Support nil pointers to structs in properties

Allow primary builders to reduce allocations of empty structures by
allowing nil pointers to concrete struct types.  Property readers will
not recurse into nil pointers, property writers will replace the nil
pointer with a pointer to the zero value of the pointer element type.

Allows a >50% primary builder time improvement with a trivial change in
Soong.

Change-Id: If6ad674bf7bf2a694c335378a074643a97d3c50b

bootstrap/bpdoc/bpdoc.go

@@ -152,15 +152,18 @@ func setDefaults(properties []Property, defaults reflect.Value) {
 			continue
 		}
 
-		if f.Type().Kind() == reflect.Interface {
+		if f.Kind() == reflect.Interface {
 			f = f.Elem()
 		}
 
-		if f.Type().Kind() == reflect.Ptr {
+		if f.Kind() == reflect.Ptr {
+			if f.IsNil() {
+				continue
+			}
 			f = f.Elem()
 		}
 
-		if f.Type().Kind() == reflect.Struct {
+		if f.Kind() == reflect.Struct {
 			setDefaults(prop.Properties, f)
 		} else {
 			prop.Default = fmt.Sprintf("%v", f.Interface())

proptools/clone.go

@@ -43,6 +43,7 @@ func CopyProperties(dstValue, srcValue reflect.Value) {
 		srcFieldValue := srcValue.Field(i)
 		dstFieldValue := dstValue.Field(i)
 		dstFieldInterfaceValue := reflect.Value{}
+		origDstFieldValue := dstFieldValue
 
 		switch srcFieldValue.Kind() {
 		case reflect.Bool, reflect.String, reflect.Int, reflect.Uint:
@@ -93,7 +94,7 @@ func CopyProperties(dstValue, srcValue reflect.Value) {
 			fallthrough
 		case reflect.Ptr:
 			if srcFieldValue.IsNil() {
-				dstFieldValue.Set(srcFieldValue)
+				origDstFieldValue.Set(srcFieldValue)
 				break
 			}
 
@@ -110,13 +111,13 @@ func CopyProperties(dstValue, srcValue reflect.Value) {
 					if dstFieldInterfaceValue.IsValid() {
 						dstFieldInterfaceValue.Set(newValue)
 					} else {
-						dstFieldValue.Set(newValue)
+						origDstFieldValue.Set(newValue)
 					}
 				}
 			case reflect.Bool, reflect.String:
 				newValue := reflect.New(srcFieldValue.Type())
 				newValue.Elem().Set(srcFieldValue)
-				dstFieldValue.Set(newValue)
+				origDstFieldValue.Set(newValue)
 			default:
 				panic(fmt.Errorf("can't clone field %q: points to a %s",
 					field.Name, srcFieldValue.Kind()))

proptools/extend.go

@@ -191,11 +191,15 @@ func extendPropertyErrorf(property string, format string, a ...interface{}) *Ext
 func extendProperties(dst interface{}, src interface{}, filter ExtendPropertyFilterFunc,
 	order ExtendPropertyOrderFunc) error {
 
-	dstValue, err := getStruct(dst)
+	srcValue, err := getStruct(src)
 	if err != nil {
+		if _, ok := err.(getStructEmptyError); ok {
+			return nil
+		}
 		return err
 	}
-	srcValue, err := getStruct(src)
+
+	dstValue, err := getOrCreateStruct(dst)
 	if err != nil {
 		return err
 	}
@@ -212,20 +216,23 @@ func extendProperties(dst interface{}, src interface{}, filter ExtendPropertyFil
 func extendMatchingProperties(dst []interface{}, src interface{}, filter ExtendPropertyFilterFunc,
 	order ExtendPropertyOrderFunc) error {
 
+	srcValue, err := getStruct(src)
+	if err != nil {
+		if _, ok := err.(getStructEmptyError); ok {
+			return nil
+		}
+		return err
+	}
+
 	dstValues := make([]reflect.Value, len(dst))
 	for i := range dst {
 		var err error
-		dstValues[i], err = getStruct(dst[i])
+		dstValues[i], err = getOrCreateStruct(dst[i])
 		if err != nil {
 			return err
 		}
 	}
 
-	srcValue, err := getStruct(src)
-	if err != nil {
-		return err
-	}
-
 	return extendPropertiesRecursive(dstValues, srcValue, "", filter, false, order)
 }
 
