Generates code to reference protocol shadow classes from classes that implement the protocols. This allows access to protocol reflection metadata when app is built without -ObjC flag.

PiperOrigin-RevId: 628159766

Author: tomball

translator/src/main/java/com/google/devtools/j2objc/Options.java

@@ -111,6 +111,7 @@ public class Options {
   private boolean linkSourcePathHeaders = false;
   private boolean javacWarnings = true;
   private boolean stripReflectionErrors = false;
+  private boolean linkProtocols = false;
 
   private Mappings mappings = new Mappings();
   private FileUtil fileUtil = new FileUtil();
@@ -417,6 +418,8 @@ private void processArg(Iterator<String> args) throws IOException {
         headerMap.setIncludeGeneratedSources();
       } else if (arg.equals("-Xpublic-hdrs")) {
         fileUtil.setHeaderOutputDirectory(new File(getArgValue(args, arg)));
+      } else if (arg.equals("-Xlink-protocols")) {
+        linkProtocols = true;
       } else if (arg.equals("-use-arc")) {
         checkMemoryManagementOption(MemoryManagementOption.ARC);
       } else if (arg.equals("-Xstrict-field-assign")) {
@@ -1294,4 +1297,13 @@ public void setStripReflectionErrors(boolean b) {
   public boolean stripReflectionErrors() {
     return stripReflectionErrors;
   }
+
+  public boolean linkProtocols() {
+    return linkProtocols;
+  }
+
+  @VisibleForTesting
+  public void setLinkProtocols(boolean b) {
+    linkProtocols = b;
+  }
 }

translator/src/main/java/com/google/devtools/j2objc/gen/TypeImplementationGenerator.java

@@ -30,11 +30,13 @@
 import com.google.devtools.j2objc.ast.VariableDeclarationFragment;
 import com.google.devtools.j2objc.util.ElementUtil;
 import com.google.devtools.j2objc.util.NameTable;
+import com.google.devtools.j2objc.util.TranslationUtil;
 import com.google.devtools.j2objc.util.TypeUtil;
 import com.google.j2objc.annotations.Property;
 import java.lang.reflect.Modifier;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Optional;
@@ -116,6 +118,7 @@ protected void generate() {
       printStaticAccessors();
       printInnerDeclarations();
       printInitializeMethod();
+      printLinkProtocolsMethod();
       println("\n@end");
     }
 
@@ -266,6 +269,24 @@ private void printTypeLiteralImplementation() {
     }
   }
 
+  private void printLinkProtocolsMethod() {
+    if (!options.linkProtocols() || options.stripReflection()) {
+      return;
+    }
+    List<String> interfaceNames = new ArrayList<>();
+    for (TypeElement intrface : TranslationUtil.getInterfaceTypes(typeNode)) {
+      interfaceNames.add(nameTable.getFullName(intrface));
+    }
+    if (!interfaceNames.isEmpty()) {
+      newline();
+      printf("+ (void)__linkProtocols {\n");
+      for (String name : interfaceNames) {
+        printf("  %s_class_();\n", NameTable.camelCaseQualifiedName(name));
+      }
+      printf("}\n");
+    }
+  }
+
   private void printNameMapping() {
     if (!options.stripNameMapping()) {
       Optional<String> mapping = nameTable.getNameMapping(typeElement, typeName);

translator/src/test/java/com/google/devtools/j2objc/gen/TypeImplementationGeneratorTest.java

@@ -222,4 +222,15 @@ public void testSynthesizeProperties() throws IOException {
     assertTranslation(translation, "@synthesize foo = foo_;");
     assertNotInTranslation(translation, "@synthesize bar");
   }
+
+  public void testLinkProtocolsFunctions() throws IOException {
+    options.setLinkProtocols(true);
+    String source =
+        "import java.io.Serializable;\n"
+            + "class Test implements Runnable, Serializable { public void run() {} }";
+    String translation = translateSourceFile(source, "Test", "Test.m");
+    assertTranslation(translation, "+ (void)__linkProtocols {");
+    assertTranslation(translation, "JavaIoSerializable_class_();");
+    assertTranslation(translation, "JavaLangRunnable_class_();");
+  }
 }