Add pip inspect command

docs/html/cli/index.md

@@ -16,6 +16,7 @@ pip
 
 pip_install
 pip_uninstall
+pip_inspect
 pip_list
 pip_show
 pip_freeze

docs/html/cli/pip_inspect.rst

@@ -0,0 +1,32 @@
+.. _`pip inspect`:
+
+===========
+pip inspect
+===========
+
+
+
+Usage
+=====
+
+.. tab:: Unix/macOS
+
+   .. pip-command-usage:: inspect "python -m pip"
+
+.. tab:: Windows
+
+   .. pip-command-usage:: inspect "py -m pip"
+
+
+Description
+===========
+
+.. pip-command-description:: inspect
+
+The format of the JSON output is described in :doc:`../reference/inspect-report`.
+
+
+Options
+=======
+
+.. pip-command-options:: inspect

docs/html/reference/index.md

@@ -9,4 +9,5 @@ interoperability standards that pip utilises/implements.
 build-system/index
 requirement-specifiers
 requirements-file-format
+inspect-report
 ```

docs/html/reference/inspect-report.md

@@ -0,0 +1,79 @@
+# `pip inspect` JSON output specification
+
+The `pip inspect` command produces a detailed JSON report of the Python
+environment, including installed distributions.
+
+## Specification
+
+The report is a JSON object with the following properties:
+
+- `version`: the string `0`, denoting that the inspect command is an experimental
+  feature. This value will change to `1`, when the feature is deemed stable after
+  gathering user feedback (likely in pip 22.3 or 23.0). Backward incompatible changes
+  may be introduced in version `1` without notice. After that, it will change only if
+  and when backward incompatible changes are introduced, such as removing mandatory
+  fields or changing the semantics or data type of existing fields. The introduction of
+  backward incompatible changes will follow the usual pip processes such as the
+  deprecation cycle or feature flags. Tools must check this field to ensure they support
+  the corresponding version.
+
+- `pip_version`: a string with the version of pip used to produce the report.
+
+- `installed`: an array of `InspectReportItem` (see below) representing the
+  distribution packages that are installed.
+
+- `environment`: an object describing the environment where the installation report was
+  generated. See [PEP 508 environment
+  markers](https://peps.python.org/pep-0508/#environment-markers) for more information.
+  Values have a string type.
+
+An `InspectReportItem` is an object describing a (to be) installed distribution
+package with the following properties:
+
+- `metadata`: the metadata of the distribution, converted to a JSON object according to
+  the [PEP 566
+  transformation](https://www.python.org/dev/peps/pep-0566/#json-compatible-metadata).
+
+- `metadata_location`: the location of the metadata of the installed distribution. Most
+  of the time this is the `.dist-info` directory. For legacy installs it is the
+  `.egg-info` directory.
+
+  ```{warning}
+  This field may not necessary point to a directory, for instance, in the case of older
+  `.egg` installs.
+  ```
+
+- `direct_url`: Information about the direct URL that was used for installation, if any,
+  using the [direct
+  URL](https://packaging.python.org/en/latest/specifications/direct-url/) data
+  structure. In most case, this field the `direct_url.json` metadata, except for legacy
+  editable installs, where it is emulated.
+
+- `requested`: `true` if the `REQUESTED` metadata is present, `false` otherwise. This
+  field is only present for modern `.dist-info` installations.
+
+  ```{note}
+  The `REQUESTED` metadata may not be generated by all installers.
+  It is generated by pip since version 20.2.
+  ```
+
+- `installer`: the content of the `INSTALLER` metadata, if present and not empty.
+
+## Example
+
+The following command:
+
+```console
+pip inspect
+```
+
+will produce an output similar to this (metadata abriged for brevity):
+
+```json
+{
+  "version": "0",
+  "pip_version": "22.2",
+  "installed": [],
+  "environment": {}
+}
+```

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(),
+            # TODO tags? scheme?
+        }
+        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,
+            "metadata_location": dist.info_location,
+        }
+        # direct_url. Note that we don't have download_info (as in the installation
+        # report) since it is not recorded in installed metadata.
+        direct_url = dist.direct_url
+        if direct_url is not None:
+            res["direct_url"] = direct_url.to_dict()
+        else:
+            # Emulate direct_url for 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,
+                    },
+                }
+        # installer
+        installer = dist.installer
+        if dist.installer:
+            res["installer"] = installer
+        # requested
+        if dist.installed_with_dist_info:
+            res["requested"] = dist.requested
+        return res