feat(externalselect): add initialOption + option_groups (vercel/chat#410, #397) (#84)

* feat(externalselect): add initialOption + option_groups (vercel/chat#410, #397)

Ports two upstream PRs that together complete ExternalSelect support:

- vercel/chat#397 introduced ExternalSelectElement and the
  block_suggestion / onOptionsLoad runtime; the runtime half landed
  here in #66 but the modal element type was deferred. This PR adds
  the missing ExternalSelectElement TypedDict + ExternalSelect builder
  and wires up _external_select_to_block in the Slack modal renderer.
- vercel/chat#410 adds two new optional fields on top: initialOption
  (pre-selected option object) and option_groups (labeled sections,
  Slack max 100 groups x 100 options, label max 75 chars). The
  handler return type widens to OptionsLoadResult = list[options] |
  list[OptionsLoadGroup]; the Slack adapter detects grouped form by
  the presence of an "options" key on the first entry and emits
  Slack's option_groups response (mutually exclusive with options
  per Slack's spec).

Hazard #1 (truthiness): min_query_length=0 is preserved (0 means
"fire on every keystroke"); not silently dropped by an `or` fallback.

Hazard #7 (omit vs None): unset initial_option / placeholder /
min_query_length are omitted from the rendered Block Kit element,
not serialized as null.

https://claude.ai/code/session_01FyMxQn2BEAzmwKS1GZczKj

* fix(slack): use is-not-None guard for initial_option in external_select renderer

Address review on PR #84 (modals.py:209). The TS expression
``if (select.initialOption)`` only filters null/undefined since ``{}`` is
truthy in JS. Python ``if initial_option:`` falsely drops a
hand-constructed ``initial_option={}`` because empty dicts are falsy.
Switch to ``is not None`` for parity with TS and consistency with the
``min_query_length is not None`` check three lines above.

Adds test_external_select_initial_option_empty_dict_renders regression
test that fails before the fix.

https://claude.ai/code/session_01FyMxQn2BEAzmwKS1GZczKj

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: patrick-chinchill

src/chat_sdk/__init__.py

@@ -67,9 +67,12 @@
 from chat_sdk.logger import ConsoleLogger, Logger, LogLevel
 from chat_sdk.message_history import MessageHistoryCache, MessageHistoryConfig
 from chat_sdk.modals import (
+    ExternalSelect,
+    ExternalSelectElement,
     Modal,
     ModalChild,
     ModalElement,
+    OptionsLoadGroup,
     RadioSelect,
     RadioSelectElement,
     Select,
@@ -78,6 +81,7 @@
     SelectOptionElement,
     TextInput,
     TextInputElement,
+    external_select,
     filter_modal_children,
     is_modal_element,
     modal,
@@ -158,6 +162,7 @@
     ModalResponse,
     ModalSubmitEvent,
     OptionsLoadEvent,
+    OptionsLoadResult,
     PlanUpdateChunk,
     Postable,
     PostableAst,
@@ -296,6 +301,7 @@
     "MessageHistoryCache",
     "MessageHistoryConfig",
     # Modal builders (PascalCase primary — matches source TS SDK)
+    "ExternalSelect",
     "Modal",
     "RadioSelect",
     "Select",
@@ -305,11 +311,14 @@
     "modal",
     "text_input",
     "select",
+    "external_select",
     "select_option",
     "radio_select",
     # Modal types
+    "ExternalSelectElement",
     "ModalChild",
     "ModalElement",
+    "OptionsLoadGroup",
     "RadioSelectElement",
     "SelectElement",
     "SelectOptionElement",
@@ -363,6 +372,7 @@
     "ModalSubmitEvent",
     "OptionsLoadEvent",
     "OptionsLoadHandler",
+    "OptionsLoadResult",
     "PlanUpdateChunk",
     "Postable",
     "PostableAst",

src/chat_sdk/adapters/slack/adapter.py

@@ -52,7 +52,7 @@
 )
 from chat_sdk.emoji import convert_emoji_placeholders, emoji_to_slack, resolve_emoji_from_slack
 from chat_sdk.logger import ConsoleLogger, Logger
-from chat_sdk.modals import ModalElement, SelectOptionElement
+from chat_sdk.modals import ModalElement, OptionsLoadGroup, SelectOptionElement
 from chat_sdk.shared.adapter_utils import extract_card, extract_files
 from chat_sdk.shared.errors import AdapterRateLimitError, AuthenticationError, ValidationError
 from chat_sdk.types import (
@@ -1098,24 +1098,70 @@ def _late_error(t: asyncio.Task[Any]) -> None:
 
         return self._options_load_response(result if result is not None else [])
 
