := DefaultHook()
 	var metadata mapstructure.Metadata
 	decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
 		Result:           &config,
@@ -89,6 +91,7 @@ func (c ConfigRelatedOptions) Parse(out io.Writer, component string, config inte
 			return key == field
 		},
 		DecodeHook: mapstructure.ComposeDecodeHookFunc(
+			defaultHook,
 			flow.ConfigurationUnmarshalerHook(),
 			clickhouse.NetworkNamesUnmarshalerHook(),
 			mapstructure.TextUnmarshallerHookFunc(),
@@ -102,6 +105,7 @@ func (c ConfigRelatedOptions) Parse(out io.Writer, component string, config inte
 	if err := decoder.Decode(rawConfig); err != nil {
 		return fmt.Errorf("unable to parse configuration: %w", err)
 	}
+	disableDefaultHook()
 
 	// Override with environment variables
 	for _, keyval := range os.Environ() {
@@ -171,3 +175,42 @@ func (c ConfigRelatedOptions) Parse(out io.Writer, component string, config inte
 
 	return nil
 }
+
+// DefaultHook will reset the destination value to its default using
+// the Reset() method if present.
+func DefaultHook() (mapstructure.DecodeHookFunc, func()) {
+	disabled := false
+	hook := func(from, to reflect.Value) (interface{}, error) {
+		if disabled {
+			return from.Interface(), nil
+		}
+		if to.Kind() == reflect.Ptr {
+			// We already have a pointer
+			method, ok := to.Type().MethodByName("Reset")
+			if !ok {
+				return from.Interface(), nil
+			}
+			if to.IsNil() {
+				new := reflect.New(to.Type().Elem())
+				method.Func.Call([]reflect.Value{new})
+				to.Set(new)
+				return from.Interface(), nil
+			}
+			method.Func.Call([]reflect.Value{to})
+			return from.Interface(), nil
+		}
+		// Not a pointer, let's check if we take a pointer
+		method, ok := reflect.PointerTo(to.Type()).MethodByName("Reset")
+		if !ok {
+			return from.Interface(), nil
+		}
+		method.Func.Call([]reflect.Value{to.Addr()})
+
+		// Resume decoding
+		return from.Interface(), nil
+	}
+	disable := func() {
+		disabled = true
+	}
+	return hook, disable
+}

cmd/config_test.go

@@ -47,8 +47,8 @@ type dummyModule2DetailsConfiguration struct {
 	IntervalValue time.Duration
 }
 
-func dummyDefaultConfiguration() dummyConfiguration {
-	return dummyConfiguration{
+func (c *dummyConfiguration) Reset() {
+	*c = dummyConfiguration{
 		Module1: dummyModule1Configuration{
 			Listen:  "127.0.0.1:8080",
 			Topic:   "nothingness",
@@ -79,7 +79,7 @@ module1:
 		Path: configFile,
 	}
 
-	parsed := dummyDefaultConfiguration()
+	parsed := dummyConfiguration{}
 	out := bytes.NewBuffer([]byte{})
 	if err := c.Parse(out, "dummy", &parsed); err == nil {
 		t.Fatal("Parse() didn't error")
@@ -113,7 +113,7 @@ module2:
 		Dump: true,
 	}
 
-	parsed := dummyDefaultConfiguration()
+	parsed := dummyConfiguration{}
 	out := bytes.NewBuffer([]byte{})
 	if err := c.Parse(out, "dummy", &parsed); err != nil {
 		t.Fatalf("Parse() error:\n%+v", err)
@@ -213,7 +213,7 @@ module2:
 		Dump: true,
 	}
 
-	parsed := dummyDefaultConfiguration()
+	parsed := dummyConfiguration{}
 	out := bytes.NewBuffer([]byte{})
 	if err := c.Parse(out, "dummy", &parsed); err != nil {
 		t.Fatalf("Parse() error:\n%+v", err)
@@ -267,7 +267,7 @@ module2:
 		Dump: true,
 	}
 
