Add initial support for remapping new API references (proof of concept)

README.md

@@ -148,6 +148,11 @@ Configurable system properties:
       Reduces the amount of logging.
       Disabled by default. Enable by setting to "true"
 
+  retrolambda.apiMappings
+      Maps static field and method references to backported classes.
+      Disabled by default.
+      Provide a list of mapping files separated by ':' to enable.
+
 If the Java agent is used, then Retrolambda will use it to capture the
 lambda classes generated by Java. Otherwise Retrolambda will hook into
 Java's internal lambda dumping API, which is more susceptible to suddenly
@@ -215,10 +220,34 @@ updated. This may cause weird error messages if static methods on
 interfaces are accidentally used without enabling default method support.*
 
 
+Backported APIs
+---------------
+
+Retrolambda can be configured to automatically replace references to
+new Java APIs with backported versions.
+
+You can use one of the prepackaged mappings, or write your own. For
+details on the syntax of the mapping files, see the included
+[java7-guava](retrolambda/src/main/resources/net/orfjackal/retrolambda/api/java7-guava) or
+[streamsupport](retrolambda/src/main/resources/net/orfjackal/retrolambda/api/streamsupport).
+
+Currently included mappings:
+
+  * **java6-guava**: Maps new Java 1.7 APIs to existing guava methods.
+    For example, from `java.nio.StandardCharsets` to `com.google.common.base.Charsets`
+
+  * **java7-guava**: Maps new Java 1.8 APIs to existing guava methods.
+    For example, from `java.lang.Integer.toUnsignedLong()` to `com.google.common.primitives.UnsignedInts.toLong()`
+
+  * **streamsupport**: Maps java.util.function.* interfaces to the
+    java8.util.function replacements in the [streamsupport](http://sourceforge.net/projects/streamsupport/)  library.
+
+
+
 Known Limitations
 -----------------
 
-Does not backport Java 8 APIs.
+Does not backport all Java 8 APIs.
 
 Backporting default methods and static methods on interfaces requires all
 backported interfaces and all classes which implement them or call their

end-to-end-tests/pom.xml

@@ -49,6 +49,12 @@
             <systemPath>${basedir}/src/test/lib/java-lang-dummies.jar</systemPath>
         </dependency>
 
+        <dependency>
+            <groupId>net.sourceforge.streamsupport</groupId>
+            <artifactId>streamsupport</artifactId>
+            <version>1.6.3</version>
+        </dependency>
+
     </dependencies>
 
     <build>
@@ -119,6 +125,10 @@
                     <defaultMethods>${testDefaultMethods}</defaultMethods>
                     <fork>${testFork}</fork>
                     <javacHacks>true</javacHacks>
+                    <apiMappings>
+                        <mapping>java7-guava</mapping>
+                        <mapping>streamsupport</mapping>
+                    </apiMappings>
                 </configuration>
             </plugin>
 

end-to-end-tests/src/test/java/net/orfjackal/retrolambda/test/ApiMapperTest.java

@@ -0,0 +1,39 @@
+// Copyright © 2013-2018 Esko Luontola and other Retrolambda contributors
+// This software is released under the Apache License 2.0.
+// The license text is at http://www.apache.org/licenses/LICENSE-2.0
+
+package net.orfjackal.retrolambda.test;
+
+import org.junit.Test;
+
+import java.nio.charset.*;
+import java.util.*;
+import java.util.function.Predicate;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.Matchers.hasSize;
+import static org.junit.Assert.assertThat;
+
+public class ApiMapperTest {
+
+    @Test
+    public void toUnsignedLong() {
+
+        assertThat(Integer.toUnsignedLong(0xffffffff), equalTo(4294967295L));
+    }
+
+    @Test
+    public void predicates() {
+        assertThat(filter(Arrays.asList("Hello World", "Goodbye World"), x -> x.startsWith("Hello")), hasSize(1));
+    }
+
+    private List<String> filter(List<String> strings, Predicate<String> predicate) {
+        List<String> result = new ArrayList<>();
+        for (String string : strings) {
+            if(predicate.test(string)) {
+                result.add(string);
+            }
+        }
+        return result;
+    }
+}

end-to-end-tests/src/test/java/net/orfjackal/retrolambda/test/BackportedApis.java

