Converters for contributions to systemapi and vendorapi

The module types in scope of this conversion are
1. cc_library and cc_library_shared (non-null llndk or stubs prop)
2. cc_library_headers (all)

For (2), we need some postprocessing on the results of the parser
bp2BuildParseBaseProps. This is necessary because arch and os specific
API exports need to be flattened and added to the generateed API headers
target along NoConfigAxis
e.g.
```
The api equivalent of
cc_library_headers (
  name = "lifoo",
  deps = select({
  	"//build/bazel/platforms/arch:arm": ["arm_deps"],
  	"//build/bazel/platforms/arch:arm64": ["arm64_deps"],
	}),
)
should be
cc_api_library_headers (
  name = "lifoo",
  deps = ["arm_deps", "arm64_deps"],
)
```

For (1), we also need to generate 1:many header api targets so that
arch-specific deps can propagate arch metadata to the top-level
api_domain rule

Test: go test ./bp2build
Test: go test ./cc

Change-Id: Ie40cba1ac8e89f290b3d926c190d5e93abd52859

cc/library.go

@@ -30,6 +30,7 @@ import (
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/pathtools"
+	"github.com/google/blueprint/proptools"
 )
 
 // LibraryProperties is a collection of properties shared by cc library rules/cc.
@@ -466,6 +467,147 @@ func createStubsBazelTargetIfNeeded(ctx android.TopDownMutatorContext, m *Module
 	}
 }
 
+func apiContributionBp2Build(ctx android.TopDownMutatorContext, module *Module) {
+	apiSurfaces := make([]string, 0)
+	apiHeaders := make([]string, 0)
+	// systemapi (non-null `stubs` property)
+	if module.HasStubsVariants() {
+		apiSurfaces = append(apiSurfaces, android.SystemApi.String())
+		apiIncludes := getSystemApiIncludes(ctx, module)
+		if !apiIncludes.isEmpty() {
+			createApiHeaderTarget(ctx, apiIncludes)
+			apiHeaders = append(apiHeaders, apiIncludes.name)
+		}
+	}
+	// vendorapi (non-null `llndk` property)
+	if module.HasLlndkStubs() {
+		apiSurfaces = append(apiSurfaces, android.VendorApi.String())
+		apiIncludes := getVendorApiIncludes(ctx, module)
+		if !apiIncludes.isEmpty() {
+			createApiHeaderTarget(ctx, apiIncludes)
+			apiHeaders = append(apiHeaders, apiIncludes.name)
+		}
+	}
+	// create a target only if this module contributes to an api surface
+	// TODO: Currently this does not distinguish systemapi-only headers and vendrorapi-only headers
+	// TODO: Update so that systemapi-only headers do not get exported to vendorapi (and vice-versa)
+	if len(apiSurfaces) > 0 {
+		props := bazel.BazelTargetModuleProperties{
+			Rule_class:        "cc_api_contribution",
+			Bzl_load_location: "//build/bazel/rules/apis:cc_api_contribution.bzl",
+		}
+		attrs := &bazelCcApiContributionAttributes{
+			Library_name: module.Name(),
+			Api_surfaces: bazel.MakeStringListAttribute(apiSurfaces),
+			Api:          apiLabelAttribute(ctx, module),
+			Hdrs: bazel.MakeLabelListAttribute(
+				bazel.MakeLabelListFromTargetNames(apiHeaders),
+			),
+		}
+		ctx.CreateBazelTargetModule(
+			props,
+			android.CommonAttributes{
+				Name:     android.ApiContributionTargetName(module.Name()),
+				SkipData: proptools.BoolPtr(true),
+			},
+			attrs,
+		)
+	}
+}
+
+// Native apis are versioned in a single .map.txt for all api surfaces
+// Pick any one of the .map.txt files
+func apiLabelAttribute(ctx android.TopDownMutatorContext, module *Module) bazel.LabelAttribute {
+	var apiFile *string
+	linker := module.linker.(*libraryDecorator)
+	if llndkApi := linker.Properties.Llndk.Symbol_file; llndkApi != nil {
+		apiFile = llndkApi
+	} else if systemApi := linker.Properties.Stubs.Symbol_file; systemApi != nil {
+		apiFile = systemApi
+	} else {
+		ctx.ModuleErrorf("API surface library does not have any API file")
+	}
+	apiLabel := android.BazelLabelForModuleSrcSingle(ctx, proptools.String(apiFile)).Label
+	return *bazel.MakeLabelAttribute(apiLabel)
+}
+
+// wrapper struct to flatten the arch and os specific export_include_dirs
+// flattening is necessary since we want to export apis of all arches even when we build for x86 (e.g.)
+type bazelCcApiLibraryHeadersAttributes struct {
+	bazelCcLibraryHeadersAttributes
+
+	Arch *string
+}
+
+func (a *bazelCcApiLibraryHeadersAttributes) isEmpty() bool {
+	return a.Export_includes.IsEmpty() &&
+		a.Export_system_includes.IsEmpty() &&
+		a.Deps.IsEmpty()
+}
+
+type apiIncludes struct {
+	name  string // name of the Bazel target in the generated bp2build workspace
+	attrs bazelCcApiLibraryHeadersAttributes
+}
+
+func (includes *apiIncludes) isEmpty() bool {
+	return includes.attrs.isEmpty()
+}
+
+func (includes *apiIncludes) addDep(name string) {
+	l := bazel.Label{Label: ":" + name}
+	ll := bazel.MakeLabelList([]bazel.Label{l})
+	lla := bazel.MakeLabelListAttribute(ll)
+	includes.attrs.Deps.Append(lla)
+}
+
+func getSystemApiIncludes(ctx android.TopDownMutatorContext, c *Module) apiIncludes {
+	flagProps := c.library.(*libraryDecorator).flagExporter.Properties
+	linkProps := c.library.(*libraryDecorator).baseLinker.Properties
+	includes := android.FirstUniqueStrings(flagProps.Export_include_dirs)
+	systemIncludes := android.FirstUniqueStrings(flagProps.Export_system_include_dirs)
+	headerLibs := android.FirstUniqueStrings(linkProps.Export_header_lib_headers)
+	attrs := bazelCcLibraryHeadersAttributes{
+		Export_includes:        bazel.MakeStringListAttribute(includes),
+		Export_system_includes: bazel.MakeStringListAttribute(systemIncludes),
+		Deps:                   bazel.MakeLabelListAttribute(apiHeaderLabels(ctx, headerLibs)),
+	}
+
+	return apiIncludes{
+		name: c.Name() + ".systemapi.headers",
+		attrs: bazelCcApiLibraryHeadersAttributes{
+			bazelCcLibraryHeadersAttributes: attrs,
+		},
+	}
+}
+
+func getVendorApiIncludes(ctx android.TopDownMutatorContext, c *Module) apiIncludes {
+	baseProps := c.library.(*libraryDecorator).flagExporter.Properties
+	llndkProps := c.library.(*libraryDecorator).Properties.Llndk
+	includes := baseProps.Export_include_dirs
+	systemIncludes := baseProps.Export_system_include_dirs
+	// LLNDK can override the base includes
+	if llndkIncludes := llndkProps.Override_export_include_dirs; llndkIncludes != nil {
+		includes = llndkIncludes
+	}
+	if proptools.Bool(llndkProps.Export_headers_as_system) {
+		systemIncludes = append(systemIncludes, includes...)
+		includes = nil
+	}
+
+	attrs := bazelCcLibraryHeadersAttributes{
+		Export_includes:        bazel.MakeStringListAttribute(includes),
+		Export_system_includes: bazel.MakeStringListAttribute(systemIncludes),
+		Deps:                   bazel.MakeLabelListAttribute(apiHeaderLabels(ctx, llndkProps.Export_llndk_headers)),
+	}
+	return apiIncludes{
+		name: c.Name() + ".vendorapi.headers",
+		attrs: bazelCcApiLibraryHeadersAttributes{
+			bazelCcLibraryHeadersAttributes: attrs,
+		},
+	}
+}
+
 // cc_library creates both static and/or shared libraries for a device and/or
 // host. By default, a cc_library has a single variant that targets the device.
 // Specifying `host_supported: true` also creates a library that targets the