-    def _options_load_response(self, options_list: list[SelectOptionElement]) -> dict[str, Any]:
-        """Serialize ``SelectOptionElement`` entries to a Slack JSON response."""
-        slack_options: list[dict[str, Any]] = []
-        for opt in options_list[:100]:
-            entry: dict[str, Any] = {
-                "text": {"type": "plain_text", "text": opt.get("label", "")},
-                "value": opt.get("value", ""),
+    def _options_load_response(
+        self,
+        result: list[SelectOptionElement] | list[OptionsLoadGroup],
+    ) -> dict[str, Any]:
+        """Serialize a flat option list or grouped option list to a Slack JSON response.
+
+        Mirrors upstream ``optionsLoadResponse``: when the first entry has an
+        ``options`` key it is treated as a list of :class:`OptionsLoadGroup`
+        and rendered as ``option_groups``; otherwise it's a flat list of
+        :class:`SelectOptionElement` rendered as ``options``. Slack's spec is
+        explicit that the two are mutually exclusive (only one may appear in
+        the response body).
+        """
+        # Detect grouped form (TS: ``"options" in result[0]``). A grouped
+        # entry is a dict with an ``options`` list inside it; a flat entry is
+        # a dict with ``label``/``value`` keys.
+        is_groups = (
+            len(result) > 0
+            and isinstance(result[0], dict)
+            and "options" in result[0]
+            and isinstance(result[0].get("options"), list)
+        )
+
+        if is_groups:
+            groups_in = cast("list[OptionsLoadGroup]", result)[:100]
+            slack_groups: list[dict[str, Any]] = []
+            for group in groups_in:
+                group_options = group.get("options", [])[:100]
+                slack_groups.append(
+                    {
+                        # Slack spec: group label is plain_text, max 75 chars.
+                        "label": {"type": "plain_text", "text": group.get("label", "")[:75]},
+                        "options": [self._select_option_to_slack(opt) for opt in group_options],
+                    }
+                )
+            return {
+                "body": json.dumps({"option_groups": slack_groups}),
+                "status": 200,
+                "headers": {"Content-Type": "application/json"},
             }
-            desc = opt.get("description")
-            if desc:
-                entry["description"] = {"type": "plain_text", "text": desc}
-            slack_options.append(entry)
+
+        flat = cast("list[SelectOptionElement]", result)[:100]
         return {
-            "body": json.dumps({"options": slack_options}),
+            "body": json.dumps({"options": [self._select_option_to_slack(opt) for opt in flat]}),
             "status": 200,
             "headers": {"Content-Type": "application/json"},
         }
 
+    @staticmethod
+    def _select_option_to_slack(opt: SelectOptionElement) -> dict[str, Any]:
+        """Convert a :class:`SelectOptionElement` to Slack's option object shape.
+
+        Mirrors upstream ``selectOptionToSlackOption`` — the ``description``
+        key is omitted (not set to ``null``) when not provided.
+        """
+        entry: dict[str, Any] = {
+            "text": {"type": "plain_text", "text": opt.get("label", "")},
+            "value": opt.get("value", ""),
+        }
+        desc = opt.get("description")
+        if desc:
+            entry["description"] = {"type": "plain_text", "text": desc}
+        return entry
+
     # ==================================================================
     # View submission / close
     # ==================================================================

src/chat_sdk/adapters/slack/modals.py

@@ -102,6 +102,8 @@ def _modal_child_to_block(child: ModalChild) -> SlackBlock:
         return _text_input_to_block(child)  # type: ignore[arg-type]
     if child_type == "select":
         return _select_to_block(child)  # type: ignore[arg-type]
+    if child_type == "external_select":
+        return _external_select_to_block(child)  # type: ignore[arg-type]
     if child_type == "radio_select":
         return _radio_select_to_block(child)  # type: ignore[arg-type]
     if child_type == "text":
@@ -179,6 +181,58 @@ def _select_to_block(select: dict[str, Any]) -> SlackBlock:
     }
 