@@ -0,0 +1,8 @@
+// Copyright © 2013-2018 Esko Luontola and other Retrolambda contributors
+// This software is released under the Apache License 2.0.
+// The license text is at http://www.apache.org/licenses/LICENSE-2.0
+
+package net.orfjackal.retrolambda.test;
+
+public class BackportedApis {
+}

retrolambda-api/src/main/java/net/orfjackal/retrolambda/api/RetrolambdaApi.java

@@ -17,4 +17,5 @@ public class RetrolambdaApi {
     public static final String DEFAULT_METHODS = PREFIX + "defaultMethods";
     public static final String BYTECODE_VERSION = PREFIX + "bytecodeVersion";
     public static final String JAVAC_HACKS = PREFIX + "javacHacks";
+    public static final String API_MAPPINGS = PREFIX + "apiMappings";
 }

retrolambda-maven-plugin/src/main/java/net/orfjackal/retrolambda/maven/ProcessClassesMojo.java

@@ -7,6 +7,7 @@
 import com.google.common.base.*;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.io.Files;
+import net.orfjackal.retrolambda.Retrolambda;
 import net.orfjackal.retrolambda.api.RetrolambdaApi;
 import org.apache.commons.lang3.*;
 import org.apache.maven.artifact.DependencyResolutionRequiredException;
@@ -107,6 +108,9 @@ abstract class ProcessClassesMojo extends AbstractMojo {
     @Parameter(defaultValue = "false")
     public boolean fork;
 
+    @Parameter
+    public List<String> apiMappings;
+
     protected abstract File getInputDir();
 
     protected abstract File getOutputDir();
@@ -126,6 +130,7 @@ public void execute() throws MojoExecutionException {
         config.setProperty(RetrolambdaApi.OUTPUT_DIR, getOutputDir().getAbsolutePath());
         config.setProperty(RetrolambdaApi.CLASSPATH, getClasspath());
         config.setProperty(RetrolambdaApi.JAVAC_HACKS, "" + javacHacks);
+        config.setProperty(RetrolambdaApi.API_MAPPINGS, apiMappingsList());
 
         if (fork) {
             processClassesInForkedProcess(config);
@@ -134,6 +139,19 @@ public void execute() throws MojoExecutionException {
         }
     }
 
+    private String apiMappingsList() {
+        StringBuilder list = new StringBuilder();
+        if(apiMappings != null) {
+            for (String apiMapping : apiMappings) {
+                if(list.length() > 0) {
+                    list.append(File.pathSeparator);
+                }
+                list.append(apiMapping);
+            }
+        }
+        return list.toString();
+    }
+
     private void validateTarget() throws MojoExecutionException {
         if (!targetBytecodeVersions.containsKey(target)) {
             String possibleValues = Joiner.on(", ").join(new TreeSet<String>(targetBytecodeVersions.keySet()));

retrolambda/retrolambda.iml

@@ -6,6 +6,7 @@
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/src/main/java" isTestSource="false" />
       <sourceFolder url="file://$MODULE_DIR$/src/test/java" isTestSource="true" />
+      <sourceFolder url="file://$MODULE_DIR$/src/main/resources" type="java-resource" />
       <excludeFolder url="file://$MODULE_DIR$/target" />
     </content>
     <orderEntry type="inheritedJdk" />

retrolambda/src/main/java/net/orfjackal/retrolambda/Config.java

@@ -21,6 +21,8 @@ public interface Config {
 
     List<Path> getIncludedFiles();
 
