Remove null keys from DefaultHttpDataSource#getResponseHeaders

PiperOrigin-RevId: 410507648

RELEASENOTES.md

@@ -26,6 +26,7 @@
         `buildVideoRenderers()` or `buildAudioRenderers()` can access the codec
         adapter factory and pass it to `MediaCodecRenderer` instances they
         create.
+    *   Remove null keys from `DefaultHttpDataSource#getResponseHeaders`.
 *   Extractors:
     *   WAV: Add support for RF64 streams
         ([#9543](https://github.com/google/ExoPlayer/issues/9543).

library/datasource/src/androidTest/java/com/google/android/exoplayer2/upstream/DefaultHttpDataSourceContractTest.java

@@ -20,7 +20,6 @@ import androidx.test.ext.junit.runners.AndroidJUnit4;
 import com.google.android.exoplayer2.testutil.DataSourceContractTest;
 import com.google.android.exoplayer2.testutil.HttpDataSourceTestEnv;
 import com.google.common.collect.ImmutableList;
-import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.runner.RunWith;
 
@@ -44,8 +43,4 @@ public class DefaultHttpDataSourceContractTest extends DataSourceContractTest {
   protected Uri getNotFoundUri() {
     return Uri.parse(httpDataSourceTestEnv.getNonexistentUrl());
   }
-
-  @Override
-  @Ignore("internal b/205811776")
-  public void getResponseHeaders_noNullKeysOrValues() {}
 }

library/datasource/src/main/java/com/google/android/exoplayer2/upstream/DefaultHttpDataSource.java

@@ -29,6 +29,9 @@ import com.google.android.exoplayer2.upstream.DataSpec.HttpMethod;
 import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.Util;
 import com.google.common.base.Predicate;
+import com.google.common.collect.ForwardingMap;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Sets;
 import com.google.common.net.HttpHeaders;
 import java.io.IOException;
 import java.io.InputStream;
@@ -39,10 +42,10 @@ import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
 import java.net.NoRouteToHostException;
 import java.net.URL;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.zip.GZIPInputStream;
 
 /**
@@ -310,7 +313,18 @@ public class DefaultHttpDataSource extends BaseDataSource implements HttpDataSou
 
   @Override
   public Map<String, List<String>> getResponseHeaders() {
-    return connection == null ? Collections.emptyMap() : connection.getHeaderFields();
+    if (connection == null) {
+      return ImmutableMap.of();
+    }
+    // connection.getHeaderFields() always contains a null key with a value like
+    // ["HTTP/1.1 200 OK"]. The response code is available from HttpURLConnection#getResponseCode()
+    // and the HTTP version is fixed when establishing the connection.
+    // DataSource#getResponseHeaders() doesn't allow null keys in the returned map, so we need to
+    // remove it.
+    // connection.getHeaderFields() returns a special unmodifiable case-insensitive Map
+    // so we can't just remove the null key or make a copy without the null key. Instead we wrap it
+    // in a ForwardingMap subclass that ignores and filters out null keys in the read methods.
+    return new NullFilteringHeadersMap(connection.getHeaderFields());
   }
 
   @Override
@@ -815,4 +829,64 @@ public class DefaultHttpDataSource extends BaseDataSource implements HttpDataSou
     String contentEncoding = connection.getHeaderField("Content-Encoding");
     return "gzip".equalsIgnoreCase(contentEncoding);
   }
+
+  private static class NullFilteringHeadersMap extends ForwardingMap<String, List<String>> {
+
+    private final Map<String, List<String>> headers;
+
+    public NullFilteringHeadersMap(Map<String, List<String>> headers) {
+      this.headers = headers;
+    }
+
+    @Override
+    protected Map<String, List<String>> delegate() {
+      return headers;
+    }
+
+    @Override
+    public boolean containsKey(@Nullable Object key) {
+      return key != null && super.containsKey(key);
+    }
+
+    @Nullable
+    @Override
+    public List<String> get(@Nullable Object key) {
+      return key == null ? null : super.get(key);
+    }
+
+    @Override
+    public Set<String> keySet() {
+      return Sets.filter(super.keySet(), key -> key != null);
+    }
+
+    @Override
+    public Set<Entry<String, List<String>>> entrySet() {
+      return Sets.filter(super.entrySet(), entry -> entry.getKey() != null);
+    }
+
+    @Override
+    public int size() {
+      return super.size() - (super.containsKey(null) ? 1 : 0);
+    }
+
+    @Override
+    public boolean isEmpty() {
+      return super.isEmpty() || (super.size() == 1 && super.containsKey(null));
+    }
+
+    @Override
+    public boolean containsValue(@Nullable Object value) {
+      return super.standardContainsValue(value);
+    }
+
+    @Override
+    public boolean equals(@Nullable Object object) {
+      return object != null && super.standardEquals(object);
+    }
+
+    @Override
+    public int hashCode() {
+      return super.standardHashCode();
+    }
+  }
 }

testutils/src/main/java/com/google/android/exoplayer2/testutil/DataSourceContractTest.java

@@ -545,11 +545,6 @@ public abstract class DataSourceContractTest {
 
         Map<String, List<String>> responseHeaders = dataSource.getResponseHeaders();
         for (String key : responseHeaders.keySet()) {
-          // TODO(internal b/205811776): Remove this when DefaultHttpDataSource is fixed to not
-          // return a null key.
-          if (key == null) {
-            continue;
-          }
           String caseFlippedKey = invertAsciiCaseOfEveryOtherCharacter(key);
           assertWithMessage("key='%s', caseFlippedKey='%s'", key, caseFlippedKey)
               .that(responseHeaders.get(caseFlippedKey))