pure-py-mb
PurePy in MoonBit: a tokenizer and parser for Python 3.12 producing a
CPython-shaped abstract syntax tree, a sieve that rejects the Python PurePy
excludes, a well-formedness checker, an interpreter, a printer, a
command-line tool and an embedding interface.
PurePy is a pure functional subset of Python with a small-step operational
semantics and a static well-formedness judgement, specified in
pure-py/pure-py-spec. This is a
port of that specification. The reference checker is the specification for
what check decides; CPython is the oracle for what run prints.
Playground: https://marianoguerra.github.io/pure-py-mb/ — the whole
library in a browser tab, with 27 examples. The page is a real embedder: the
host module its examples import is supplied through the embedding
interface.
What is here
The repository root is a development module that is never published. It
exists so that the harness, the corpora, the documentation and the playground
reach the two real modules through their public API only, which is what keeps
that API honest — and so that publishing the library does not publish half a
megabyte of test fixtures.
moon add marianoguerra/pure-py # the library
moon add marianoguerra/pure-py-cli # the command
Conformance
Eight oracles, every one compared against something outside this port, over
the conformance suite of specification v0.23.0.
| oracle | compared with | result |
|---|
| tokens | CPython's tokenize | 1005/1005 |
| trees, no positions | CPython's ast | 1005/1005 |
| trees, with positions | CPython's ast | 1005/1005 |
| printer round trip | this parser and CPython's | 1004/1004 |
parse | the reference checker | 982/982 |
check | the reference checker | 982/982 |
check-program | the reference checker | 93/93 |
run | CPython's output | 321/321 |
The conformance suite under test/conformance/ is the reference's own,
copied verbatim, and the expected answers under test/golden/ are the
reference's answers. Both are committed, so the suite runs with nothing but
MoonBit and Python 3.
Development
just lists every task, grouped. The ones that matter:
just quick type-check, format, unit tests, layering, conformance
just conform every oracle, held to its ratchet
just one PATTERN the tests whose name contains PATTERN, in full
just diffrun generated programs, compared against CPython
just playground build the page and serve it on :8000
just publish-dry what would go to mooncakes, without sending it
Regenerating the goldens needs the reference checkout: just reference-fetch,
then just goldens. Neither runs in CI.
License
Apache-2.0.
