#!/usr/bin/env python
# Copyright (c) 2009, Willow Garage, Inc.
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#       this software without specific prior written permission.
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# Author Tully Foote/tfoote@willowgarage.com

from __future__ import print_function

import subprocess

from ..core import InstallFailed
from ..installers import PackageManagerInstaller
from ..shell_utils import read_stdout

# pip package manager key
PIP_INSTALLER = 'pip'


def register_installers(context):
    context.set_installer(PIP_INSTALLER, PipInstaller())


def is_pip_installed():
    try:
        subprocess.Popen(['pip'], stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()
        return True
    except OSError:
        return False


def pip_detect(pkgs, exec_fn=None):
    """
    Given a list of package, return the list of installed packages.

    :param exec_fn: function to execute Popen and read stdout (for testing)
    """
    fallback_to_pip_show = False
    if exec_fn is None:
        exec_fn = read_stdout
        fallback_to_pip_show = True
    pkg_list = exec_fn(['pip', 'freeze']).split('\n')

    ret_list = []
    for pkg in pkg_list:
        pkg_row = pkg.split("==")
        if pkg_row[0] in pkgs:
            ret_list.append(pkg_row[0])

    # Try to detect with the return code of `pip show`.
    # This can show the existance of things like `argparse` which
    # otherwise do not show up.
    # See:
    #   https://github.com/pypa/pip/issues/1570#issuecomment-71111030
    if fallback_to_pip_show:
        for pkg in [p for p in pkgs if p not in ret_list]:
            # does not see retcode but stdout for old pip to check if installed
            output = subprocess.check_output(['pip', 'show', pkg]).strip()
            if not output:
                # `pip show` detected it, add it to the list.
                ret_list.append(pkg)

    return ret_list


class PipInstaller(PackageManagerInstaller):
    """
    :class:`Installer` support for pip.
    """

    def __init__(self):
        super(PipInstaller, self).__init__(pip_detect, supports_depends=True)

    def get_install_command(self, resolved, interactive=True, reinstall=False, quiet=False):
        if not is_pip_installed():
            raise InstallFailed((PIP_INSTALLER, "pip is not installed"))
        packages = self.get_packages_to_install(resolved, reinstall=reinstall)
        if not packages:
            return []
        else:
            return [self.elevate_priv(['pip', 'install', '-U', p]) for p in packages]

@@ -3171,20 +3171,16 @@
      if 
-not 
 output:%0A

Correct logic for wrong package detection with 'pip show'