Output bootclasspath_fragment's fragments property to sdk snapshot

Adds support for printing a PropertySet that has a property whose value
is an array of structs.

Bug: 179354495
Test: m nothing
      m conscrypt-module-sdk
      - check generated Android.bp file
Change-Id: I71be04188465610bcbea4d3c9a5e8204171a1eeb
diff --git a/android/sdk.go b/android/sdk.go
index 36c576d..93beb6e 100644
--- a/android/sdk.go
+++ b/android/sdk.go
@@ -300,6 +300,22 @@
 	Name() string
 }
 
+// BpPrintable is a marker interface that must be implemented by any struct that is added as a
+// property value.
+type BpPrintable interface {
+	bpPrintable()
+}
+
+// BpPrintableBase must be embedded within any struct that is added as a
+// property value.
+type BpPrintableBase struct {
+}
+
+func (b BpPrintableBase) bpPrintable() {
+}
+
+var _ BpPrintable = BpPrintableBase{}
+
 // An individual member of the SDK, includes all of the variants that the SDK
 // requires.
 type SdkMember interface {
diff --git a/java/bootclasspath.go b/java/bootclasspath.go
index eddcc83..ccb69a0 100644
--- a/java/bootclasspath.go
+++ b/java/bootclasspath.go
@@ -144,6 +144,8 @@
 
 // ApexVariantReference specifies a particular apex variant of a module.
 type ApexVariantReference struct {
+	android.BpPrintableBase
+
 	// The name of the module apex variant, i.e. the apex containing the module variant.
 	//
 	// If this is not specified then it defaults to "platform" which will cause a dependency to be
diff --git a/java/bootclasspath_fragment.go b/java/bootclasspath_fragment.go
index c9d5917..c7249b0 100644
--- a/java/bootclasspath_fragment.go
+++ b/java/bootclasspath_fragment.go
@@ -749,6 +749,9 @@
 	Stub_libs               []string
 	Core_platform_stub_libs []string
 
+	// Fragment properties
+	Fragments []ApexVariantReference
+
 	// Flag files by *hiddenAPIFlagFileCategory
 	Flag_files_by_category FlagFilesByCategory
 
@@ -789,6 +792,9 @@
 	// Copy stub_libs properties.
 	b.Stub_libs = module.properties.Api.Stub_libs
 	b.Core_platform_stub_libs = module.properties.Core_platform_api.Stub_libs
+
+	// Copy fragment properties.
+	b.Fragments = module.properties.Fragments
 }
 
 func (b *bootclasspathFragmentSdkMemberProperties) AddToPropertySet(ctx android.SdkMemberContext, propertySet android.BpPropertySet) {
@@ -811,6 +817,9 @@
 		corePlatformApiPropertySet := propertySet.AddPropertySet("core_platform_api")
 		corePlatformApiPropertySet.AddPropertyWithTag("stub_libs", b.Core_platform_stub_libs, requiredMemberDependency)
 	}
+	if len(b.Fragments) > 0 {
+		propertySet.AddProperty("fragments", b.Fragments)
+	}
 
 	hiddenAPISet := propertySet.AddPropertySet("hidden_api")
 	hiddenAPIDir := "hiddenapi"
diff --git a/sdk/bootclasspath_fragment_sdk_test.go b/sdk/bootclasspath_fragment_sdk_test.go
index 378f7cf..d47eb1f 100644
--- a/sdk/bootclasspath_fragment_sdk_test.go
+++ b/sdk/bootclasspath_fragment_sdk_test.go
@@ -511,6 +511,127 @@
 	)
 }
 
