Specify module dependency in the srcs list

* "srcs" list contains one main Rust source file,
  followed by optional dependent modules.
* A dependent module included in the "srcs" list is
  the module name prefixed with ":".
* Add a simple test.

Bug: 160331255
Test: make and manual test build dependencies on genrule modules
Change-Id: I4f079138c2599158810b6412fce81b612a3f64a4

1 files changed, 19 insertions, 5 deletions

diff --git a/rust/compiler.go b/rust/compiler.go
index 92a3b07f2..c20179bd0 100644
--- a/rust/compiler.go
+++ b/rust/compiler.go
@@ -253,10 +253,24 @@ func (compiler *baseCompiler) relativeInstallPath() string {
 	return String(compiler.Properties.Relative_install_path)
 }
 
-func srcPathFromModuleSrcs(ctx ModuleContext, srcs []string) android.Path {
-	srcPaths := android.PathsForModuleSrc(ctx, srcs)
-	if len(srcPaths) != 1 {
-		ctx.PropertyErrorf("srcs", "srcs can only contain one path for rust modules")
+func srcPathFromModuleSrcs(ctx ModuleContext, srcs []string) (android.Path, android.Paths) {
+	// The srcs can contain strings with prefix ":".
+	// They are dependent modules of this module, with android.SourceDepTag.
+	// They are not the main source file compiled by rustc.
+	numSrcs := 0
+	srcIndex := 0
+	for i, s := range srcs {
+		if android.SrcIsModule(s) == "" {
+			numSrcs++
+			srcIndex = i
+		}
+	}
+	if numSrcs != 1 {
+		ctx.PropertyErrorf("srcs", "srcs can only contain one path for a rust file")
+	}
+	if srcIndex != 0 {
+		ctx.PropertyErrorf("srcs", "main source file must be the first in srcs")
 	}
-	return srcPaths[0]
+	paths := android.PathsForModuleSrc(ctx, srcs)
+	return paths[srcIndex], paths
 }