fix: error when lockfile without metadata entry is encountered

src/poetry/packages/locker.py

@@ -323,6 +323,14 @@ def _get_lock_data(self) -> dict[str, Any]:
  except tomllib.TOMLDecodeError as e:
  raise RuntimeError(f"Unable to read the lock file ({e}).")
 
+ # if the lockfile doesn't contain a metadata section at all,
+ # it probably needs to be rebuilt completely
+ if "metadata" not in lock_data:
+ raise RuntimeError(
+ "The lock file does not have a metadata entry.\n"
+ "Regenerate the lock file with the `poetry lock` command."
+ )
+
  metadata = lock_data["metadata"]
  lock_version = Version.parse(metadata.get("lock-version", "1.0"))
  current_version = Version.parse(self._VERSION)

tests/packages/test_locker.py

@@ -622,6 +622,38 @@ def test_reading_lock_file_should_raise_an_error_on_invalid_data(
  assert "Unable to read the lock file" in str(e.value)
 
 
+def test_reading_lock_file_should_raise_an_error_on_missing_metadata(
+ locker: Locker,
+) -> None:
+ content = f"""\
+# {GENERATED_COMMENT}
+
+[[package]]
+name = "A"
+version = "1.0.0"
+description = ""
+optional = false
+python-versions = "*"
+files = []
+
+[package.source]
+type = "legacy"
+url = "https://foo.bar"
+reference = "legacy"
+"""
+ with locker.lock.open("w", encoding="utf-8") as f:
+ f.write(content)
+
+ with pytest.raises(RuntimeError) as e:
+ _ = locker.lock_data
+
+ assert (
+ "The lock file does not have a metadata entry.\nRegenerate the lock file with"
+ " the `poetry lock` command."
+ in str(e.value)
+ )
+
+
 def test_locking_legacy_repository_package_should_include_source_section(
  root: ProjectPackage, locker: Locker
 ) -> None: