fix: Effectively apply dry-run on installation from PyPI (#3644)

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

libmamba/src/api/install.cpp

@@ -537,10 +537,13 @@ namespace mamba
 
                 trans.execute(ctx, channel_context, prefix_data);
 
-                for (auto other_spec : config.at("others_pkg_mgrs_specs")
-                                           .value<std::vector<detail::other_pkg_mgr_spec>>())
+                if (!ctx.dry_run)
                 {
-                    install_for_other_pkgmgr(ctx, other_spec, pip::Update::No);
+                    for (auto other_spec : config.at("others_pkg_mgrs_specs")
+                                               .value<std::vector<detail::other_pkg_mgr_spec>>())
+                    {
+                        install_for_other_pkgmgr(ctx, other_spec, pip::Update::No);
+                    }
                 }
             }
             else

micromamba/tests/test_install.py

@@ -796,3 +796,37 @@ def test_install_empty_base(tmp_home, tmp_root_prefix, tmp_path):
     packages = helpers.umamba_list("-p", env_prefix, "--json")
     assert any(package["name"] == "xtensor" for package in packages)
     assert any(package["name"] == "python" for package in packages)
+
+
+env_specific_pip = """
+channels:
+  - conda-forge
+dependencies:
+  - python
+  - pip:
+    - numpy
+"""
+
+
+# Test that dry runs works if package are specified for the `pip:` section
+def test_dry_run_pip_section(tmp_home, tmp_root_prefix, tmp_path):
+    env_prefix = tmp_path / "env-specific-pip"
+
+    env_file_yml = tmp_path / "test_install_env_specific_pip.yaml"
+    env_file_yml.write_text(env_specific_pip)
+
+    res = helpers.create("-p", env_prefix, "--json", "pip")
+    assert res["success"]
+    packages_at_creation = helpers.umamba_list("-p", env_prefix, "--json")
+
+    # Install from the environment file
+    res = helpers.install("-p", env_prefix, "-f", env_file_yml, "--json", "--dry-run")
+    assert res["success"]
+    assert res["dry_run"]
+
+    packages = helpers.umamba_list("-p", env_prefix, "--json")
+    assert packages == packages_at_creation
+
+    # Check that the packages are not installed using `pip`
+    res = helpers.umamba_run("-p", env_prefix, "pip", "list")
+    assert "numpy" not in res