Explicitly install pip with python

Signed-off-by: Julien Jerphanion <git@jjerphan.xyz>

libmamba/src/api/install.cpp

@@ -5,7 +5,6 @@
 // The full license is in the file LICENSE, distributed with this software.
 
 #include <algorithm>
-#include <cctype>
 #include <stdexcept>
 
 #include <fmt/format.h>
@@ -377,6 +376,33 @@ namespace mamba
     {
         using Request = solver::Request;
 
+        // When the user explicitly asks for ``python`` in the requested specs, also inject a
+        // plain ``pip`` request unless it is already present. This complements
+        // ``add_pip_as_python_dependency`` at the repo level and makes sure that the Request
+        // is in phase with the root packages including both ``python`` and ``pip`` when requested.
+        bool wants_python = false;
+        bool wants_pip = false;
+        for (const auto& s : specs)
+        {
+            const auto maybe_name = specs::MatchSpec::extract_name(s);
+            if (!maybe_name.has_value())
+            {
+                continue;
+            }
+            if (maybe_name.value() == "python")
+            {
+                wants_python = true;
+            }
+            else if (maybe_name.value() == "pip")
+            {
+                wants_pip = true;
+            }
+        }
+        if (wants_python && !wants_pip)
+        {
+            specs.emplace_back("pip");
+        }
+
         const auto& prefix_pkgs = prefix_data.records();
 
         auto request = Request();