Support both manual and generate conversions

pkg/conversion/converter.go

@@ -40,7 +40,8 @@ type DebugLogger interface {
 type Converter struct {
 	// Map from the conversion pair to a function which can
 	// do the conversion.
-	conversionFuncs map[typePair]reflect.Value
+	conversionFuncs          map[typePair]reflect.Value
+	generatedConversionFuncs map[typePair]reflect.Value
 
 	// This is a map from a source field type and name, to a list of destination
 	// field type and name.
@@ -72,11 +73,12 @@ type Converter struct {
 // NewConverter creates a new Converter object.
 func NewConverter() *Converter {
 	c := &Converter{
-		conversionFuncs:    map[typePair]reflect.Value{},
+		conversionFuncs:          map[typePair]reflect.Value{},
-		defaultingFuncs:    map[reflect.Type]reflect.Value{},
+		generatedConversionFuncs: map[typePair]reflect.Value{},
-		nameFunc:           func(t reflect.Type) string { return t.Name() },
+		defaultingFuncs:          map[reflect.Type]reflect.Value{},
-		structFieldDests:   map[typeNamePair][]typeNamePair{},
+		nameFunc:                 func(t reflect.Type) string { return t.Name() },
-		structFieldSources: map[typeNamePair][]typeNamePair{},
+		structFieldDests:         map[typeNamePair][]typeNamePair{},
+		structFieldSources:       map[typeNamePair][]typeNamePair{},
 
 		inputFieldMappingFuncs: map[reflect.Type]FieldMappingFunc{},
 		inputDefaultFlags:      map[reflect.Type]FieldMatchingFlags{},
@@ -238,20 +240,8 @@ func (s *scope) error(message string, args ...interface{}) error {
 	return fmt.Errorf(where+message, args...)
 }
 
-// RegisterConversionFunc registers a conversion func with the
+// Verifies whether a conversion function has a correct signature.
-// Converter. conversionFunc must take three parameters: a pointer to the input
+func verifyConversionFunctionSignature(ft reflect.Type) error {
-// type, a pointer to the output type, and a conversion.Scope (which should be
-// used if recursive conversion calls are desired).  It must return an error.
-//
-// Example:
-// c.RegisteConversionFunc(
-//         func(in *Pod, out *v1beta1.Pod, s Scope) error {
-//                 // conversion logic...
-//                 return nil
-//          })
-func (c *Converter) RegisterConversionFunc(conversionFunc interface{}) error {
-	fv := reflect.ValueOf(conversionFunc)
-	ft := fv.Type()
 	if ft.Kind() != reflect.Func {
 		return fmt.Errorf("expected func, got: %v", ft)
 	}
@@ -278,10 +268,47 @@ func (c *Converter) RegisterConversionFunc(conversionFunc interface{}) error {
 	if ft.Out(0) != errorType {
 		return fmt.Errorf("expected error return, got: %v", ft)
 	}
+	return nil
+}
+
+// RegisterConversionFunc registers a conversion func with the
+// Converter. conversionFunc must take three parameters: a pointer to the input
+// type, a pointer to the output type, and a conversion.Scope (which should be
+// used if recursive conversion calls are desired).  It must return an error.
+//
+// Example:
+// c.RegisteConversionFunc(
+//         func(in *Pod, out *v1beta1.Pod, s Scope) error {
+//                 // conversion logic...
+//                 return nil
+//          })
+func (c *Converter) RegisterConversionFunc(conversionFunc interface{}) error {
+	fv := reflect.ValueOf(conversionFunc)
+	ft := fv.Type()
+	if err := verifyConversionFunctionSignature(ft); err != nil {
+		return err
+	}
 	c.conversionFuncs[typePair{ft.In(0).Elem(), ft.In(1).Elem()}] = fv
 	return nil
 }
 
