rust: Add support to emit certain Cargo env vars.

Some crates expect Cargo to provide certain environment variables. This
CL adds a compatability flag that emulates the behavior of Cargo by
setting these environment variables when building.

Bug: 171011485
Test: New soong tests pass
Test: quiche no longer requires patch removing CARGO_PKG_VERSION
Change-Id: I4c95c284846f6075428c6f61fe8c260f2e35fbd9

rust/builder.go

@@ -269,6 +269,17 @@ func transformSrctoCrate(ctx ModuleContext, main android.Path, deps PathDeps, fl
 
 	envVars = append(envVars, "ANDROID_RUST_VERSION="+config.RustDefaultVersion)
 
+	if ctx.RustModule().compiler.CargoEnvCompat() {
+		if _, ok := ctx.RustModule().compiler.(*binaryDecorator); ok {
+			envVars = append(envVars, "CARGO_BIN_NAME="+strings.TrimSuffix(outputFile.Base(), outputFile.Ext()))
+		}
+		envVars = append(envVars, "CARGO_CRATE_NAME="+ctx.RustModule().CrateName())
+		pkgVersion := ctx.RustModule().compiler.CargoPkgVersion()
+		if pkgVersion != "" {
+			envVars = append(envVars, "CARGO_PKG_VERSION="+pkgVersion)
+		}
+	}
+
 	if flags.Clippy {
 		clippyFile := android.PathForModuleOut(ctx, outputFile.Base()+".clippy")
 		ctx.Build(pctx, android.BuildParams{

rust/compiler.go

@@ -154,6 +154,14 @@ type BaseCompilerProperties struct {
 	// linkage if all dependencies of the root binary module do not link against libstd\
 	// the same way.
 	Prefer_rlib *bool `android:"arch_variant"`
+
+	// Enables emitting certain Cargo environment variables. Only intended to be used for compatibility purposes.
+	// Will set CARGO_CRATE_NAME to the crate_name property's value.
+	// Will set CARGO_BIN_NAME to the output filename value without the extension.
+	Cargo_env_compat *bool
+
+	// If cargo_env_compat is true, sets the CARGO_PKG_VERSION env var to this value.
+	Cargo_pkg_version *string
 }
 
 type baseCompiler struct {
@@ -309,6 +317,14 @@ func (compiler *baseCompiler) CargoOutDir() android.OptionalPath {
 	return android.OptionalPathForPath(compiler.cargoOutDir)
 }
 
+func (compiler *baseCompiler) CargoEnvCompat() bool {
+	return Bool(compiler.Properties.Cargo_env_compat)
+}
+
+func (compiler *baseCompiler) CargoPkgVersion() string {
+	return String(compiler.Properties.Cargo_pkg_version)
+}
+
 func (compiler *baseCompiler) strippedOutputFilePath() android.OptionalPath {
 	return compiler.strippedOutputFile
 }

rust/compiler_test.go

@@ -98,6 +98,30 @@ func TestEnforceSingleSourceFile(t *testing.T) {
 		}`)
 }
 
+// Test environment vars for Cargo compat are set.
+func TestCargoCompat(t *testing.T) {
+	ctx := testRust(t, `
+		rust_binary {
+			name: "fizz",
+			srcs: ["foo.rs"],
+			crate_name: "foo",
+			cargo_env_compat: true,
+			cargo_pkg_version: "1.0.0"
+		}`)
+
+	fizz := ctx.ModuleForTests("fizz", "android_arm64_armv8-a").Rule("rustc")
+
+	if !strings.Contains(fizz.Args["envVars"], "CARGO_BIN_NAME=fizz") {
+		t.Fatalf("expected 'CARGO_BIN_NAME=fizz' in envVars, actual envVars: %#v", fizz.Args["envVars"])
+	}
+	if !strings.Contains(fizz.Args["envVars"], "CARGO_CRATE_NAME=foo") {
+		t.Fatalf("expected 'CARGO_CRATE_NAME=foo' in envVars, actual envVars: %#v", fizz.Args["envVars"])
+	}
+	if !strings.Contains(fizz.Args["envVars"], "CARGO_PKG_VERSION=1.0.0") {
+		t.Fatalf("expected 'CARGO_PKG_VERSION=1.0.0' in envVars, actual envVars: %#v", fizz.Args["envVars"])
+	}
+}
+
 func TestInstallDir(t *testing.T) {
 	ctx := testRust(t, `
 		rust_library_dylib {

rust/rust.go

@@ -433,6 +433,12 @@ type compiler interface {
 	// copied. This is equivalent to Cargo's OUT_DIR variable.
 	CargoOutDir() android.OptionalPath
 
+	// CargoPkgVersion returns the value of the Cargo_pkg_version property.
+	CargoPkgVersion() string
+
+	// CargoEnvCompat returns whether Cargo environment variables should be used.
+	CargoEnvCompat() bool
+
 	inData() bool
 	install(ctx ModuleContext)
 	relativeInstallPath() string