Fixes attribute reordering in configclass with partial type annotations

[0xadvait]

Description

When type annotations are provided on only some attributes of a configclass, the resulting field order does not follow the declaration order: all annotated attributes jump ahead of the non-annotated ones. This breaks the documented guarantee that attribute order is preserved, which matters in particular for InteractiveSceneCfg, where the attribute order determines the scene entity creation order.

@configclass
class SceneCfg(InteractiveSceneCfg):
    plane = AssetBaseCfg(...)
    robot = ArticulationCfg(...)
    peg: ArticulationCfg = ArticulationCfg(...)
    hole: ArticulationCfg = ArticulationCfg(...)
    camera = TiledCameraCfg(...)
    light = AssetBaseCfg(...)

# before this fix:
# ['peg', 'hole', 'plane', 'robot', 'camera', 'light']
# with this fix:
# ['plane', 'robot', 'peg', 'hole', 'camera', 'light']

Root cause: _add_annotation_types bulk-adds each base class's __annotations__ into the type-hints dictionary before iterating over the class members (hints.update(ann) prior to the base.__dict__ walk), so annotated fields are always inserted first.

Fix: build the hints dictionary in a single pass over base.__dict__ (which preserves declaration order), picking up the explicit annotation when one exists and deducing the type from the default value otherwise. A trailing hints.update(ann) keeps the previous behavior for corner cases (annotation-only declarations, re-annotated inherited members, members skipped by _skippable_class_member) — for keys already present it only refreshes the type and keeps the position.

The semantics are otherwise unchanged: cross-base ordering (parent fields first, overrides keep the parent position), MISSING handling, ClassVar handling, and nested-class handling all behave as before.

Verification

• New regression test test_configclass_mixed_type_annotations_ordering (mirrors the issue repro, plus an inheritance case). It fails before the fix and passes after.
• Full test_configclass.py suite passes (44 tests).
• The complete source/isaaclab/test/utils/ suite was run on CPU before and after the change with byte-identical results (the only failing tests are CUDA-/Nucleus-dependent and fail identically on both sides).
• An AST scan over source/ found 81 configclasses whose field order changes with this fix (i.e., classes currently affected by the silent reordering), of which ~15 are InteractiveSceneCfg subclasses. For these, entity creation order now matches the declaration order, which is what the documentation promises (e.g., terrain/ground declared first now actually spawns first). Managers and scene entities are referenced by name, so no name-based lookups are affected.

Fixes #1949
Related to #1743 (the same hoisting also affected None-typed members before it was special-cased)

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[greptile-apps]

Greptile Summary

This PR fixes a long-standing attribute reordering bug in _add_annotation_types inside configclass.py, where annotated fields (with explicit type hints) were bulk-inserted into the hints dictionary before the member-iteration loop, causing them to always precede non-annotated fields regardless of declaration order.

• The fix builds the hints dict in a single pass over base.__dict__ (which preserves Python insertion/declaration order), applying explicit annotations in-loop and deferring a trailing hints.update(ann) to pick up annotation-only declarations and refresh types on re-annotated inherited members.
• A new regression test (test_configclass_mixed_type_annotations_ordering) covers both the base-class and inheritance cases and would have caught the original bug; all 44 existing tests continue to pass.

Confidence Score: 4/5

Safe to merge. The change is surgical and isolated to _add_annotation_types; existing semantics for all common configclass patterns are preserved and verified by the full test suite.

The fix is well-reasoned and the new test directly reproduces the reported bug. The one subtlety is that pure annotation-only fields (no default, not even MISSING) will now be appended after value-bearing members rather than before non-annotated ones — an unusual pattern in practice but a real behavioral difference not covered by the new tests.

A second look at source/isaaclab/isaaclab/utils/configclass.py lines 320-323 is worthwhile to confirm the comment is accurate for the annotation-only edge case and to decide whether an additional test is warranted.

Important Files Changed

Filename	Overview
source/isaaclab/isaaclab/utils/configclass.py	Core fix: moves hints.update(ann) from before the member-iteration loop to after it, and adds an in-loop if key in ann branch; correctly preserves declaration order for mixed-annotation classes while a trailing update handles annotation-only and re-annotated inherited members.
source/isaaclab/test/utils/test_configclass.py	Adds two new test fixtures and one test function that directly reproduces the issue and the inheritance variant; assertions cover both __dict__ key order and to_dict() key order.
source/isaaclab/changelog.d/0xadvait-fix-configclass-ordering.rst	New changelog fragment; accurately describes the bug and the affected surface. No issues.
CONTRIBUTORS.md	Adds the contributor's name in alphabetical order. No issues.

_{Reviews (1): Last reviewed commit: "Fix configclass field reordering with mi..." | Re-trigger Greptile}

[AntoineRichard]

Thanks a lot @0xadvait ! Merging this :)