refactor(reflex-base): consolidate BaseContext into context.base (#6514)

[BABTUNA]

Summary

• Removes the duplicate BaseContext defined in reflex_base.plugins.compiler and points PageContext / CompileContext at the canonical reflex_base.context.base.BaseContext.
• Reworks BaseContext from a frozen dataclass into a plain class with __slots__ = () so frozen subclasses (RegistrationContext, EventContext) and non-frozen subclasses (PageContext, CompileContext) can both inherit. Ports the async __aenter__ / __aexit__ helpers over from the removed copy.
• Pins identity equality on the base via __eq__ = object.__eq__ / __hash__ = object.__hash__, and propagates eq=False to the (formerly compiler-local) dataclass subclasses.

Closes #6514.

Test plan

• uv run pytest tests/units/reflex_base/context/test_base.py tests/units/compiler/test_plugins.py
• uv run pytest tests/units (full unit suite)
• uv run ruff check . && uv run ruff format --check .
• uv run pyright reflex tests

[codspeed-hq]

Merging this PR will not alter performance

✅ 24 untouched benchmarks

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_{Comparing BABTUNA:issue-6514-consolidate-basecontext (94c05d2) with main (6bb44d5)}

[greptile-apps]

Greptile Summary

This PR consolidates the duplicate BaseContext class by removing the one in reflex_base.plugins.compiler and pointing PageContext and CompileContext at the canonical reflex_base.context.base.BaseContext. The base class is reworked from a frozen dataclass to a plain class with __slots__ = (), allowing both frozen and non-frozen dataclass subclasses to coexist, and identity equality is pinned via __eq__ = object.__eq__ / __hash__ = object.__hash__ with eq=False propagated to the two compiler dataclasses.

• Removes ~90 lines of duplicated context-manager boilerplate from compiler.py and adds async __aenter__/__aexit__ to the canonical base.
• ensure_context_attached in the new base only checks _attached_context_token (was the instance entered?), whereas the old compiler.py implementation additionally verified cls.get() is self (is this instance currently active?). This makes the safety guard in CompileContext.compile() slightly weaker.
• Test coverage for the new identity-equality and async-context-manager behaviour is added to test_base.py; test_plugins.py is updated to match the new exception types and attribute names.

Confidence Score: 4/5

Safe to merge; the consolidation is straightforward and the test suite covers the important paths.

The refactor is clean and well-tested. The one substantive concern is that ensure_context_attached now only confirms the instance was entered rather than also verifying it is the currently active value in the ContextVar. Normal single-compile-context usage is unaffected.

packages/reflex-base/src/reflex_base/context/base.py — specifically the ensure_context_attached method and whether the weaker check is intentional.

Important Files Changed

Filename	Overview
packages/reflex-base/src/reflex_base/context/base.py	Reworked from a frozen dataclass to a plain class with __slots__ = (); adds async context-manager support and identity equality. The ensure_context_attached guard is slightly weaker than the old compiler.py version — it only checks the token dict, not the live ContextVar value.
packages/reflex-base/src/reflex_base/plugins/compiler.py	Removes the local BaseContext duplicate and redirects PageContext/CompileContext to the canonical reflex_base.context.base.BaseContext; adds eq=False to both dataclass decorators to preserve identity equality.
tests/units/reflex_base/context/test_base.py	Adds three new tests covering identity equality, isolated attachment state, and the async context manager. test_async_context_manager is an async def without @pytest.mark.asyncio, but the project's asyncio_mode = "auto" covers it.
tests/units/compiler/test_plugins.py	Updates exception-type assertions from RuntimeError to LookupError to match the new ContextVar.get() behaviour, and updates the context-var attribute name from __context_var__ to _context_var.

Comments Outside Diff (1)

1. packages/reflex-base/src/reflex_base/context/base.py, line 118-126 (link)

   ensure_context_attached no longer verifies self is the active context

   The old compiler.py implementation performed two checks: (1) that a context is currently active at all, and (2) that current is self. The new implementation only checks _attached_context_token.get(self) is not None, which merely confirms self.__enter__ was called and not yet exited — it does not verify self is still the context actually visible in the current ContextVar.

   Concretely: if a nested CompileContext instance is pushed via another __enter__ call (or an explicit cls.set(other)), the outer instance's ensure_context_attached() silently passes while CompileContext.get() would return the inner instance. CompileContext.compile() calls this as a safety guard, so a false pass here means the method proceeds with the wrong context active.

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