WIP... get_installation_order has side effects

Author: sbidoul

src/pip/_internal/commands/install.py

@@ -367,22 +367,16 @@ def run(self, options: Values, args: List[str]) -> int:
             requirement_set = resolver.resolve(
                 reqs, check_supported_wheels=not options.target_dir
             )
+            to_install = resolver.get_installation_order(requirement_set)
 
             if options.json_report_file:
-                report = InstallationReport(
-                    # Use get_installation_order because it does some important
-                    # filtering with the legacy resolver.
-                    resolver.get_installation_order(requirement_set)
-                )
+                report = InstallationReport(to_install)
                 with open(options.json_report_file, "w") as f:
                     json.dump(report.to_dict(), f)
 
             if options.dry_run:
                 would_install_items = sorted(
-                    (r.metadata["name"], r.metadata["version"])
-                    # Use get_installation_order because it does some important
-                    # filtering with the legacy resolver.
-                    for r in resolver.get_installation_order(requirement_set)
+                    (r.metadata["name"], r.metadata["version"]) for r in to_install
                 )
                 if would_install_items:
                     write_output(
@@ -437,8 +431,6 @@ def run(self, options: Values, args: List[str]) -> int:
                 if not r.use_pep517:
                     r.legacy_install_reason = 8368
 
-            to_install = resolver.get_installation_order(requirement_set)
-
             # Check for conflicts in the package set we're installing.
             conflicts: Optional[ConflictDetails] = None
             should_warn_about_conflicts = (