Add pip inspect command

Author: sbidoul

news/11245.feature.rst

@@ -0,0 +1,2 @@
+Add ``pip inspect`` command to obtain the list of installed distributions and other
+information about the Python environment, in JSON format.

src/pip/_internal/commands/__init__.py

@@ -38,6 +38,11 @@
         "FreezeCommand",
         "Output installed packages in requirements format.",
     ),
+    "inspect": CommandInfo(
+        "pip._internal.commands.inspect",
+        "InspectCommand",
+        "Inspect the python environment.",
+    ),
     "list": CommandInfo(
         "pip._internal.commands.list",
         "ListCommand",

src/pip/_internal/commands/inspect.py

@@ -0,0 +1,91 @@
+import json
+import sys
+from optparse import Values
+from typing import Any, Dict, List
+
+from pip._vendor.packaging.markers import default_environment
+
+from pip import __version__
+from pip._internal.cli import cmdoptions
+from pip._internal.cli.req_command import Command
+from pip._internal.cli.status_codes import SUCCESS
+from pip._internal.metadata import BaseDistribution, get_environment
+from pip._internal.utils.compat import stdlib_pkgs
+from pip._internal.utils.urls import path_to_url
+
+
+class InspectCommand(Command):
+    """
+    Inspect the content of a Python environment.
+    """
+
+    ignore_require_venv = True
+    usage = """
+      %prog [options]"""
+
+    def add_options(self) -> None:
+        self.cmd_opts.add_option(
+            "-l",
+            "--local",
+            action="store_true",
+            default=False,
+            help=(
+                "If in a virtualenv that has global access, do not list "
+                "globally-installed packages."
+            ),
+        )
+        self.cmd_opts.add_option(
+            "--user",
+            dest="user",
+            action="store_true",
+            default=False,
+            help="Only output packages installed in user-site.",
+        )
+        self.cmd_opts.add_option(cmdoptions.list_path())
+        self.parser.insert_option_group(0, self.cmd_opts)
+
+    def run(self, options: Values, args: List[str]) -> int:
+        cmdoptions.check_list_path_option(options)
+        dists = get_environment(options.path).iter_installed_distributions(
+            local_only=options.local,
+            user_only=options.user,
+            skip=set(stdlib_pkgs),
+        )
+        output = {
+            "version": "0",
+            "pip_version": __version__,
+            "installed": [self._dist_to_dict(dist) for dist in dists],
+            "environment": default_environment(),
+        }
+        json.dump(output, sys.stdout, indent=2, ensure_ascii=True)
+        return SUCCESS
+
+    def _dist_to_dict(self, dist: BaseDistribution) -> Dict[str, Any]:
+        res: Dict[str, Any] = {
+            "metadata": dist.metadata_dict,
+            "location": dist.location,  # TODO is this the best location to report ?
+        }
+        # direct_url
+        direct_url = dist.direct_url
+        if direct_url is not None:
+            res["direct_url"] = direct_url.to_dict()
+        else:
+            # Handle legacy editable installs.
+            editable_project_location = dist.editable_project_location
+            if editable_project_location is not None:
+                res["direct_url"] = {
+                    "url": path_to_url(editable_project_location),
+                    "dir_info": {
+                        "editable": True,
+                    },
+                }
+        # is_direct is redundant but present for symmetry with the installation report.
+        res["is_direct"] = "direct_url" in res
+        # installer
+        installer = dist.installer
+        if dist.installer:
+            res["installer"] = installer
+        # requested
+        if dist.installed_with_dist_info:
+            res["requested"] = dist.requested
+        return res