Add get_refs() to BaseExpression and WhereNode (#2586)

This ORM method gathers a set of strings that ultimately come from the `Ref` class.

`BaseExpression` source:

https://github.com/django/django/blob/d752ec8259a3a3123733cacbfb4f207ee61f6242/django/db/models/expressions.py#L421-L427

`Ref` source:

https://github.com/django/django/blob/d752ec8259a3a3123733cacbfb4f207ee61f6242/django/db/models/expressions.py#L1356-L1357

`WhereNode` source:

https://github.com/django/django/blob/d752ec8259a3a3123733cacbfb4f207ee61f6242/django/db/models/sql/where.py#L240C5-L240C17

Author: adamchainz

django-stubs/db/models/expressions.pyi

@@ -96,6 +96,7 @@ class BaseExpression:
     def get_lookup(self, lookup: str) -> type[Lookup] | None: ...
     def get_transform(self, name: str) -> type[Transform] | None: ...
     def relabeled_clone(self, change_map: Mapping[str, str]) -> Self: ...
+    def get_refs(self) -> set[str]: ...
     def copy(self) -> Self: ...
     def get_group_by_cols(self) -> list[BaseExpression]: ...
     def get_source_fields(self) -> list[Field | None]: ...

django-stubs/db/models/sql/where.pyi

@@ -27,6 +27,7 @@ class WhereNode(tree.Node):
     def resolve_expression(self, *args: Any, **kwargs: Any) -> WhereNode: ...
     @cached_property
     def output_field(self) -> BooleanField: ...
+    def get_refs(self) -> set[str]: ...
     @cached_property
     def contains_aggregate(self) -> bool: ...
     @cached_property

scripts/stubtest/allowlist_todo.txt

@@ -744,7 +744,6 @@ django.db.models.constraints.CheckConstraint.validate
 django.db.models.constraints.UniqueConstraint.contains_expressions
 django.db.models.constraints.UniqueConstraint.validate
 django.db.models.expressions.BaseExpression.empty_result_set_value
-django.db.models.expressions.BaseExpression.get_refs
 django.db.models.expressions.BaseExpression.prefix_references
 django.db.models.expressions.BaseExpression.replace_expressions
 django.db.models.expressions.Case.as_sql
@@ -758,7 +757,6 @@ django.db.models.expressions.Exists.empty_result_set_value
 django.db.models.expressions.Expression.identity
 django.db.models.expressions.OrderBy.as_oracle
 django.db.models.expressions.OrderBy.as_sql
-django.db.models.expressions.Ref.get_refs
 django.db.models.expressions.Ref.relabeled_clone
 django.db.models.expressions.ResolvedOuterRef.as_sql
 django.db.models.expressions.ResolvedOuterRef.get_group_by_cols
@@ -1074,7 +1072,6 @@ django.db.models.sql.where.SubqueryConstraint.contains_over_clause
 django.db.models.sql.where.WhereNode.get_db_converters
 django.db.models.sql.where.WhereNode.get_group_by_cols
 django.db.models.sql.where.WhereNode.get_lookup
-django.db.models.sql.where.WhereNode.get_refs
 django.db.models.sql.where.WhereNode.get_source_expressions
 django.db.models.sql.where.WhereNode.leaves
 django.db.models.sql.where.WhereNode.output_field

scripts/stubtest/allowlist_todo_django51.txt

@@ -45,7 +45,6 @@ django.db.migrations.autodetector.OperationDependency
 django.db.models.ForeignObjectRel.accessor_name
 django.db.models.fields.related.ForeignObjectRel.accessor_name
 django.db.models.fields.reverse_related.ForeignObjectRel.accessor_name
-django.db.models.lookups.In.get_refs
 django.forms.ModelChoiceField.validate_no_null_characters
 django.forms.models.ModelChoiceField.validate_no_null_characters