Improve checks for sourced components (#7490)

* Improve checks for sourced components

* Remove language class checks

* Convert python warning to logger warning

* Remove unused warning

* Fix formatting

spacy/errors.py

@@ -159,6 +159,8 @@ class Warnings:
             "http://spacy.io/usage/v3#jupyter-notebook-gpu")
     W112 = ("The model specified to use for initial vectors ({name}) has no "
             "vectors. This is almost certainly a mistake.")
+    W113 = ("Sourced component '{name}' may not work as expected: source "
+            "vectors are not identical to current pipeline vectors.")
 
 
 @add_codes
@@ -651,8 +653,8 @@ class Errors:
             "returned the initialized nlp object instead?")
     E944 = ("Can't copy pipeline component '{name}' from source '{model}': "
             "not found in pipeline. Available components: {opts}")
-    E945 = ("Can't copy pipeline component '{name}' from source. Expected loaded "
-            "nlp object, but got: {source}")
+    E945 = ("Can't copy pipeline component '{name}' from source. Expected "
+            "loaded nlp object, but got: {source}")
     E947 = ("`Matcher.add` received invalid `greedy` argument: expected "
             "a string value from {expected} but got: '{arg}'")
     E948 = ("`Matcher.add` received invalid 'patterns' argument: expected "

spacy/language.py

@@ -682,9 +682,14 @@ class Language:
         name (str): Optional alternative name to use in current pipeline.
         RETURNS (Tuple[Callable, str]): The component and its factory name.
         """
-        # TODO: handle errors and mismatches (vectors etc.)
-        if not isinstance(source, self.__class__):
+        # Check source type
+        if not isinstance(source, Language):
             raise ValueError(Errors.E945.format(name=source_name, source=type(source)))
+        # Check vectors, with faster checks first
+        if self.vocab.vectors.shape != source.vocab.vectors.shape or \
+                self.vocab.vectors.key2row != source.vocab.vectors.key2row or \
+                self.vocab.vectors.to_bytes() != source.vocab.vectors.to_bytes():
+            util.logger.warning(Warnings.W113.format(name=source_name))
         if not source_name in source.component_names:
             raise KeyError(
                 Errors.E944.format(

spacy/tests/pipeline/test_pipe_factories.py

@@ -1,4 +1,6 @@
 import pytest
+import mock
+import logging
 from spacy.language import Language
 from spacy.lang.en import English
 from spacy.lang.de import German
@@ -402,6 +404,38 @@ def test_pipe_factories_from_source():
         nlp.add_pipe("custom", source=source_nlp)
 
 
+def test_pipe_factories_from_source_language_subclass():
+    class CustomEnglishDefaults(English.Defaults):
+        stop_words = set(["custom", "stop"])
+
+    @registry.languages("custom_en")
+    class CustomEnglish(English):
+        lang = "custom_en"
+        Defaults = CustomEnglishDefaults
+
+    source_nlp = English()
+    source_nlp.add_pipe("tagger")
+
+    # custom subclass
+    nlp = CustomEnglish()
+    nlp.add_pipe("tagger", source=source_nlp)
+    assert "tagger" in nlp.pipe_names
+
+    # non-subclass
+    nlp = German()
+    nlp.add_pipe("tagger", source=source_nlp)
+    assert "tagger" in nlp.pipe_names
+
+    # mismatched vectors
+    nlp = English()
+    nlp.vocab.vectors.resize((1, 4))
+    nlp.vocab.vectors.add("cat", vector=[1, 2, 3, 4])
+    logger = logging.getLogger("spacy")
+    with mock.patch.object(logger, "warning") as mock_warning:
+        nlp.add_pipe("tagger", source=source_nlp)
+        mock_warning.assert_called()
+
+
 def test_pipe_factories_from_source_custom():
     """Test adding components from a source model with custom components."""
     name = "test_pipe_factories_from_source_custom"