Add the outline for structured output

Author: krishanbhasin-px

src/pip/_internal/cli/cmdoptions.py

@@ -887,6 +887,14 @@ def _handle_config_settings(
     "pip only finds stable versions.",
 )
 
+json: Callable[..., Option] = partial(
+    Option,
+    "--json",
+    action="store_true",
+    default=False,
+    help="Output data in a machine-readable JSON format.",
+)
+
 disable_pip_version_check: Callable[..., Option] = partial(
     Option,
     "--disable-pip-version-check",

src/pip/_internal/commands/index.py

@@ -1,7 +1,9 @@
+import json
 import logging
 from optparse import Values
 from typing import Any, Iterable, List, Optional
 
+from pip._internal.metadata import get_default_environment
 from pip._vendor.packaging.version import Version
 
 from pip._internal.cli import cmdoptions
@@ -34,6 +36,7 @@ def add_options(self) -> None:
 
         self.cmd_opts.add_option(cmdoptions.ignore_requires_python())
         self.cmd_opts.add_option(cmdoptions.pre())
+        self.cmd_opts.add_option(cmdoptions.json())
         self.cmd_opts.add_option(cmdoptions.no_binary())
         self.cmd_opts.add_option(cmdoptions.only_binary())
 
@@ -134,6 +137,22 @@ def get_available_package_versions(self, options: Values, args: List[Any]) -> No
             formatted_versions = [str(ver) for ver in sorted(versions, reverse=True)]
             latest = formatted_versions[0]
 
+        if options.json:
+            env = get_default_environment()
+            dist = env.get_distribution(query)
+            structured_output = {
+                    "name": query,
+                    "versions": formatted_versions,
+                    "latest": latest,
+                }
+
+            if dist is not None:
+                structured_output["installed_version"] = dist.version
+
+
+            write_output(json.dumps(structured_output))
+            return
+
         write_output(f"{query} ({latest})")
         write_output("Available versions: {}".format(", ".join(formatted_versions)))
         print_dist_installation_info(query, latest)

tests/functional/test_index.py

@@ -1,3 +1,4 @@
+import json
 import pytest
 
 from pip._internal.cli.status_codes import ERROR, SUCCESS
@@ -6,6 +7,31 @@
 from tests.lib import PipTestEnvironment
 
 
+@pytest.mark.network
+def test_json_structured_output(script: PipTestEnvironment) -> None:
+    """
+    Test that --json flag returns structured output
+    """
+    output = script.pip("index", "versions", "pip", "--json", allow_stderr_warning=True)
+    structured_output = json.loads(output.stdout)
+
+    assert "name" in structured_output
+    assert "versions" in structured_output
+    assert "latest" in structured_output
+    assert (
+        "20.2.3, 20.2.2, 20.2.1, 20.2, 20.1.1, 20.1, 20.0.2"
+        ", 20.0.1, 19.3.1, 19.3, 19.2.3, 19.2.2, 19.2.1, 19.2, 19.1.1"
+        ", 19.1, 19.0.3, 19.0.2, 19.0.1, 19.0, 18.1, 18.0, 10.0.1, 10.0.0, "
+        "9.0.3, 9.0.2, 9.0.1, 9.0.0, 8.1.2, 8.1.1, "
+        "8.1.0, 8.0.3, 8.0.2, 8.0.1, 8.0.0, 7.1.2, 7.1.1, 7.1.0, 7.0.3, "
+        "7.0.2, 7.0.1, 7.0.0, 6.1.1, 6.1.0, 6.0.8, 6.0.7, 6.0.6, 6.0.5, "
+        "6.0.4, 6.0.3, 6.0.2, 6.0.1, 6.0, 1.5.6, 1.5.5, 1.5.4, 1.5.3, "
+        "1.5.2, 1.5.1, 1.5, 1.4.1, 1.4, 1.3.1, 1.3, 1.2.1, 1.2, 1.1, 1.0.2,"
+        " 1.0.1, 1.0, 0.8.3, 0.8.2, 0.8.1, 0.8, 0.7.2, 0.7.1, 0.7, 0.6.3, "
+        "0.6.2, 0.6.1, 0.6, 0.5.1, 0.5, 0.4, 0.3.1, "
+        "0.3, 0.2.1, 0.2" in structured_output.get("versions")
+    )
+
 @pytest.mark.network
 def test_list_all_versions_basic_search(script: PipTestEnvironment) -> None:
     """