[REFACTOR](build) Migrate workspace to uv_build and PEP 420 namespace packages

[Seth Fitzsimmons (sethfitz)]

Three commits.

refactor(build): migrate all packages from hatchling to uv_build

Switch every workspace package's build backend to uv_build. Because the packages share the overture.schema namespace, each declares an explicit [tool.uv.build-backend] module-name (e.g. overture.schema.common); name normalization would derive the wrong module. The overture-schema aggregator uses module-name = "overture.schema" with namespace = true and ships only overture/schema/py.typed — uv_build requires a module root, so a deps-only package still owns the namespace marker.

Convert the pkgutil namespaces to PEP 420: uv_build ships shared namespaces implicitly and never packages an overture/__init__.py, so the extend_path shims are removed. Wheels and editable installs both merge the namespace natively.

Deleting those __init__.py files removes the signal ruff's isort uses to detect overture as first-party (detect-same-package walks __init__ chains), so add src = ["packages/*/src"]. With overture now first-party everywhere, imports across the test suite and a few pyspark modules recanonicalize into their own group; that reformat is folded in here because it cannot land as a separately-green commit.

refactor(build): emit PEP 420 generated pyspark tree

Stop the pyspark codegen from emitting empty __init__.py files so the generated expression and test trees are PEP 420 namespace packages, matching the rest of the workspace. The mirrored layout (generated/overture/schema/<theme>/) is kept — only the init emission is dropped.

Removing the inits broke three things, each given a real fix:

• pytest collection: generated conformance tests reached _support via deep relative imports. Under PEP 420 the module resolves as generated.*, so those imports overshoot the top level. Emit absolute from _support.X import ..., delete the _support_prefix machinery, and move the hand-written tests to the same form. Set --import-mode=importlib and consider_namespace_packages = true.
• type checking: add the pyspark tests dir to mypy_path; keep the hand-written tests/__init__.py so pyspark's test_cli doesn't collide with codegen's under importlib.
• runtime registry: pkgutil.walk_packages skips directories without __init__.py, finding zero generated modules. Walk the namespace roots as files instead; test_registry.py covers this — no existing test exercised the on-disk walk, so an empty registry would have passed silently.

chore(build): guard PEP 420 namespace roots against __init__.py

Add a check-namespace gate that fails if overture/ or overture/schema/ gains an __init__.py, which would turn a namespace root back into a regular package and shadow other workspace packages' contributions at import. Wired into the check gate so the PEP 420 invariant this stack establishes cannot silently regress.

Stacked on #620. Closes #618

[github-actions]

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🕐 Updated	Jul 31, 2026 18:41 UTC
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