Repair missing packages during environment sync

tools/repo/sync-python-environment.py

@@ -149,6 +149,7 @@ def main() -> int:
             requirements=requirements,
             python=python,
             local_requirements=local_requirements,
+            repair_requirements=environment.stale_requirements,
             force=args.force,
         )
 
@@ -250,6 +251,7 @@ def build_install_plan(
     python: str,
     local_requirements: tuple[RequirementEntry, ...],
     force: bool,
+    repair_requirements: tuple[RequirementEntry, ...] = (),
 ) -> InstallPlan:
     full_command = (python, "-m", "pip", "install", "-r", str(requirements))
     if force:
@@ -273,7 +275,12 @@ def build_install_plan(
     removed_paths = set(previous_inputs) - set(current_inputs)
     stale_requirements = requirements_key in changed_paths or requirements_key in removed_paths
 
-    installs: list[tuple[str, ...]] = []
+    # Metadata changes and installation drift can happen together. Keep both
+    # sets in one resolver transaction so a selective metadata sync also
+    # repairs local distributions omitted from the current environment.
+    installs: list[tuple[str, ...]] = [
+        requirement.install_args for requirement in repair_requirements
+    ]
     warnings: list[str] = []
 
     if stale_requirements:
@@ -322,7 +329,7 @@ def build_install_plan(
         )
         return InstallPlan(
             "Selective Python environment sync",
-            f"installing {len(deduped_installs)} stale local requirement(s) in one resolver transaction.",
+            f"installing {len(deduped_installs)} stale or missing local requirement(s) in one resolver transaction.",
             (command,),
             tuple(warnings),
         )