 
+def _external_select_to_block(select: dict[str, Any]) -> SlackBlock:
+    """Convert an :class:`ExternalSelectElement` to a Slack input block with external_select.
+
+    Mirrors upstream ``externalSelectToBlock``. Options are loaded at runtime
+    by an ``onOptionsLoad`` handler — this just emits the placeholder element.
+    Optional fields (``placeholder``, ``min_query_length``, ``initial_option``)
+    are omitted from the output when not set, matching upstream behavior.
+    """
+    element: dict[str, Any] = {
+        "type": "external_select",
+        "action_id": select.get("id", ""),
+    }
+
+    placeholder = select.get("placeholder")
+    if placeholder:
+        element["placeholder"] = {"type": "plain_text", "text": placeholder}
+
+    min_query_length = select.get("min_query_length")
+    # Use ``is not None`` (hazard #1): ``0`` is a valid Slack value meaning
+    # "fire on every keystroke" and must not silently fall back to omitting
+    # the key (which would default to Slack's 3-character minimum).
+    if min_query_length is not None:
+        element["min_query_length"] = min_query_length
+
+    initial_option = select.get("initial_option")
+    if initial_option is not None:
+        # Hazard #1: ``is not None`` (not truthiness) so a hand-constructed
+        # empty dict ``{}`` doesn't silently render as no initial_option,
+        # matching the TS ``if (select.initialOption)`` semantics where
+        # ``{}`` is truthy. Also keeps consistency with the
+        # ``min_query_length is not None`` check above.
+        # Unlike static select, ``initial_option`` is the full
+        # ``{label, value}`` object — the loader hasn't run yet so a value
+        # string would be ambiguous. Mirrors selectOptionToSlackOption.
+        slack_initial: dict[str, Any] = {
+            "text": {"type": "plain_text", "text": initial_option.get("label", "")},
+            "value": initial_option.get("value", ""),
+        }
+        desc = initial_option.get("description")
+        if desc:
+            slack_initial["description"] = {"type": "plain_text", "text": desc}
+        element["initial_option"] = slack_initial
+
+    return {
+        "type": "input",
+        "block_id": select.get("id", ""),
+        "optional": select.get("optional", False),
+        "label": {"type": "plain_text", "text": select.get("label", "")},
+        "element": element,
+    }
+
+
 def _radio_select_to_block(radio_select: dict[str, Any]) -> SlackBlock:
     """Convert a RadioSelectElement to a Slack input block with radio_buttons."""
     limited_options = radio_select.get("options", [])[:10]

src/chat_sdk/chat.py

@@ -21,7 +21,6 @@
 from chat_sdk.channel import ChannelImpl, _ChannelImplConfigWithAdapter
 from chat_sdk.errors import ChatError, LockError
 from chat_sdk.logger import ConsoleLogger, Logger
-from chat_sdk.modals import SelectOptionElement
 from chat_sdk.thread import (
     ThreadImpl,
     _active_chat,
@@ -56,6 +55,7 @@
     ModalSubmitEvent,
     OnLockConflict,
     OptionsLoadEvent,
+    OptionsLoadResult,
     QueueEntry,
     ReactionEvent,
     SlashCommandEvent,
@@ -87,7 +87,7 @@
 ActionHandler = Callable[[ActionEvent], Any]
 OptionsLoadHandler = Callable[
     [OptionsLoadEvent],
-    Awaitable[list[SelectOptionElement] | None] | list[SelectOptionElement] | None,
+    Awaitable[OptionsLoadResult | None] | OptionsLoadResult | None,
 ]
 ModalSubmitHandler = Callable[[ModalSubmitEvent], Any]
 ModalCloseHandler = Callable[[ModalCloseEvent], Any]
@@ -953,7 +953,7 @@ async def process_options_load(
         self,
         event: OptionsLoadEvent,
         options: WebhookOptions | None = None,  # noqa: ARG002 (match upstream signature)
-    ) -> list[SelectOptionElement] | None:
+    ) -> OptionsLoadResult | None:
         """Process an options-load event (external-select suggestion lookup).
 
