[rust] Add SourceProviders as crates support.

This allows SourceProvider modules to create rust_library variants so
that generated source can be referenced as an external crate rather than
via an include macro. This is done by including rust_bindgen modules
like any other library, as a dependency in either rlibs, dylibs, or
rustlibs.

This renames the stem and flags properties for rust_bindgen modules to
source_stem and bindgen_flags, respectively. This deconflicts with the
usage in baseCompiler.

This also removes 'subName' from the Module struct and moves it over to
SourceProvider, which was the only user. This allows us to set it in
baseSourceProvider's AndroidMk; setting it in Module's AndroidMk was
causing problems finding NOTICE files for bindgen library variants.

Bug: 159064919
Test: New Soong tests pass.
Test: Local test rust_binary can use rust_bindgen module as a crate.

Change-Id: Ieb2cb614c2dd0b5aa7120541d77f6f822a6a1806

rust/library.go

@@ -69,6 +69,10 @@ type LibraryMutatedProperties struct {
 	VariantIsShared bool `blueprint:"mutated"`
 	// This variant is a static library
 	VariantIsStatic bool `blueprint:"mutated"`
+
+	// This variant is disabled and should not be compiled
+	// (used for SourceProvider variants that produce only source)
+	VariantIsDisabled bool `blueprint:"mutated"`
 }
 
 type libraryDecorator struct {
@@ -78,6 +82,7 @@ type libraryDecorator struct {
 	Properties        LibraryCompilerProperties
 	MutatedProperties LibraryMutatedProperties
 	includeDirs       android.Paths
+	sourceProvider    SourceProvider
 }
 
 type libraryInterface interface {
@@ -367,8 +372,13 @@ func (library *libraryDecorator) compilerFlags(ctx ModuleContext, flags Flags) F
 
 func (library *libraryDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) android.Path {
 	var outputFile android.WritablePath
+	var srcPath android.Path
 
-	srcPath, _ := srcPathFromModuleSrcs(ctx, library.baseCompiler.Properties.Srcs)
+	if library.sourceProvider != nil {
+		srcPath = library.sourceProvider.Srcs()[0]
+	} else {
+		srcPath, _ = srcPathFromModuleSrcs(ctx, library.baseCompiler.Properties.Srcs)
+	}
 
 	flags.RustFlags = append(flags.RustFlags, deps.depFlags...)
 
@@ -430,6 +440,14 @@ func (library *libraryDecorator) getStem(ctx ModuleContext) string {
 	return stem + String(library.baseCompiler.Properties.Suffix)
 }
 
+func (library *libraryDecorator) Disabled() bool {
+	return library.MutatedProperties.VariantIsDisabled
+}
+
+func (library *libraryDecorator) SetDisabled() {
+	library.MutatedProperties.VariantIsDisabled = true
+}
+
 var validCrateName = regexp.MustCompile("[^a-zA-Z0-9_]+")
 
 func validateLibraryStem(ctx BaseModuleContext, filename string, crate_name string) {
@@ -455,12 +473,23 @@ func LibraryMutator(mctx android.BottomUpMutatorContext) {
 		switch library := m.compiler.(type) {
 		case libraryInterface:
 			if library.buildRlib() && library.buildDylib() {
-				modules := mctx.CreateLocalVariations("rlib", "dylib")
+				variants := []string{"rlib", "dylib"}
+				if m.sourceProvider != nil {
+					variants = append(variants, "")
+				}
+				modules := mctx.CreateLocalVariations(variants...)
+
 				rlib := modules[0].(*Module)
 				dylib := modules[1].(*Module)
-
 				rlib.compiler.(libraryInterface).setRlib()
 				dylib.compiler.(libraryInterface).setDylib()
+
+				if m.sourceProvider != nil {
+					// This library is SourceProvider generated, so the non-library-producing
+					// variant needs to disable it's compiler and skip installation.
+					sourceProvider := modules[2].(*Module)
+					sourceProvider.compiler.SetDisabled()
+				}
 			} else if library.buildRlib() {
 				modules := mctx.CreateLocalVariations("rlib")
 				modules[0].(*Module).compiler.(libraryInterface).setRlib()
@@ -468,6 +497,11 @@ func LibraryMutator(mctx android.BottomUpMutatorContext) {
 				modules := mctx.CreateLocalVariations("dylib")
 				modules[0].(*Module).compiler.(libraryInterface).setDylib()
 			}
+
+			if m.sourceProvider != nil {
+				// Alias the non-library variant to the empty-string variant.
+				mctx.AliasVariation("")
+			}
 		}
 	}
 }