Add --json flag to print download/install information

Fixes #5398

news/5398.feature

@@ -0,0 +1 @@
+Add machine readable --json to pip download and add --log-stderr

src/pip/_internal/basecommand.py

@@ -135,7 +135,9 @@ def main(self, args):
         logger_class = "pip._internal.utils.logging.ColorizedStreamHandler"
         handler_class = "pip._internal.utils.logging.BetterRotatingFileHandler"
 
-        logging.config.dictConfig({
+        stdout, stderr = self.log_streams
+
+        config = {
             "version": 1,
             "disable_existing_loggers": False,
             "filters": {
@@ -155,15 +157,15 @@ def main(self, args):
                     "level": level,
                     "class": logger_class,
                     "no_color": options.no_color,
-                    "stream": self.log_streams[0],
+                    "stream": stderr if options.log_stderr else stdout,
                     "filters": ["exclude_warnings"],
                     "formatter": "indent",
                 },
                 "console_errors": {
                     "level": "WARNING",
                     "class": logger_class,
                     "no_color": options.no_color,
-                    "stream": self.log_streams[1],
+                    "stream": stderr,
                     "formatter": "indent",
                 },
                 "user_log": {
@@ -173,6 +175,13 @@ def main(self, args):
                     "delay": True,
                     "formatter": "indent",
                 },
+                "structured_output": {
+                    "level": "DEBUG",
+                    "class": logger_class,
+                    "no_color": True,
+                    "stream": stdout,
+                    "formatter": "indent",
+                },
             },
             "root": {
                 "level": root_level,
@@ -194,7 +203,11 @@ def main(self, args):
                     "pip._vendor", "distlib", "requests", "urllib3"
                 ]
             },
-        })
+        }
+        config["loggers"]["pip.__structured_output"] = {
+            "handlers": ["structured_output"],
+        }
+        logging.config.dictConfig(config)
 
         # TODO: try to get these passing down from the command?
         #      without resorting to os.environ to hold these.

src/pip/_internal/cmdoptions.py

@@ -274,6 +274,15 @@ def extra_index_url():
     help='Ignore package index (only looking at --find-links URLs instead).',
 )  # type: Any
 
+log_stderr = partial(
+    Option,
+    '--log-stderr',
+    dest='log_stderr',
+    action='store_true',
+    default=False,
+    help="Log logger warnings to stderr",
+)
+
 
 def find_links():
     return Option(
@@ -604,6 +613,7 @@ def _merge_hash(option, opt_str, value, parser):
         no_cache,
         disable_pip_version_check,
         no_color,
+        log_stderr,
     ]
 }
 

src/pip/_internal/commands/download.py

@@ -1,5 +1,6 @@
 from __future__ import absolute_import
 
+import json
 import logging
 import os
 
@@ -115,6 +116,15 @@ def __init__(self, *args, **kw):
                   "this option."),
         )
 
+        cmd_opts.add_option(
+            '--json',
+            dest='json',
+            action='store_true',
+            default=False,
+            help=("Output information about downloaded packages as json. "
+                  "See documentation for caveats."),
+        )
+
         index_opts = cmdoptions.make_option_group(
             cmdoptions.index_group,
             self.parser,
@@ -227,8 +237,34 @@ def run(self, options, args):
                 if downloaded:
                     logger.info('Successfully downloaded %s', downloaded)
 
+                if options.json:
+                    details = self._get_download_details(
+                        resolver, requirement_set, options.download_dir)
+                    logging.getLogger('pip.__structured_output').info(
+                        json.dumps(details))
+
                 # Clean up
                 if not options.no_clean:
                     requirement_set.cleanup_files()
 
         return requirement_set
+
+    def _get_download_details(self, resolver, requirement_set, download_dir):
+        downloaded = []
+        download_dir = os.path.abspath(download_dir)
+        for req in requirement_set.successfully_downloaded:
+            deps = resolver.get_dependencies().get(req.name, [])
+            download_path = os.path.join(download_dir, req.link.filename)
+            downloaded.append(
+                {
+                    'name': req.name,
+                    'download_path': download_path,
+                    'url': req.link.url,
+                    'version': req.version,
+                    'dependencies': [
+                        {'name': dep.name, 'version': dep.version}
+                        for dep in deps
+                    ],
+                }
+            )
+        return downloaded

src/pip/_internal/index.py

@@ -486,7 +486,7 @@ def find_requirement(self, req, upgrade):
         """Try to find a Link matching req
 
         Expects req, an InstallRequirement and upgrade, a boolean
-        Returns a Link if found,
+        Returns an InstallationCandidate if found,
         Raises DistributionNotFound or BestVersionAlreadyInstalled otherwise
         """
         all_candidates = self.find_all_candidates(req.name)
@@ -579,7 +579,7 @@ def find_requirement(self, req, upgrade):
             best_candidate.version,
             ', '.join(sorted(compatible_versions, key=parse_version))
         )
-        return best_candidate.location
+        return best_candidate
 
     def _get_pages(self, locations, project_name):
         """

src/pip/_internal/req/req_install.py

@@ -27,7 +27,9 @@
 from pip._internal.download import (
     is_archive_file, is_url, path_to_url, url_to_path,
 )
-from pip._internal.exceptions import InstallationError, UninstallationError
+from pip._internal.exceptions import (
+    InstallationError, InvalidWheelFilename, UninstallationError,
+)
 from pip._internal.locations import (
     PIP_DELETE_MARKER_FILENAME, running_under_virtualenv,
 )
@@ -304,7 +306,9 @@ def populate_link(self, finder, upgrade, require_hashes):
         to file modification times.
         """
         if self.link is None:
-            self.link = finder.find_requirement(self, upgrade)
+            candidate = finder.find_requirement(self, upgrade)
+            self.link = candidate.location
+            self._found_version = candidate.version
         if self._wheel_cache is not None and not require_hashes:
             old_link = self.link
             self.link = self._wheel_cache.get(self.link, self.name)
@@ -325,6 +329,27 @@ def is_pinned(self):
         return (len(specifiers) == 1 and
                 next(iter(specifiers)).operator in {'==', '==='})
 
+    _found_version = None
+
+    @property
+    def version(self):
+        """ The version if available, else None
+
+        The version determined during requirement resolution if available,
+        the wheel version from the filename if available, or None if no
+        version information could be obtained
+        """
+        if self._found_version:
+            return str(self._found_version)
+        # If we didn't lookup the version from the internet/a finder, try to
+        # guess it
+        if self.is_wheel:
+            try:
+                return Wheel(self.link.filename).version
+            except InvalidWheelFilename:
+                pass
+        return None
+
     def from_path(self):
         if self.req is None:
             return None

src/pip/_internal/resolve.py

@@ -352,3 +352,10 @@ def schedule(req):
         for install_req in req_set.requirements.values():
             schedule(install_req)
         return order
+
+    def get_dependencies(self):
+        """ Gets dependencies discovered after resolution
+
+        Returns a mapping of package names to lists of requirement objects
+        """
+        return self._discovered_dependencies

tests/functional/test_download.py

@@ -1,7 +1,10 @@
+import json
 import os
+import sys
 import textwrap
 
 import pytest
+from pip._vendor.six.moves.urllib.parse import urlparse
 
 from pip._internal.status_codes import ERROR
 from tests.lib.path import Path
@@ -88,6 +91,82 @@ def test_basic_download_should_download_dependencies(script):
     assert script.site_packages / 'openid' not in result.files_created
 
 
+@pytest.mark.network
+def test_prints_json(script):
+    result = script.pip(
+        'download', 'flake8==3.5.0', '-d', '.', '--log-stderr', '--json',
+        expect_stderr=True
+    )
+
+    expected = {
+        'flake8': {
+            'dependencies': [
+                'pyflakes',
+                'enum34',
+                'configparser',
+                'pycodestyle',
+                'mccabe',
+            ],
+            'filename': 'flake8-{version}-py2.py3-none-any.whl'
+        },
+        'pyflakes': {
+            'dependencies': [],
+            'filename': 'pyflakes-{version}-py2.py3-none-any.whl'
+        },
+        'pycodestyle': {
+            'dependencies': [],
+            'filename': 'pycodestyle-{version}-py2.py3-none-any.whl'
+        },
+        'mccabe': {
+            'dependencies': [],
+            'filename': 'mccabe-{version}-py2.py3-none-any.whl'
+        },
+        'configparser': {
+            'dependencies': [],
+            'filename': 'configparser-{version}.tar.gz',
+        },
+        'enum34': {
+            'dependencies': [],
+            'filename': 'enum34-{version}-py{py_version}-none-any.whl',
+        },
+    }
+    expected_keys = ['dependencies', 'download_path', 'name', 'url', 'version']
+
+    actual = json.loads(result.stdout)
+    transformed = {package['name']: package for package in actual}
+
+    assert 'flake8' in transformed
+    assert 'pyflakes' in transformed
+
+    for package in actual:
+        assert sorted(package.keys()) == expected_keys
+
+        expected_package = expected[package['name']]
+        version = package['version']
+        url = urlparse(package['url'])
+        filename = expected_package['filename'].format(
+            version=version, py_version=sys.version_info[0])
+
+        created = result.files_created[Path('scratch') / filename]
+        created_path = os.path.join(created.base_path, created.path)
+
+        # Windows likes to spit this path out lowercase.
+        assert package['download_path'].lower() == created_path.lower()
+        assert url.scheme == 'https'
+        assert url.hostname == 'files.pythonhosted.org'
+        assert Path(url.path).name == filename
+        if package['dependencies']:
+            # Dependencies can change between python versions. Just try to get
+            # /something/ matched
+            assert any(
+                (dep['name'] in expected for dep in package['dependencies']))
+            for dep in package['dependencies']:
+                assert sorted(dep.keys()) == ['name', 'version']
+                if dep['name'] in expected:
+                    expected_version = transformed[dep['name']]['version']
+                    assert dep['version'] == expected_version
+
+
 def test_download_wheel_archive(script, data):
     """
     It should download a wheel archive path