@@ -270,6 +277,7 @@ func extendPropertiesRecursive(dstValues []reflect.Value, srcValue reflect.Value
 			found = true
 
 			dstFieldValue := dstValue.FieldByIndex(dstField.Index)
+			origDstFieldValue := dstFieldValue
 
 			if srcFieldValue.Kind() != dstFieldValue.Kind() {
 				return extendPropertyErrorf(propertyName, "mismatched types %s and %s",
@@ -306,11 +314,12 @@ func extendPropertiesRecursive(dstValues []reflect.Value, srcValue reflect.Value
 				}
 
 				// Pointer to a struct
-				if dstFieldValue.IsNil() != srcFieldValue.IsNil() {
+				if srcFieldValue.IsNil() {
-					return extendPropertyErrorf(propertyName, "nilitude mismatch")
+					continue
 				}
 				if dstFieldValue.IsNil() {
-					continue
+					dstFieldValue = reflect.New(srcFieldValue.Type().Elem())
+					origDstFieldValue.Set(dstFieldValue)
 				}
 
 				dstFieldValue = dstFieldValue.Elem()
@@ -435,14 +444,32 @@ func extendPropertiesRecursive(dstValues []reflect.Value, srcValue reflect.Value
 	return nil
 }
 
+type getStructEmptyError struct{}
+
+func (getStructEmptyError) Error() string { return "interface containing nil pointer" }
+
+func getOrCreateStruct(in interface{}) (reflect.Value, error) {
+	value, err := getStruct(in)
+	if _, ok := err.(getStructEmptyError); ok {
+		value := reflect.ValueOf(in)
+		newValue := reflect.New(value.Type().Elem())
+		value.Set(newValue)
+	}
+
+	return value, err
+}
+
 func getStruct(in interface{}) (reflect.Value, error) {
 	value := reflect.ValueOf(in)
 	if value.Kind() != reflect.Ptr {
 		return reflect.Value{}, fmt.Errorf("expected pointer to struct, got %T", in)
 	}
-	value = value.Elem()
+	if value.Type().Elem().Kind() != reflect.Struct {
-	if value.Kind() != reflect.Struct {
 		return reflect.Value{}, fmt.Errorf("expected pointer to struct, got %T", in)
 	}
+	if value.IsNil() {
+		return reflect.Value{}, getStructEmptyError{}
+	}
+	value = value.Elem()
 	return value, nil
 }

proptools/extend_test.go

@@ -496,12 +496,69 @@ func appendPropertiesTestCases() []appendPropertyTestCase {
 				},
 			},
 		},
+		{
+			// Nil pointer to a struct
+			in1: &struct {
+				Nested *struct {
+					S string
+				}
+			}{},
+			in2: &struct {
+				Nested *struct {
+					S string
+				}
+			}{
+				Nested: &struct {
+					S string
+				}{
+					S: "string",
+				},
+			},
+			out: &struct {
+				Nested *struct {
+					S string
+				}
+			}{
+				Nested: &struct {
+					S string
+				}{
+					S: "string",
+				},
+			},
+		},
+		{
+			// Nil pointer to a struct in an interface
+			in1: &struct {
+				Nested interface{}
+			}{
+				Nested: (*struct{ S string })(nil),
+			},
+			in2: &struct {
+				Nested interface{}
+			}{
+				Nested: &struct {
+					S string
+				}{
+					S: "string",
+				},
+			},
+			out: &struct {
+				Nested interface{}
+			}{
+				Nested: &struct {
+					S string
+				}{
+					S: "string",
+				},
+			},
+		},
 