+    List<String> getApiMappings();
+
     boolean isJavacHacksEnabled();
 
     boolean isQuiet();

retrolambda/src/main/java/net/orfjackal/retrolambda/Retrolambda.java

@@ -5,6 +5,7 @@
 package net.orfjackal.retrolambda;
 
 import com.esotericsoftware.minlog.Log;
+import net.orfjackal.retrolambda.api.ApiMappingSet;
 import net.orfjackal.retrolambda.files.*;
 import net.orfjackal.retrolambda.interfaces.ClassInfo;
 import net.orfjackal.retrolambda.lambdas.*;
@@ -33,6 +34,7 @@ public static void run(Config config) throws Throwable {
         List<Path> classpath = config.getClasspath();
         List<Path> includedFiles = config.getIncludedFiles();
         boolean isJavacHacksEnabled = config.isJavacHacksEnabled();
+        List<String> apiMappings = config.getApiMappings();
         if (config.isQuiet()) {
             Log.WARN();
         } else {
@@ -57,7 +59,8 @@ public static void run(Config config) throws Throwable {
 
         ClassAnalyzer analyzer = new ClassAnalyzer();
         OutputDirectory outputDirectory = new OutputDirectory(outputDir);
-        Transformers transformers = new Transformers(bytecodeVersion, defaultMethodsEnabled, analyzer);
+        ApiMappingSet apiMappingSet = new ApiMappingSet(config.getApiMappings());
+        Transformers transformers = new Transformers(bytecodeVersion, defaultMethodsEnabled, analyzer, apiMappingSet);
         LambdaClassSaver lambdaClassSaver = new LambdaClassSaver(outputDirectory, transformers, isJavacHacksEnabled);
 
         try (LambdaClassDumper dumper = new LambdaClassDumper(lambdaClassSaver)) {

retrolambda/src/main/java/net/orfjackal/retrolambda/SystemPropertiesConfig.java

@@ -200,6 +200,8 @@ public List<Path> getIncludedFiles() {
 
     }
 
+
+
     @Override
     public boolean isJavacHacksEnabled() {
         return Boolean.parseBoolean(p.getProperty(JAVAC_HACKS, "false"));
@@ -221,6 +223,27 @@ public boolean isQuiet() {
     }
 
 
+
+    // API Mappings
+
+    static {
+        optionalParameterHelp(API_MAPPINGS,
+                "Maps static field and method references to backported classes.",
+                        "Disabled by default.",
+                        "Provide a list of mapping files separated by '" + File.pathSeparator + "' to enable.");
+    }
+
+
+    @Override
+    public List<String> getApiMappings() {
+        String list = p.getProperty(API_MAPPINGS, "");
+        if(list.isEmpty()) {
+            return Collections.emptyList();
+        } else {
+            return Arrays.asList(list.split(File.pathSeparator));
+        }
+    }
+
     // help
 
     public String getHelp() {

retrolambda/src/main/java/net/orfjackal/retrolambda/Transformers.java

@@ -4,6 +4,7 @@
 
 package net.orfjackal.retrolambda;
 
+import net.orfjackal.retrolambda.api.*;
 import net.orfjackal.retrolambda.interfaces.*;
 import net.orfjackal.retrolambda.lambdas.*;
 import net.orfjackal.retrolambda.requirenonnull.RequireNonNull;
@@ -19,11 +20,13 @@ public class Transformers {
     private final int targetVersion;
     private final boolean defaultMethodsEnabled;
     private final ClassAnalyzer analyzer;
+    private final ApiMappingSet mapping;
 
-    public Transformers(int targetVersion, boolean defaultMethodsEnabled, ClassAnalyzer analyzer) {
+    public Transformers(int targetVersion, boolean defaultMethodsEnabled, ClassAnalyzer analyzer, ApiMappingSet mapping) {
         this.targetVersion = targetVersion;
         this.defaultMethodsEnabled = defaultMethodsEnabled;
         this.analyzer = analyzer;
+        this.mapping = mapping;
     }
 
     public byte[] backportLambdaClass(ClassReader reader) {
@@ -50,6 +53,9 @@ public byte[] backportClass(ClassReader reader) {
                 next = new AddMethodDefaultImplementations(next, analyzer);
             }
             next = new BackportLambdaInvocations(next, analyzer);
+            if (mapping.isEnabled()) {
+                next = new RewriteApiReferences(next, mapping);
+            }
             return next;
         });
     }