bp2build: add configurable attribute (select) support.
This CL adds a basic framework to support configurable string_list
attributes, selecting on the Arch variant (x86, x86_64, arm, arm64).
It offers fine-grained controls to map individual configurable
properties (arch_variant) to configurable Bazel attributes, starting
with the string_list type for the copts property for cc_object.
This design is primarily motivated to have minimal boilerplate in
bp2build mutators, allowing anyone to opt-in configurable attributes,
and modify intermediate states before passing them on into the
CreateBazelTargetModule instantiator.
Fixes: 178130668
Test: go tests
Test: build/bazel/scripts/milestone-2/demo.sh
Change-Id: Id6f04d7c560312a93e193d7ca4e1b7ceb6062260
diff --git a/android/arch.go b/android/arch.go
index f719ddc..20b4ab0 100644
--- a/android/arch.go
+++ b/android/arch.go
@@ -1615,3 +1615,97 @@
return buildTargets, nil
}
+
+// GetArchProperties returns a map of architectures to the values of the
+// properties of the 'dst' struct that are specific to that architecture.
+//
+// For example, passing a struct { Foo bool, Bar string } will return an
+// interface{} that can be type asserted back into the same struct, containing
+// the arch specific property value specified by the module if defined.
+func (m *ModuleBase) GetArchProperties(dst interface{}) map[ArchType]interface{} {
+ // Return value of the arch types to the prop values for that arch.
+ archToProp := map[ArchType]interface{}{}
+
+ // Nothing to do for non-arch-specific modules.
+ if !m.ArchSpecific() {
+ return archToProp
+ }
+
+ // archProperties has the type of [][]interface{}. Looks complicated, so let's
+ // explain this step by step.
+ //
+ // Loop over the outer index, which determines the property struct that
+ // contains a matching set of properties in dst that we're interested in.
+ // For example, BaseCompilerProperties or BaseLinkerProperties.
+ for i := range m.archProperties {
+ if m.archProperties[i] == nil {
+ // Skip over nil arch props
+ continue
+ }
+
+ // Non-nil arch prop, let's see if the props match up.
+ for _, arch := range ArchTypeList() {
+ // e.g X86, Arm
+ field := arch.Field
+
+ // If it's not nil, loop over the inner index, which determines the arch variant
+ // of the prop type. In an Android.bp file, this is like looping over:
+ //
+ // arch: { arm: { key: value, ... }, x86: { key: value, ... } }
+ for _, archProperties := range m.archProperties[i] {
+ archPropValues := reflect.ValueOf(archProperties).Elem()
+
+ // This is the archPropRoot struct. Traverse into the Arch nested struct.
+ src := archPropValues.FieldByName("Arch").Elem()
+
+ // Step into non-nil pointers to structs in the src value.
+ if src.Kind() == reflect.Ptr {
+ if src.IsNil() {
+ // Ignore nil pointers.
+ continue
+ }
+ src = src.Elem()
+ }
+
+ // Find the requested field (e.g. x86, x86_64) in the src struct.
+ src = src.FieldByName(field)
+ if !src.IsValid() {
+ continue
+ }
+
+ // We only care about structs. These are not the droids you are looking for.
+ if src.Kind() != reflect.Struct {
+ continue
+ }
+
+ // If the value of the field is a struct then step into the
+ // BlueprintEmbed field. The special "BlueprintEmbed" name is
+ // used by createArchPropTypeDesc to embed the arch properties
+ // in the parent struct, so the src arch prop should be in this
+ // field.
+ //
+ // See createArchPropTypeDesc for more details on how Arch-specific
+ // module properties are processed from the nested props and written
+ // into the module's archProperties.
+ src = src.FieldByName("BlueprintEmbed")
+
+ // Clone the destination prop, since we want a unique prop struct per arch.
+ dstClone := reflect.New(reflect.ValueOf(dst).Elem().Type()).Interface()
+
+ // Copy the located property struct into the cloned destination property struct.
+ err := proptools.ExtendMatchingProperties([]interface{}{dstClone}, src.Interface(), nil, proptools.OrderReplace)
+ if err != nil {
+ // This is fine, it just means the src struct doesn't match.
+ continue
+ }
+
+ // Found the prop for the arch, you have.
+ archToProp[arch] = dstClone
+
+ // Go to the next prop.
+ break
+ }
+ }
+ }
+ return archToProp
+}
diff --git a/android/module.go b/android/module.go
index 5342246..1936d3c 100644
--- a/android/module.go
+++ b/android/module.go
@@ -1123,8 +1123,15 @@
variableProperties interface{}
hostAndDeviceProperties hostAndDeviceProperties
generalProperties []interface{}
- archProperties [][]interface{}
- customizableProperties []interface{}
+
+ // Arch specific versions of structs in generalProperties. The outer index
+ // has the same order as generalProperties as initialized in
+ // InitAndroidArchModule, and the inner index chooses the props specific to
+ // the architecture. The interface{} value is an archPropRoot that is
+ // filled with arch specific values by the arch mutator.
+ archProperties [][]interface{}
+
+ customizableProperties []interface{}
// Properties specific to the Blueprint to BUILD migration.
bazelTargetModuleProperties bazel.BazelTargetModuleProperties