[red-knot] PEP 561 compliant module resolver

[carljm]

(Or intentional choices to diverge from PEP 561 compliance.)

Subtasks:

• Vendor typeshed's stubs: [red-knot] Vendor typeshed's stdlib #11340
• Add automation for keeping typeshed's stubs up to date: Add automation for updating our vendored typeshed stubs #11427
• Implement --custom-typeshed-dir internally: [red-knot] Encapsulate module resolution logic in module.rs #11767
• Implement the typing spec's module resolution order:
  • [red-knot] Encapsulate module resolution logic in module.rs #11767
  • Proposal for tweaking the spec posted at https://discuss.python.org/t/pep-561-s-module-resolution-order-seems-incorrect/55048/1
• Make vendored typeshed stubs available from the built Ruff binary: [red-knot] Include vendored typeshed stubs as a zipfile in the Ruff binary #11779
• Use vendored typeshed stubs at runtime to resolve symbols to stdlib definitions if --custom-typeshed-dir is not passed
  • Add a VendoredFileSystem implementation: [red-knot]: Add a VendoredFileSystem implementation #11863
  • Use the VendoredFileSystem implementation to resolve stdlib stubs: [red-knot] Use vendored typeshed stubs for stdlib module resolution #12224
• Add support for stubs packages suffixed with -stubs installed into site-packages (must take priority over other packages installed into site-packages)
• Add support for typeshed's VERSIONS file: we shouldn't fallback to a typeshed module if the VERSIONS file specifies it does not exist with the --target-version the user passes.
  • Add a parser for VERSIONS: [red-knot] Add a parser for typeshed's VERSIONS file #11836
  • Use the VERSIONS file when resolving stdlib modules: [red-knot] Respect typeshed's VERSIONS file when resolving stdlib modules #12141
• Add support for editable installs that use static ._pth files:
  • [red-knot] Add a read_directory() method to the ruff_db::system::System trait #12289
  • [red-knot] Add support for editable installs to the module resolver #12307
• Fix [red-knot] Module resolver has incorrect behaviour if a single-file module and potential namespace package coexist #12278
• Audit mypy's and pyright's module resolvers to see if there's anything that's not in the spec that still needs to be implemented

[MichaReiser]

One thing that we need to implement as part of this is a vendored filesystem. It's not a functionality but a task to complete on our way to get there.

[AlexWaygood]

One thing that we need to implement as part of this is a vendored filesystem. It's not a functionality but a task to complete on our way to get there.

Right. I was considering that part of

Use vendored typeshed stubs at runtime to resolve symbols to stdlib definitions if --custom-typeshed-dir is not passed

since, as you say, it's necessary to implement a vendored filesystem in order to be able to do that