 		// Errors
 
 		{
 			// Non-pointer in1
 			in1: struct{}{},
+			in2: &struct{}{},
 			err: errors.New("expected pointer to struct, got struct {}"),
 			out: struct{}{},
 		},
@@ -515,6 +572,7 @@ func appendPropertiesTestCases() []appendPropertyTestCase {
 		{
 			// Non-struct in1
 			in1: &[]string{"bad"},
+			in2: &struct{}{},
 			err: errors.New("expected pointer to struct, got *[]string"),
 			out: &[]string{"bad"},
 		},
@@ -606,23 +664,6 @@ func appendPropertiesTestCases() []appendPropertyTestCase {
 			},
 			err: extendPropertyErrorf("s", "interface not a pointer"),
 		},
-		{
-			// Pointer nilitude mismatch
-			in1: &struct{ S *struct{ S string } }{
-				S: &struct{ S string }{
-					S: "string1",
-				},
-			},
-			in2: &struct{ S *struct{ S string } }{
-				S: nil,
-			},
-			out: &struct{ S *struct{ S string } }{
-				S: &struct{ S string }{
-					S: "string1",
-				},
-			},
-			err: extendPropertyErrorf("s", "nilitude mismatch"),
-		},
 		{
 			// Pointer not a struct
 			in1: &struct{ S *[]string }{
@@ -912,6 +953,7 @@ func appendMatchingPropertiesTestCases() []appendMatchingPropertiesTestCase {
 		{
 			// Non-pointer in1
 			in1: []interface{}{struct{}{}},
+			in2: &struct{}{},
 			err: errors.New("expected pointer to struct, got struct {}"),
 			out: []interface{}{struct{}{}},
 		},
@@ -925,6 +967,7 @@ func appendMatchingPropertiesTestCases() []appendMatchingPropertiesTestCase {
 		{
 			// Non-struct in1
 			in1: []interface{}{&[]string{"bad"}},
+			in2: &struct{}{},
 			err: errors.New("expected pointer to struct, got *[]string"),
 			out: []interface{}{&[]string{"bad"}},
 		},

proptools/typeequal.go

@@ -46,12 +46,14 @@ func typeEqual(v1, v2 reflect.Value) bool {
 		if v1.Type().Elem().Kind() != reflect.Struct {
 			return true
 		}
-		if v1.IsNil() != v2.IsNil() {
+		if v1.IsNil() && !v2.IsNil() {
-			return false
+			return concreteType(v2)
-		}
+		} else if v2.IsNil() && !v1.IsNil() {
-		if v1.IsNil() {
+			return concreteType(v1)
+		} else if v1.IsNil() && v2.IsNil() {
 			return true
 		}
+
 		v1 = v1.Elem()
 		v2 = v2.Elem()
 	}
@@ -74,3 +76,34 @@ func typeEqual(v1, v2 reflect.Value) bool {
 
 	return true
 }
+
+// Returns true if v recursively contains no interfaces
+func concreteType(v reflect.Value) bool {
+	if v.Kind() == reflect.Interface {
+		return false
+	}
+
+	if v.Kind() == reflect.Ptr {
+		if v.IsNil() {
+			return true
+		}
+		v = v.Elem()
+	}
+
+	if v.Kind() != reflect.Struct {
+		return true
+	}
+
+	for i := 0; i < v.NumField(); i++ {
+		v := v.Field(i)
+
+		switch kind := v.Kind(); kind {
+		case reflect.Interface, reflect.Ptr, reflect.Struct:
+			if !concreteType(v) {
+				return false
+			}
+		}
+	}
+
+	return true
+}

proptools/typeequal_test.go

@@ -88,7 +88,7 @@ var typeEqualTestCases = []struct {
 		// Mismatching nilitude embedded  pointer to struct
 		in1: &struct{ S *struct{ S1 string } }{S: &struct{ S1 string }{}},
 		in2: &struct{ S *struct{ S1 string } }{},
-		out: false,
+		out: true,
 	},
 	{
 		// Matching embedded interface to pointer to struct
@@ -116,13 +116,13 @@ var typeEqualTestCases = []struct {
 	},
 	{
 		// Matching pointer to non-struct
-		in1: struct{ S1 *string }{ S1: StringPtr("test1") },
+		in1: struct{ S1 *string }{S1: StringPtr("test1")},
-		in2: struct{ S1 *string }{ S1: StringPtr("test2") },
+		in2: struct{ S1 *string }{S1: StringPtr("test2")},
 		out: true,
 	},
 	{
 		// Matching nilitude pointer to non-struct
-		in1: struct{ S1 *string }{ S1: StringPtr("test1") },
+		in1: struct{ S1 *string }{S1: StringPtr("test1")},
 		in2: struct{ S1 *string }{},
 		out: true,
 	},

unpack.go

@@ -139,6 +139,8 @@ func unpackStructValue(namePrefix string, structValue reflect.Value,
 			panic(fmt.Errorf("field %s is not settable", propertyName))
 		}
 
