Automatically process Kotlin metadata when keeping the annotation

Add dontprocesskotlinmetadata configuration option.

base/src/main/java/proguard/Configuration.java

@@ -418,6 +418,11 @@ public class Configuration
      */
     public boolean                      keepKotlinMetadata               = false;
 
+    /**
+     * Specifies not to process Kotlin metadata. Overwrites KeepKotlinMetadata.
+     */
+    public boolean                      dontProcessKotlinMetadata        = false;
+
     // INTERNAL OPTIONS
 
     /**

base/src/main/java/proguard/ConfigurationConstants.java

@@ -113,6 +113,7 @@ public class ConfigurationConstants
     public static final String FORCE_PROCESSING_OPTION                           = "-forceprocessing";
 
     public static final String KEEP_KOTLIN_METADATA                              = "-keepkotlinmetadata";
+    public static final String DONT_PROCESS_KOTLIN_METADATA                      = "-dontprocesskotlinmetadata";
 
     public static final String ANY_FILE_KEYWORD            = "**";
 

base/src/main/java/proguard/ConfigurationParser.java

@@ -210,7 +210,8 @@ else if (ConfigurationConstants.REPACKAGE_CLASSES_OPTION
             else if (ConfigurationConstants.ADAPT_CLASS_STRINGS_OPTION                       .startsWith(nextWord)) configuration.adaptClassStrings                     = parseCommaSeparatedList("class name", true, true, false, false, true, false, false, true, false, configuration.adaptClassStrings);
             else if (ConfigurationConstants.ADAPT_RESOURCE_FILE_NAMES_OPTION                 .startsWith(nextWord)) configuration.adaptResourceFileNames                = parseCommaSeparatedList("resource file name", true, true, false, true, false, true, false, false, false, configuration.adaptResourceFileNames);
             else if (ConfigurationConstants.ADAPT_RESOURCE_FILE_CONTENTS_OPTION              .startsWith(nextWord)) configuration.adaptResourceFileContents             = parseCommaSeparatedList("resource file name", true, true, false, true, false, true, false, false, false, configuration.adaptResourceFileContents);
-            else if (ConfigurationConstants.KEEP_KOTLIN_METADATA                             .startsWith(nextWord)) configuration.keepKotlinMetadata                    = parseNoArgument(true);
+            else if (ConfigurationConstants.DONT_PROCESS_KOTLIN_METADATA                     .startsWith(nextWord)) configuration.dontProcessKotlinMetadata             = parseNoArgument(true);
+            else if (ConfigurationConstants.KEEP_KOTLIN_METADATA                             .startsWith(nextWord)) configuration.keepKotlinMetadata                    = parseKeepKotlinMetadata();
 
             else if (ConfigurationConstants.DONT_PREVERIFY_OPTION                            .startsWith(nextWord)) configuration.preverify                             = parseNoArgument(false);
             else if (ConfigurationConstants.MICRO_EDITION_OPTION                             .startsWith(nextWord)) configuration.microEdition                          = parseNoArgument(true);
@@ -250,6 +251,14 @@ public void close() throws IOException
     }
 
 
+    private boolean parseKeepKotlinMetadata() throws IOException
+    {
+        System.err.println("The `-keepkotlinmetadata` option is deprecated and will be removed in a future ProGuard release." +
+                           "Please use `-keep class kotlin.Metadata` instead.");
+        return parseNoArgument(true);
+    }
+
+
     private long parseIncludeArgument(long lastModified) throws ParseException, IOException
     {
         // Read the configuration file name.

base/src/main/java/proguard/ConfigurationWriter.java

@@ -144,6 +144,7 @@ public void write(Configuration configuration) throws IOException
         writeOption(ConfigurationConstants.ADAPT_RESOURCE_FILE_NAMES_OPTION,                 configuration.adaptResourceFileNames);
         writeOption(ConfigurationConstants.ADAPT_RESOURCE_FILE_CONTENTS_OPTION,              configuration.adaptResourceFileContents);
         writeOption(ConfigurationConstants.KEEP_KOTLIN_METADATA,                             configuration.keepKotlinMetadata);
+        writeOption(ConfigurationConstants.DONT_PROCESS_KOTLIN_METADATA,                     configuration.dontProcessKotlinMetadata);
 
         writeOption(ConfigurationConstants.DONT_PREVERIFY_OPTION,     !configuration.preverify);
         writeOption(ConfigurationConstants.MICRO_EDITION_OPTION,      configuration.microEdition);

base/src/main/java/proguard/ProGuard.java

@@ -92,6 +92,12 @@ public void execute() throws Exception
         {
             checkGpl();
 
+            // Set the -keepkotlinmetadata option if necessary.
+            if (!configuration.dontProcessKotlinMetadata)
+            {
+                configuration.keepKotlinMetadata = requiresKotlinMetadata();
+            }
+
             if (configuration.printConfiguration != null)
             {
                 printConfiguration();
@@ -268,6 +274,17 @@ private void checkGpl()
         GPL.check();
     }
 
