# Copyright (c) Streamlit Inc. (2018-2022) Snowflake Inc. (2022-2024)
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import annotations
import textwrap
from types import MappingProxyType
from typing import TYPE_CHECKING, Final, Mapping
from typing_extensions import TypeAlias
from streamlit.errors import DuplicateWidgetID
from streamlit.proto.WidgetStates_pb2 import WidgetState, WidgetStates
from streamlit.runtime.state.common import (
RegisterWidgetResult,
T,
WidgetArgs,
WidgetCallback,
WidgetDeserializer,
WidgetKwargs,
WidgetMetadata,
WidgetProto,
WidgetSerializer,
user_key_from_widget_id,
)
from streamlit.type_util import ValueFieldName
if TYPE_CHECKING:
from streamlit.runtime.scriptrunner import ScriptRunContext
ElementType: TypeAlias = str
# NOTE: We use this table to start with a best-effort guess for the value_type
# of each widget. Once we actually receive a proto for a widget from the
# frontend, the guess is updated to be the correct type. Unfortunately, we're
# not able to always rely on the proto as the type may be needed earlier.
# Thankfully, in these cases (when value_type == "trigger_value"), the static
# table here being slightly inaccurate should never pose a problem.
ELEMENT_TYPE_TO_VALUE_TYPE: Final[
Mapping[ElementType, ValueFieldName]
] = MappingProxyType(
{
"button": "trigger_value",
"camera_input": "file_uploader_state_value",
"checkbox": "bool_value",
"chat_input": "string_trigger_value",
"color_picker": "string_value",
"component_instance": "json_value",
"data_editor": "string_value",
"dataframe": "string_value",
"date_input": "string_array_value",
"download_button": "trigger_value",
"file_uploader": "file_uploader_state_value",
"multiselect": "int_array_value",
"number_input": "double_value",
"plotly_chart": "string_value",
"radio": "int_value",
"selectbox": "int_value",
"slider": "double_array_value",
"text_area": "string_value",
"text_input": "string_value",
"time_input": "string_value",
"vega_lite_chart": "string_value",
}
)
class NoValue:
"""Return this from DeltaGenerator.foo_widget() when you want the st.foo_widget()
call to return None. This is needed because `DeltaGenerator._enqueue`
replaces `None` with a `DeltaGenerator` (for use in non-widget elements).
"""
pass
def register_widget(
element_type: ElementType,
element_proto: WidgetProto,
deserializer: WidgetDeserializer[T],
serializer: WidgetSerializer[T],
ctx: ScriptRunContext | None,
user_key: str | None = None,
widget_func_name: str | None = None,
on_change_handler: WidgetCallback | None = None,
args: WidgetArgs | None = None,
kwargs: WidgetKwargs | None = None,
) -> RegisterWidgetResult[T]:
"""Register a widget with Streamlit, and return its current value.
NOTE: This function should be called after the proto has been filled.
Parameters
----------
element_type : ElementType
The type of the element as stored in proto.
element_proto : WidgetProto
The proto of the specified type (e.g. Button/Multiselect/Slider proto)
deserializer : WidgetDeserializer[T]
Called to convert a widget's protobuf value to the value returned by
its st.<widget_name> function.
serializer : WidgetSerializer[T]
Called to convert a widget's value to its protobuf representation.
ctx : ScriptRunContext or None
Used to ensure uniqueness of widget IDs, and to look up widget values.
user_key : str or None
Optional user-specified string to use as the widget ID.
If this is None, we'll generate an ID by hashing the element.
widget_func_name : str or None
The widget's DeltaGenerator function name, if it's different from
its element_type. Custom components are a special case: they all have
the element_type "component_instance", but are instantiated with
dynamically-named functions.
on_change_handler : WidgetCallback or None
An optional callback invoked when the widget's value changes.
args : WidgetArgs or None
args to pass to on_change_handler when invoked
kwargs : WidgetKwargs or None
kwargs to pass to on_change_handler when invoked
Returns
-------
register_widget_result : RegisterWidgetResult[T]
Provides information on which value to return to the widget caller,
and whether the UI needs updating.
- Unhappy path:
- Our ScriptRunContext doesn't exist (meaning that we're running
as a "bare script" outside streamlit).
- We are disconnected from the SessionState instance.
In both cases we'll return a fallback RegisterWidgetResult[T].
- Happy path:
- The widget has already been registered on a previous run but the
user hasn't interacted with it on the client. The widget will have
the default value it was first created with. We then return a
RegisterWidgetResult[T], containing this value.