+// TestSnapshotWithBootClasspathFragment_Fragments makes sure that the fragments property of a
+// bootclasspath_fragment is correctly output to the sdk snapshot.
+func TestSnapshotWithBootClasspathFragment_Fragments(t *testing.T) {
+	result := android.GroupFixturePreparers(
+		prepareForSdkTestWithJava,
+		java.PrepareForTestWithJavaDefaultModules,
+		java.PrepareForTestWithJavaSdkLibraryFiles,
+		java.FixtureWithLastReleaseApis("mysdklibrary", "myothersdklibrary"),
+		prepareForSdkTestWithApex,
+
+		// Some additional files needed for the myotherapex.
+		android.FixtureMergeMockFs(android.MockFS{
+			"system/sepolicy/apex/myotherapex-file_contexts": nil,
+			"myotherapex/apex_manifest.json":                 nil,
+			"myotherapex/Test.java":                          nil,
+		}),
+
+		android.FixtureAddTextFile("myotherapex/Android.bp", `
+			apex {
+				name: "myotherapex",
+				key: "myapex.key",
+				min_sdk_version: "2",
+				bootclasspath_fragments: ["myotherbootclasspathfragment"],
+			}
+
+			bootclasspath_fragment {
+				name: "myotherbootclasspathfragment",
+				apex_available: ["myotherapex"],
+				contents: [
+					"myotherlib",
+				],
+			}
+
+			java_library {
+				name: "myotherlib",
+				apex_available: ["myotherapex"],
+				srcs: ["Test.java"],
+				min_sdk_version: "2",
+				permitted_packages: ["myothersdklibrary"],
+				compile_dex: true,
+			}
+		`),
+
+		android.FixtureWithRootAndroidBp(`
+			sdk {
+				name: "mysdk",
+				bootclasspath_fragments: ["mybootclasspathfragment"],
+			}
+
+			bootclasspath_fragment {
+				name: "mybootclasspathfragment",
+				contents: [
+					"mysdklibrary",
+				],
+				fragments: [
+					{
+						apex: "myotherapex",
+						module: "myotherbootclasspathfragment"
+					},
+				],
+			}
+
+			java_sdk_library {
+				name: "mysdklibrary",
+				srcs: ["Test.java"],
+				shared_library: false,
+				public: {enabled: true},
+				min_sdk_version: "2",
+			}
+		`),
+	).RunTest(t)
+
+	// A preparer to update the test fixture used when processing an unpackage snapshot.
+	preparerForSnapshot := fixtureAddPrebuiltApexForBootclasspathFragment("myapex", "mybootclasspathfragment")
+
+	CheckSnapshot(t, result, "mysdk", "",
+		checkUnversionedAndroidBpContents(`
+// This is auto-generated. DO NOT EDIT.
+
+prebuilt_bootclasspath_fragment {
+    name: "mybootclasspathfragment",
+    prefer: false,
+    visibility: ["//visibility:public"],
+    apex_available: ["//apex_available:platform"],
+    contents: ["mysdklibrary"],
+    fragments: [
+        {
+            apex: "myotherapex",
+            module: "myotherbootclasspathfragment",
+        },
+    ],
+    hidden_api: {
+        stub_flags: "hiddenapi/stub-flags.csv",
+        annotation_flags: "hiddenapi/annotation-flags.csv",
+        metadata: "hiddenapi/metadata.csv",
+        index: "hiddenapi/index.csv",
+        all_flags: "hiddenapi/all-flags.csv",
+    },
+}
+
+java_sdk_library_import {
+    name: "mysdklibrary",
+    prefer: false,
+    visibility: ["//visibility:public"],
+    apex_available: ["//apex_available:platform"],
+    shared_library: false,
+    public: {
+        jars: ["sdk_library/public/mysdklibrary-stubs.jar"],
+        stub_srcs: ["sdk_library/public/mysdklibrary_stub_sources"],
+        current_api: "sdk_library/public/mysdklibrary.txt",
+        removed_api: "sdk_library/public/mysdklibrary-removed.txt",
+        sdk_version: "current",
+    },
+}
+		`),
+		snapshotTestPreparer(checkSnapshotWithoutSource, preparerForSnapshot),
+		snapshotTestPreparer(checkSnapshotWithSourcePreferred, preparerForSnapshot),
+		snapshotTestPreparer(checkSnapshotPreferredWithSource, preparerForSnapshot),
+	)
+}
+
 // Test that bootclasspath_fragment works with sdk.
 func TestBasicSdkWithBootclasspathFragment(t *testing.T) {
 	android.GroupFixturePreparers(
diff --git a/sdk/update.go b/sdk/update.go
index 7d6780a..e2e5997 100644
--- a/sdk/update.go
+++ b/sdk/update.go
@@ -824,32 +824,65 @@
 	case reflect.String:
 		contents.UnindentedPrintf("%q", value)
 
+	case reflect.Ptr:
+		outputUnnamedValue(contents, value.Elem())
+
 	case reflect.Slice:
 		length := value.Len()
 		if length == 0 {
 			contents.UnindentedPrintf("[]")
-		} else if length == 1 {
-			contents.UnindentedPrintf("[")
-			outputUnnamedValue(contents, value.Index(0))
-			contents.UnindentedPrintf("]")
 		} else {
-			contents.UnindentedPrintf("[\n")
-			contents.Indent()
-			for i := 0; i < length; i++ {
-				itemValue := value.Index(i)
-				contents.IndentedPrintf("")
-				outputUnnamedValue(contents, itemValue)
-				contents.UnindentedPrintf(",\n")
+			firstValue := value.Index(0)
+			if length == 1 && !multiLineValue(firstValue) {
+				contents.UnindentedPrintf("[")
+				outputUnnamedValue(contents, firstValue)
+				contents.UnindentedPrintf("]")
+			} else {
+				contents.UnindentedPrintf("[\n")
+				contents.Indent()
+				for i := 0; i < length; i++ {
+					itemValue := value.Index(i)
+					contents.IndentedPrintf("")
+					outputUnnamedValue(contents, itemValue)
+					contents.UnindentedPrintf(",\n")
+				}
+				contents.Dedent()
+				contents.IndentedPrintf("]")
 			}
-			contents.Dedent()
-			contents.IndentedPrintf("]")
 		}
 
+	case reflect.Struct:
+		// Avoid unlimited recursion by requiring every structure to implement android.BpPrintable.
+		v := value.Interface()
+		if _, ok := v.(android.BpPrintable); !ok {
+			panic(fmt.Errorf("property value %#v of type %T does not implement android.BpPrintable", v, v))
+		}
+		contents.UnindentedPrintf("{\n")
+		contents.Indent()
+		for f := 0; f < valueType.NumField(); f++ {
+			fieldType := valueType.Field(f)
+			if fieldType.Anonymous {
+				continue
+			}
+			fieldValue := value.Field(f)
+			fieldName := fieldType.Name
+			propertyName := proptools.PropertyNameForField(fieldName)
+			outputNamedValue(contents, propertyName, fieldValue)
+		}
+		contents.Dedent()
+		contents.IndentedPrintf("}")
+
 	default:
 		panic(fmt.Errorf("Unknown type: %T of value %#v", value, value))
 	}
 }
 
+// multiLineValue returns true if the supplied value may require multiple lines in the output.
+func multiLineValue(value reflect.Value) bool {
+	kind := value.Kind()
+	return kind == reflect.Slice || kind == reflect.Struct
+}
+
 func (s *sdk) GetAndroidBpContentsForTests() string {
 	contents := &generatedContents{}
 	generateBpContents(contents, s.builderForTests.bpFile)