Unblock AndroidX integration: add prefab exportLibraries

AndroidX build has been using a hack to modify Prefab module.json
in-flight to add linker flags. That hack doesn't work after recent
changes to fix order-of-configure issues.

This CL adds an experimental flag that users can use to properly
set export libraries:

   android
     .externalNativeBuild
     .experimentalProperties["prefab.foo.exportLibraries"] =
      ["-lfoo"]

This would eventually map to this DSL during the actual work for
b/214034366:

  prefab {
    foo {
      exportLibraries = ["-lfoo"]
    }
  }

Bug: 214034366
Test: Added integration test
Change-Id: I4bbd5ff9711f2a25c386bee5d7b390091aad4fe4

5 files changed, 69 insertions, 5 deletions

diff --git a/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/configure/ExperimentalPropertyExtensions.kt b/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/configure/ExperimentalPropertyExtensions.kt
index 696e515ba3..2783c47390 100644
--- a/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/configure/ExperimentalPropertyExtensions.kt
+++ b/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/configure/ExperimentalPropertyExtensions.kt
@@ -121,9 +121,42 @@ private fun Map<String, Any>.propertyAsSet(name : String) : Set<String> {
  */
 private fun Map<String, Any>.propertyAsList(name : String) : List<String> {
     val value = get(name) ?: return listOf()
+    return propertyValueAsList(value)
+}
+
+/**
+ * Convert [Any] from Gradle DSL to a List<String>.
+ */
+private fun propertyValueAsList(value : Any) : List<String> {
     return when (value) {
         is List<*> -> value.map { "$it" }
         is Set<*> -> value.map { "$it" }
-        else -> error("${value.javaClass}")
+        else -> error("Could not convert from ${value.javaClass} to List<String>")
+    }
+}
+
+/**
+ * This is the experimental flag analog of [com.android.build.api.dsl.PrefabPackagingOptions].
+ */
+data class PrefabExperimentalPackagingOptions(
+    /**
+     * export_libraries may specify either literal arguments to be used as-is, intra-package
+     * references, or inter-package references. This field is optional.
+     */
+    val exportLibraries : List<String>?
+)
+
+/**
+ * Retrieve user's experimental settings for an individual Prefab publishing module.
+ */
+fun VariantCreationConfig.getPrefabExperimentalPackagingOptions(module : String)
+    : PrefabExperimentalPackagingOptions {
+    var exportLibraries : List<String>? = null
+    for((key, value) in externalNativeExperimentalProperties) {
+        if (key != "prefab.${module}.exportLibraries") continue
+        exportLibraries = propertyValueAsList(value)
     }
+    return PrefabExperimentalPackagingOptions(
+        exportLibraries = exportLibraries
+    )
 }
diff --git a/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/CreatePublicationModel.kt b/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/CreatePublicationModel.kt
index 9230edb2fc..4dda257ecf 100644
--- a/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/CreatePublicationModel.kt
+++ b/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/CreatePublicationModel.kt
@@ -17,6 +17,7 @@
 package com.android.build.gradle.internal.cxx.prefab
 
