platform_build_blueprint/proptools/extend.go
Cole Faust 6437d4e737 Select statements
Select statements are a new blueprint feature inspired by bazel's select
statements. They are essentially alternative syntax for soong config
variables that require less boilerplate. In addition, they support
making decisions based on a module's variant, which will eliminate
the need for manual property struct manipulation, such as the arch
mutator's arch: and target: properties.

In order to support decisions based on the variant, select statements
cannot be evaluated as soon as they're parsed. Instead, they must be
stored in the property struct unevaluated. This means that individual
properties need to change their type from say, string, to
Configurable[string]. Currently, only configurable strings, bools, and
string slices are supported, but more types can be added later.
The module implementation must call my_property.Evaluate(ctx) in order
to get the final, resolved value of the select statement.

Bug: 323382414
Test: go tests
Change-Id: I62f8721d7f0ac3d1df4a06d7eaa260a5aa7fcba3
2024-03-06 15:00:39 -08:00

603 lines
21 KiB
Go

// Copyright 2015 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package proptools
import (
"fmt"
"reflect"
"strings"
)
// AppendProperties appends the values of properties in the property struct src to the property
// struct dst. dst and src must be the same type, and both must be pointers to structs. Properties
// tagged `blueprint:"mutated"` are skipped.
//
// The filter function can prevent individual properties from being appended by returning false, or
// abort AppendProperties with an error by returning an error. Passing nil for filter will append
// all properties.
//
// An error returned by AppendProperties that applies to a specific property will be an
// *ExtendPropertyError, and can have the property name and error extracted from it.
//
// The append operation is defined as appending strings and slices of strings normally, OR-ing bool
// values, replacing non-nil pointers to booleans or strings, and recursing into
// embedded structs, pointers to structs, and interfaces containing
// pointers to structs. Appending the zero value of a property will always be a no-op.
func AppendProperties(dst interface{}, src interface{}, filter ExtendPropertyFilterFunc) error {
return extendProperties(dst, src, filter, OrderAppend)
}
// PrependProperties prepends the values of properties in the property struct src to the property
// struct dst. dst and src must be the same type, and both must be pointers to structs. Properties
// tagged `blueprint:"mutated"` are skipped.
//
// The filter function can prevent individual properties from being prepended by returning false, or
// abort PrependProperties with an error by returning an error. Passing nil for filter will prepend
// all properties.
//
// An error returned by PrependProperties that applies to a specific property will be an
// *ExtendPropertyError, and can have the property name and error extracted from it.
//
// The prepend operation is defined as prepending strings, and slices of strings normally, OR-ing
// bool values, replacing non-nil pointers to booleans or strings, and recursing into
// embedded structs, pointers to structs, and interfaces containing
// pointers to structs. Prepending the zero value of a property will always be a no-op.
func PrependProperties(dst interface{}, src interface{}, filter ExtendPropertyFilterFunc) error {
return extendProperties(dst, src, filter, OrderPrepend)
}
// AppendMatchingProperties appends the values of properties in the property struct src to the
// property structs in dst. dst and src do not have to be the same type, but every property in src
// must be found in at least one property in dst. dst must be a slice of pointers to structs, and
// src must be a pointer to a struct. Properties tagged `blueprint:"mutated"` are skipped.
//
// The filter function can prevent individual properties from being appended by returning false, or
// abort AppendProperties with an error by returning an error. Passing nil for filter will append
// all properties.
//
// An error returned by AppendMatchingProperties that applies to a specific property will be an
// *ExtendPropertyError, and can have the property name and error extracted from it.
//
// The append operation is defined as appending strings, and slices of strings normally, OR-ing bool
// values, replacing pointers to booleans or strings whether they are nil or not, and recursing into
// embedded structs, pointers to structs, and interfaces containing
// pointers to structs. Appending the zero value of a property will always be a no-op.
func AppendMatchingProperties(dst []interface{}, src interface{},
filter ExtendPropertyFilterFunc) error {
return extendMatchingProperties(dst, src, filter, OrderAppend)
}
// PrependMatchingProperties prepends the values of properties in the property struct src to the
// property structs in dst. dst and src do not have to be the same type, but every property in src
// must be found in at least one property in dst. dst must be a slice of pointers to structs, and
// src must be a pointer to a struct. Properties tagged `blueprint:"mutated"` are skipped.
