Refactor `show` command a bit (#5738)

Refactor `show` command a tiny bit to separate the different cases into
dedicated functions, since right now `handle` method is 300 lines long.
This also has the advantage of making some imports necessary only on a
specific variant of the command.

The package named is also canonicalized only once, for a minor performance
improvement/to avoid extra work.

src/poetry/console/commands/show.py

@@ -69,15 +69,6 @@ lists all packages available."""
     colors = ["cyan", "yellow", "green", "magenta", "blue"]
 
     def handle(self) -> int:
-        import shutil
-
-        from cleo.io.null_io import NullIO
-
-        from poetry.puzzle.solver import Solver
-        from poetry.repositories.installed_repository import InstalledRepository
-        from poetry.repositories.pool import Pool
-        from poetry.utils.helpers import get_package_version_display_string
-
         package = self.argument("package")
 
         if self.option("tree"):
@@ -111,48 +102,34 @@ lists all packages available."""
             return 1
 
         locked_repo = self.poetry.locker.locked_repository()
-        root = self.project_with_activated_groups_only()
 
-        # Show tree view if requested
-        if self.option("tree") and package is None:
-            requires = root.all_requires
-            packages = locked_repo.packages
-            for p in packages:
-                for require in requires:
-                    if p.name == require.name:
-                        self.display_package_tree(self.io, p, packages)
-                        break
+        if package:
+            return self._display_single_package_information(package, locked_repo)
 
-            return 0
+        root = self.project_with_activated_groups_only()
 
-        table = self.table(style="compact")
-        locked_packages = locked_repo.packages
-        pool = Pool(ignore_repository_names=True)
-        pool.add_repository(locked_repo)
-        solver = Solver(
-            root,
-            pool=pool,
-            installed=[],
-            locked=locked_packages,
-            io=NullIO(),
-        )
-        solver.provider.load_deferred(False)
-        with solver.use_environment(self.env):
-            ops = solver.solve().calculate_operations()
+        # Show tree view if requested
+        if self.option("tree"):
+            return self._display_packages_tree_information(locked_repo, root)
 
-        required_locked_packages = {op.package for op in ops if not op.skipped}
+        return self._display_packages_information(locked_repo, root)
 
-        if package:
+    def _display_single_package_information(
+        self, package: str, locked_repository: Repository
+    ) -> int:
+        locked_packages = locked_repository.packages
+        canonicalized_package = canonicalize_name(package)
         pkg = None
+
         for locked in locked_packages:
-                if canonicalize_name(package) == locked.name:
+            if locked.name == canonicalized_package:
                 pkg = locked
                 break
 
         if not pkg:
             raise ValueError(f"Package {package} not found")
 
-            required_by = reverse_deps(pkg, locked_repo)
+        required_by = reverse_deps(pkg, locked_repository)
 
         if self.option("tree"):
             if self.option("why"):
@@ -189,8 +166,7 @@ lists all packages available."""
             ["<info>description</>", f" : {pkg.description}"],
         ]
 
-            table.add_rows(rows)
-            table.render()
+        self.table(rows=rows, style="compact").render()
 
         if pkg.requires:
             self.line("")
@@ -209,6 +185,34 @@ lists all packages available."""
 
         return 0
 
+    def _display_packages_information(
+        self, locked_repository: Repository, root: ProjectPackage
+    ) -> int:
+        import shutil
+
+        from cleo.io.null_io import NullIO
+
+        from poetry.puzzle.solver import Solver
+        from poetry.repositories.installed_repository import InstalledRepository
+        from poetry.repositories.pool import Pool
+        from poetry.utils.helpers import get_package_version_display_string
+
+        locked_packages = locked_repository.packages
+        pool = Pool(ignore_repository_names=True)
+        pool.add_repository(locked_repository)
+        solver = Solver(
+            root,
+            pool=pool,
+            installed=[],
+            locked=locked_packages,
+            io=NullIO(),
+        )
+        solver.provider.load_deferred(False)
+        with solver.use_environment(self.env):
+            ops = solver.solve().calculate_operations()
+
+        required_locked_packages = {op.package for op in ops if not op.skipped}
+
         show_latest = self.option("latest")
         show_all = self.option("all")
         width = shutil.get_terminal_size().columns
@@ -261,7 +265,7 @@ lists all packages available."""
                     )
 
                     if self.option("why"):
-                        required_by = reverse_deps(locked, locked_repo)
+                        required_by = reverse_deps(locked, locked_repository)
                         required_by_length = max(
                             required_by_length,
                             len(" from " + ",".join(required_by.keys())),
@@ -278,7 +282,7 @@ lists all packages available."""
                 )
 
                 if self.option("why"):
-                    required_by = reverse_deps(locked, locked_repo)
+                    required_by = reverse_deps(locked, locked_repository)
                     required_by_length = max(
                         required_by_length, len(" from " + ",".join(required_by.keys()))
                     )
@@ -345,7 +349,7 @@ lists all packages available."""
                     line += f" <fg={color}>{version:{latest_length}}</>"
 
             if write_why:
-                required_by = reverse_deps(locked, locked_repo)
+                required_by = reverse_deps(locked, locked_repository)
                 if required_by:
                     content = ",".join(required_by.keys())
                     # subtract 6 for ' from '
@@ -371,6 +375,19 @@ lists all packages available."""
 
         return 0
 
+    def _display_packages_tree_information(
+        self, locked_repository: Repository, root: ProjectPackage
+    ) -> int:
+        packages = locked_repository.packages
+
+        for p in packages:
+            for require in root.all_requires:
+                if p.name == require.name:
+                    self.display_package_tree(self.io, p, packages)
+                    break
+
+        return 0
+
     def display_package_tree(
         self,
         io: IO,