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🐛 fix: build the frozendict backport the way the built-in does; document subclassing - #85
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nstarman merged 4 commits intoOct 16, 2026
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The backport kept its contents in a slot named `_data`. The built-in has no such attribute, so on Python 3.15 a subclass is free to use `_data` for itself; on the backport, assigning it rebound the slot and replaced the mapping's contents. galax and coordinax both declared a `_data` field on their subclasses. Name-mangle the slot to `_frozendict__data`, so `self._data` on a subclass is just another attribute, as with the built-in. Pickles are unaffected: they rebuild through `__new__` from the data, not from slot state. Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
The built-in fills itself in C, so a subclass that overrides `__setattr__` constructs normally: a frozen dataclass subclass works on Python 3.15. The backport assigned its storage with `self.__data = ...`, which goes through the subclass's `__setattr__` and raised `FrozenInstanceError` there instead. Assign it with `object.__setattr__`. This also makes an `equinox.Module` subclass behave the same on every Python: its `__new__` drops the arguments, so it is an empty mapping, as on 3.15, rather than failing only on older Pythons. Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Since 0.3.0 `ImmutableMap` is a `frozendict`, which takes its contents in
`__new__`. Say so in a README section on subclassing: override `__new__` to
transform input, register the subclass as a PyTree node, and don't combine
it with an `equinox.Module` or a dataclass, which galax and coordinax both
did (via `ImmutableMap.__init__` and the private `_data`, now gone).
The `tree_unflatten` doctest passed `tree_flatten`'s `(children, keys)` as
`(aux_data, children)`, and documented the swapped result
`ImmutableMap({1: 'a', 2: 'b'})`; the `jax.tree.unflatten` example passed
that pair as the leaves. Both now round-trip `d`.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Pylint's protected-access fires on `other.__data` now that the slot is name-mangled; `other` is a `frozendict` too. Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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…lt-in does; document subclassing (#86) Co-authored-by: Nathaniel Starkman <nstarman@users.noreply.github.com>
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0.3.1 builds its pre-3.15 `frozendict` backport the way the built-in does (GalacticDynamics/xmmutablemap#85), so galax now behaves the same on every supported Python. The lock already had 0.3.1; only the specifiers move. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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The release with GalacticDynamics/xmmutablemap#85. galax no longer depends on how `ImmutableMap` stores its contents, so this is a floor on the fixed release rather than a functional need. The lock already had 0.3.1; only the specifier moves. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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xmmutablemap 0.3.0 broke both known subclassers, galax (
CompositePotential,AbstractCompositePhaseSpaceCoordinate) and coordinax (KinematicSpace). Each is anequinox.Modulethat also subclassedImmutableMap, calledImmutableMap.__init__, and declared the private_dataas a field. That can't work onceImmutableMapis afrozendict, which gets its contents in__new__, and they are being fixed downstream (GalacticDynamics/coordinax#1047, GalacticDynamics/coordinax#1048). Looking into it turned up two places where the backport doesn't behave like the 3.15 built-in, plus a missing doc.Commits
_data→_frozendict__data). The built-in has no_data, so a subclass is free to set its own; on the backport that rebound the slot and replaced the mapping's contents. Pickles are unaffected: they rebuild through__new__from the data.object.__setattr__. The built-in fills itself in C, so a subclass's__setattr__never runs during construction: a frozen-dataclass subclass constructs on 3.15 but raisedFrozenInstanceErroron the backport. As a result, anequinox.Modulesubclass now behaves the same on every Python: an empty mapping, as on 3.15, instead of failing only on older Pythons.__new__to transform input; register the subclass as a PyTree node (subclasses are opaque leaves otherwise); and a warning against combining it with anequinox.Moduleor a dataclass, saying what to do instead. Also fixes thetree_unflattendoctest, which passedtree_flatten's(children, keys)in swapped order and documented the resultingImmutableMap({1: 'a', 2: 'b'}).Testing
Each of the two fixes adds a test that fails on the backport and passes on the built-in. The full suite passes on 3.10, 3.12, 3.14 and 3.15.
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