+		origFieldValue := fieldValue
+
 		// To make testing easier we validate the struct field's type regardless
 		// of whether or not the property was specified in the parsed string.
 		switch kind := fieldValue.Kind(); kind {
@@ -163,7 +165,8 @@ func unpackStructValue(namePrefix string, structValue reflect.Value,
 			switch ptrKind := fieldValue.Type().Elem().Kind(); ptrKind {
 			case reflect.Struct:
 				if fieldValue.IsNil() {
-					panic(fmt.Errorf("field %s contains a nil pointer", propertyName))
+					fieldValue = reflect.New(fieldValue.Type().Elem())
+					origFieldValue.Set(fieldValue)
 				}
 				fieldValue = fieldValue.Elem()
 			case reflect.Bool, reflect.String:

unpack_test.go

@@ -28,15 +28,17 @@ import (
 var validUnpackTestCases = []struct {
 	input  string
 	output []interface{}
+	empty  []interface{}
 	errs   []error
 }{
-	{`
+	{
-		m {
+		input: `
-			name: "abc",
+			m {
-			blank: "",
+				name: "abc",
-		}
+				blank: "",
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Name  *string
 				Blank *string
@@ -47,46 +49,46 @@ var validUnpackTestCases = []struct {
 				Unset: nil,
 			},
 		},
-		nil,
 	},
 
-	{`
+	{
-		m {
+		input: `
-			name: "abc",
+			m {
-		}
+				name: "abc",
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Name string
 			}{
 				Name: "abc",
 			},
 		},
-		nil,
 	},
 
-	{`
+	{
-		m {
+		input: `
-			isGood: true,
+			m {
-		}
+				isGood: true,
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				IsGood bool
 			}{
 				IsGood: true,
 			},
 		},
-		nil,
 	},
 
-	{`
+	{
-		m {
+		input: `
-			isGood: true,
+			m {
-			isBad: false,
+				isGood: true,
-		}
+				isBad: false,
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				IsGood *bool
 				IsBad  *bool
@@ -97,17 +99,17 @@ var validUnpackTestCases = []struct {
 				IsUgly: nil,
 			},
 		},
-		nil,
 	},
 
-	{`
+	{
-		m {
+		input: `
-			stuff: ["asdf", "jkl;", "qwert",
+			m {
-				"uiop", "bnm,"],
+				stuff: ["asdf", "jkl;", "qwert",
-			empty: []
+					"uiop", "bnm,"],
-		}
+				empty: []
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Stuff []string
 				Empty []string
@@ -118,17 +120,17 @@ var validUnpackTestCases = []struct {
 				Nil:   nil,
 			},
 		},
-		nil,
 	},
 
-	{`
+	{
-		m {
+		input: `
-			nested: {
+			m {
-				name: "abc",
+				nested: {
+					name: "abc",
+				}
 			}
-		}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested struct {
 					Name string
@@ -139,17 +141,17 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
-	{`
+	{
-		m {
+		input: `
-			nested: {
+			m {
-				name: "def",
+				nested: {
+					name: "def",
+				}
 			}
-		}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested interface{}
 			}{
@@ -158,19 +160,19 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
-	{`
+	{
-		m {
+		input: `
-			nested: {
+			m {
-				foo: "abc",
+				nested: {
-			},
+					foo: "abc",
-			bar: false,
+				},
-			baz: ["def", "ghi"],
+				bar: false,
-		}
+				baz: ["def", "ghi"],
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested struct {
 					Foo string
@@ -185,19 +187,19 @@ var validUnpackTestCases = []struct {
 				Baz: []string{"def", "ghi"},
 			},
 		},
-		nil,
 	},
 
-	{`
+	{
-		m {
+		input: `
-			nested: {
+			m {
-				foo: "abc",
+				nested: {
-			},
+					foo: "abc",
-			bar: false,
+				},
-			baz: ["def", "ghi"],
+				bar: false,
-		}
+				baz: ["def", "ghi"],
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested struct {
 					Foo string `allowNested:"true"`
@@ -214,19 +216,19 @@ var validUnpackTestCases = []struct {
 				Baz: []string{"def", "ghi"},
 			},
 		},
-		nil,
 	},
 
-	{`
+	{
-		m {
+		input: `
-			nested: {
+			m {
-				foo: "abc",
+				nested: {
-			},
+					foo: "abc",
-			bar: false,
+				},
-			baz: ["def", "ghi"],
+				bar: false,
-		}
+				baz: ["def", "ghi"],
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested struct {
 					Foo string
@@ -241,24 +243,25 @@ var validUnpackTestCases = []struct {
 				Baz: []string{"def", "ghi"},
 			},
 		},
-		[]error{
+		errs: []error{
 			&Error{
 				Err: fmt.Errorf("filtered field nested.foo cannot be set in a Blueprint file"),
-				Pos: mkpos(27, 4, 8),
+				Pos: mkpos(30, 4, 9),
 			},
 		},
 	},
 