-	parsed := dummyDefaultConfiguration()
+	parsed := dummyConfiguration{}
 	out := bytes.NewBuffer([]byte{})
 	if err := c.Parse(out, "dummy", &parsed); err != nil {
 		t.Fatalf("Parse() error:\n%+v", err)
@@ -312,7 +312,7 @@ module1:
 
 		c := cmd.ConfigRelatedOptions{Path: configFile}
 
-		parsed := dummyDefaultConfiguration()
+		parsed := dummyConfiguration{}
 		out := bytes.NewBuffer([]byte{})
 		if err := c.Parse(out, "dummy", &parsed); err != nil {
 			t.Fatalf("Parse() error:\n%+v", err)
@@ -332,7 +332,7 @@ module1:
 
 		c := cmd.ConfigRelatedOptions{Path: configFile}
 
-		parsed := dummyDefaultConfiguration()
+		parsed := dummyConfiguration{}
 		out := bytes.NewBuffer([]byte{})
 		if err := c.Parse(out, "dummy", &parsed); err == nil {
 			t.Fatal("Parse() didn't error")
@@ -343,3 +343,87 @@ invalid key "unused"`); diff != "" {
 		}
 	})
 }
+
+func TestDefaultInSlice(t *testing.T) {
+	try := func(t *testing.T, parse func(cmd.ConfigRelatedOptions, *bytes.Buffer) interface{}) {
+		// Configuration file
+		config := `---
+modules:
+- module1:
+    topic: flows1
+- module1:
+    topic: flows2
+`
+		configFile := filepath.Join(t.TempDir(), "config.yaml")
+		ioutil.WriteFile(configFile, []byte(config), 0644)
+
+		c := cmd.ConfigRelatedOptions{
+			Path: configFile,
+			Dump: true,
+		}
+
+		out := bytes.NewBuffer([]byte{})
+		parsed := parse(c, out)
+		// Expected configuration
+		expected := map[string][]dummyConfiguration{
+			"Modules": {
+				{
+					Module1: dummyModule1Configuration{
+						Listen:  "127.0.0.1:8080",
+						Topic:   "flows1",
+						Workers: 100,
+					},
+					Module2: dummyModule2Configuration{
+						MoreDetails: MoreDetails{
+							Stuff: "hello",
+						},
+						Details: dummyModule2DetailsConfiguration{
+							Workers:       1,
+							IntervalValue: time.Minute,
+						},
+					},
+				}, {
+					Module1: dummyModule1Configuration{
+						Listen:  "127.0.0.1:8080",
+						Topic:   "flows2",
+						Workers: 100,
+					},
+					Module2: dummyModule2Configuration{
+						MoreDetails: MoreDetails{
+							Stuff: "hello",
+						},
+						Details: dummyModule2DetailsConfiguration{
+							Workers:       1,
+							IntervalValue: time.Minute,
+						},
+					},
+				},
+			},
+		}
+		if diff := helpers.Diff(parsed, expected); diff != "" {
+			t.Errorf("Parse() (-got, +want):\n%s", diff)
+		}
+	}
+	t.Run("without pointer", func(t *testing.T) {
+		try(t, func(c cmd.ConfigRelatedOptions, out *bytes.Buffer) interface{} {
+			parsed := struct {
+				Modules []dummyConfiguration
+			}{}
+			if err := c.Parse(out, "dummy", &parsed); err != nil {
+				t.Fatalf("Parse() error:\n%+v", err)
+			}
+			return parsed
+		})
+	})
+	t.Run("with pointer", func(t *testing.T) {
+		try(t, func(c cmd.ConfigRelatedOptions, out *bytes.Buffer) interface{} {
+			parsed := struct {
+				Modules []*dummyConfiguration
+			}{}
+			if err := c.Parse(out, "dummy", &parsed); err != nil {
+				t.Fatalf("Parse() error:\n%+v", err)
+			}
+			return parsed
+		})
+	})
+}

cmd/console.go

@@ -27,9 +27,9 @@ type ConsoleConfiguration struct {
 	Database   database.Configuration
 }
 
-// DefaultConsoleConfiguration is the default configuration for the console command.
-func DefaultConsoleConfiguration() ConsoleConfiguration {
-	return ConsoleConfiguration{
+// Reset resets the console configuration to its default value.
+func (c *ConsoleConfiguration) Reset() {
+	*c = ConsoleConfiguration{
 		HTTP:       http.DefaultConfiguration(),
 		Reporting:  reporter.DefaultConfiguration(),
 		Console:    console.DefaultConfiguration(),
@@ -55,7 +55,7 @@ var consoleCmd = &cobra.Command{
 manage collected flows.`,
 	Args: cobra.ExactArgs(1),
 	RunE: func(cmd *cobra.Command, args []string) error {
-		config := DefaultConsoleConfiguration()
+		config := ConsoleConfiguration{}
 		ConsoleOptions.Path = args[0]
 		if err := ConsoleOptions.Parse(cmd.OutOrStdout(), "console", &config); err != nil {
 			return err

