Source code for httpstan.build_ext

"""Lightly modified build_ext which captures stderr.

The customization of build_ext here is non-standard and confusing.
It does, however, work.

isort:skip_file
"""

import setuptools
import setuptools.command.build_ext as build_ext
import io
import logging
import os
import sys
import tempfile
from typing import IO, Any, List, TextIO

from httpstan.config import HTTPSTAN_DEBUG


def run_build_ext(extensions: List[setuptools.Extension], build_lib: str) -> str:
    """Configure and call `build_ext.run()`, capturing stderr.

    Compiled extension module will be placed in `build_lib`.

    All messages sent to stderr will be saved and returned. These
    messages are typically messages from the compiler or linker.

    """

    # utility functions for silencing compiler output
    def _has_fileno(stream: TextIO) -> bool:
        """Returns whether the stream object has a working fileno()

        Suggests whether _redirect_stderr is likely to work.
        """
        try:
            stream.fileno()
        except (AttributeError, OSError, IOError, io.UnsupportedOperation):  # pragma: no cover
            return False
        return True

    def _redirect_stderr_to(stream: IO[Any]) -> int:
        """Redirect stderr for subprocesses to /dev/null.

        Returns
        -------
        orig_stderr: copy of original stderr file descriptor
        """
        sys.stderr.flush()
        stderr_fileno = sys.stderr.fileno()
        orig_stderr = os.dup(stderr_fileno)
        os.dup2(stream.fileno(), stderr_fileno)
        return orig_stderr

    if HTTPSTAN_DEBUG:  # pragma: no cover
        logging.getLogger().setLevel(logging.DEBUG)

    dist = setuptools.Distribution()
    # Make sure build respects distutils configuration
    dist.parse_config_files(dist.find_config_files())  # type: ignore
    build_extension = build_ext.build_ext(dist)  # type: ignore

    build_extension.build_lib = build_lib

    # silence stderr for compilation, if stderr is silenceable
    stream = tempfile.TemporaryFile(prefix="httpstan_")
    redirect_stderr = _has_fileno(sys.stderr) and not HTTPSTAN_DEBUG
    compiler_output = ""
    if redirect_stderr:
        orig_stderr = _redirect_stderr_to(stream)

    # NOTE: work-around for differences between setuptools and distutils. A bit of a hack.
    # The sequence here is important. `finalize_options` needs to be called first.
    # A cleaner approach would make a custom command, following instructions here:
    # https://setuptools.pypa.io/en/latest/userguide/extension.html
    build_extension.finalize_options()
    for extension in extensions:
        # WISHLIST: understand setuptools internals enough to know what this is
        # and why setting this here is required when using setuptools but not
        # when using distutils.
        extension._needs_stub = False
    build_extension.extensions = extensions

    try:
        build_extension.run()
    finally:
        if redirect_stderr:
            stream.seek(0)
            compiler_output = stream.read().decode()
            stream.close()
            # restore
            os.dup2(orig_stderr, sys.stderr.fileno())

    return compiler_output