rust: internalize srcPathFromModuleSrcs

This was frequently misused (for example, in the prebuilts module, it
was used as a complex "assert(len(srcs))==1"), and can be superceded by
getCrateRoot anywhere it was used. It's now only called from
compiler.go, and can drop the second return parameter, as it was only
actually used by the prebuilt assert misuse.

Bug: 309943184
Test: m nothing
Change-Id: I6c92580bc8f0ecb7586c544056b5409e6dd280e7

5 files changed, 20 insertions, 21 deletions

diff --git a/rust/binary.go b/rust/binary.go
index 860dc948a..146c683fb 100644
--- a/rust/binary.go
+++ b/rust/binary.go
@@ -137,12 +137,7 @@ func (binary *binaryDecorator) compile(ctx ModuleContext, flags Flags, deps Path
 	fileName := binary.getStem(ctx) + ctx.toolchain().ExecutableSuffix()
 	outputFile := android.PathForModuleOut(ctx, fileName)
 	ret := buildOutput{outputFile: outputFile}
-	var crateRootPath android.Path
-	if binary.baseCompiler.Properties.Crate_root == nil {
-		crateRootPath, _ = srcPathFromModuleSrcs(ctx, binary.baseCompiler.Properties.Srcs)
-	} else {
-		crateRootPath = android.PathForModuleSrc(ctx, *binary.baseCompiler.Properties.Crate_root)
-	}
+	crateRootPath := binary.crateRootPath(ctx)
 
 	flags.RustFlags = append(flags.RustFlags, deps.depFlags...)
 	flags.LinkFlags = append(flags.LinkFlags, deps.depLinkFlags...)
diff --git a/rust/compiler.go b/rust/compiler.go
index 98bbcb645..899502a64 100644
--- a/rust/compiler.go
+++ b/rust/compiler.go
@@ -541,7 +541,7 @@ func (compiler *baseCompiler) relativeInstallPath() string {
 
 func (compiler *baseCompiler) crateRootPath(ctx ModuleContext) android.Path {
 	if compiler.Properties.Crate_root == nil {
-		path, _ := srcPathFromModuleSrcs(ctx, compiler.Properties.Srcs)
+		path := srcPathFromModuleSrcs(ctx, compiler.Properties.Srcs)
 		return path
 	} else {
 		return android.PathForModuleSrc(ctx, *compiler.Properties.Crate_root)
@@ -549,7 +549,7 @@ func (compiler *baseCompiler) crateRootPath(ctx ModuleContext) android.Path {
 }
 
 // Returns the Path for the main source file along with Paths for generated source files from modules listed in srcs.
-func srcPathFromModuleSrcs(ctx ModuleContext, srcs []string) (android.Path, android.Paths) {
+func srcPathFromModuleSrcs(ctx ModuleContext, srcs []string) android.Path {
 	if len(srcs) == 0 {
 		ctx.PropertyErrorf("srcs", "srcs must not be empty")
 	}
@@ -580,5 +580,5 @@ func srcPathFromModuleSrcs(ctx ModuleContext, srcs []string) (android.Path, andr
 	// TODO: b/297264540 - once all modules are sandboxed, we need to select the proper
 	// entry point file from Srcs rather than taking the first one
 	paths := android.PathsForModuleSrc(ctx, srcs)
-	return paths[srcIndex], paths[1:]
+	return paths[srcIndex]
 }
diff --git a/rust/compiler_test.go b/rust/compiler_test.go
index ec6829a1b..89f4d1abf 100644
--- a/rust/compiler_test.go
+++ b/rust/compiler_test.go
@@ -67,6 +67,7 @@ func TestCfgsToFlags(t *testing.T) {
 func TestEnforceSingleSourceFile(t *testing.T) {
 
 	singleSrcError := "srcs can only contain one path for a rust file and source providers prefixed by \":\""
+	prebuiltSingleSrcError := "prebuilt libraries can only have one entry in srcs"
 
 	// Test libraries
 	testRustError(t, singleSrcError, `
@@ -90,7 +91,7 @@ func TestEnforceSingleSourceFile(t *testing.T) {
 		}`)
 
