releasetools: Skip on empty care_map.

common.GetCareMap() may return an empty list on unavailable care_map
since the change in commit 8bdfb990ea.
Caller needs to handle such a case accordingly. This CL fixes the caller
in add_img_to_target_files.py, and changes the return value to None to
break legacy callers loudly.

Fixes: 131794385
Test: `atest releasetools_test`
Change-Id: I7c94f456064199237e84ef75732bdd10ebe31736

tools/releasetools/add_img_to_target_files.py

@@ -113,7 +113,7 @@ def GetCareMap(which, imgname):
 
   Returns:
     (which, care_map_ranges): care_map_ranges is the raw string of the care_map
-    RangeSet; or an empty list.
+    RangeSet; or None.
   """
   assert which in common.PARTITIONS_WITH_CARE_MAP
 
@@ -123,7 +123,7 @@ def GetCareMap(which, imgname):
   # invalid reads.
   image_size = OPTIONS.info_dict.get(which + "_image_size")
   if not image_size:
-    return []
+    return None
 
   image_blocks = int(image_size) / 4096 - 1
   assert image_blocks > 0, "blocks for {} must be positive".format(which)
@@ -592,7 +592,11 @@ def AddCareMapForAbOta(output_zip, ab_partitions, image_paths):
         OPTIONS.info_dict.get(avb_hashtree_enable) == "true"):
       image_path = image_paths[partition]
       assert os.path.exists(image_path)
-      care_map_list += GetCareMap(partition, image_path)
+
+      care_map = GetCareMap(partition, image_path)
+      if not care_map:
+        continue
+      care_map_list += care_map
 
       # adds fingerprint field to the care_map
       build_props = OPTIONS.info_dict.get(partition + ".build.prop", {})

tools/releasetools/test_add_img_to_target_files.py

@@ -283,6 +283,35 @@ class AddImagesToTargetFilesTest(test_utils.ReleaseToolsTestCase):
 
     self._verifyCareMap(expected, care_map_file)
 
+  @test_utils.SkipIfExternalToolsUnavailable()
+  def test_AddCareMapForAbOta_skipPartition(self):
+    image_paths = self._test_AddCareMapForAbOta()
+
+    # Remove vendor_image_size to invalidate the care_map for vendor.img.
+    del OPTIONS.info_dict['vendor_image_size']
+
+    AddCareMapForAbOta(None, ['system', 'vendor'], image_paths)
+
+    care_map_file = os.path.join(OPTIONS.input_tmp, 'META', 'care_map.pb')
+    expected = ['system', RangeSet("0-5 10-15").to_string_raw(),
+                "ro.system.build.fingerprint",
+                "google/sailfish/12345:user/dev-keys"]
+
+    self._verifyCareMap(expected, care_map_file)
+
+  @test_utils.SkipIfExternalToolsUnavailable()
+  def test_AddCareMapForAbOta_skipAllPartitions(self):
+    image_paths = self._test_AddCareMapForAbOta()
+
+    # Remove the image_size properties for all the partitions.
+    del OPTIONS.info_dict['system_image_size']
+    del OPTIONS.info_dict['vendor_image_size']
+
+    AddCareMapForAbOta(None, ['system', 'vendor'], image_paths)
+
+    self.assertFalse(
+        os.path.exists(os.path.join(OPTIONS.input_tmp, 'META', 'care_map.pb')))
+
   def test_AddCareMapForAbOta_verityNotEnabled(self):
     """No care_map.pb should be generated if verity not enabled."""
     image_paths = self._test_AddCareMapForAbOta()