         Runs specific-action-ID handlers before catch-all handlers and returns

src/chat_sdk/modals.py

@@ -52,8 +52,35 @@ class RadioSelectElement(TypedDict, total=False):
     optional: bool
 
 
+class OptionsLoadGroup(TypedDict):
+    """A labeled group of options returned by an ``onOptionsLoad`` handler.
+
+    Maps to upstream TS ``OptionsLoadGroup``. Slack ``external_select`` renders
+    grouped results as ``option_groups`` (mutually exclusive with top-level
+    ``options`` per Slack's spec).
+    """
+
+    label: str
+    options: list[SelectOptionElement]
+
+
+class ExternalSelectElement(TypedDict, total=False):
+    """External select form element (loads options dynamically from a handler)."""
+
+    type: str  # "external_select"
+    id: str
+    label: str
+    placeholder: str
+    min_query_length: int
+    optional: bool
+    # Pre-selected option when the modal opens (must match an option returned
+    # by the loader). Unlike static :class:`SelectElement`, the initial value
+    # is the full ``{label, value}`` object since the loader has not run yet.
+    initial_option: SelectOptionElement
+
+
 # Union of all modal child types
-ModalChild = TextInputElement | SelectElement | RadioSelectElement | TextElement | FieldsElement
+ModalChild = TextInputElement | SelectElement | ExternalSelectElement | RadioSelectElement | TextElement | FieldsElement
 
 
 class ModalElement(TypedDict, total=False):
@@ -69,7 +96,7 @@ class ModalElement(TypedDict, total=False):
     children: list[ModalChild]
 
 
-VALID_MODAL_CHILD_TYPES = {"text_input", "select", "radio_select", "text", "fields"}
+VALID_MODAL_CHILD_TYPES = {"text_input", "select", "external_select", "radio_select", "text", "fields"}
 
 
 def is_modal_element(value: Any) -> bool:
@@ -180,6 +207,38 @@ def Select(
     return result
 
 
+def ExternalSelect(
+    *,
+    id: str,
+    label: str,
+    placeholder: str | None = None,
+    min_query_length: int | None = None,
+    optional: bool | None = None,
+    initial_option: SelectOptionElement | None = None,
+) -> ExternalSelectElement:
+    """Build an :class:`ExternalSelectElement` dict.
+
+    Slack-only: renders to a Block Kit ``external_select`` element whose
+    options are populated by an :func:`Chat.on_options_load` handler at
+    runtime. ``initial_option`` is the full ``{label, value}`` object (the
+    loader hasn't run yet so just a value string would be ambiguous).
+    """
+    result: ExternalSelectElement = {
+        "type": "external_select",
+        "id": id,
+        "label": label,
+    }
+    if placeholder is not None:
+        result["placeholder"] = placeholder
+    if min_query_length is not None:
+        result["min_query_length"] = min_query_length
+    if optional is not None:
+        result["optional"] = optional
+    if initial_option is not None:
+        result["initial_option"] = initial_option
+    return result
+
+
 def SelectOption(
     *,
     label: str,
@@ -227,5 +286,6 @@ def RadioSelect(
 modal = Modal
 text_input = TextInput
 select = Select
+external_select = ExternalSelect
 select_option = SelectOption
 radio_select = RadioSelect

src/chat_sdk/types.py

@@ -19,7 +19,12 @@
 from chat_sdk.cards import CardElement
 from chat_sdk.errors import ChatNotImplementedError
 from chat_sdk.logger import Logger, LogLevel
-from chat_sdk.modals import SelectOptionElement
+from chat_sdk.modals import OptionsLoadGroup, SelectOptionElement
+
+# A handler may return either a flat list of options or a list of labeled
+# groups (Slack's ``option_groups`` shape). Mirrors upstream TS
+# ``OptionsLoadResult = SelectOptionElement[] | OptionsLoadGroup[]``.
+OptionsLoadResult = list[SelectOptionElement] | list[OptionsLoadGroup]
 
 
 def _parse_iso(s: str) -> datetime:
@@ -1424,7 +1429,7 @@ def process_modal_submit(
     ) -> Awaitable[ModalResponse | None]: ...
     def process_options_load(
         self, event: OptionsLoadEvent, options: WebhookOptions | None = None
-    ) -> Awaitable[list[SelectOptionElement] | None]: ...
+    ) -> Awaitable[OptionsLoadResult | None]: ...
     def process_modal_close(
         self, event: Any, context_id: str | None = None, options: WebhookOptions | None = None
     ) -> None: ...