fix: Allow table class names with underscores (with warning)

For table class names containing underscores:
1. Emit a warning about underscores
2. Remove underscores
3. Proceed with normal CamelCase validation

This restores compatibility with legacy schemas that use names like
MouseScoreSheet_BodyCondition.

Also adds "fetch" to supported_class_attrs for class-level access.

Fixes compatibility for users migrating from DataJoint <= 0.14.1.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: dimitri-yatsenko

src/datajoint/table.py

@@ -151,11 +151,20 @@ def declare(self, context=None):
         """
         if self.connection.in_transaction:
             raise DataJointError("Cannot declare new tables inside a transaction, e.g. from inside a populate/make call")
-        # Enforce strict CamelCase #1150
-        if not is_camel_case(self.class_name):
+        # Validate class name #1150
+        class_name = self.class_name
+        if "_" in class_name:
+            warnings.warn(
+                f"Table class name `{class_name}` contains underscores. "
+                "CamelCase names without underscores are recommended.",
+                UserWarning,
+                stacklevel=2,
+            )
+            class_name = class_name.replace("_", "")
+        if not is_camel_case(class_name):
             raise DataJointError(
-                "Table class name `{name}` is invalid. Please use CamelCase. ".format(name=self.class_name)
-                + "Classes defining tables should be formatted in strict CamelCase."
+                f"Table class name `{self.class_name}` is invalid. "
+                "Class names must be in CamelCase, starting with a capital letter."
             )
         sql, _external_stores, primary_key, fk_attribute_map = declare(self.full_table_name, self.definition, context)
 

src/datajoint/user_tables.py

@@ -32,6 +32,7 @@
     "to_arrow",
     "to_arrays",
     "keys",
+    "fetch",
     "fetch1",
     "head",
     "tail",

src/datajoint/utils.py

@@ -2,6 +2,7 @@
 
 import re
 import shutil
+import warnings
 from pathlib import Path
 
 from .errors import DataJointError
@@ -86,6 +87,14 @@ def from_camel_case(s):
     def convert(match):
         return ("_" if match.groups()[0] else "") + match.group(0).lower()
 
+    # Handle underscores: warn and remove them
+    if "_" in s:
+        warnings.warn(
+            f"Table class name `{s}` contains underscores. " "CamelCase names without underscores are recommended.",
+            UserWarning,
+            stacklevel=3,
+        )
+        s = s.replace("_", "")
     if not is_camel_case(s):
         raise DataJointError("ClassName must be alphanumeric in CamelCase, begin with a capital letter")
     return re.sub(r"(\B[A-Z])|(\b[A-Z])", convert, s)

tests/integration/test_declare.py

@@ -348,8 +348,8 @@ class IndexAttribute(dj.Manual):
 
 def test_table_name_with_underscores(schema_any):
     """
-    Test issue #1150 -- Reject table names containing underscores. Tables should be in strict
-    CamelCase.
+    Test issue #1150 -- Table names with underscores should produce a warning but still work.
+    Strict CamelCase is recommended.
     """
 
     class TableNoUnderscores(dj.Manual):
@@ -363,5 +363,8 @@ class Table_With_Underscores(dj.Manual):
         """
 
     schema_any(TableNoUnderscores)
-    with pytest.raises(dj.DataJointError, match="must be alphanumeric in CamelCase"):
+    # Underscores now produce a warning instead of an error (legacy support)
+    with pytest.warns(UserWarning, match="contains underscores"):
         schema_any(Table_With_Underscores)
+    # Verify the table was created successfully
+    assert Table_With_Underscores.is_declared

tests/integration/test_utils.py

@@ -26,12 +26,14 @@ def test_from_camel_case():
     assert from_camel_case("AllGroups") == "all_groups"
     with pytest.raises(DataJointError):
         from_camel_case("repNames")
-    with pytest.raises(DataJointError):
-        from_camel_case("10_all")
+    with pytest.warns(UserWarning, match="contains underscores"):
+        with pytest.raises(DataJointError):
+            from_camel_case("10_all")
     with pytest.raises(DataJointError):
         from_camel_case("hello world")
-    with pytest.raises(DataJointError):
-        from_camel_case("#baisc_names")
+    with pytest.warns(UserWarning, match="contains underscores"):
+        with pytest.raises(DataJointError):
+            from_camel_case("#baisc_names")
 
 
 def test_to_camel_case():