# pants: no-infer-dep not always respected by the 2.17 Rust parser

[lowvoltage]

Describe the bug
The new Rust inference parser disrespects a # pants: no-infer-dep on a conditional import:

if TYPE_CHECKING:
    from a import ClassA  # pants: no-infer-dep

Dependencies' diff below:

❯ pants --python-infer-no-use-rust-parser peek main.py
[
  {
    "address": "//main.py",
    "target_type": "python_source",
    "dependencies": [],
    "dependencies_raw": null,

❯ pants --python-infer-use-rust-parser peek main.py
[
  {
    "address": "//main.py",
    "target_type": "python_source",
    "dependencies": [
      "//a.py"
    ],
    "dependencies_raw": null,
    "description": null,

Note and workarounds
This seems to break only when # pants: no-infer-dep is on the last line inside the if block:

• With mulitple import statements, only the last one is handled incorrectly
• A multiline import seems to work fine

    from a import (
        ClassA,  # pants: no-infer-dep
    )

• A placeholder pass statement at the end of the if TYPE_CHECKING block also results in a correct behavior

Pants version
2.17.0

OS
Both: MacOS and Linux

Additional info
Minimalist setup to reproduce

main.py

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from a import ClassA  # pants: no-infer-dep

print('Hello, world!')

a.py

class ClassA:
    pass

pants.toml

[GLOBAL]
pants_version = "2.17.0"
backend_packages = ["pants.backend.python"]

[python]
interpreter_constraints = ["==3.9.*"]

BUILD

python_sources()

[huonw]

Thanks for taking the time to file an issue.

As an additional work around that you may be aware of, you can continue using the non-Rust parser, i.e. set use_rust_parser = false instead of true. The Rust parser is new and somewhat experimental, so thanks for helping shake out the bugs.

[thejcannon]

OK, oddly adding

  assert_imports(
    r"
    from typing import TYPE_CHECKING

    if TYPE_CHECKING:
        from a import ClassA  # pants: no-infer-dep

    print('Hello, world!')",
    &["typing.TYPE_CHECKING"],
  );

to src/rust/engine/dep_inference/src/python/tests.rs results in... tests passing.

[thejcannon]

Oh, but I'm on main...

if I checkout 2.17.x it fails.

So I think #19293 fixed this. I'll get it cherry picked backwards.

Kudos @lilatomic

[lilatomic]

I'm not sure what part of #19293 fixes this. I think it might be the newer version of the tree-sitter grammar.