Make badly-behaving caches cause a checked exception, not NPE

Android bug: https://code.google.com/p/android/issues/detail?id=160522

okhttp-android-support/src/main/java/com/squareup/okhttp/internal/huc/JavaApiConverter.java

@@ -338,19 +338,23 @@ private static String extractStatusLine(HttpURLConnection httpUrlConnection) {
 
   /**
    * Extracts the status line from the supplied Java API {@link java.net.CacheResponse}.
-   * As per the spec, the status line is held as the header with the null key. Returns {@code null}
-   * if there is no status line.
+   * As per the spec, the status line is held as the header with the null key. Throws a
+   * {@link ProtocolException} if there is no status line.
    */
   private static String extractStatusLine(CacheResponse javaResponse) throws IOException {
     Map<String, List<String>> javaResponseHeaders = javaResponse.getHeaders();
     return extractStatusLine(javaResponseHeaders);
   }
 
   // VisibleForTesting
-  static String extractStatusLine(Map<String, List<String>> javaResponseHeaders) {
+  static String extractStatusLine(Map<String, List<String>> javaResponseHeaders)
+      throws ProtocolException {
     List<String> values = javaResponseHeaders.get(null);
     if (values == null || values.size() == 0) {
-      return null;
+      // The status line is missing. This suggests a badly behaving cache.
+      throw new ProtocolException(
+          "CacheResponse is missing a \'null\' header containing the status line. Headers="
+          + javaResponseHeaders);
     }
     return values.get(0);
   }

okhttp-android-support/src/test/java/com/squareup/okhttp/internal/huc/JavaApiConverterTest.java

@@ -233,6 +233,30 @@ private void testCreateOkResponseInternal(HttpURLConnectionFactory httpUrlConnec
     assertNull(response.handshake());
   }
 
+  /** Test for https://code.google.com/p/android/issues/detail?id=160522 */
+  @Test public void createOkResponse_fromCacheResponseWithMissingStatusLine() throws Exception {
+    URI uri = new URI("http://foo/bar");
+    Request request = new Request.Builder().url(uri.toURL()).build();
+    CacheResponse cacheResponse = new CacheResponse() {
+      @Override public Map<String, List<String>> getHeaders() throws IOException {
+        Map<String, List<String>> headers = new HashMap<>();
+        // Headers is deliberately missing an entry with a null key.
+        headers.put("xyzzy", Arrays.asList("bar", "baz"));
+        return headers;
+      }
+
+      @Override public InputStream getBody() throws IOException {
+        return null; // Should never be called
+      }
+    };
+
+    try {
+      JavaApiConverter.createOkResponse(request, cacheResponse);
+      fail();
+    } catch (IOException expected) {
+    }
+  }
+
   @Test public void createOkResponse_fromSecureCacheResponse() throws Exception {
     final String statusLine = "HTTP/1.1 200 Fantastic";
     final Principal localPrincipal = LOCAL_CERT.getSubjectX500Principal();
@@ -669,15 +693,18 @@ private void assertHeadersContainsMapping(Map<String, List<String>> headers, Str
     assertEquals(Arrays.asList("value2"), okHeaders.values("key2"));
   }
 
-  @Test public void extractStatusLine() {
+  @Test public void extractStatusLine() throws Exception {
     Map<String, List<String>> javaResponseHeaders = new HashMap<>();
     javaResponseHeaders.put(null, Arrays.asList("StatusLine"));
     javaResponseHeaders.put("key1", Arrays.asList("value1_1", "value1_2"));
     javaResponseHeaders.put("key2", Arrays.asList("value2"));
     assertEquals("StatusLine", JavaApiConverter.extractStatusLine(javaResponseHeaders));
 
-    assertNull(
-        JavaApiConverter.extractStatusLine(Collections.<String, List<String>>emptyMap()));
+    try {
+      JavaApiConverter.extractStatusLine(Collections.<String, List<String>>emptyMap());
+      fail();
+    } catch (IOException expected) {
+    }
   }
 
   private URL configureServer(MockResponse mockResponse) throws Exception {

okhttp-android-support/src/test/java/com/squareup/okhttp/internal/huc/ResponseCacheTest.java

@@ -40,12 +40,14 @@
 import java.net.CookieManager;
 import java.net.HttpCookie;
 import java.net.HttpURLConnection;
+import java.net.ProtocolException;
 import java.net.ResponseCache;
 import java.net.SecureCacheResponse;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.net.URLConnection;
+import java.nio.charset.StandardCharsets;
 import java.security.Principal;
 import java.security.cert.Certificate;
 import java.util.ArrayList;
@@ -1303,6 +1305,48 @@ public void assertCookies(CookieManager cookieManager, URL url, String... expect
     assertFalse(aborted.get()); // The best behavior is ambiguous, but RI 6 doesn't abort here
   }
 
+  /**
+   * Fail if a badly-behaved cache returns a null status line header.
+   * https://code.google.com/p/android/issues/detail?id=160522
+   */
+  @Test public void responseCacheReturnsNullStatusLine() throws Exception {
+    String cachedContentString = "Hello";
+    final byte[] cachedContent = cachedContentString.getBytes(StandardCharsets.US_ASCII);
+
+    Internal.instance.setCache(client, new CacheAdapter(new AbstractResponseCache() {
+      @Override
+      public CacheResponse get(URI uri, String requestMethod,
+          Map<String, List<String>> requestHeaders)
+          throws IOException {
+        return new CacheResponse() {
+          @Override public Map<String, List<String>> getHeaders() throws IOException {
+            String contentType = "text/plain";
+            Map<String, List<String>> headers = new HashMap<>();
+            headers.put("Content-Length", Arrays.asList(Integer.toString(cachedContent.length)));
+            headers.put("Content-Type", Arrays.asList(contentType));
+            headers.put("Expires", Arrays.asList(formatDate(-1, TimeUnit.HOURS)));
+            headers.put("Cache-Control", Arrays.asList("max-age=60"));
+            // Crucially, the header with a null key is missing, which renders the cache response
+            // unusable because OkHttp only caches responses with cacheable response codes.
+            return headers;
+          }
+
+          @Override public InputStream getBody() throws IOException {
+            return new ByteArrayInputStream(cachedContent);
+          }
+        };
+      }
+    }));
+    HttpURLConnection connection = openConnection(server.getUrl("/"));
+    // If there was no status line from the cache an exception will be thrown. No network request
+    // should be made.
+    try {
+      connection.getResponseCode();
+      fail();
+    } catch (ProtocolException expected) {
+    }
+  }
+
   /**
    * @param delta the offset from the current date to use. Negative
    * values yield dates in the past; positive values yield dates in the