fix: CoverageData(no_disk=True).update() now works. #1323

CHANGES.rst

@@ -39,7 +39,10 @@ Unreleased
 - On Python 3.11, the ``[toml]`` extra no longer installs tomli, instead using
   tomllib from the standard library.  Thanks `Shantanu <pull 1359_>`_.
 
+- In-memory CoverageData objects now properly update(), closing `issue 1323`_.
+
 .. _issue 1310: https://github.com/nedbat/coveragepy/issues/1310
+.. _issue 1323: https://github.com/nedbat/coveragepy/issues/1323
 .. _issue 1351: https://github.com/nedbat/coveragepy/issues/1351
 .. _pull 1354: https://github.com/nedbat/coveragepy/pull/1354
 .. _pull 1359: https://github.com/nedbat/coveragepy/pull/1359

coverage/sqldata.py

@@ -253,10 +253,10 @@ def _choose_filename(self):
 
     def _reset(self):
         """Reset our attributes."""
-        if self._dbs:
+        if not self._no_disk:
             for db in self._dbs.values():
                 db.close()
-        self._dbs = {}
+            self._dbs = {}
         self._file_map = {}
         self._have_used = False
         self._current_context_id = None
@@ -679,6 +679,7 @@ def update(self, other_data, aliases=None):
                 path: id
                 for id, path in conn.execute("select id, path from file")
             }
+            self._file_map.update(file_ids)
             conn.executemany(
                 "insert or ignore into context (context) values (?)",
                 ((context,) for context in contexts)
@@ -752,9 +753,10 @@ def update(self, other_data, aliases=None):
                 ((file_ids[filename], tracer) for filename, tracer in tracer_map.items())
             )
 
-        # Update all internal cache data.
-        self._reset()
-        self.read()
+        if not self._no_disk:
+            # Update all internal cache data.
+            self._reset()
+            self.read()
 
     def erase(self, parallel=False):
         """Erase the data in this object.

tests/test_data.py

@@ -891,3 +891,19 @@ def test_misfed_serialization(self):
         )
         with pytest.raises(DataError, match=msg):
             covdata.loads(bad_data)
+
+
+class NoDiskTest(CoverageTest):
+    """Tests of in-memory CoverageData."""
+
+    run_in_temp_dir = False
+
+    def test_updating(self):
+        # https://github.com/nedbat/coveragepy/issues/1323
+        a = CoverageData(no_disk=True)
+        a.add_lines({'foo.py': [10, 20, 30]})
+        assert a.measured_files() == {'foo.py'}
+
+        b = CoverageData(no_disk=True)
+        b.update(a)
+        assert b.measured_files() == {'foo.py'}