mypy/test/testoutput.py

"""Test cases for `--output=json`.

These cannot be run by the usual unit test runner because of the backslashes in
the output, which get normalized to forward slashes by the test suite on Windows.
"""

from __future__ import annotations

import os
import os.path

from mypy import api
from mypy.defaults import PYTHON3_VERSION
from mypy.test.config import test_temp_dir
from mypy.test.data import DataDrivenTestCase, DataSuite


class OutputJSONsuite(DataSuite):
    files = ["outputjson.test"]

    def run_case(self, testcase: DataDrivenTestCase) -> None:
        test_output_json(testcase)


def test_output_json(testcase: DataDrivenTestCase) -> None:
    """Runs Mypy in a subprocess, and ensures that `--output=json` works as intended."""
    mypy_cmdline = ["--output=json"]
    mypy_cmdline.append(f"--python-version={'.'.join(map(str, PYTHON3_VERSION))}")

    # Write the program to a file.
    program_path = os.path.join(test_temp_dir, "main")
    mypy_cmdline.append(program_path)
    with open(program_path, "w", encoding="utf8") as file:
        for s in testcase.input:
            file.write(f"{s}\n")

    output = []
    # Type check the program.
    out, err, returncode = api.run(mypy_cmdline)
    # split lines, remove newlines, and remove directory of test case
    for line in (out + err).rstrip("\n").splitlines():
        if line.startswith(test_temp_dir + os.sep):
            output.append(line[len(test_temp_dir + os.sep) :].rstrip("\r\n"))
        else:
            output.append(line.rstrip("\r\n"))

    if returncode > 1:
        output.append("!!! Mypy crashed !!!")

    # Remove temp file.
    os.remove(program_path)

    # JSON encodes every `\` character into `\\`, so we need to remove `\\` from windows paths
    # and `/` from POSIX paths
    json_os_separator = os.sep.replace("\\", "\\\\")
    normalized_output = [line.replace(test_temp_dir + json_os_separator, "") for line in output]

    assert normalized_output == testcase.output