Support kotlin multiplatform sources

Add a common_srcs property and propagate it to the module.xml file
passed to kotlinc.

Test: m checkbuild
Change-Id: Ief768bafb943513c9ffbc01e829abc078f0a72bc
diff --git a/java/java.go b/java/java.go
index 0d46672..46ef98b 100644
--- a/java/java.go
+++ b/java/java.go
@@ -140,10 +140,15 @@
 // Findbugs
 
 type CompilerProperties struct {
-	// list of source files used to compile the Java module.  May be .java, .logtags, .proto,
+	// list of source files used to compile the Java module.  May be .java, .kt, .logtags, .proto,
 	// or .aidl files.
 	Srcs []string `android:"path,arch_variant"`
 
+	// list Kotlin of source files containing Kotlin code that should be treated as common code in
+	// a codebase that supports Kotlin multiplatform.  See
+	// https://kotlinlang.org/docs/reference/multiplatform.html.  May be only be .kt files.
+	Common_srcs []string `android:"path,arch_variant"`
+
 	// list of source files that should not be used to build the Java module.
 	// This is most useful in the arch/multilib variants to remove non-common files
 	Exclude_srcs []string `android:"path,arch_variant"`
@@ -1300,6 +1305,11 @@
 		flags = protoFlags(ctx, &j.properties, &j.protoProperties, flags)
 	}
 
+	kotlinCommonSrcFiles := android.PathsForModuleSrcExcludes(ctx, j.properties.Common_srcs, nil)
+	if len(kotlinCommonSrcFiles.FilterOutByExt(".kt")) > 0 {
+		ctx.PropertyErrorf("common_srcs", "common_srcs must be .kt files")
+	}
+
 	srcFiles = j.genSources(ctx, srcFiles, flags)
 
 	srcJars := srcFiles.FilterByExt(".srcjar")
@@ -1353,6 +1363,7 @@
 
 		// Collect .kt files for AIDEGen
 		j.expandIDEInfoCompiledSrcs = append(j.expandIDEInfoCompiledSrcs, srcFiles.FilterByExt(".kt").Strings()...)
+		j.expandIDEInfoCompiledSrcs = append(j.expandIDEInfoCompiledSrcs, kotlinCommonSrcFiles.Strings()...)
 
 		flags.classpath = append(flags.classpath, deps.kotlinStdlib...)
 		flags.classpath = append(flags.classpath, deps.kotlinAnnotations...)
@@ -1364,7 +1375,7 @@
 			// Use kapt for annotation processing
 			kaptSrcJar := android.PathForModuleOut(ctx, "kapt", "kapt-sources.jar")
 			kaptResJar := android.PathForModuleOut(ctx, "kapt", "kapt-res.jar")
-			kotlinKapt(ctx, kaptSrcJar, kaptResJar, kotlinSrcFiles, srcJars, flags)
+			kotlinKapt(ctx, kaptSrcJar, kaptResJar, kotlinSrcFiles, kotlinCommonSrcFiles, srcJars, flags)
 			srcJars = append(srcJars, kaptSrcJar)
 			kotlinJars = append(kotlinJars, kaptResJar)
 			// Disable annotation processing in javac, it's already been handled by kapt
@@ -1373,7 +1384,7 @@
 		}
 
