ruff/crates/ty_python_semantic/resources/mdtest
David Peter dfd6ed0524
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[ty] mdtests with external dependencies (#20904)
## Summary

This PR adds the possibility to write mdtests that specify external
dependencies in a `project` section of TOML blocks. For example, here is
a test that makes sure that we understand Pydantic's dataclass-transform
setup:

````markdown
```toml
[environment]
python-version = "3.12"
python-platform = "linux"

[project]
dependencies = ["pydantic==2.12.2"]
```

```py
from pydantic import BaseModel

class User(BaseModel):
    id: int
    name: str

user = User(id=1, name="Alice")
reveal_type(user.id)  # revealed: int
reveal_type(user.name)  # revealed: str

# error: [missing-argument] "No argument provided for required parameter
`name`"
invalid_user = User(id=2)
```
````

## How?

Using the `python-version` and the `dependencies` fields from the
Markdown section, we generate a `pyproject.toml` file, write it to a
temporary directory, and use `uv sync` to install the dependencies into
a virtual environment. We then copy the Python source files from that
venv's `site-packages` folder to a corresponding directory structure in
the in-memory filesystem. Finally, we configure the search paths
accordingly, and run the mdtest as usual.

I fully understand that there are valid concerns here:
* Doesn't this require network access? (yes, it does)
* Is this fast enough? (`uv` caching makes this almost unnoticeable,
actually)
* Is this deterministic? ~~(probably not, package resolution can depend
on the platform you're on)~~ (yes, hopefully)

For this reason, this first version is opt-in, locally. ~~We don't even
run these tests in CI (even though they worked fine in a previous
iteration of this PR).~~ You need to set `MDTEST_EXTERNAL=1`, or use the
new `-e/--enable-external` command line option of the `mdtest.py`
runner. For example:
```bash
# Skip mdtests with external dependencies (default):
uv run crates/ty_python_semantic/mdtest.py

# Run all mdtests, including those with external dependencies:
uv run crates/ty_python_semantic/mdtest.py -e

# Only run the `pydantic` tests. Use `-e` to make sure it is not skipped:
uv run crates/ty_python_semantic/mdtest.py -e pydantic
```

## Why?

I believe that this can be a useful addition to our testing strategy,
which lies somewhere between ecosystem tests and normal mdtests.
Ecosystem tests cover much more code, but they have the disadvantage
that we only see second- or third-order effects via diagnostic diffs. If
we unexpectedly gain or lose type coverage somewhere, we might not even
notice (assuming the gradual guarantee holds, and ecosystem code is
mostly correct). Another disadvantage of ecosystem checks is that they
only test checked-in code that is usually correct. However, we also want
to test what happens on wrong code, like the code that is momentarily
written in an editor, before fixing it. On the other end of the spectrum
we have normal mdtests, which have the disadvantage that they do not
reflect the reality of complex real-world code. We experience this
whenever we're surprised by an ecosystem report on a PR.

That said, these tests should not be seen as a replacement for either of
these things. For example, we should still strive to write detailed
self-contained mdtests for user-reported issues. But we might use this
new layer for regression tests, or simply as a debugging tool. It can
also serve as a tool to document our support for popular third-party
libraries.

