Add error on non-list target-version in config file (#1284)

diff --git a/black.py b/black.py
index ff4f098db0271e964b9602553b38a1dcbd2455d6..b3f387ac24465ca5fa7a99ec8076f6832886e15f 100644 (file)
--- a/black.py
+++ b/black.py
@@ -296,6 +296,12 @@ def read_pyproject_toml(
     if not config:
         return None
 
+    target_version = config.get("target_version")
+    if target_version is not None and not isinstance(target_version, list):
+        raise click.BadOptionUsage(
+            "target-version", f"Config key target-version must be a list"
+        )
+
     default_map: Dict[str, Any] = {}
     if ctx.default_map:
         default_map.update(ctx.default_map)