pyodide/pyodide_build/testing.py

import pytest
import inspect
from typing import Optional, List, Callable


def run_in_pyodide(
    _function: Optional[Callable] = None,
    standalone: bool = False,
    packages: List[str] = [],
) -> Callable:
    """
    This decorator can be called in two ways --- with arguments and without
    arguments. If it is called without arguments, then the `_function` kwarg
    catches the function the decorator is applied to. Otherewise, standalone
    and packages are the actual arguments to the decorator.

    See docs/testing.md for details on how to use this.

    Parameters
    ----------
    standalone : bool, default=False
        Whether to use a standalone selenium instance to run the test or not
    packages : List[str]
        List of packages to load before running the test
    """

    def decorator(f):
        def inner(selenium):
            if len(packages) > 0:
                selenium.load_package(packages)
            lines, start_line = inspect.getsourcelines(f)
            # Remove first line, which is the decorator. Then pad with empty lines to fix line number.
            lines = ["\n"] * start_line + lines[1:]
            source = "".join(lines)

            err = None
            try:
                # When writing the function, we set the filename to the file
                # containing the source. This results in a more helpful
                # traceback
                selenium.run_js(
                    """pyodide._module.pyodide_py.eval_code({!r}, // code
                            pyodide._module.globals, // globals
                            pyodide._module.globals, // locals
                            "last_expr", // return_mode
                            true, // quiet_trailing_semicolon
                            {!r} // filename
                        )""".format(
                        source, inspect.getsourcefile(f)
                    )
                )
                # When invoking the function, use the default filename <eval>
                selenium.run_js(
                    """pyodide._module.pyodide_py.eval_code("{}()", pyodide._module.globals)""".format(
                        f.__name__
                    )
                )
            except selenium.JavascriptException as e:
                err = e

            if err is not None:
                pytest.fail(
                    "Error running function in pyodide\n\n" + str(err),
                    pytrace=False,
                )

        if standalone:

            def wrapped_standalone(selenium_standalone):
                inner(selenium_standalone)

            return wrapped_standalone

        else:

            def wrapped(selenium):
                inner(selenium)

            return wrapped

    if _function is not None:
        return decorator(_function)
    else:
        return decorator