+// Similar to RegisterConversionFunc, but registers conversion function that were
+// automatically generated.
+func (c *Converter) RegisterGeneratedConversionFunc(conversionFunc interface{}) error {
+	fv := reflect.ValueOf(conversionFunc)
+	ft := fv.Type()
+	if err := verifyConversionFunctionSignature(ft); err != nil {
+		return err
+	}
+	c.generatedConversionFuncs[typePair{ft.In(0).Elem(), ft.In(1).Elem()}] = fv
+	return nil
+}
+
+func (c *Converter) HasConversionFunc(inType, outType reflect.Type) bool {
+	_, found := c.conversionFuncs[typePair{inType, outType}]
+	return found
+}
+
 // SetStructFieldCopy registers a correspondence. Whenever a struct field is encountered
 // which has a type and name matching srcFieldType and srcFieldName, it wil be copied
 // into the field in the destination struct matching destFieldType & Name, if such a
@@ -469,6 +496,12 @@ func (c *Converter) convert(sv, dv reflect.Value, scope *scope) error {
 		}
 		return c.callCustom(sv, dv, fv, scope)
 	}
+	if fv, ok := c.generatedConversionFuncs[typePair{st, dt}]; ok {
+		if c.Debug != nil {
+			c.Debug.Logf("Calling custom conversion of '%v' to '%v'", st, dt)
+		}
+		return c.callCustom(sv, dv, fv, scope)
+	}
 
 	return c.defaultConvert(sv, dv, scope)
 }

pkg/conversion/converter_test.go

@@ -187,6 +187,28 @@ func TestConverter_CallsRegisteredFunctions(t *testing.T) {
 	}
 }
 
+func TestConverter_GeneratedConversionOverriden(t *testing.T) {
+	type A struct{}
+	type B struct{}
+	c := NewConverter()
+	if err := c.RegisterConversionFunc(func(in *A, out *B, s Scope) error {
+		return nil
+	}); err != nil {
+		t.Fatalf("unexpected error %v", err)
+	}
+	if err := c.RegisterGeneratedConversionFunc(func(in *A, out *B, s Scope) error {
+		return fmt.Errorf("generated function should be overriden")
+	}); err != nil {
+		t.Fatalf("unexpected error %v", err)
+	}
+
+	a := A{}
+	b := B{}
+	if err := c.Convert(&a, &b, 0, nil); err != nil {
+		t.Errorf("%v", err)
+	}
+}
+
 func TestConverter_MapsStringArrays(t *testing.T) {
 	type A struct {
 		Foo   string

pkg/conversion/generator.go

@@ -64,6 +64,8 @@ func (g *generator) GenerateConversionsForType(version string, reflection reflec
 }
 
