Really support removing / adding partitions.

- When removing a partition, BlockDifference() object
will have tgt=EmptyImage(). Fix the asserts accordingly.
Also, BlockDifference object now allow tgt=None case.

- When adding a partition, BlockDifference() object
will have src=None. Fix the asserts accordingly.

Also, add unit tests to DynamicPartitionsDifference.

Test: create incremental OTA
Test: test_common.DynamicPartitionsDifferenceTest
Bug: 111801737

Change-Id: I3a35378ecf93111b8f44545cff6ae9696b6b4851
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index be2c108..a3790cd 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -2221,12 +2221,6 @@
              collections.Counter(e.partition for e in block_diffs).items()
              if count > 1])
 
-    dynamic_partitions = set(shlex.split(info_dict.get(
-        "dynamic_partition_list", "").strip()))
-    assert set(block_diff_dict.keys()) == dynamic_partitions, \
-        "Dynamic partitions: {}, BlockDifference objects: {}".format(
-            list(dynamic_partitions), list(block_diff_dict.keys()))
-
     self._partition_updates = dict()
 
     for p, block_diff in block_diff_dict.items():
@@ -2258,6 +2252,22 @@
             "object is provided.".format(p, g)
         self._partition_updates[p].src_group = g
 
+    target_dynamic_partitions = set(shlex.split(info_dict.get(
+        "dynamic_partition_list", "").strip()))
+    block_diffs_with_target = set(p for p, u in self._partition_updates.items()
+                                  if u.tgt_size)
+    assert block_diffs_with_target == target_dynamic_partitions, \
+        "Target Dynamic partitions: {}, BlockDifference with target: {}".format(
+            list(target_dynamic_partitions), list(block_diffs_with_target))
+
+    source_dynamic_partitions = set(shlex.split(source_info_dict.get(
+        "dynamic_partition_list", "").strip()))
+    block_diffs_with_source = set(p for p, u in self._partition_updates.items()
+                                  if u.src_size)
+    assert block_diffs_with_source == source_dynamic_partitions, \
+        "Source Dynamic partitions: {}, BlockDifference with source: {}".format(
+            list(source_dynamic_partitions), list(block_diffs_with_source))
+
     if self._partition_updates:
       logger.info("Updating dynamic partitions %s",
                   self._partition_updates.keys())