Use contact hash codes only on Android 7+ (workaround)

vcard4android: don't hash CATEGORIES, more verbose logging

app/src/main/java/at/bitfire/davdroid/resource/LocalAddressBook.java

@@ -14,6 +14,7 @@ import android.content.ContentUris;
 import android.content.ContentValues;
 import android.database.Cursor;
 import android.net.Uri;
+import android.os.Build;
 import android.os.Bundle;
 import android.os.Parcel;
 import android.os.RemoteException;
@@ -92,15 +93,22 @@ public class LocalAddressBook extends AndroidAddressBook implements LocalCollect
      * @return number of "really dirty" contacts
      */
     public int verifyDirty() throws ContactsStorageException {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N)
+            App.log.severe("verifyDirty() should not be called on Android <7");
+
         int reallyDirty = 0;
         for (LocalContact contact : getDirtyContacts()) {
             try {
-                if (contact.getLastHashCode() == contact.dataHashCode()) {
+                int lastHash = contact.getLastHashCode(),
+                    currentHash = contact.dataHashCode();
+                if (lastHash == currentHash) {
                     // hash is code still the same, contact is not "really dirty" (only metadata been have changed)
                     App.log.log(Level.FINE, "Contact data hash has not changed, resetting dirty flag", contact);
                     contact.resetDirty();
-                } else
+                } else {
+                    App.log.log(Level.FINE, "Contact data has changed from hash " + lastHash + " to " + currentHash, contact);
                     reallyDirty++;
+                }
             } catch(FileNotFoundException e) {
                 throw new ContactsStorageException("Couldn't calculate hash code", e);
             }

app/src/main/java/at/bitfire/davdroid/resource/LocalContact.java

@@ -12,6 +12,7 @@ import android.content.ContentProviderOperation;
 import android.content.ContentValues;
 import android.database.Cursor;
 import android.net.Uri;
+import android.os.Build;
 import android.os.RemoteException;
 import android.provider.ContactsContract;
 import android.provider.ContactsContract.CommonDataKinds.GroupMembership;
@@ -82,9 +83,12 @@ public class LocalContact extends AndroidContact implements LocalResource {
             values.put(COLUMN_ETAG, eTag);
             values.put(ContactsContract.RawContacts.DIRTY, 0);
 
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+                // workaround for Android 7 which sets DIRTY flag when only meta-data is changed
                 int hashCode = dataHashCode();
                 values.put(COLUMN_HASHCODE, hashCode);
                 App.log.finer("Clearing dirty flag with eTag = " + eTag + ", contact hash = " + hashCode);
+            }
 
             addressBook.provider.update(rawContactSyncURI(), values, null, null);
 
@@ -161,14 +165,24 @@ public class LocalContact extends AndroidContact implements LocalResource {
     @Override
     public int update(Contact contact) throws ContactsStorageException {
         int result = super.update(contact);
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+            // workaround for Android 7 which sets DIRTY flag when only meta-data is changed
             updateHashCode();
+        }
+
         return result;
     }
 
     @Override
     public Uri create() throws ContactsStorageException {
         Uri uri = super.create();
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+            // workaround for Android 7 which sets DIRTY flag when only meta-data is changed
             updateHashCode();
+        }
+
         return uri;
     }
 
@@ -177,11 +191,17 @@ public class LocalContact extends AndroidContact implements LocalResource {
      * @return hash code of contact data (including group memberships)
      */
     public int dataHashCode() throws FileNotFoundException, ContactsStorageException {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N)
+            App.log.severe("dataHashCode() should not be called on Android <7");
+
         // groupMemberships is filled by getContact()
         return getContact().hashCode() ^ groupMemberships.hashCode();
     }
 
     protected void updateHashCode() throws ContactsStorageException {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N)
+            App.log.severe("updateHashCode() should not be called on Android <7");
+
         ContentValues values = new ContentValues(1);
         try {
             int hashCode = dataHashCode();
@@ -194,6 +214,9 @@ public class LocalContact extends AndroidContact implements LocalResource {
     }
 
     int getLastHashCode() throws ContactsStorageException {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N)
+            App.log.severe("getLastHashCode() should not be called on Android <7");
+
         try {
             @Cleanup Cursor c = addressBook.provider.query(rawContactSyncURI(), new String[] { COLUMN_HASHCODE }, null, null, null);
             if (c == null || !c.moveToNext() || c.isNull(0))

app/src/main/java/at/bitfire/davdroid/syncadapter/ContactsSyncManager.java

@@ -14,6 +14,7 @@ import android.content.ContentResolver;
 import android.content.ContentValues;
 import android.content.Context;
 import android.content.SyncResult;
+import android.os.Build;
 import android.os.Bundle;
 import android.provider.ContactsContract;
 
@@ -82,11 +83,14 @@ public class ContactsSyncManager extends SyncManager {
         LocalAddressBook localAddressBook = localAddressBook();
         localAddressBook.setURL(info.url);
 
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+            // workaround for Android 7 which sets DIRTY flag when only meta-data is changed
             int reallyDirty = localAddressBook.verifyDirty();
             if (extras.containsKey(ContentResolver.SYNC_EXTRAS_UPLOAD) && reallyDirty == 0) {
                 App.log.info("This sync was called to upload dirty contacts, but no contact data have been changed");
                 return false;
             }
+        }
 
         // set up Contacts Provider Settings
         ContentValues values = new ContentValues(2);