//
// The filter function can prevent individual properties from being prepended by returning false, or
// abort PrependProperties with an error by returning an error. Passing nil for filter will prepend
// all properties.
//
// An error returned by PrependProperties that applies to a specific property will be an
// *ExtendPropertyError, and can have the property name and error extracted from it.
//
// The prepend operation is defined as prepending strings, and slices of strings normally, OR-ing
// bool values, replacing nil pointers to booleans or strings, and recursing into
// embedded structs, pointers to structs, and interfaces containing
// pointers to structs. Prepending the zero value of a property will always be a no-op.
func PrependMatchingProperties(dst []interface{}, src interface{},
filter ExtendPropertyFilterFunc) error {
return extendMatchingProperties(dst, src, filter, OrderPrepend)
}
// ExtendProperties appends or prepends the values of properties in the property struct src to the
// property struct dst. dst and src must be the same type, and both must be pointers to structs.
// Properties tagged `blueprint:"mutated"` are skipped.
//
// The filter function can prevent individual properties from being appended or prepended by
// returning false, or abort ExtendProperties with an error by returning an error. Passing nil for
// filter will append or prepend all properties.
//
// The order function is called on each non-filtered property to determine if it should be appended
// or prepended.
//
// An error returned by ExtendProperties that applies to a specific property will be an
// *ExtendPropertyError, and can have the property name and error extracted from it.
//
// The append operation is defined as appending strings and slices of strings normally, OR-ing bool
// values, replacing non-nil pointers to booleans or strings, and recursing into
// embedded structs, pointers to structs, and interfaces containing
// pointers to structs. Appending or prepending the zero value of a property will always be a
// no-op.
func ExtendProperties(dst interface{}, src interface{}, filter ExtendPropertyFilterFunc,
order ExtendPropertyOrderFunc) error {
return extendProperties(dst, src, filter, order)
}
// ExtendMatchingProperties appends or prepends the values of properties in the property struct src
// to the property structs in dst. dst and src do not have to be the same type, but every property
// in src must be found in at least one property in dst. dst must be a slice of pointers to
// structs, and src must be a pointer to a struct. Properties tagged `blueprint:"mutated"` are
// skipped.
//
// The filter function can prevent individual properties from being appended or prepended by
// returning false, or abort ExtendMatchingProperties with an error by returning an error. Passing
// nil for filter will append or prepend all properties.
//
// The order function is called on each non-filtered property to determine if it should be appended
// or prepended.
//
// An error returned by ExtendMatchingProperties that applies to a specific property will be an
// *ExtendPropertyError, and can have the property name and error extracted from it.
//
// The append operation is defined as appending strings, and slices of strings normally, OR-ing bool
// values, replacing non-nil pointers to booleans or strings, and recursing into
// embedded structs, pointers to structs, and interfaces containing
// pointers to structs. Appending or prepending the zero value of a property will always be a
// no-op.
