Add rust_test and rust_test_host.

* Rust tests are like binary files compiled with --test.
  New test.go follows binary.go code patterns and reuses
  some code in binary.go.
* Generate one test per source file as testPerSrc in cc/test.go.
  The "all tests" variation feature of cc/test.go is not copied yet.
  Fix some Stem and SubName settings to make testPerSrc work.
* Move cc.CheckDuplicate to android.CheckDuplicate,
  which is now shared by cc and rust.
* Refactor tests in binary_test.go and add new test_test.go.

Bug: 140938178
Test: mm in rust projects, added rust_test and rust_test_host
Change-Id: Ia6fec8b4cf2572fd352ab1938a1f3c7b5cca2212

rust/test.go

@@ -0,0 +1,116 @@
+// Copyright 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rust
+
+import (
+	"path/filepath"
+	"strings"
+
+	"android/soong/android"
+)
+
+// A test module is a binary module with extra --test compiler flag
+// and different default installation directory.
+// In golang, inheriance is written as a component.
+type testBinaryDecorator struct {
+	*binaryDecorator
+}
+
+func NewRustTest(hod android.HostOrDeviceSupported) (*Module, *testBinaryDecorator) {
+	module := newModule(hod, android.MultilibFirst)
+
+	test := &testBinaryDecorator{
+		binaryDecorator: &binaryDecorator{
+			// TODO(chh): set up dir64?
+			baseCompiler: NewBaseCompiler("testcases", ""),
+		},
+	}
+
+	module.compiler = test
+
+	return module, test
+}
+
+func (test *testBinaryDecorator) compilerFlags(ctx ModuleContext, flags Flags) Flags {
+	flags = test.binaryDecorator.compilerFlags(ctx, flags)
+	flags.RustFlags = append(flags.RustFlags, "--test")
+	return flags
+}
+
+func init() {
+	// Rust tests are binary files built with --test.
+	android.RegisterModuleType("rust_test", RustTestFactory)
+	android.RegisterModuleType("rust_test_host", RustTestHostFactory)
+}
+
+func RustTestFactory() android.Module {
+	module, _ := NewRustTest(android.HostAndDeviceSupported)
+	return module.Init()
+}
+
+func RustTestHostFactory() android.Module {
+	module, _ := NewRustTest(android.HostSupported)
+	return module.Init()
+}
+
+func (test *testBinaryDecorator) testPerSrc() bool {
+	return true
+}
+
+func (test *testBinaryDecorator) srcs() []string {
+	return test.Properties.Srcs
+}
+
+func (test *testBinaryDecorator) setSrc(name, src string) {
+	test.Properties.Srcs = []string{src}
+	test.baseCompiler.Properties.Stem = StringPtr(name)
+}
+
+func (test *testBinaryDecorator) unsetSrc() {
+	test.Properties.Srcs = nil
+	test.baseCompiler.Properties.Stem = StringPtr("")
+}
+
+type testPerSrc interface {
+	testPerSrc() bool
+	srcs() []string
+	setSrc(string, string)
+	unsetSrc()
+}
+
+var _ testPerSrc = (*testBinaryDecorator)(nil)
+
+func TestPerSrcMutator(mctx android.BottomUpMutatorContext) {
+	if m, ok := mctx.Module().(*Module); ok {
+		if test, ok := m.compiler.(testPerSrc); ok {
+			numTests := len(test.srcs())
+			if test.testPerSrc() && numTests > 0 {
+				if duplicate, found := android.CheckDuplicate(test.srcs()); found {
+					mctx.PropertyErrorf("srcs", "found a duplicate entry %q", duplicate)
+					return
+				}
+				testNames := make([]string, numTests)
+				for i, src := range test.srcs() {
+					testNames[i] = strings.TrimSuffix(filepath.Base(src), filepath.Ext(src))
+				}
+				// TODO(chh): Add an "all tests" variation like cc/test.go?
+				tests := mctx.CreateLocalVariations(testNames...)
+				for i, src := range test.srcs() {
+					tests[i].(*Module).compiler.(testPerSrc).setSrc(testNames[i], src)
+				}
+			}
+		}
+	}
+}