[WebNFC] Support NDEF tag with no message

This CL makes sure NDEF tags still fire an onreading Web NFC event
even if there are no messages yet. This results in a NDEFMessage with
no records as discussed in https://github.com/w3c/web-nfc/issues/367.

Bug: 520391, 1012463
Change-Id: Ib87980cfc7354561146f7854272b247fb6df5a79
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1871550
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
Reviewed-by: Rijubrata Bhaumik <rijubrata.bhaumik@intel.com>
Cr-Commit-Position: refs/heads/master@{#708145}

services/device/nfc/android/java/src/org/chromium/device/nfc/NfcImpl.java

@@ -29,6 +29,7 @@ import org.chromium.device.mojom.NdefErrorType;
 import org.chromium.device.mojom.NdefMessage;
 import org.chromium.device.mojom.NdefPushOptions;
 import org.chromium.device.mojom.NdefPushTarget;
+import org.chromium.device.mojom.NdefRecord;
 import org.chromium.device.mojom.NdefScanOptions;
 import org.chromium.device.mojom.Nfc;
 import org.chromium.device.mojom.NfcClient;
@@ -550,14 +551,21 @@ public class NfcImpl implements Nfc {
             mTagHandler.connect();
             message = mTagHandler.read();
             if (message == null) {
-                Log.w(TAG, "Cannot read data from NFC tag. Tag is empty.");
+                // Tag is formatted to support NDEF but does not contain a message yet.
+                // Let's create one with no records so that watchers can be notified.
+                NdefMessage webNdefMessage = new NdefMessage();
+                webNdefMessage.data = new NdefRecord[0];
+                notifyMatchingWatchers(webNdefMessage);
                 return;
             }
             if (message.getByteArrayLength() > NdefMessage.MAX_SIZE) {
                 Log.w(TAG, "Cannot read data from NFC tag. NdefMessage exceeds allowed size.");
                 return;
             }
-            notifyMatchingWatchers(message);
+            NdefMessage webNdefMessage = NdefMessageUtils.toNdefMessage(message);
+            notifyMatchingWatchers(webNdefMessage);
+        } catch (UnsupportedEncodingException e) {
+            Log.w(TAG, "Cannot read data from NFC tag. Cannot convert to NdefMessage.");
         } catch (TagLostException e) {
             Log.w(TAG, "Cannot read data from NFC tag. Tag is lost.");
         } catch (FormatException | IllegalStateException | IOException e) {
@@ -569,26 +577,21 @@ public class NfcImpl implements Nfc {
      * Iterates through active watchers and if any of those match NdefScanOptions criteria,
      * delivers NdefMessage to the client.
      */
-    private void notifyMatchingWatchers(android.nfc.NdefMessage message) {
-        try {
-            NdefMessage ndefMessage = NdefMessageUtils.toNdefMessage(message);
-            List<Integer> watchIds = new ArrayList<Integer>();
-            for (int i = 0; i < mWatchers.size(); i++) {
-                NdefScanOptions options = mWatchers.valueAt(i);
-                if (matchesWatchOptions(ndefMessage, options)) {
-                    watchIds.add(mWatchers.keyAt(i));
-                }
+    private void notifyMatchingWatchers(NdefMessage message) {
+        List<Integer> watchIds = new ArrayList<Integer>();
+        for (int i = 0; i < mWatchers.size(); i++) {
+            NdefScanOptions options = mWatchers.valueAt(i);
+            if (matchesWatchOptions(message, options)) {
+                watchIds.add(mWatchers.keyAt(i));
             }
+        }
 
-            if (watchIds.size() != 0) {
-                int[] ids = new int[watchIds.size()];
-                for (int i = 0; i < watchIds.size(); ++i) {
-                    ids[i] = watchIds.get(i).intValue();
-                }
-                mClient.onWatch(ids, mTagHandler.serialNumber(), ndefMessage);
+        if (watchIds.size() != 0) {
+            int[] ids = new int[watchIds.size()];
+            for (int i = 0; i < watchIds.size(); ++i) {
+                ids[i] = watchIds.get(i).intValue();
             }
-        } catch (UnsupportedEncodingException e) {
-            Log.w(TAG, "Cannot convert NdefMessage to NdefMessage.");
+            mClient.onWatch(ids, mTagHandler.serialNumber(), message);
         }
     }
 

services/device/nfc/android/junit/src/org/chromium/device/nfc/NFCTest.java

@@ -544,6 +544,32 @@ public class NFCTest {
         assertEquals(watchId2, mOnWatchCallbackCaptor.getValue()[1]);
     }
 
+    /**
+     * Test that Nfc.watch() notifies client when tag is not formatted.
+     */
+    @Test
+    @Feature({"NFCTest"})
+    public void testWatchNotFormattedTag() throws IOException, FormatException {
+        TestNfcImpl nfc = new TestNfcImpl(mContext, mDelegate);
+        mDelegate.invokeCallback();
+        nfc.setClient(mNfcClient);
+        int watchId = mNextWatchId++;
+        WatchResponse mockWatchCallback = mock(WatchResponse.class);
+        nfc.watch(createNdefScanOptions(), watchId, mockWatchCallback);
+        verify(mockWatchCallback).call(mErrorCaptor.capture());
+        assertNull(mErrorCaptor.getValue());
+
+        // Returning null means tag is not formatted.
+        doReturn(null).when(mNfcTagHandler).read();
+        nfc.processPendingOperationsForTesting(mNfcTagHandler);
+
+        // Check that client was notified and correct watch id was provided.
+        verify(mNfcClient, times(1))
+                .onWatch(mOnWatchCallbackCaptor.capture(), nullable(String.class),
+                        any(NdefMessage.class));
+        assertEquals(watchId, mOnWatchCallbackCaptor.getValue()[0]);
+    }
+
     /**
      * Test that Nfc.watch() matching function works correctly.
      */