Add tests for CompatDexBuilder cache

Author: mgalindo-sc

src/test/java/com/google/devtools/build/android/r8/CompatDexBuilderTest.java

@@ -18,14 +18,19 @@
 
 import com.android.tools.r8.D8;
 import com.android.tools.r8.D8Command;
+import com.android.tools.r8.DiagnosticsHandler;
 import com.android.tools.r8.OutputMode;
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
 import com.google.common.collect.ImmutableList;
 import com.google.devtools.common.options.OptionsParsingException;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
+import java.io.PrintWriter;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.concurrent.ExecutionException;
@@ -122,6 +127,54 @@ public void compileWithSyntheticLambdas() throws Exception {
     }
   }
 
+  @Test
+  public void compileWithCachedSyntheticLambdas() throws Exception {
+    // Test synthetic context information is cached alongside dexed classes
+    CompatDexBuilder compatDexBuilder = new CompatDexBuilder();
+    Cache<CompatDexBuilder.DexingKeyR8, CompatDexBuilder.DexingEntryR8> dexCache =
+        CacheBuilder.newBuilder().build();
+    DiagnosticsHandler diagnostics = new DiagnosticsHandler() {};
+    PrintWriter pw = new PrintWriter(System.err);
+
+    final String contextName = "com/google/devtools/build/android/r8/testdata/lambda/Lambda";
+    final String inputJar = System.getProperty("CompatDexBuilderTests.lambda");
+    final Path outputZipA = temp.getRoot().toPath().resolve("outA.zip");
+    final Path outputZipB = temp.getRoot().toPath().resolve("outB.zip");
+
+    String[] args = new String[] {"--input_jar", inputJar, "--output_zip", outputZipA.toString()};
+    compatDexBuilder.processRequest(dexCache, diagnostics, Arrays.asList(args), pw);
+
+    args = new String[] {"--input_jar", inputJar, "--output_zip", outputZipB.toString()};
+    compatDexBuilder.processRequest(dexCache, diagnostics, Arrays.asList(args), pw);
+
+    Path[] outputZips = new Path[] {outputZipA, outputZipB};
+    for (Path outputZip: outputZips) {
+        try (ZipFile zipFile = new ZipFile(outputZip.toFile(), UTF_8)) {
+            assertThat(zipFile.getEntry(contextName + ".class.dex")).isNotNull();
+            ZipEntry entry = zipFile.getEntry("META-INF/synthetic-contexts.map");
+            assertThat(entry).isNotNull();
+            try (BufferedReader reader =
+                new BufferedReader(new InputStreamReader(zipFile.getInputStream(entry), UTF_8))) {
+                String line = reader.readLine();
+                assertThat(line).isNotNull();
+                // Format of mapping is: <synthetic-binary-name>;<context-binary-name>\n
+                int sep = line.indexOf(';');
+                String syntheticNameInMap = line.substring(0, sep);
+                String contextNameInMap = line.substring(sep + 1);
+                // The synthetic will be prefixed by the context type. This checks the synthetic name
+                // is larger than the context to avoid hardcoding the synthetic names, which may change.
+                assertThat(syntheticNameInMap).startsWith(contextName);
+                assertThat(syntheticNameInMap).isNotEqualTo(contextName);
+                // Check expected context.
+                assertThat(contextNameInMap).isEqualTo(contextName);
+                // Only one synthetic and its context should be present.
+                line = reader.readLine();
+                assertThat(line).isNull();
+            }
+        }
+    }
+  }
+
   @Test
   public void compileTwoClassesAndRun() throws Exception {
     // Run CompatDexBuilder on dexMergeSample.jar

src/tools/android/java/com/google/devtools/build/android/r8/CompatDexBuilder.java

@@ -33,6 +33,7 @@
 import com.android.tools.r8.references.ClassReference;
 import com.android.tools.r8.utils.StringDiagnostic;
 import com.google.auto.value.AutoValue;
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.cache.Cache;
 import com.google.common.cache.CacheBuilder;
 import com.google.common.cache.Weigher;
@@ -190,7 +191,8 @@ public int weigh(DexingKeyR8 key, DexingEntryR8 value) {
     }
   }
 
-  private int processRequest(
+  @VisibleForTesting
+  int processRequest(
       @Nullable Cache<DexingKeyR8, DexingEntryR8> dexCache,
       DiagnosticsHandler diagnosticsHandler,
       List<String> args,