 	// Test prebuilts
-	testRustError(t, singleSrcError, `
+	testRustError(t, prebuiltSingleSrcError, `
 		rust_prebuilt_dylib {
 			name: "foo-bar-prebuilt",
 			srcs: ["liby.so", "libz.so"],
diff --git a/rust/prebuilt.go b/rust/prebuilt.go
index fe9d0b5dd..e35e510da 100644
--- a/rust/prebuilt.go
+++ b/rust/prebuilt.go
@@ -76,6 +76,17 @@ var _ compiler = (*prebuiltProcMacroDecorator)(nil)
 var _ exportedFlagsProducer = (*prebuiltProcMacroDecorator)(nil)
 var _ rustPrebuilt = (*prebuiltProcMacroDecorator)(nil)
 
+func prebuiltPath(ctx ModuleContext, prebuilt rustPrebuilt) android.Path {
+	srcs := android.PathsForModuleSrc(ctx, prebuilt.prebuiltSrcs())
+	if len(srcs) == 0 {
+		ctx.PropertyErrorf("srcs", "srcs must not be empty")
+	}
+	if len(srcs) > 1 {
+		ctx.PropertyErrorf("srcs", "prebuilt libraries can only have one entry in srcs (the prebuilt path)")
+	}
+	return srcs[0]
+}
+
 func PrebuiltLibraryFactory() android.Module {
 	module, _ := NewPrebuiltLibrary(android.HostAndDeviceSupported)
 	return module.Init()
@@ -148,11 +159,7 @@ func (prebuilt *prebuiltLibraryDecorator) compilerProps() []interface{} {
 func (prebuilt *prebuiltLibraryDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) buildOutput {
 	prebuilt.flagExporter.exportLinkDirs(android.PathsForModuleSrc(ctx, prebuilt.Properties.Link_dirs).Strings()...)
 	prebuilt.flagExporter.setProvider(ctx)
-
-	srcPath, paths := srcPathFromModuleSrcs(ctx, prebuilt.prebuiltSrcs())
-	if len(paths) > 0 {
-		ctx.PropertyErrorf("srcs", "prebuilt libraries can only have one entry in srcs (the prebuilt path)")
-	}
+	srcPath := prebuiltPath(ctx, prebuilt)
 	prebuilt.baseCompiler.unstrippedOutputFile = srcPath
 	return buildOutput{outputFile: srcPath}
 }
@@ -205,11 +212,7 @@ func (prebuilt *prebuiltProcMacroDecorator) compilerProps() []interface{} {
 func (prebuilt *prebuiltProcMacroDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) buildOutput {
 	prebuilt.flagExporter.exportLinkDirs(android.PathsForModuleSrc(ctx, prebuilt.Properties.Link_dirs).Strings()...)
 	prebuilt.flagExporter.setProvider(ctx)
-
-	srcPath, paths := srcPathFromModuleSrcs(ctx, prebuilt.prebuiltSrcs())
-	if len(paths) > 0 {
-		ctx.PropertyErrorf("srcs", "prebuilt libraries can only have one entry in srcs (the prebuilt path)")
-	}
+	srcPath := prebuiltPath(ctx, prebuilt)
 	prebuilt.baseCompiler.unstrippedOutputFile = srcPath
 	return buildOutput{outputFile: srcPath}
 }
diff --git a/rust/proc_macro.go b/rust/proc_macro.go
index b93b24f15..e3a48bff6 100644
--- a/rust/proc_macro.go
+++ b/rust/proc_macro.go
@@ -79,7 +79,7 @@ func (procMacro *procMacroDecorator) compile(ctx ModuleContext, flags Flags, dep
 	fileName := procMacro.getStem(ctx) + ctx.toolchain().ProcMacroSuffix()
 	outputFile := android.PathForModuleOut(ctx, fileName)
 
-	srcPath, _ := srcPathFromModuleSrcs(ctx, procMacro.baseCompiler.Properties.Srcs)
+	srcPath := procMacro.crateRootPath(ctx)
 	ret := TransformSrctoProcMacro(ctx, srcPath, deps, flags, outputFile)
 	procMacro.baseCompiler.unstrippedOutputFile = outputFile
 	return ret