 		kotlinJar := android.PathForModuleOut(ctx, "kotlin", jarName)
-		kotlinCompile(ctx, kotlinJar, kotlinSrcFiles, srcJars, flags)
+		kotlinCompile(ctx, kotlinJar, kotlinSrcFiles, kotlinCommonSrcFiles, srcJars, flags)
 		if ctx.Failed() {
 			return
 		}
diff --git a/java/kotlin.go b/java/kotlin.go
index e3356be..e8c030a 100644
--- a/java/kotlin.go
+++ b/java/kotlin.go
@@ -33,7 +33,7 @@
 			`${config.ZipSyncCmd} -d $srcJarDir -l $srcJarDir/list -f "*.java" $srcJars && ` +
 			`${config.GenKotlinBuildFileCmd} --classpath "$classpath" --name "$name"` +
 			` --out_dir "$classesDir" --srcs "$out.rsp" --srcs "$srcJarDir/list"` +
-			` --out "$kotlinBuildFile" && ` +
+			` $commonSrcFilesArg --out "$kotlinBuildFile" && ` +
 			`${config.KotlincCmd} ${config.JavacHeapFlags} $kotlincFlags ` +
 			`-jvm-target $kotlinJvmTarget -Xbuild-file=$kotlinBuildFile -kotlin-home $emptyDir && ` +
 			`${config.SoongZipCmd} -jar -o $out -C $classesDir -D $classesDir && ` +
@@ -54,21 +54,43 @@
 		Rspfile:        "$out.rsp",
 		RspfileContent: `$in`,
 	},
-	"kotlincFlags", "classpath", "srcJars", "srcJarDir", "classesDir", "kotlinJvmTarget", "kotlinBuildFile",
-	"emptyDir", "name")
+	"kotlincFlags", "classpath", "srcJars", "commonSrcFilesArg", "srcJarDir", "classesDir",
+	"kotlinJvmTarget", "kotlinBuildFile", "emptyDir", "name")
+
+func kotlinCommonSrcsList(ctx android.ModuleContext, commonSrcFiles android.Paths) android.OptionalPath {
+	if len(commonSrcFiles) > 0 {
+		// The list of common_srcs may be too long to put on the command line, but
+		// we can't use the rsp file because it is already being used for srcs.
+		// Insert a second rule to write out the list of resources to a file.
+		commonSrcsList := android.PathForModuleOut(ctx, "kotlinc_common_srcs.list")
+		rule := android.NewRuleBuilder()
+		rule.Command().Text("cp").FlagWithRspFileInputList("", commonSrcFiles).Output(commonSrcsList)
+		rule.Build(pctx, ctx, "kotlin_common_srcs_list", "kotlin common_srcs list")
+		return android.OptionalPathForPath(commonSrcsList)
+	}
+	return android.OptionalPath{}
+}
 
 // kotlinCompile takes .java and .kt sources and srcJars, and compiles the .kt sources into a classes jar in outputFile.
 func kotlinCompile(ctx android.ModuleContext, outputFile android.WritablePath,
-	srcFiles, srcJars android.Paths,
+	srcFiles, commonSrcFiles, srcJars android.Paths,
 	flags javaBuilderFlags) {
 
 	var deps android.Paths
 	deps = append(deps, flags.kotlincClasspath...)
 	deps = append(deps, srcJars...)
+	deps = append(deps, commonSrcFiles...)
 
 	kotlinName := filepath.Join(ctx.ModuleDir(), ctx.ModuleSubDir(), ctx.ModuleName())
 	kotlinName = strings.ReplaceAll(kotlinName, "/", "__")
 