cmd/console_test.go

@@ -11,7 +11,9 @@ import (
 
 func TestConsoleStart(t *testing.T) {
 	r := reporter.NewMock(t)
-	if err := consoleStart(r, DefaultConsoleConfiguration(), true); err != nil {
+	config := ConsoleConfiguration{}
+	config.Reset()
+	if err := consoleStart(r, config, true); err != nil {
 		t.Fatalf("consoleStart() error:\n%+v", err)
 	}
 }

cmd/inlet.go

@@ -29,9 +29,9 @@ type InletConfiguration struct {
 	Core      core.Configuration
 }
 
-// DefaultInletConfiguration is the default configuration for the inlet command.
-func DefaultInletConfiguration() InletConfiguration {
-	return InletConfiguration{
+// Reset resets the configuration for the inlet command to its default value.
+func (c *InletConfiguration) Reset() {
+	*c = InletConfiguration{
 		HTTP:      http.DefaultConfiguration(),
 		Reporting: reporter.DefaultConfiguration(),
 		Flow:      flow.DefaultConfiguration(),
@@ -58,7 +58,7 @@ var inletCmd = &cobra.Command{
 hydration and export to Kafka.`,
 	Args: cobra.ExactArgs(1),
 	RunE: func(cmd *cobra.Command, args []string) error {
-		config := DefaultInletConfiguration()
+		config := InletConfiguration{}
 		InletOptions.Path = args[0]
 		if err := InletOptions.Parse(cmd.OutOrStdout(), "inlet", &config); err != nil {
 			return err

cmd/inlet_test.go

@@ -11,7 +11,9 @@ import (
 
 func TestInletStart(t *testing.T) {
 	r := reporter.NewMock(t)
-	if err := inletStart(r, DefaultInletConfiguration(), true); err != nil {
+	config := InletConfiguration{}
+	config.Reset()
+	if err := inletStart(r, config, true); err != nil {
 		t.Fatalf("inletStart() error:\n%+v", err)
 	}
 }

cmd/orchestrator.go

@@ -30,9 +30,9 @@ type OrchestratorConfiguration struct {
 	Console []ConsoleConfiguration
 }
 
-// DefaultOrchestratorConfiguration is the default configuration for the orchestrator command.
-func DefaultOrchestratorConfiguration() OrchestratorConfiguration {
-	return OrchestratorConfiguration{
+// Reset resets the configuration of the orchestrator command to its default value.
+func (c *OrchestratorConfiguration) Reset() {
+	*c = OrchestratorConfiguration{
 		Reporting:    reporter.DefaultConfiguration(),
 		HTTP:         http.DefaultConfiguration(),
 		ClickHouseDB: clickhousedb.DefaultConfiguration(),
@@ -40,8 +40,8 @@ func DefaultOrchestratorConfiguration() OrchestratorConfiguration {
 		Kafka:        kafka.DefaultConfiguration(),
 		Orchestrator: orchestrator.DefaultConfiguration(),
 		// Other service configurations
-		Inlet:   []InletConfiguration{DefaultInletConfiguration()},
-		Console: []ConsoleConfiguration{DefaultConsoleConfiguration()},
+		Inlet:   []InletConfiguration{},
+		Console: []ConsoleConfiguration{},
 	}
 }
 
@@ -61,7 +61,7 @@ var orchestratorCmd = &cobra.Command{
 components and centralizes configuration of the various other components.`,
 	Args: cobra.ExactArgs(1),
 	RunE: func(cmd *cobra.Command, args []string) error {
-		config := DefaultOrchestratorConfiguration()
+		config := OrchestratorConfiguration{}
 		OrchestratorOptions.Path = args[0]
 		OrchestratorOptions.BeforeDump = func() {
 			// Override some parts of the configuration

cmd/orchestrator_test.go

@@ -11,7 +11,9 @@ import (
 
 func TestOrchestratorStart(t *testing.T) {
 	r := reporter.NewMock(t)
-	if err := orchestratorStart(r, DefaultOrchestratorConfiguration(), true); err != nil {
+	config := OrchestratorConfiguration{}
+	config.Reset()
+	if err := orchestratorStart(r, config, true); err != nil {
 		t.Fatalf("orchestratorStart() error:\n%+v", err)
 	}
 }