Add more comments to path_properties.go
Bug: 173449605
Test: m checkbuild
Change-Id: I2638da9cc56726f5d646424e72f52289ad093781
diff --git a/android/path_properties.go b/android/path_properties.go
index 6b1cdb3..4bb706a 100644
--- a/android/path_properties.go
+++ b/android/path_properties.go
@@ -21,27 +21,31 @@
"github.com/google/blueprint/proptools"
)
+// This file implements support for automatically adding dependencies on any module referenced
+// with the ":module" module reference syntax in a property that is annotated with `android:"path"`.
+// The dependency is used by android.PathForModuleSrc to convert the module reference into the path
+// to the output file of the referenced module.
+
func registerPathDepsMutator(ctx RegisterMutatorsContext) {
ctx.BottomUp("pathdeps", pathDepsMutator).Parallel()
}
-// The pathDepsMutator automatically adds dependencies on any module that is listed with ":module" syntax in a
-// property that is tagged with android:"path".
+// The pathDepsMutator automatically adds dependencies on any module that is listed with the
+// ":module" module reference syntax in a property that is tagged with `android:"path"`.
func pathDepsMutator(ctx BottomUpMutatorContext) {
- m := ctx.Module().(Module)
- if m == nil {
- return
- }
+ props := ctx.Module().base().generalProperties
- props := m.base().generalProperties
-
+ // Iterate through each property struct of the module extracting the contents of all properties
+ // tagged with `android:"path"`.
var pathProperties []string
for _, ps := range props {
- pathProperties = append(pathProperties, pathPropertiesForPropertyStruct(ctx, ps)...)
+ pathProperties = append(pathProperties, pathPropertiesForPropertyStruct(ps)...)
}
+ // Remove duplicates to avoid multiple dependencies.
pathProperties = FirstUniqueStrings(pathProperties)
+ // Add dependencies to anything that is a module reference.
for _, s := range pathProperties {
if m, t := SrcIsModuleWithTag(s); m != "" {
ctx.AddDependency(ctx.Module(), sourceOrOutputDepTag(t), m)
@@ -49,34 +53,45 @@
}
}
-// pathPropertiesForPropertyStruct uses the indexes of properties that are tagged with android:"path" to extract
-// all their values from a property struct, returning them as a single slice of strings..
-func pathPropertiesForPropertyStruct(ctx BottomUpMutatorContext, ps interface{}) []string {
+// pathPropertiesForPropertyStruct uses the indexes of properties that are tagged with
+// android:"path" to extract all their values from a property struct, returning them as a single
+// slice of strings.
+func pathPropertiesForPropertyStruct(ps interface{}) []string {
v := reflect.ValueOf(ps)
if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct {
panic(fmt.Errorf("type %s is not a pointer to a struct", v.Type()))
}
+
+ // If the property struct is a nil pointer it can't have any paths set in it.
if v.IsNil() {
return nil
}
+
+ // v is now the reflect.Value for the concrete property struct.
v = v.Elem()
+ // Get or create the list of indexes of properties that are tagged with `android:"path"`.
pathPropertyIndexes := pathPropertyIndexesForPropertyStruct(ps)
var ret []string
for _, i := range pathPropertyIndexes {
+ // Turn an index into a field.
sv := fieldByIndex(v, i)
if !sv.IsValid() {
+ // Skip properties inside a nil pointer.
continue
}
+ // If the field is a non-nil pointer step into it.
if sv.Kind() == reflect.Ptr {
if sv.IsNil() {
continue
}
sv = sv.Elem()
}
+
+ // Collect paths from all strings and slices of strings.
switch sv.Kind() {
case reflect.String:
ret = append(ret, sv.String())
@@ -91,8 +106,8 @@
return ret
}
-// fieldByIndex is like reflect.Value.FieldByIndex, but returns an invalid reflect.Value when traversing a nil pointer
-// to a struct.
+// fieldByIndex is like reflect.Value.FieldByIndex, but returns an invalid reflect.Value when
+// traversing a nil pointer to a struct.
func fieldByIndex(v reflect.Value, index []int) reflect.Value {
if len(index) == 1 {
return v.Field(index[0])
@@ -111,9 +126,9 @@
var pathPropertyIndexesCache OncePer
-// pathPropertyIndexesForPropertyStruct returns a list of all of the indexes of properties in property struct type that
-// are tagged with android:"path". Each index is a []int suitable for passing to reflect.Value.FieldByIndex. The value
-// is cached in a global cache by type.
+// pathPropertyIndexesForPropertyStruct returns a list of all of the indexes of properties in
+// property struct type that are tagged with `android:"path"`. Each index is a []int suitable for
+// passing to reflect.Value.FieldByIndex. The value is cached in a global cache by type.
func pathPropertyIndexesForPropertyStruct(ps interface{}) [][]int {
key := NewCustomOnceKey(reflect.TypeOf(ps))
return pathPropertyIndexesCache.Once(key, func() interface{} {