 	// Anonymous struct
-	{`
+	{
-		m {
+		input: `
-			name: "abc",
+			m {
-			nested: {
+				name: "abc",
-				name: "def",
+				nested: {
-			},
+					name: "def",
-		}
+				},
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				EmbeddedStruct
 				Nested struct {
@@ -277,19 +280,19 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
 	// Anonymous interface
-	{`
+	{
-		m {
+		input: `
-			name: "abc",
+			m {
-			nested: {
+				name: "abc",
-				name: "def",
+				nested: {
-			},
+					name: "def",
-		}
+				},
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				EmbeddedInterface
 				Nested struct {
@@ -308,19 +311,19 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
 	// Anonymous struct with name collision
-	{`
+	{
-		m {
+		input: `
-			name: "abc",
+			m {
-			nested: {
+				name: "abc",
-				name: "def",
+				nested: {
-			},
+					name: "def",
-		}
+				},
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Name string
 				EmbeddedStruct
@@ -344,19 +347,19 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
 	// Anonymous interface with name collision
-	{`
+	{
-		m {
+		input: `
-			name: "abc",
+			m {
-			nested: {
+				name: "abc",
-				name: "def",
+				nested: {
-			},
+					name: "def",
-		}
+				},
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Name string
 				EmbeddedInterface
@@ -380,21 +383,21 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
 	// Variables
-	{`
+	{
-		list = ["abc"]
+		input: `
-		string = "def"
+			list = ["abc"]
-		list_with_variable = [string]
+			string = "def"
-		m {
+			list_with_variable = [string]
-			name: string,
+			m {
-			list: list,
+				name: string,
-			list2: list_with_variable,
+				list: list,
-		}
+				list2: list_with_variable,
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Name  string
 				List  []string
@@ -405,18 +408,18 @@ var validUnpackTestCases = []struct {
 				List2: []string{"def"},
 			},
 		},
-		nil,
 	},
 
 	// Multiple property structs
-	{`
+	{
-		m {
+		input: `
-			nested: {
+			m {
-				name: "abc",
+				nested: {
+					name: "abc",
+				}
 			}
-		}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested struct {
 					Name string
@@ -438,7 +441,62 @@ var validUnpackTestCases = []struct {
 			struct {
 			}{},
 		},
-		nil,
+	},
+
+	// Nil pointer to struct
+	{
+		input: `
+			m {
+				nested: {
+					name: "abc",
+				}
+			}
+		`,
+		output: []interface{}{
+			struct {
+				Nested *struct {
+					Name string
+				}
+			}{
+				Nested: &struct{ Name string }{
+					Name: "abc",
+				},
+			},
+		},
+		empty: []interface{}{
+			&struct {
+				Nested *struct {
+					Name string
+				}
+			}{},
+		},
+	},
+
+	// Interface containing nil pointer to struct
+	{
+		input: `
+			m {
+				nested: {
+					name: "abc",
+				}
+			}
+		`,
+		output: []interface{}{
+			struct {
+				Nested interface{}
+			}{
+				Nested: &EmbeddedStruct{
+					Name: "abc",
+				},
+			},
+		},
+		empty: []interface{}{
+			&struct {
+				Nested interface{}
+			}{
+				Nested: (*EmbeddedStruct)(nil),
+			},
+		},
 	},
 }
 
@@ -464,9 +522,13 @@ func TestUnpackProperties(t *testing.T) {
 				continue
 			}
 
-			output := []interface{}{}
+			var output []interface{}
-			for _, p := range testCase.output {
+			if len(testCase.empty) > 0 {
-				output = append(output, proptools.CloneEmptyProperties(reflect.ValueOf(p)).Interface())
+				output = testCase.empty
+			} else {
+				for _, p := range testCase.output {
+					output = append(output, proptools.CloneEmptyProperties(reflect.ValueOf(p)).Interface())
+				}
 			}
 			_, errs = unpackProperties(module.Properties, output...)
 			if len(errs) != 0 && len(testCase.errs) == 0 {