Don't error on malformed date input

CHANGELOG.md

@@ -34,6 +34,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Fixed several issues with `page_navbar()` styling. (#1124)
 * Fixed `Renderer.output_id` to not contain the module namespace prefix, only the output id. (#1130)
 * Fixed gap-driven spacing between children in fillable `nav_panel()` containers. (#1152)
+* Fixed #1138: An empty value in a date or date range input would cause an error; now it is treated as `None`. (#1139)
 
 ### Other changes
 

shiny/input_handler.py

@@ -99,13 +99,24 @@ def _(value, name, session):
 @input_handlers.add("shiny.date")
 def _(
     value: str | list[str], name: ResolvedId, session: Session
-) -> date | tuple[date, date]:
+) -> date | None | tuple[date | None, date | None]:
+
     if isinstance(value, str):
+        return _safe_strptime_date(value)
+    else:
+        return (
+            _safe_strptime_date(value[0]),
+            _safe_strptime_date(value[1]),
+        )
+
+
+def _safe_strptime_date(value: str | None) -> date | None:
+    if value is None:
+        return None
+    try:
         return datetime.strptime(value, "%Y-%m-%d").date()
-    return (
-        datetime.strptime(value[0], "%Y-%m-%d").date(),
-        datetime.strptime(value[1], "%Y-%m-%d").date(),
-    )
+    except ValueError:
+        return None
 
 
 @input_handlers.add("shiny.datetime")