v4.2.0b4

What's New in astroid 4.2.0b4?

Release date: 2026-07-04

• Removed the **kwargs argument from all infer functions.
  Users upgrading their astroid versions should ensure they do no pass values other than
  context to infer.

• Fix crash (TypeError: 'UninferableBase' object is not iterable) in the
  multiprocessing brain when a local package shadows the stdlib
  multiprocessing module.

  Closes pylint-dev/pylint#10014

• Bound string/bytes multiplication ("x" * n) and integer left shifts
  (1 << n) in const_infer_binary_op the same way list/tuple
  multiplication and ** already are. Inferring a constant such as
  "A" * 10 ** 10 previously materialized the multi-gigabyte result
  eagerly; these operations now infer as Uninferable when the result
  would be oversized.

  Refs #3107

• Remove the asname keyword argument from Import._infer and
  ImportFrom._infer. The alias-to-real-name translation that
  asname=True performed is now hoisted into ImportNode._infer_name,
  which runs in _infer_stmts before _infer is dispatched. Direct
  callers of Import.infer / ImportFrom.infer (previously the
  asname=False path) now consistently resolve the lookup name as-is.

  The two flows used to collapse into a single inference cache entry
  because the asname kwarg was not part of the cache key, so the
  second call returned the cached result of the first regardless of
  which one ran. With the translation hoisted upstream, the two flows
  set different lookupname values and therefore land on distinct
  cache keys, eliminating the collision.

  Refs pylint-dev/pylint#10193
  Closes #3007

• Fix uncaught IndentationError when parsing code whose lines end in
  \r: the slice of source tokenized to compute a class or function
  position is split on \n only and could be misaligned with the AST
  line numbers. Such nodes now simply have no position information, as
  already done when tokenize raises TokenError.

  Closes #3091

• Fix astroid bootstrap crash on PyPy 7.3.22 (TypeError: expected str, got getset_descriptor object) by also catching TypeError from
  getattr(obj, alias) in InspectBuilder.object_build. PyPy 7.3.22
  raises TypeError instead of AttributeError for unset getset
  descriptors like types.FunctionType.__text_signature__, which made
  _astroid_bootstrapping() blow up on any call into astroid.

  Refs pylint-dev/pylint#10999

• Shorten import astroid by deferring imports only needed on cold paths.
  logging (used by modutils and raw_building solely to report
  stderr/stdout captured while importing a module) and pprint (used only
  to format debug __repr__ / repr_tree output) are now imported
  lazily, and astroid.exceptions imports astroid.typing under
  TYPE_CHECKING.

• Fix AttributeError crash in starred_assigned_stmts when a starred
  unpacking target is an attribute (e.g. for *o.attr, x in ...) rather
  than a simple name.

  Closes #2646

• Fix AttributeError crash in the Arguments assigned_stmts
  protocol when called without an inference context (the public
  assigned_stmts API defaults context to None). Resolving a
  function's first parameter dereferenced context.boundnode while the
  matching context and ... guard a few lines below was missing; it now
  degrades to Uninferable.

• Fix AttributeError crash in ClassDef.infer_call_result when called
  through the public API without a context (it defaults to None) for a
  class whose metaclass defines __call__: the callee was assigned to
  context.callcontext.callee without checking that a call context exists.
  It is now guarded, matching the surrounding code.

• Wrap assignment expressions (:=) in parentheses when emitting
  as_string output so the rendered code remains syntactically valid in
  contexts such as comparisons, where Python requires the walrus expression
  to be parenthesized.

  Closes #2668

• Catch MemoryError/RecursionError (and ValueError) when validating
  type comments with ast.parse. Pathological type comments produced by
  fuzzers (e.g. # type: i{{{{{{{...) previously crashed parsing with a
  MemoryError or RecursionError depending on the runtime; astroid now
  treats them as invalid type comments and skips them, mirroring the f-string
  fix from #2762.

  Closes #2993

• Fix TypeError in brain_random when random.sample is called with a
  sequence containing nodes whose __init__ does not accept lineno
  (e.g. Module). The clone helper now filters init params to those the
  class actually accepts.

  Closes #3043

• Fix RecursionError in _compute_mro() when circular class hierarchies
  are created through runtime name rebinding. Circular bases are now resolved
  to the original class instead of recursing.

  Closes #3023
  Closes pylint-dev/pylint#10821

• Changed block_range to consider else its own block, allowing pylint to apply
  disables to just the block.

  References pylint-dev/pylint#872

• Fix uncaught TokenError when building a class or function whose source
  slice is malformed. tokenize.generate_tokens may raise (e.g. on an
  unterminated bracket on Python < 3.12); position computation now treats such
  a node as having no position information instead of crashing.

  Closes #2527

• str() of a constant argument now infers the actual string value instead
  of always inferring "". When every inference path of the argument
  resolves to Const values that stringify to the same string, infer_str
  returns that string; otherwise it keeps falling back to Const("").

  Closes #2994

• Fix AttributeError crash when looking up a special method on a class
  whose explicit metaclass infers to a non-class node (e.g. a function). Such
  a metaclass has no MRO, so the dunder lookup now raises
  AttributeInferenceError instead of crashing.

  Closes #3063

• Fix AttributeError crash in ClassDef.getitem when __class_getitem__
  resolves to a non-callable node (e.g. an AssignName). getitem now
  raises AstroidTypeError in that case, consistent with its documented
  behaviour.

  Closes #3064

• Fix DuplicateBasesError crash in the enum brain when inferring an enum
  class with duplicate bases (e.g. class C(enum.Enum, enum.Enum)).
  infer_enum_class now catches MroError and leaves such a malformed
  class untransformed.

  Closes #3065

• Fix InferenceError crash in ClassDef.slots() when __slots__ is
  declared as an annotation without a value (e.g. __slots__: None). Such a
  __slots__ cannot be inferred, so slots() now returns None.

  Closes #3067

• Fix TypeError crash in the enum brain when a functional Enum call
  has a non-string member name (e.g. Enum("e", (1,))). Such a definition
  is invalid, so inference now falls back to the default instead of crashing.

  Closes #3068

Note that this changelog also includes changes from previous betas.