+	commonSrcsList := kotlinCommonSrcsList(ctx, commonSrcFiles)
+	commonSrcFilesArg := ""
+	if commonSrcsList.Valid() {
+		deps = append(deps, commonSrcsList.Path())
+		commonSrcFilesArg = "--common_srcs " + commonSrcsList.String()
+	}
+
 	ctx.Build(pctx, android.BuildParams{
 		Rule:        kotlinc,
 		Description: "kotlinc",
@@ -76,13 +98,14 @@
 		Inputs:      srcFiles,
 		Implicits:   deps,
 		Args: map[string]string{
-			"classpath":       flags.kotlincClasspath.FormJavaClassPath(""),
-			"kotlincFlags":    flags.kotlincFlags,
-			"srcJars":         strings.Join(srcJars.Strings(), " "),
-			"classesDir":      android.PathForModuleOut(ctx, "kotlinc", "classes").String(),
-			"srcJarDir":       android.PathForModuleOut(ctx, "kotlinc", "srcJars").String(),
-			"kotlinBuildFile": android.PathForModuleOut(ctx, "kotlinc-build.xml").String(),
-			"emptyDir":        android.PathForModuleOut(ctx, "kotlinc", "empty").String(),
+			"classpath":         flags.kotlincClasspath.FormJavaClassPath(""),
+			"kotlincFlags":      flags.kotlincFlags,
+			"commonSrcFilesArg": commonSrcFilesArg,
+			"srcJars":           strings.Join(srcJars.Strings(), " "),
+			"classesDir":        android.PathForModuleOut(ctx, "kotlinc", "classes").String(),
+			"srcJarDir":         android.PathForModuleOut(ctx, "kotlinc", "srcJars").String(),
+			"kotlinBuildFile":   android.PathForModuleOut(ctx, "kotlinc-build.xml").String(),
+			"emptyDir":          android.PathForModuleOut(ctx, "kotlinc", "empty").String(),
 			// http://b/69160377 kotlinc only supports -jvm-target 1.6 and 1.8
 			"kotlinJvmTarget": "1.8",
 			"name":            kotlinName,
@@ -97,7 +120,7 @@
 			`${config.ZipSyncCmd} -d $srcJarDir -l $srcJarDir/list -f "*.java" $srcJars && ` +
 			`${config.GenKotlinBuildFileCmd} --classpath "$classpath" --name "$name"` +
 			` --srcs "$out.rsp" --srcs "$srcJarDir/list"` +
-			` --out "$kotlinBuildFile" && ` +
+			` $commonSrcFilesArg --out "$kotlinBuildFile" && ` +
 			`${config.KotlincCmd} ${config.KotlincSuppressJDK9Warnings} ${config.JavacHeapFlags} $kotlincFlags ` +
 			`-Xplugin=${config.KotlinKaptJar} ` +
 			`-P plugin:org.jetbrains.kotlin.kapt3:sources=$kaptDir/sources ` +
@@ -124,21 +147,31 @@
 		RspfileContent: `$in`,
 	},
 	"kotlincFlags", "encodedJavacFlags", "kaptProcessorPath", "kaptProcessor",
-	"classpath", "srcJars", "srcJarDir", "kaptDir", "kotlinJvmTarget", "kotlinBuildFile", "name",
-	"classesJarOut")
+	"classpath", "srcJars", "commonSrcFilesArg", "srcJarDir", "kaptDir", "kotlinJvmTarget",
+	"kotlinBuildFile", "name", "classesJarOut")
 
 // kotlinKapt performs Kotlin-compatible annotation processing.  It takes .kt and .java sources and srcjars, and runs
 // annotation processors over all of them, producing a srcjar of generated code in outputFile.  The srcjar should be
 // added as an additional input to kotlinc and javac rules, and the javac rule should have annotation processing
 // disabled.
 func kotlinKapt(ctx android.ModuleContext, srcJarOutputFile, resJarOutputFile android.WritablePath,
-	srcFiles, srcJars android.Paths,
+	srcFiles, commonSrcFiles, srcJars android.Paths,
 	flags javaBuilderFlags) {
 
+	srcFiles = append(android.Paths(nil), srcFiles...)
+
 	var deps android.Paths
 	deps = append(deps, flags.kotlincClasspath...)
 	deps = append(deps, srcJars...)
 	deps = append(deps, flags.processorPath...)
+	deps = append(deps, commonSrcFiles...)
+
+	commonSrcsList := kotlinCommonSrcsList(ctx, commonSrcFiles)
+	commonSrcFilesArg := ""
+	if commonSrcsList.Valid() {
+		deps = append(deps, commonSrcsList.Path())
+		commonSrcFilesArg = "--common_srcs " + commonSrcsList.String()
+	}
 
 	kaptProcessorPath := flags.processorPath.FormRepeatedClassPath("-P plugin:org.jetbrains.kotlin.kapt3:apclasspath=")
 
@@ -168,6 +201,7 @@
 		Args: map[string]string{
 			"classpath":         flags.kotlincClasspath.FormJavaClassPath(""),
 			"kotlincFlags":      flags.kotlincFlags,
+			"commonSrcFilesArg": commonSrcFilesArg,
 			"srcJars":           strings.Join(srcJars.Strings(), " "),
 			"srcJarDir":         android.PathForModuleOut(ctx, "kapt", "srcJars").String(),
 			"kotlinBuildFile":   android.PathForModuleOut(ctx, "kapt", "build.xml").String(),