 func (g *generator) generateConversionsBetween(inType, outType reflect.Type) error {
+	existingConversion := g.scheme.Converter().HasConversionFunc(inType, outType) && g.scheme.Converter().HasConversionFunc(outType, inType)
+
 	// Avoid processing the same type multiple times.
 	if value, found := g.convertibles[inType]; found {
 		if value != outType {
@@ -79,19 +81,50 @@ func (g *generator) generateConversionsBetween(inType, outType reflect.Type) err
 	if inType.Kind() != outType.Kind() {
 		return fmt.Errorf("cannot convert types of different kinds: %v %v", inType, outType)
 	}
+	// We should be able to generate conversions both sides.
 	switch inType.Kind() {
 	case reflect.Map:
-		return g.generateConversionsForMap(inType, outType)
+		inErr := g.generateConversionsForMap(inType, outType)
-	case reflect.Ptr:
+		outErr := g.generateConversionsForMap(outType, inType)
-		return g.generateConversionsBetween(inType.Elem(), outType.Elem())
+		if !existingConversion && (inErr != nil || outErr != nil) {
-	case reflect.Slice:
+			return inErr
-		return g.generateConversionsForSlice(inType, outType)
+		}
-	case reflect.Interface:
+		// We don't add it to g.convertibles - maps should be handled correctly
-		// TODO(wojtek-t): Currently we rely on default conversion functions for interfaces.
+		// inside appropriate conversion functions.
-		// Add support for reflect.Interface.
 		return nil
+	case reflect.Ptr:
+		inErr := g.generateConversionsBetween(inType.Elem(), outType.Elem())
+		outErr := g.generateConversionsBetween(outType.Elem(), inType.Elem())
+		if !existingConversion && (inErr != nil || outErr != nil) {
+			return inErr
+		}
+		// We don't add it to g.convertibles - maps should be handled correctly
+		// inside appropriate conversion functions.
+		return nil
+	case reflect.Slice:
+		inErr := g.generateConversionsForSlice(inType, outType)
+		outErr := g.generateConversionsForSlice(outType, inType)
+		if !existingConversion && (inErr != nil || outErr != nil) {
+			return inErr
+		}
+		// We don't add it to g.convertibles - slices should be handled correctly
+		// inside appropriate conversion functions.
+		return nil
+	case reflect.Interface:
+		// TODO(wojtek-t): Currently we don't support converting interfaces.
+		return fmt.Errorf("interfaces are not supported")
 	case reflect.Struct:
-		return g.generateConversionsForStruct(inType, outType)
+		inErr := g.generateConversionsForStruct(inType, outType)
+		outErr := g.generateConversionsForStruct(outType, inType)
+		if !existingConversion && (inErr != nil || outErr != nil) {
+			return inErr
+		}
+		if !existingConversion {
+			if _, found := g.convertibles[outType]; !found {
+				g.convertibles[inType] = outType
+			}
+		}
+		return nil
 	default:
 		// All simple types should be handled correctly with default conversion.
 		return nil
@@ -119,8 +152,6 @@ func (g *generator) generateConversionsForMap(inType, outType reflect.Type) erro
 	if err := g.generateConversionsBetween(inValue, outValue); err != nil {
 		return err
 	}
-	// We don't add it to g.convertibles - maps should be handled correctly
-	// inside appropriate conversion functions.
 	return nil
 }
 
@@ -130,8 +161,6 @@ func (g *generator) generateConversionsForSlice(inType, outType reflect.Type) er
 	if err := g.generateConversionsBetween(inElem, outElem); err != nil {
 		return err
 	}
-	// We don't add it to g.convertibles - slices should be handled correctly
-	// inside appropriate conversion functions.
 	return nil
 }
 
@@ -151,7 +180,6 @@ func (g *generator) generateConversionsForStruct(inType, outType reflect.Type) e
 			}
 		}
 	}
-	g.convertibles[inType] = outType
 	return nil
 }
 
@@ -477,6 +505,22 @@ func (g *generator) writeConversionForStruct(w io.Writer, inType, outType reflec
 		inField := inType.Field(i)
 		outField, _ := outType.FieldByName(inField.Name)
 
+		if g.scheme.Converter().HasConversionFunc(inField.Type, outField.Type) {
+			// Use the conversion method that is already defined.
+			assignFormat := "if err := s.Convert(&in.%s, &out.%s, 0); err != nil {\n"
+			assignStmt := fmt.Sprintf(assignFormat, inField.Name, outField.Name)
+			if err := writeLine(w, indent, assignStmt); err != nil {
+				return err
+			}
+			if err := writeLine(w, indent+1, "return err\n"); err != nil {
+				return err
+			}
+			if err := writeLine(w, indent, "}\n"); err != nil {
+				return err
+			}
+			continue
+		}
+
 		switch inField.Type.Kind() {
 		case reflect.Map, reflect.Ptr, reflect.Slice, reflect.Interface, reflect.Struct:
 			// Don't copy these via assignment/conversion!

pkg/conversion/scheme.go

@@ -259,7 +259,12 @@ func (s *Scheme) AddConversionFuncs(conversionFuncs ...interface{}) error {
 // Similar to AddConversionFuncs, but registers conversion functions that were
 // automatically generated.
 func (s *Scheme) AddGeneratedConversionFuncs(conversionFuncs ...interface{}) error {
-	return s.AddConversionFuncs(conversionFuncs...)
+	for _, f := range conversionFuncs {
+		if err := s.converter.RegisterGeneratedConversionFunc(f); err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 // AddStructFieldConversion allows you to specify a mechanical copy for a moved