 import com.android.build.gradle.internal.component.LibraryCreationConfig
+import com.android.build.gradle.internal.cxx.configure.getPrefabExperimentalPackagingOptions
 import com.android.build.gradle.internal.cxx.gradle.generator.CxxConfigurationModel
 import com.android.build.gradle.internal.cxx.logging.errorln
 import com.android.build.gradle.internal.cxx.model.jsonFile
@@ -37,6 +38,7 @@ fun createPrefabPublication(
     configurationModel: CxxConfigurationModel,
     libraryVariant : LibraryCreationConfig
 ) : PrefabPublication {
+
     val abis = configurationModel.activeAbis.map { abi ->
         PrefabAbiPublication(
             abiName = abi.abi.tag,
@@ -48,12 +50,15 @@ fun createPrefabPublication(
         )
     }
     val modules = libraryVariant.global.prefab.map { options ->
+        val experimentalSettings = libraryVariant.getPrefabExperimentalPackagingOptions(options.name)
+
         PrefabModulePublication(
             moduleName = options.name,
             moduleLibraryName = options.libraryName,
             moduleHeaders = options.headers?.let { headers ->
                 libraryVariant.services.projectInfo.projectDirectory.dir(headers).asFile.absoluteFile
             },
+            moduleExportLibraries = experimentalSettings.exportLibraries ?: listOf(),
             abis = abis
         )
     }
diff --git a/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/PackageBuilder.kt b/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/PackageBuilder.kt
index c3d79f9d37..98acb5a911 100644
--- a/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/PackageBuilder.kt
+++ b/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/PackageBuilder.kt
@@ -141,7 +141,7 @@ private class PrefabPackageBuilder(
         writeJsonFileIfDifferent(
             moduleDir.resolve("module.json"),
             ModuleMetadataV1(
-                exportLibraries = emptyList(),
+                exportLibraries = module.moduleExportLibraries,
                 libraryName = module.moduleLibraryName
             )
         )
diff --git a/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/PublicationModel.kt b/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/PublicationModel.kt
index d3055f4d5a..bc21b41dd7 100644
--- a/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/PublicationModel.kt
+++ b/build-system/gradle-core/src/main/java/com/android/build/gradle/internal/cxx/prefab/PublicationModel.kt
@@ -68,6 +68,9 @@ data class PrefabModulePublication(
     val moduleHeaders : File?,
     @get:Input
     @get:Optional
+    val moduleExportLibraries : List<String>,
+    @get:Input
+    @get:Optional
     val moduleLibraryName : String?,
     @get:Nested
     val abis : List<PrefabAbiPublication>
diff --git a/build-system/integration-test/native/src/test/java/com/android/build/gradle/integration/ndk/ModuleToModuleDepsTest.kt b/build-system/integration-test/native/src/test/java/com/android/build/gradle/integration/ndk/ModuleToModuleDepsTest.kt
index b0d76e3f3c..ac70ef8940 100644
--- a/build-system/integration-test/native/src/test/java/com/android/build/gradle/integration/ndk/ModuleToModuleDepsTest.kt
+++ b/build-system/integration-test/native/src/test/java/com/android/build/gradle/integration/ndk/ModuleToModuleDepsTest.kt
@@ -31,9 +31,11 @@ import com.android.build.gradle.integration.ndk.ModuleToModuleDepsTest.BuildSyst
 import com.android.build.gradle.internal.core.Abi
 import com.android.build.gradle.internal.cxx.configure.CMakeVersion
 import com.android.build.gradle.internal.cxx.json.AndroidBuildGradleJsons
+import com.android.build.gradle.internal.cxx.json.readJsonFile
 import com.android.build.gradle.internal.cxx.logging.LoggingMessage
 import com.android.build.gradle.internal.cxx.logging.decodeLoggingMessage
 import com.android.build.gradle.internal.cxx.logging.text
+import com.android.build.gradle.internal.cxx.prefab.ModuleMetadataV1
 import com.android.builder.model.v2.ide.SyncIssue
 import com.google.common.truth.Truth.assertThat
 import org.junit.Assume
@@ -109,11 +111,18 @@ class ModuleToModuleDepsTest(
         .dependency(app, lib)
         .build()
 
+    private val appOutputRoot : File get() =
+        if (outputStructureType == OutputStructureType.Normal) project.getSubproject("app").buildDir.parentFile
+        else {
+            // The output folder for lib is at $PROJECT_ROOT/out/lib
+            project.getSubproject("app").buildDir.parentFile.parentFile.resolve("out/app")
+        }
+
     private val libOutputRoot : File get() =
         if (outputStructureType == OutputStructureType.Normal) project.getSubproject("lib").buildDir.parentFile
         else {
             // The output folder for lib is at $PROJECT_ROOT/out/lib
-            project.getSubproject("lib").buildDir.parentFile.parentFile.parentFile.resolve("out/lib")
+            project.getSubproject("lib").buildDir.parentFile.parentFile.resolve("out/lib")
         }
 
     @get:Rule
@@ -172,7 +181,6 @@ class ModuleToModuleDepsTest(
             .buildFile
             .parentFile
             .parentFile
-            .parentFile
             .absolutePath.replace("\\", "/")
         val appStructureStanza = if (outputStructureType == OutputStructureType.Normal) "" else when(appBuildSystem) {
             is CMake -> """
@@ -196,6 +204,8 @@ class ModuleToModuleDepsTest(
                 """.trimIndent()
             else -> error("$appBuildSystem")
         }
+        val libExportLibrariesStanza =
+            "android.externalNativeBuild.experimentalProperties[\"prefab.foo.exportLibraries\"] = [\"-llog\"]"
 
         project.getSubproject(":app").buildFile.appendText(
             """
@@ -263,6 +273,7 @@ class ModuleToModuleDepsTest(
             $libStanza
             $libStlStanza
             $libStructureStanza
+            $libExportLibrariesStanza
             """)
         val header =
             project.getSubproject(":lib").buildFile.resolveSibling("src/main/cpp/include/foo.h")
@@ -354,7 +365,6 @@ class ModuleToModuleDepsTest(
                 int callFoo() { return foo(); }
                 """.trimIndent())
         }
-
         enableCxxStructuredLogging(project)
     }
 
@@ -470,6 +480,19 @@ class ModuleToModuleDepsTest(
         assertThat(libOutput.isFile)
             .named("$libOutput")
             .isFalse()
+
+        // Check that export libraries informations winds up in the final prefab structure
+        var sawAtleastOneModule = false
+        appOutputRoot.walkTopDown().forEach { file ->
+            if (file.name == "module.json") {
+                val module = readJsonFile<ModuleMetadataV1>(file)
+                assertThat(module.exportLibraries).containsExactly("-llog")
+                sawAtleastOneModule = true
+            }
+        }
+        assertThat(sawAtleastOneModule)
+            .named("Expected at least one Prefab module")
+            .isTrue()
     }
 
     @Test