rust: Add cfgs property

Rust configuration options ("--cfg") are currently defined using the
"flags" property. Adds a specific property to be able to forward these
to the rust-analyzer configuration (rust-project.json).

Bug: 183727250
Test: m libstd
Change-Id: Ida89097814bcd1a45c02a8a79ec5a8e9e59701bd

rust/compiler.go

@@ -76,7 +76,7 @@ type BaseCompilerProperties struct {
 	// errors). The default value is "default".
 	Lints *string
 
-	// flags to pass to rustc
+	// flags to pass to rustc. To enable configuration options or features, use the "cfgs" or "features" properties.
 	Flags []string `android:"path,arch_variant"`
 
 	// flags to pass to the linker
@@ -125,6 +125,9 @@ type BaseCompilerProperties struct {
 	// list of features to enable for this crate
 	Features []string `android:"arch_variant"`
 
+	// list of configuration options to enable for this crate. To enable features, use the "features" property.
+	Cfgs []string `android:"arch_variant"`
+
 	// specific rust edition that should be used if the default version is not desired
 	Edition *string `android:"arch_variant"`
 
@@ -210,9 +213,17 @@ func (compiler *baseCompiler) compilerProps() []interface{} {
 	return []interface{}{&compiler.Properties}
 }
 
-func (compiler *baseCompiler) featuresToFlags(features []string) []string {
+func (compiler *baseCompiler) cfgsToFlags() []string {
 	flags := []string{}
-	for _, feature := range features {
+	for _, cfg := range compiler.Properties.Cfgs {
+		flags = append(flags, "--cfg '"+cfg+"'")
+	}
+	return flags
+}
+
+func (compiler *baseCompiler) featuresToFlags() []string {
+	flags := []string{}
+	for _, feature := range compiler.Properties.Features {
 		flags = append(flags, "--cfg 'feature=\""+feature+"\"'")
 	}
 	return flags
@@ -226,7 +237,8 @@ func (compiler *baseCompiler) compilerFlags(ctx ModuleContext, flags Flags) Flag
 	}
 	flags.RustFlags = append(flags.RustFlags, lintFlags)
 	flags.RustFlags = append(flags.RustFlags, compiler.Properties.Flags...)
-	flags.RustFlags = append(flags.RustFlags, compiler.featuresToFlags(compiler.Properties.Features)...)
+	flags.RustFlags = append(flags.RustFlags, compiler.cfgsToFlags()...)
+	flags.RustFlags = append(flags.RustFlags, compiler.featuresToFlags()...)
 	flags.RustFlags = append(flags.RustFlags, "--edition="+compiler.edition())
 	flags.LinkFlags = append(flags.LinkFlags, compiler.Properties.Ld_flags...)
 	flags.GlobalRustFlags = append(flags.GlobalRustFlags, config.GlobalRustFlags...)

rust/compiler_test.go

@@ -42,6 +42,27 @@ func TestFeaturesToFlags(t *testing.T) {
 	}
 }
 
+// Test that cfgs flags are being correctly generated.
+func TestCfgsToFlags(t *testing.T) {
+	ctx := testRust(t, `
+		rust_library_host {
+			name: "libfoo",
+			srcs: ["foo.rs"],
+			crate_name: "foo",
+			cfgs: [
+				"std",
+				"cfg1=\"one\""
+			],
+		}`)
+
+	libfooDylib := ctx.ModuleForTests("libfoo", "linux_glibc_x86_64_dylib").Rule("rustc")
+
+	if !strings.Contains(libfooDylib.Args["rustcFlags"], "cfg 'std'") ||
+		!strings.Contains(libfooDylib.Args["rustcFlags"], "cfg 'cfg1=\"one\"'") {
+		t.Fatalf("missing std and cfg1 flags for libfoo dylib, rustcFlags: %#v", libfooDylib.Args["rustcFlags"])
+	}
+}
+
 // Test that we reject multiple source files.
 func TestEnforceSingleSourceFile(t *testing.T) {