bpo-28411: Remove PyInterpreterState.modules. by ericsnowcurrently · Pull Request #3606 · python/cpython (original) (raw)
The status quo for sys.modules is broken. While importlib (and a few other places) use sys.modules directly, the C-API (including PyImport_Import(), etc.) use PyInterpreterState.modules directly. Since assigning to sys.modules does not update PyInterpreterState.modules, the two can get out of sync. The workaround, which we use in the test suite, is complicated. This patch resolves the issue by getting rid of PyInterpreterState.modules and making sys.modules authoritative in the C-API.
Note that this code was landed earlier (PR #1638), but reverted due to problems when a bogus value (e.g. []) is assigned to sys.modules (see bpo-31404), which is very much a corner case. I've broken that original patch up and already landed the majority. The remaining piece here is to actually drop PyInterpreterState.modules. This PR should not be merged until the problem described in bpo-31404 is resolved.