func ExtendMatchingProperties(dst []interface{}, src interface{},
filter ExtendPropertyFilterFunc, order ExtendPropertyOrderFunc) error {
return extendMatchingProperties(dst, src, filter, order)
}
type Order int
const (
Append Order = iota
Prepend
Replace
)
type ExtendPropertyFilterFunc func(dstField, srcField reflect.StructField) (bool, error)
type ExtendPropertyOrderFunc func(dstField, srcField reflect.StructField) (Order, error)
func OrderAppend(dstField, srcField reflect.StructField) (Order, error) {
return Append, nil
}
func OrderPrepend(dstField, srcField reflect.StructField) (Order, error) {
return Prepend, nil
}
func OrderReplace(dstField, srcField reflect.StructField) (Order, error) {
return Replace, nil
}
type ExtendPropertyError struct {
Err error
Property string
}
func (e *ExtendPropertyError) Error() string {
return fmt.Sprintf("can't extend property %q: %s", e.Property, e.Err)
}
func extendPropertyErrorf(property string, format string, a ...interface{}) *ExtendPropertyError {
return &ExtendPropertyError{
Err: fmt.Errorf(format, a...),
Property: property,
}
}
func extendProperties(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
}
dstValue, err := getOrCreateStruct(dst)
if err != nil {
return err
}
if dstValue.Type() != srcValue.Type() {
return fmt.Errorf("expected matching types for dst and src, got %T and %T", dst, src)
}
dstValues := []reflect.Value{dstValue}
return extendPropertiesRecursive(dstValues, srcValue, make([]string, 0, 8), filter, true, order)
}
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 = getOrCreateStruct(dst[i])
if err != nil {
return err
}
}
return extendPropertiesRecursive(dstValues, srcValue, make([]string, 0, 8), filter, false, order)
}
func extendPropertiesRecursive(dstValues []reflect.Value, srcValue reflect.Value,
prefix []string, filter ExtendPropertyFilterFunc, sameTypes bool,
orderFunc ExtendPropertyOrderFunc) error {
dstValuesCopied := false
propertyName := func(field reflect.StructField) string {
names := make([]string, 0, len(prefix)+1)
for _, s := range prefix {
names = append(names, PropertyNameForField(s))
}
names = append(names, PropertyNameForField(field.Name))
return strings.Join(names, ".")
}
srcType := srcValue.Type()
for i, srcField := range typeFields(srcType) {
if ShouldSkipProperty(srcField) {
continue
}
srcFieldValue := srcValue.Field(i)
// Step into source interfaces
if srcFieldValue.Kind() == reflect.Interface {
if srcFieldValue.IsNil() {
continue
}
srcFieldValue = srcFieldValue.Elem()
if srcFieldValue.Kind() != reflect.Ptr {
return extendPropertyErrorf(propertyName(srcField), "interface not a pointer")
}
}
// Step into source pointers to structs
if isStructPtr(srcFieldValue.Type()) {
if srcFieldValue.IsNil() {
continue
}
srcFieldValue = srcFieldValue.Elem()
}
found := false
var recurse []reflect.Value
// Use an iteration loop so elements can be added to the end of dstValues inside the loop.
for j := 0; j < len(dstValues); j++ {
dstValue := dstValues[j]
dstType := dstValue.Type()
var dstField reflect.StructField
dstFields := typeFields(dstType)
if dstType == srcType {
dstField = dstFields[i]
} else {
var ok bool
for _, field := range dstFields {
if field.Name == srcField.Name {
dstField = field
ok = true
} else if IsEmbedded(field) {
embeddedDstValue := dstValue.FieldByIndex(field.Index)
if isStructPtr(embeddedDstValue.Type()) {
if embeddedDstValue.IsNil() {
newEmbeddedDstValue := reflect.New(embeddedDstValue.Type().Elem())
embeddedDstValue.Set(newEmbeddedDstValue)
}
embeddedDstValue = embeddedDstValue.Elem()
}
if !isStruct(embeddedDstValue.Type()) {
return extendPropertyErrorf(propertyName(srcField), "%s is not a struct (%s)",
propertyName(field), embeddedDstValue.Type())
}
// The destination struct contains an embedded struct, add it to the list
// of destinations to consider. Make a copy of dstValues if necessary
// to avoid modifying the backing array of an input parameter.
if !dstValuesCopied {
dstValues = append([]reflect.Value(nil), dstValues...)
