Repository: pypa/pip
File: src/pip/_internal/commands/install.py (Python)

Code before:
                home=target_temp_dir_path,
                prefix=options.prefix_path,
                warn_script_location=warn_script_location,
                use_user_site=options.use_user_site,
                pycompile=options.compile,
            )

            lib_locations = get_lib_location_guesses(
                user=options.use_user_site,
                home=target_temp_dir_path,
                root=options.root_path,
                prefix=options.prefix_path,
                isolated=options.isolated_mode,
            )
            env = get_environment(lib_locations)

            # Display a summary of installed packages, with extra care to
            # display a package name as it was requested by the user.
            installed.sort(key=operator.attrgetter("name"))
            items = []
            installed_versions = {}
            for distribution in env.iter_all_distributions():
                installed_versions[distribution.canonical_name] = distribution.version
            for package in installed:
                display_name = package.name
                version = installed_versions.get(canonicalize_name(display_name), None)
                item = f"{display_name}-{version}"
                items.append(item)

            if conflicts is not None:
                self._warn_about_conflicts(
                    conflicts,
                    resolver_variant=self.determine_resolver_variant(options),
                )

            installed_desc = " ".join(items)
            if installed_desc:
                write_output(
                    "Successfully installed %s",
                    installed_desc,
                )
        except OSError as error:
            show_traceback = self.verbosity >= 1

            message = create_os_error_message(
                error,
                show_traceback,
                options.use_user_site,
            )
            logger.error(message, exc_info=show_traceback)


Review comment (performance):
While I'm not aware of a scenario where a distribution is installed and yet the metadata backend is unable to find the package, displaying `Successfully installed six-None` doesn't seem like a good idea. The old logic simply fell back to displaying only the distribution name. 

```console
(pip-20240621) ichard26@asus-ubuntu:~/dev/oss/pip$ pip install six
Collecting six
  Using cached six-1.16.0-py2.py3-none-any.whl.metadata (1.8 kB)
Using cached six-1.16.0-py2.py3-none-any.whl (11 kB)
Installing collected packages: six
Successfully installed six
```

Code after:
                home=target_temp_dir_path,
                prefix=options.prefix_path,
                warn_script_location=warn_script_location,
                use_user_site=options.use_user_site,
                pycompile=options.compile,
            )

            lib_locations = get_lib_location_guesses(
                user=options.use_user_site,
                home=target_temp_dir_path,
                root=options.root_path,
                prefix=options.prefix_path,
                isolated=options.isolated_mode,
            )
            env = get_environment(lib_locations)

            # Display a summary of installed packages, with extra care to
            # display a package name as it was requested by the user.
            installed.sort(key=operator.attrgetter("name"))
            summary = []
            installed_versions = {}
            for distribution in env.iter_all_distributions():
                installed_versions[distribution.canonical_name] = distribution.version
            for package in installed:
                display_name = package.name
                version = installed_versions.get(canonicalize_name(display_name), None)
                if version:
                    text = f"{display_name}-{version}"
                else:
                    text = display_name
                summary.append(text)

            if conflicts is not None:
                self._warn_about_conflicts(
                    conflicts,
                    resolver_variant=self.determine_resolver_variant(options),
                )

            installed_desc = " ".join(summary)
            if installed_desc:
                write_output(
                    "Successfully installed %s",
                    installed_desc,
                )
        except OSError as error:
            show_traceback = self.verbosity >= 1

            message = create_os_error_message(
                error,
                show_traceback,
                options.use_user_site,