rust: Allow rustlibs to fallback to rlibs.

Allow adding rlib-only libraries to rustlibs by having it fallback to
selecting the rlib variant if a dylib variant is requested but not
available.

Bug: 224771894
Test: m nothing
Test: New Soong test
Change-Id: I47b19ec9dbf3da90a2b090aeda04556a0400c7d1

rust/library_test.go

@@ -200,23 +200,34 @@ func TestStaticLibraryLinkage(t *testing.T) {
 func TestAutoDeps(t *testing.T) {
 
 	ctx := testRust(t, `
-                rust_library_host {
-                        name: "libbar",
-                        srcs: ["bar.rs"],
-                        crate_name: "bar",
-                }
+		rust_library_host {
+			name: "libbar",
+			srcs: ["bar.rs"],
+			crate_name: "bar",
+		}
+		rust_library_host_rlib {
+			name: "librlib_only",
+			srcs: ["bar.rs"],
+			crate_name: "rlib_only",
+		}
 		rust_library_host {
 			name: "libfoo",
 			srcs: ["foo.rs"],
 			crate_name: "foo",
-                        rustlibs: ["libbar"],
+			rustlibs: [
+				"libbar",
+				"librlib_only",
+			],
 		}
-                rust_ffi_host {
-                        name: "libfoo.ffi",
-                        srcs: ["foo.rs"],
-                        crate_name: "foo",
-                        rustlibs: ["libbar"],
-                }`)
+		rust_ffi_host {
+			name: "libfoo.ffi",
+			srcs: ["foo.rs"],
+			crate_name: "foo",
+			rustlibs: [
+				"libbar",
+				"librlib_only",
+			],
+		}`)
 
 	libfooRlib := ctx.ModuleForTests("libfoo", "linux_glibc_x86_64_rlib_rlib-std")
 	libfooDylib := ctx.ModuleForTests("libfoo", "linux_glibc_x86_64_dylib")
@@ -239,7 +250,9 @@ func TestAutoDeps(t *testing.T) {
 		if android.InList("libbar.dylib-std", dyn.Module().(*Module).Properties.AndroidMkRlibs) {
 			t.Errorf("libbar present as rlib dependency in dynamic lib")
 		}
-
+		if !android.InList("librlib_only.dylib-std", dyn.Module().(*Module).Properties.AndroidMkRlibs) {
+			t.Errorf("librlib_only should be selected by rustlibs as an rlib.")
+		}
 	}
 }
 

rust/rust.go

@@ -1371,13 +1371,12 @@ func (mod *Module) DepsMutator(actx android.BottomUpMutatorContext) {
 	}
 
 	// rlibs
+	rlibDepVariations = append(rlibDepVariations, blueprint.Variation{Mutator: "rust_libraries", Variation: rlibVariation})
 	for _, lib := range deps.Rlibs {
 		depTag := rlibDepTag
 		lib = cc.RewriteSnapshotLib(lib, cc.GetSnapshot(mod, &snapshotInfo, actx).Rlibs)
 
-		actx.AddVariationDependencies(append(rlibDepVariations, []blueprint.Variation{
-			{Mutator: "rust_libraries", Variation: rlibVariation},
-		}...), depTag, lib)
+		actx.AddVariationDependencies(rlibDepVariations, depTag, lib)
 	}
 
 	// dylibs
@@ -1389,21 +1388,25 @@ func (mod *Module) DepsMutator(actx android.BottomUpMutatorContext) {
 	// rustlibs
 	if deps.Rustlibs != nil && !mod.compiler.Disabled() {
 		autoDep := mod.compiler.(autoDeppable).autoDep(ctx)
-		if autoDep.depTag == rlibDepTag {
-			for _, lib := range deps.Rustlibs {
-				depTag := autoDep.depTag
-				lib = cc.RewriteSnapshotLib(lib, cc.GetSnapshot(mod, &snapshotInfo, actx).Rlibs)
-				actx.AddVariationDependencies(append(rlibDepVariations, []blueprint.Variation{
-					{Mutator: "rust_libraries", Variation: autoDep.variation},
-				}...), depTag, lib)
+		for _, lib := range deps.Rustlibs {
+			if autoDep.depTag == rlibDepTag {
+				// Handle the rlib deptag case
+				addRlibDependency(actx, lib, mod, snapshotInfo, rlibDepVariations)
+			} else {
+				// autoDep.depTag is a dylib depTag. Not all rustlibs may be available as a dylib however.
+				// Check for the existence of the dylib deptag variant. Select it if available,
+				// otherwise select the rlib variant.
+				autoDepVariations := append(commonDepVariations,
+					blueprint.Variation{Mutator: "rust_libraries", Variation: autoDep.variation})
+				if actx.OtherModuleDependencyVariantExists(autoDepVariations, lib) {
+					actx.AddVariationDependencies(autoDepVariations, autoDep.depTag, lib)
+				} else {
+					// If there's no dylib dependency available, try to add the rlib dependency instead.
+					addRlibDependency(actx, lib, mod, snapshotInfo, rlibDepVariations)
+				}
 			}
-		} else {
-			actx.AddVariationDependencies(
-				append(commonDepVariations, blueprint.Variation{Mutator: "rust_libraries", Variation: autoDep.variation}),
-				autoDep.depTag, deps.Rustlibs...)
 		}
 	}
-
 	// stdlibs
 	if deps.Stdlibs != nil {
 		if mod.compiler.stdLinkage(ctx) == RlibLinkage {
@@ -1479,6 +1482,12 @@ func (mod *Module) DepsMutator(actx android.BottomUpMutatorContext) {
 	actx.AddFarVariationDependencies(ctx.Config().BuildOSTarget.Variations(), procMacroDepTag, deps.ProcMacros...)
 }
 
+// addRlibDependency will add an rlib dependency, rewriting to the snapshot library if available.
+func addRlibDependency(actx android.BottomUpMutatorContext, lib string, mod *Module, snapshotInfo *cc.SnapshotInfo, variations []blueprint.Variation) {
+	lib = cc.RewriteSnapshotLib(lib, cc.GetSnapshot(mod, &snapshotInfo, actx).Rlibs)
+	actx.AddVariationDependencies(variations, rlibDepTag, lib)
+}
+
 func BeginMutator(ctx android.BottomUpMutatorContext) {
 	if mod, ok := ctx.Module().(*Module); ok && mod.Enabled() {
 		mod.beginMutator(ctx)