dstValuesCopied = true
}
dstValues = append(dstValues, embeddedDstValue)
}
}
if !ok {
continue
}
}
found = true
dstFieldValue := dstValue.FieldByIndex(dstField.Index)
origDstFieldValue := dstFieldValue
// Step into destination interfaces
if dstFieldValue.Kind() == reflect.Interface {
if dstFieldValue.IsNil() {
return extendPropertyErrorf(propertyName(srcField), "nilitude mismatch")
}
dstFieldValue = dstFieldValue.Elem()
if dstFieldValue.Kind() != reflect.Ptr {
return extendPropertyErrorf(propertyName(srcField), "interface not a pointer")
}
}
// Step into destination pointers to structs
if isStructPtr(dstFieldValue.Type()) {
if dstFieldValue.IsNil() {
dstFieldValue = reflect.New(dstFieldValue.Type().Elem())
origDstFieldValue.Set(dstFieldValue)
}
dstFieldValue = dstFieldValue.Elem()
}
switch srcFieldValue.Kind() {
case reflect.Struct:
if isConfigurable(srcField.Type) {
if srcFieldValue.Type() != dstFieldValue.Type() {
return extendPropertyErrorf(propertyName(srcField), "mismatched types %s and %s",
dstFieldValue.Type(), srcFieldValue.Type())
}
} else {
if sameTypes && dstFieldValue.Type() != srcFieldValue.Type() {
return extendPropertyErrorf(propertyName(srcField), "mismatched types %s and %s",
dstFieldValue.Type(), srcFieldValue.Type())
}
// Recursively extend the struct's fields.
recurse = append(recurse, dstFieldValue)
continue
}
case reflect.Bool, reflect.String, reflect.Slice, reflect.Map:
if srcFieldValue.Type() != dstFieldValue.Type() {
return extendPropertyErrorf(propertyName(srcField), "mismatched types %s and %s",
dstFieldValue.Type(), srcFieldValue.Type())
}
case reflect.Ptr:
if srcFieldValue.Type() != dstFieldValue.Type() {
return extendPropertyErrorf(propertyName(srcField), "mismatched types %s and %s",
dstFieldValue.Type(), srcFieldValue.Type())
}
switch ptrKind := srcFieldValue.Type().Elem().Kind(); ptrKind {
case reflect.Bool, reflect.Int64, reflect.String, reflect.Struct:
// Nothing
default:
return extendPropertyErrorf(propertyName(srcField), "pointer is a %s", ptrKind)
}
default:
return extendPropertyErrorf(propertyName(srcField), "unsupported kind %s",
srcFieldValue.Kind())
}
if filter != nil {
b, err := filter(dstField, srcField)
if err != nil {
return &ExtendPropertyError{
Property: propertyName(srcField),
Err: err,
}
}
if !b {
continue
}
}
order := Append
if orderFunc != nil {
var err error
order, err = orderFunc(dstField, srcField)
if err != nil {
return &ExtendPropertyError{
Property: propertyName(srcField),
Err: err,
}
}
}
ExtendBasicType(dstFieldValue, srcFieldValue, order)
}
if len(recurse) > 0 {
err := extendPropertiesRecursive(recurse, srcFieldValue,
append(prefix, srcField.Name), filter, sameTypes, orderFunc)
if err != nil {
return err
}
} else if !found {
return extendPropertyErrorf(propertyName(srcField), "failed to find property to extend")
}
}
return nil
}
func ExtendBasicType(dstFieldValue, srcFieldValue reflect.Value, order Order) {
prepend := order == Prepend
switch srcFieldValue.Kind() {
case reflect.Struct:
if !isConfigurable(srcFieldValue.Type()) {
panic("Should be unreachable")
}
if dstFieldValue.Interface().(configurableReflection).isEmpty() {
dstFieldValue.Set(srcFieldValue)
} else if prepend {
srcFieldValue.Interface().(configurableReflection).setAppend(dstFieldValue.Interface())
dstFieldValue.Set(srcFieldValue)
} else {
dstFieldValue.Interface().(configurableReflection).setAppend(srcFieldValue.Interface())
}
case reflect.Bool:
// Boolean OR
dstFieldValue.Set(reflect.ValueOf(srcFieldValue.Bool() || dstFieldValue.Bool()))
case reflect.String:
if prepend {
dstFieldValue.SetString(srcFieldValue.String() +
dstFieldValue.String())
} else {
dstFieldValue.SetString(dstFieldValue.String() +
srcFieldValue.String())
}
case reflect.Slice:
if srcFieldValue.IsNil() {
break
}
newSlice := reflect.MakeSlice(srcFieldValue.Type(), 0,
dstFieldValue.Len()+srcFieldValue.Len())
if prepend {
newSlice = reflect.AppendSlice(newSlice, srcFieldValue)
newSlice = reflect.AppendSlice(newSlice, dstFieldValue)
} else if order == Append {
newSlice = reflect.AppendSlice(newSlice, dstFieldValue)
newSlice = reflect.AppendSlice(newSlice, srcFieldValue)
} else {
// replace
newSlice = reflect.AppendSlice(newSlice, srcFieldValue)
}
dstFieldValue.Set(newSlice)
case reflect.Map:
if srcFieldValue.IsNil() {
break
}
var mapValue reflect.Value
// for append/prepend, maintain keys from original value
// for replace, replace entire map
if order == Replace || dstFieldValue.IsNil() {
mapValue = srcFieldValue
} else {
mapValue = dstFieldValue
iter := srcFieldValue.MapRange()
for iter.Next() {
dstValue := dstFieldValue.MapIndex(iter.Key())
if prepend {
// if the key exists in the map, keep the original value.