+    private boolean requiresKotlinMetadata()
+    {
+        return configuration.keepKotlinMetadata ||
+            (configuration.keep != null &&
+                configuration.keep.stream().anyMatch(
+                    keepClassSpecification -> ! keepClassSpecification.allowObfuscation &&
+                                              ! keepClassSpecification.allowShrinking   &&
+                                              "kotlin/Metadata".equals(keepClassSpecification.className)
+                ));
+    }
+
 
     /**
      * Prints out the configuration that ProGuard is using.

base/src/test/kotlin/proguard/MarkerTest.kt

@@ -114,6 +114,9 @@ class MarkerTest : FreeSpec({
             -keep class Test {
                 <methods>;
             }
+            # This option is deprecated and one should use '-keep class kotlin.Metadata' instead.
+            # In this test we use the deprecated option, as its value is set in ProGuard.java and not in
+            # the ConfigurationParser which is used by this unit test.
             -keepkotlinmetadata
             """.asConfiguration()
             val marker = Marker(config)
@@ -153,6 +156,9 @@ class MarkerTest : FreeSpec({
             -keep class Test {
                 <methods>;
             }
+            # This option is deprecated and one should use '-keep class kotlin.Metadata' instead.
+            # In this test we use the deprecated option, as its value is set in ProGuard.java and not in
+            # the ConfigurationParser which is used by this unit test.
             -keepkotlinmetadata
             """.asConfiguration()
             val marker = Marker(config)

docs/md/manual/configuration/usage.md

@@ -515,8 +515,9 @@ This page lists all available options for ProGuard, grouped logically.
   obfuscated stack traces](examples.md#stacktrace). Only applicable when
   obfuscating.
 
-`-keepkotlinmetadata`{: #keepkotlinmetadata}
-: Specifies to process `kotlin.Metadata` annotations if present.
+`-keepkotlinmetadata`{: #keepkotlinmetadata} {: .deprecated}
+: ** Deprecated: use `-keep class kotlin.Metadata` instead. **
+  Specifies to process `kotlin.Metadata` annotations if present.
   Currently only shrinking and obfuscation of its content is supported.
   Classes containing such annotations should be excuded from optimization
   if this option is enabled.

docs/md/manual/languages/kotlin.md

@@ -5,8 +5,10 @@ The Kotlin compiler injects code and metadata into the classes that it generates
 ## Configuration
 
 In most cases, you do not need to keep Kotlin metadata for app projects - therefore, no configuration changes are necessary and the Kotlin metadata can be safely removed.
+However, there are two common reasons to explicitly keep the metadata, [reflection](#reflection) and [libraries](#library-projects).
 
-ProGuard will only keep the Kotlin metadata of a class if you explicitly keep that class or one of its members and you add `-keepkotlinmetadata` option to your configuration.
+ProGuard will only keep the Kotlin metadata of a class if you explicitly keep that class or one of its members, and you add the `-keep class kotlin.Metadata` option to your configuration.
+Note that this option may also be required by an SDK of your project, and indirectly added as a consumer rule.
 
 For example, if you have the following keep rule for a Kotlin class named `com.example.KotlinExample`, by default the class will be kept but its metadata will not:
 
@@ -15,11 +17,11 @@ For example, if you have the following keep rule for a Kotlin class named `com.e
 -keep class com.example.KotlinExample
 ```
 
-You can add `-keepkotlinmetadata` to your configuration to instruct ProGuard to keep and adapt Kotlin metadata:
+You can add `-keep class kotlin.Metadata` to your configuration to instruct ProGuard to keep and adapt Kotlin metadata:
 
 ```
 # Add this option to tell ProGuard to keep and adapt Kotlin metadata
--keepkotlinmetadata
+-keep class kotlin.Metadata
 ```
 
 
@@ -31,7 +33,7 @@ The most common case to keep Kotlin metadata would be if you use the [kotlin-ref
 In this case, to instruct ProGuard to keep and adapt the corresponding Kotlin metadata, add the following to your configuration:
 
 ```
--keepkotlinmetadata
+-keep class kotlin.Metadata
 ```
 
 A popular framework that relies on reflection is [Jackson](https://github.com/FasterXML/jackson-module-kotlin).
@@ -41,11 +43,11 @@ A popular framework that relies on reflection is [Jackson](https://github.com/Fa
 When developing an SDK that exposes Kotlin-specific features to its users, you need to preserve the metadata of the public API.
 These include features such as named parameters, suspend functions, top-level functions and type aliases.
 
-In the case of a library, you would already be keeping the public API so you can simply add the following
+In the case of a library, you would already be keeping the public API, so you can simply add the following
 to your configuration:
 
 ```
--keepkotlinmetadata
+-keep class kotlin.Metadata
 ```
 
 ## Protection