- The widget has already been registered and the user *has*
interacted with it. The widget will have that most recent
user-specified value. We then return a RegisterWidgetResult[T],
containing this value.
For both paths a widget return value is provided, allowing the widgets
to be used in a non-streamlit setting.
"""
# Create the widget's updated metadata, and register it with session_state.
metadata = WidgetMetadata(
element_proto.id,
deserializer,
serializer,
value_type=ELEMENT_TYPE_TO_VALUE_TYPE[element_type],
callback=on_change_handler,
callback_args=args,
callback_kwargs=kwargs,
fragment_id=ctx.current_fragment_id if ctx else None,
)
return register_widget_from_metadata(metadata, ctx, widget_func_name, element_type)
def register_widget_from_metadata(
metadata: WidgetMetadata[T],
ctx: ScriptRunContext | None,
widget_func_name: str | None,
element_type: ElementType,
) -> RegisterWidgetResult[T]:
"""Register a widget and return its value, using an already constructed
`WidgetMetadata`.
This is split out from `register_widget` to allow caching code to replay
widgets by saving and reusing the completed metadata.
See `register_widget` for details on what this returns.
"""
# Local import to avoid import cycle
import streamlit.runtime.caching as caching
if ctx is None:
# Early-out if we don't have a script run context (which probably means
# we're running as a "bare" Python script, and not via `streamlit run`).
return RegisterWidgetResult.failure(deserializer=metadata.deserializer)
widget_id = metadata.id
user_key = user_key_from_widget_id(widget_id)
# Ensure another widget with the same user key hasn't already been registered.
if user_key is not None:
if user_key not in ctx.widget_user_keys_this_run:
ctx.widget_user_keys_this_run.add(user_key)
else:
raise DuplicateWidgetID(
_build_duplicate_widget_message(
widget_func_name if widget_func_name is not None else element_type,
user_key,
)
)
# Ensure another widget with the same id hasn't already been registered.
new_widget = widget_id not in ctx.widget_ids_this_run
if new_widget:
ctx.widget_ids_this_run.add(widget_id)
else:
raise DuplicateWidgetID(
_build_duplicate_widget_message(
widget_func_name if widget_func_name is not None else element_type,
user_key,
)
)
# Save the widget metadata for cached result replay
caching.save_widget_metadata(metadata)
return ctx.session_state.register_widget(metadata, user_key)
def coalesce_widget_states(
old_states: WidgetStates | None, new_states: WidgetStates | None
) -> WidgetStates | None:
"""Coalesce an older WidgetStates into a newer one, and return a new
WidgetStates containing the result.
For most widget values, we just take the latest version.
However, any trigger_values (which are set by buttons) that are True in
`old_states` will be set to True in the coalesced result, so that button
presses don't go missing.
"""
if not old_states and not new_states:
return None
elif not old_states:
return new_states
elif not new_states:
return old_states
states_by_id: dict[str, WidgetState] = {
wstate.id: wstate for wstate in new_states.widgets
}
trigger_value_types = [("trigger_value", False), ("string_trigger_value", None)]
for old_state in old_states.widgets:
for trigger_value_type, unset_value in trigger_value_types:
if (
old_state.WhichOneof("value") == trigger_value_type
and old_state.trigger_value != unset_value
):
# Ensure the corresponding new_state is also a trigger;
# otherwise, a widget that was previously a button but no longer is
# could get a bad value.
new_trigger_val = states_by_id.get(old_state.id)
if (
new_trigger_val
and new_trigger_val.WhichOneof("value") == trigger_value_type
):
states_by_id[old_state.id] = old_state
coalesced = WidgetStates()
coalesced.widgets.extend(states_by_id.values())
return coalesced
def _build_duplicate_widget_message(
widget_func_name: str, user_key: str | None = None
) -> str:
if user_key is not None:
message = textwrap.dedent(
"""
There are multiple widgets with the same `key='{user_key}'`.
To fix this, please make sure that the `key` argument is unique for each
widget you create.
"""
)
else:
message = textwrap.dedent(
"""
There are multiple identical `st.{widget_type}` widgets with the
same generated key.
When a widget is created, it's assigned an internal key based on
its structure. Multiple widgets with an identical structure will
result in the same internal key, which causes this error.
To fix this error, please pass a unique `key` argument to
`st.{widget_type}`.
"""
)
return message.strip("\n").format(widget_type=widget_func_name, user_key=user_key)