if !dstValue.IsValid() {
// otherwise, add the new value
mapValue.SetMapIndex(iter.Key(), iter.Value())
}
} else {
// For append, replace the original value.
mapValue.SetMapIndex(iter.Key(), iter.Value())
}
}
}
dstFieldValue.Set(mapValue)
case reflect.Ptr:
if srcFieldValue.IsNil() {
break
}
switch ptrKind := srcFieldValue.Type().Elem().Kind(); ptrKind {
case reflect.Bool:
if prepend {
if dstFieldValue.IsNil() {
dstFieldValue.Set(reflect.ValueOf(BoolPtr(srcFieldValue.Elem().Bool())))
}
} else {
// For append, replace the original value.
dstFieldValue.Set(reflect.ValueOf(BoolPtr(srcFieldValue.Elem().Bool())))
}
case reflect.Int64:
if prepend {
if dstFieldValue.IsNil() {
// Int() returns Int64
dstFieldValue.Set(reflect.ValueOf(Int64Ptr(srcFieldValue.Elem().Int())))
}
} else {
// For append, replace the original value.
// Int() returns Int64
dstFieldValue.Set(reflect.ValueOf(Int64Ptr(srcFieldValue.Elem().Int())))
}
case reflect.String:
if prepend {
if dstFieldValue.IsNil() {
dstFieldValue.Set(reflect.ValueOf(StringPtr(srcFieldValue.Elem().String())))
}
} else {
// For append, replace the original value.
dstFieldValue.Set(reflect.ValueOf(StringPtr(srcFieldValue.Elem().String())))
}
case reflect.Struct:
srcFieldValue := srcFieldValue.Elem()
if !isConfigurable(srcFieldValue.Type()) {
panic("Should be unreachable")
}
if dstFieldValue.Interface().(configurableReflection).isEmpty() {
dstFieldValue.Set(srcFieldValue)
} else if prepend {
srcFieldValue.Interface().(configurableReflection).setAppend(dstFieldValue.Interface())
dstFieldValue.Set(srcFieldValue)
} else {
dstFieldValue.Interface().(configurableReflection).setAppend(srcFieldValue.Interface())
}
default:
panic(fmt.Errorf("unexpected pointer kind %s", ptrKind))
}
}
}
// ShouldSkipProperty indicates whether a property should be skipped in processing.
func ShouldSkipProperty(structField reflect.StructField) bool {
return structField.PkgPath != "" || // The field is not exported so just skip it.
HasTag(structField, "blueprint", "mutated") // The field is not settable in a blueprint file
}
// IsEmbedded indicates whether a property is embedded. This is useful for determining nesting name
// as the name of the embedded field is _not_ used in blueprint files.
func IsEmbedded(structField reflect.StructField) bool {
return structField.Name == "BlueprintEmbed" || structField.Anonymous
}
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 !isStructPtr(value.Type()) {
return reflect.Value{}, fmt.Errorf("expected pointer to struct, got %s", value.Type())
}
if value.IsNil() {
return reflect.Value{}, getStructEmptyError{}
}
value = value.Elem()
return value, nil
}