From c2ae2ea3e78a7f974f1c22c2828d1556081cb793 Mon Sep 17 00:00:00 2001
From: Vineet Naik <naikvin@gmail.com>
Date: Sat, 31 Jul 2021 11:20:25 +0530
Subject: [PATCH] Fix --freeze option due to breaking changes in pip's internal
 api

The 'pip._internal.metadata' modules were introduced in 21.1.1 and the
'pip._internal.operations.freeze.FrozenRequirement' class now expects
dist to be a subclass of 'pip._internal.metadata.BaseDistribution',
however the 'pip._internal.utils.misc.get_installed_distributions'
continues to return objects of type
pip._vendor.pkg_resources.DistInfoDistribution.

This is a hacky backward compatible (with older versions of pip) fix.

Fixes github issue #150.
---
 pipdeptree.py | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/pipdeptree.py b/pipdeptree.py
index e00a88d..a0f68c1 100644
--- a/pipdeptree.py
+++ b/pipdeptree.py
@@ -74,6 +74,23 @@ def guess_version(pkg_key, default='?'):
 
 
 def frozen_req_from_dist(dist):
+    # The `pip._internal.metadata` modules were introduced in 21.1.1
+    # and the `pip._internal.operations.freeze.FrozenRequirement`
+    # class now expects dist to be a subclass of
+    # `pip._internal.metadata.BaseDistribution`, however the
+    # `pip._internal.utils.misc.get_installed_distributions` continues
+    # to return objects of type
+    # pip._vendor.pkg_resources.DistInfoDistribution.
+    #
+    # This is a hacky backward compatible (with older versions of pip)
+    # fix.
+    try:
+        from pip._internal import metadata
+    except ImportError:
+        pass
+    else:
+        dist = metadata.pkg_resources.Distribution(dist)
+
     try:
         return FrozenRequirement.from_dist(dist)
     except TypeError: