Refine show group formatting

Author: Yijian6

src/poetry/console/commands/show.py

@@ -310,7 +310,16 @@ def _display_packages_information(
         latest_statuses = {}
         installed_repo = InstalledRepository.load(self.env)
         requires = root.all_requires
-        package_groups = self._package_groups(root) if show_groups else {}
+        package_groups: dict[NormalizedName, list[NormalizedName]] = {}
+        default_groups = ""
+        formatted_groups: dict[NormalizedName, str] = {}
+        if show_groups:
+            package_groups = self._package_groups(root)
+            default_groups = self._format_groups([])
+            formatted_groups = {
+                package_name: self._format_groups(groups)
+                for package_name, groups in package_groups.items()
+            }
 
         # Computing widths
         for locked in locked_packages:
@@ -365,9 +374,7 @@ def _display_packages_information(
                     if show_groups:
                         groups_length = max(
                             groups_length,
-                            len(
-                                self._format_groups(package_groups.get(locked.name, []))
-                            ),
+                            len(formatted_groups.get(locked.name, default_groups)),
                         )
             else:
                 name_length = max(name_length, current_length)
@@ -389,7 +396,7 @@ def _display_packages_information(
                 if show_groups:
                     groups_length = max(
                         groups_length,
-                        len(self._format_groups(package_groups.get(locked.name, []))),
+                        len(formatted_groups.get(locked.name, default_groups)),
                     )
 
         if self.option("format") == OutputFormats.JSON:
@@ -504,7 +511,7 @@ def _display_packages_information(
                 line += f" <b>{version:{version_length}}</b>"
 
             if write_groups:
-                groups = self._format_groups(package_groups.get(locked.name, []))
+                groups = formatted_groups.get(locked.name, default_groups)
                 line += f" {groups:{groups_length}}"
 
             if show_latest: