Simplify missing whole_static_libs checking

Whole_static_libs required custom error checking when
AllowMissingDependencies was set because it could end up depending
on an empty list of objects, which would leave nothing in the
dependency tree that had been replaced with an ErrorRule.
Reuse the prebuilts case to depend on the .a file when there
are no objects and remove the custom error handling.

Test: TestEmptyWholeStaticLibsAllowMissingDependencies
Change-Id: Ic3216235f7e5ae8b5b6ab31ef2ca35c3994d82aa

cc/cc.go

@@ -2559,17 +2559,20 @@ func (c *Module) depsToPaths(ctx android.ModuleContext) PathDeps {
 					// in the context of proper cc.Modules.
 					if ccWholeStaticLib, ok := ccDep.(*Module); ok {
 						staticLib := ccWholeStaticLib.linker.(libraryInterface)
-						if missingDeps := staticLib.getWholeStaticMissingDeps(); missingDeps != nil {
-							postfix := " (required by " + ctx.OtherModuleName(dep) + ")"
-							for i := range missingDeps {
-								missingDeps[i] += postfix
-							}
-							ctx.AddMissingDependencies(missingDeps)
-						}
-						if _, ok := ccWholeStaticLib.linker.(prebuiltLinkerInterface); ok {
-							depPaths.WholeStaticLibsFromPrebuilts = append(depPaths.WholeStaticLibsFromPrebuilts, linkFile.Path())
+						if objs := staticLib.objs(); len(objs.objFiles) > 0 {
+							depPaths.WholeStaticLibObjs = depPaths.WholeStaticLibObjs.Append(objs)
 						} else {
-							depPaths.WholeStaticLibObjs = depPaths.WholeStaticLibObjs.Append(staticLib.objs())
+							// This case normally catches prebuilt static
+							// libraries, but it can also occur when
+							// AllowMissingDependencies is on and the
+							// dependencies has no sources of its own
+							// but has a whole_static_libs dependency
+							// on a missing library.  We want to depend
+							// on the .a file so that there is something
+							// in the dependency tree that contains the
+							// error rule for the missing transitive
+							// dependency.
+							depPaths.WholeStaticLibsFromPrebuilts = append(depPaths.WholeStaticLibsFromPrebuilts, linkFile.Path())
 						}
 					} else {
 						ctx.ModuleErrorf(

cc/cc_test.go

@@ -3780,3 +3780,46 @@ func TestProductVariableDefaults(t *testing.T) {
 		t.Errorf("expected -DBAR in cppflags, got %q", libfoo.flags.Local.CppFlags)
 	}
 }
+
+func TestEmptyWholeStaticLibsAllowMissingDependencies(t *testing.T) {
+	t.Parallel()
+	bp := `
+		cc_library_static {
+			name: "libfoo",
+			srcs: ["foo.c"],
+			whole_static_libs: ["libbar"],
+		}
+
+		cc_library_static {
+			name: "libbar",
+			whole_static_libs: ["libmissing"],
+		}
+	`
+
+	config := TestConfig(buildDir, android.Android, nil, bp, nil)
+	config.TestProductVariables.Allow_missing_dependencies = BoolPtr(true)
+
+	ctx := CreateTestContext()
+	ctx.SetAllowMissingDependencies(true)
+	ctx.Register(config)
+
+	_, errs := ctx.ParseFileList(".", []string{"Android.bp"})
+	android.FailIfErrored(t, errs)
+	_, errs = ctx.PrepareBuildActions(config)
+	android.FailIfErrored(t, errs)
+
+	libbar := ctx.ModuleForTests("libbar", "android_arm64_armv8-a_static").Output("libbar.a")
+	if g, w := libbar.Rule, android.ErrorRule; g != w {
+		t.Fatalf("Expected libbar rule to be %q, got %q", w, g)
+	}
+
+	if g, w := libbar.Args["error"], "missing dependencies: libmissing"; !strings.Contains(g, w) {
+		t.Errorf("Expected libbar error to contain %q, was %q", w, g)
+	}
+
+	libfoo := ctx.ModuleForTests("libfoo", "android_arm64_armv8-a_static").Output("libfoo.a")
+	if g, w := libfoo.Inputs.Strings(), libbar.Output.String(); !android.InList(w, g) {
+		t.Errorf("Expected libfoo.a to depend on %q, got %q", w, g)
+	}
+
+}

cc/library.go

@@ -338,10 +338,6 @@ type libraryDecorator struct {
 	flagExporter
 	stripper Stripper
 
-	// If we're used as a whole_static_lib, our missing dependencies need
-	// to be given
-	wholeStaticMissingDeps []string
-
 	// For whole_static_libs
 	objects Objects
 
@@ -682,7 +678,6 @@ func (library *libraryDecorator) compile(ctx ModuleContext, flags Flags, deps Pa
 }
 
 type libraryInterface interface {
-	getWholeStaticMissingDeps() []string
 	static() bool
 	shared() bool
 	objs() Objects
@@ -889,8 +884,6 @@ func (library *libraryDecorator) linkStatic(ctx ModuleContext,
 
 	library.coverageOutputFile = TransformCoverageFilesToZip(ctx, library.objects, ctx.ModuleName())
 
-	library.wholeStaticMissingDeps = ctx.GetMissingDependencies()
-
 	ctx.CheckbuildFile(outputFile)
 
 	return outputFile
@@ -1182,10 +1175,6 @@ func (library *libraryDecorator) buildShared() bool {
 		BoolDefault(library.SharedProperties.Shared.Enabled, true)
 }
 
-func (library *libraryDecorator) getWholeStaticMissingDeps() []string {
-	return append([]string(nil), library.wholeStaticMissingDeps...)
-}
-
 func (library *libraryDecorator) objs() Objects {
 	return library.objects
 }