## Test Plan

* I've been locally using this for a couple of weeks now.
* `uv run crates/ty_python_semantic/mdtest.py -e`
2025-12-08 11:44:20 +01:00
..
annotations [ty] Complete support for ParamSpec (#21445) 2025-12-05 22:00:06 +05:30
assignment [ty] Avoid expression reinference for diagnostics (#21267) 2025-11-25 09:24:00 -08:00
binary [ty] Improve the display of various special-form types (#21775) 2025-12-03 21:19:59 +00:00
boolean Revert "[ty] Better control flow for boolean expressions that are inside if (#18010)" (#18150) 2025-05-17 08:27:32 -04:00
boundness_declaredness [ty] Reformulation of public symbol inference test suite (#20667) 2025-10-01 14:26:17 +02:00
call [ty] more detailed description of "Size limit on unions of literals" in mdtest (#21804) 2025-12-05 17:34:39 +00:00
class [ty] Improve the display of various special-form types (#21775) 2025-12-03 21:19:59 +00:00
comparison [ty] Improve diagnostics for unsupported comparison operations (#21737) 2025-12-02 19:58:45 +00:00
comprehensions [ty] fix global symbol lookup from eager scopes (#21317) 2025-11-12 10:15:51 -08:00
conditional [ty] Support as-patterns in reachability analysis (#19728) 2025-08-04 20:13:50 +02:00
dataclasses [ty] Suppress false positives when dataclasses.dataclass(...)(cls) is called imperatively (#21729) 2025-12-03 08:05:25 +00:00
declaration [ty] Format conflicting types as an enumeration (#18956) 2025-06-26 14:29:33 +02:00
diagnostics [ty] Add subdiagnostic hint if the user wrote X = Any rather than X: Any (#21777) 2025-12-03 20:42:21 +00:00
directives [ty] Minor improvements to assert_type diagnostics (#21811) 2025-12-05 12:33:30 +00:00
doc ty_python_semantic: add union type context to function call type errors 2025-05-09 13:40:51 -04:00
exception [ty] Improve diagnostics for invalid exceptions (#21475) 2025-11-15 22:12:00 +00:00
expression [ty] Check method definitions on subclasses for Liskov violations (#21436) 2025-11-23 18:08:15 +00:00
external [ty] mdtests with external dependencies (#20904) 2025-12-08 11:44:20 +01:00
function [ty] Improve the display of various special-form types (#21775) 2025-12-03 21:19:59 +00:00
generics [ty] Handle various invalid explicit specializations for ParamSpec (#21821) 2025-12-08 05:20:41 +00:00
ide_support [ty] Support type[T] with type variables (#21650) 2025-11-28 09:20:24 +01:00
import [ty] cleanup test path (#21781) 2025-12-03 21:54:50 +00:00
libraries [ty] Generic types aliases (implicit and PEP 613) (#21553) 2025-11-28 20:38:24 +01:00
literal [ty] Type inference for genererator expressions (#21437) 2025-11-14 13:04:11 +00:00
loops [ty] Fix bug where ty would think all types had an __mro__ attribute (#20995) 2025-10-27 11:19:12 +00:00
narrow [ty] Improve the display of various special-form types (#21775) 2025-12-03 21:19:59 +00:00
regression [ty] handle recursive type inference properly (#20566) 2025-11-26 08:50:26 -08:00
scopes [ty] Make __getattr__ available for ModuleType instances (#21450) 2025-11-14 13:59:14 +01:00
shadowing
snapshots [ty] Minor improvements to assert_type diagnostics (#21811) 2025-12-05 12:33:30 +00:00
stubs [ty] Better invalid-assignment diagnostics (#21476) 2025-11-18 14:31:04 +01:00
subscript [ty] support type[tuple[...]] (#21652) 2025-12-01 11:49:26 +01:00
suppressions [ty] Add code action to ignore diagnostic on the current line (#21595) 2025-11-29 15:41:54 +01:00
type_compendium [ty] Improve literal promotion heuristics (#21439) 2025-11-14 16:13:56 -05:00
type_of [ty] type[T] is assignable to an inferable typevar (#21766) 2025-12-02 18:25:09 -05:00
type_properties [ty] Allow tuple[Any, ...] to assign to tuple[int, *tuple[int, ...]] (#21803) 2025-12-05 19:04:23 +00:00
type_qualifiers [ty] Avoid double-analyzing tuple in Final subscript (#21828) 2025-12-07 14:27:14 +00:00
unary Update class literal display to use <class 'Foo'> style (#17889) 2025-05-06 20:11:25 -04:00
with [ty] Complete support for ParamSpec (#21445) 2025-12-05 22:00:06 +05:30
.mdformat.toml
async.md [ty] Generic types aliases (implicit and PEP 613) (#21553) 2025-11-28 20:38:24 +01:00
attributes.md [ty] Support type[T] with type variables (#21650) 2025-11-28 09:20:24 +01:00
bidirectional.md [ty] Improve diagnostics for unsupported comparison operations (#21737) 2025-12-02 19:58:45 +00:00
classes.md [ty] Fix bug where ty would think all types had an __mro__ attribute (#20995) 2025-10-27 11:19:12 +00:00
cycle.md [ty] remove the visitor parameter in the recursive_type_normalized_impl method (#21701) 2025-12-01 08:48:43 +01:00
decorators.md ty_python_semantic: add union type context to function call type errors 2025-05-09 13:40:51 -04:00
del.md [ty] No union with Unknown for module-global symbols (#20664) 2025-10-01 16:40:30 +02:00
deprecated.md [ty] Consistent use of American english (in rules) (#19488) 2025-07-22 16:10:38 +02:00
descriptor_protocol.md [ty] Use the return type of __get__ for descriptor lookups even when __get__ is called with incorrect arguments (#21424) 2025-11-13 12:05:10 +00:00
enums.md [ty] Support type[T] with type variables (#21650) 2025-11-28 09:20:24 +01:00
exhaustiveness_checking.md [ty] Exhaustiveness checking for generic classes (#21726) 2025-12-01 13:52:36 +01:00
final.md [ty] Improve @override, @final and Liskov checks in cases where there are multiple reachable definitions (#21767) 2025-12-03 12:51:36 +00:00
implicit_type_aliases.md [ty] Complete support for ParamSpec (#21445) 2025-12-05 22:00:06 +05:30
instance_layout_conflict.md [ty] initial support for slots=True in dataclasses (#20278) 2025-09-07 18:25:35 +01:00
intersection_types.md [ty] Use "cannot" consistently over "can not" (#21255) 2025-11-03 10:38:20 -05:00
invalid_syntax.md [ty] Implicit type aliases: Add support for typing.Union (#21363) 2025-11-12 12:59:14 +01:00
known_constants.md
liskov.md [ty] Carry generic context through when converting class into Callable (#21798) 2025-12-05 08:57:21 -05:00
literal_promotion.md [ty] Narrow type context during literal promotion in generic class constructors (#21574) 2025-11-21 17:05:32 -05:00
mdtest_config.md
mdtest_custom_typeshed.md [ty] Remove Type::Tuple (#19669) 2025-08-11 22:03:32 +01:00
metaclass.md Update class literal display to use <class 'Foo'> style (#17889) 2025-05-06 20:11:25 -04:00
mro.md [ty] Improve the display of various special-form types (#21775) 2025-12-03 21:19:59 +00:00
named_tuple.md [ty] Improve @override, @final and Liskov checks in cases where there are multiple reachable definitions (#21767) 2025-12-03 12:51:36 +00:00
overloads.md [ty] Infer type of self for decorated methods and properties (#21123) 2025-10-29 21:22:38 +00:00
override.md [ty] Improve @override, @final and Liskov checks in cases where there are multiple reachable definitions (#21767) 2025-12-03 12:51:36 +00:00
pep613_type_aliases.md [ty] Improve the display of various special-form types (#21775) 2025-12-03 21:19:59 +00:00
pep695_type_aliases.md [ty] Support typevar-specialized dynamic types in generic type aliases (#21730) 2025-12-03 10:00:02 +01:00
properties.md [ty] Use the return type of __get__ for descriptor lookups even when __get__ is called with incorrect arguments (#21424) 2025-11-13 12:05:10 +00:00
protocols.md [ty] normalize typevar bounds/constraints in cycles (#21800) 2025-12-04 15:17:57 -08:00
public_types.md [ty] Disambiguate classes that live in different modules but have the same fully qualified names (#20756) 2025-10-08 18:27:40 +01:00
statically_known_branches.md [ty] Rename "possibly unbound" diagnostics to "possibly missing" (#20492) 2025-09-23 14:26:55 +00:00
sys_platform.md
sys_version_info.md [ty] support PEP 613 type aliases (#21394) 2025-11-20 17:59:35 -08:00
t_strings.md [ty] Add support for PEP 750 t-strings (#20085) 2025-08-25 18:49:49 +00:00
terminal_statements.md [ty] improve lazy scope place lookup (#19321) 2025-07-25 07:11:11 +00:00
ty_extensions.md [ty] Stop testing the (brittle) constraint set display implementation (#21743) 2025-12-02 09:17:29 +01:00
typed_dict.md [ty] Preserve quoting style when autofixing TypedDict keys (#21682) 2025-11-28 18:40:34 +00:00
union_types.md [ty] Introduce TypeRelation::Redundancy (#20602) 2025-10-03 18:35:30 +01:00
unpacking.md [ty] Infer more precise types for collection literals (#20360) 2025-09-17 18:51:50 -04:00
unreachable.md [ty] Add subdiagnostic hint if a variable with type Never is used in a type expression (#21660) 2025-11-27 12:48:18 +00:00