Type annotations in dash (+ add mypy tests in CI)

MANIFEST.in

@@ -10,3 +10,4 @@ include dash/html/*
 include dash/dash_table/*
 include dash/dash-renderer/build/*.js
 include dash/dash-renderer/build/*.map
+include dash/py.typed

dash/_callback.py

@@ -1,7 +1,9 @@
 import collections
 from functools import wraps
+from typing import Any, List, Dict, Callable, Union
 
 from .dependencies import (
+    ClientsideFunction,
     handle_callback_args,
     handle_grouped_callback_args,
     Output,
@@ -27,9 +29,9 @@ class NoUpdate:
     pass
 
 
-GLOBAL_CALLBACK_LIST = []
-GLOBAL_CALLBACK_MAP = {}
-GLOBAL_INLINE_SCRIPTS = []
+GLOBAL_CALLBACK_LIST: List[dict] = []
+GLOBAL_CALLBACK_MAP: Dict[str, dict] = {}
+GLOBAL_INLINE_SCRIPTS: List[str] = []
 
 
 def callback(*_args, **_kwargs):
@@ -106,7 +108,7 @@ def insert_callback(
 
 def register_callback(
     callback_list, callback_map, config_prevent_initial_callbacks, *_args, **_kwargs
-):
+) -> Callable:
     (
         output,
         flat_inputs,
@@ -137,9 +139,9 @@ def register_callback(
     )
 
     # pylint: disable=too-many-locals
-    def wrap_func(func):
+    def wrap_func(func: Callable) -> Callable:
         @wraps(func)
-        def add_context(*args, **kwargs):
+        def add_context(*args, **kwargs):  # type: ignore[no-untyped-def]
             output_spec = kwargs.pop("outputs_list")
             _validate.validate_output_spec(insert_output, output_spec, Output)
 
@@ -209,14 +211,14 @@ def add_context(*args, **kwargs):
 
 
 def register_clientside_callback(
-    callback_list,
-    callback_map,
-    config_prevent_initial_callbacks,
-    inline_scripts,
-    clientside_function,
-    *args,
-    **kwargs
-):
+    callback_list: List[dict],
+    callback_map: Dict[str, dict],
+    config_prevent_initial_callbacks: bool,
+    inline_scripts: List[str],
+    clientside_function: Union[ClientsideFunction, str],
+    *args: Any,
+    **kwargs: Any,
+) -> None:
     output, inputs, state, prevent_initial_call = handle_callback_args(args, kwargs)
     insert_callback(
         callback_list,
@@ -238,8 +240,8 @@ def register_clientside_callback(
         if isinstance(output, (list, tuple)):
             out0 = output[0]
 
-        namespace = "_dashprivate_{}".format(out0.component_id)
-        function_name = "{}".format(out0.component_property)
+        namespace = f"_dashprivate_{out0.component_id}"
+        function_name = str(out0.component_property)
 
         inline_scripts.append(
             _inline_clientside_template.format(

dash/_callback_context.py

@@ -35,17 +35,17 @@ def __nonzero__(self):
 
 # pylint: disable=no-init
 class CallbackContext:
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def inputs(self):
         return getattr(flask.g, "input_values", {})
 
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def states(self):
         return getattr(flask.g, "state_values", {})
 
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def triggered(self):
         # For backward compatibility: previously `triggered` always had a
@@ -54,17 +54,17 @@ def triggered(self):
         # look empty, but you can still do `triggered[0]["prop_id"].split(".")`
         return getattr(flask.g, "triggered_inputs", []) or falsy_triggered
 
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def args_grouping(self):
         return getattr(flask.g, "args_grouping", [])
 
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def outputs_grouping(self):
         return getattr(flask.g, "outputs_grouping", [])
 
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def outputs_list(self):
         if self.using_outputs_grouping:
@@ -75,7 +75,7 @@ def outputs_list(self):
 
         return getattr(flask.g, "outputs_list", [])
 
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def inputs_list(self):
         if self.using_args_grouping:
@@ -86,7 +86,7 @@ def inputs_list(self):
 
         return getattr(flask.g, "inputs_list", [])
 
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def states_list(self):
         if self.using_args_grouping:
@@ -96,7 +96,7 @@ def states_list(self):
             )
         return getattr(flask.g, "states_list", [])
 
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def response(self):
         return getattr(flask.g, "dash_response")
@@ -125,7 +125,7 @@ def record_timing(name, duration=None, description=None):
 
         setattr(flask.g, "timing_information", timing_information)
 
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def using_args_grouping(self):
         """
@@ -134,7 +134,7 @@ def using_args_grouping(self):
         """
         return getattr(flask.g, "using_args_grouping", [])
 
-    @property
+    @property  # type: ignore[misc]
     @has_context
     def using_outputs_grouping(self):
         """

dash/_configs.py

@@ -1,11 +1,12 @@
 import os
+from typing import Union, Optional, Tuple
 
 # noinspection PyCompatibility
 from . import exceptions
 from ._utils import AttributeDict
 
 
-def load_dash_env_vars():
+def load_dash_env_vars() -> AttributeDict:
     return AttributeDict(
         {
             var: os.getenv(var, os.getenv(var.lower()))
@@ -40,7 +41,9 @@ def load_dash_env_vars():
 DASH_ENV_VARS = load_dash_env_vars()  # used in tests
 
 
-def get_combined_config(name, val, default=None):
+def get_combined_config(
+    name: str, val: Optional[Union[bool, str]], default: Union[bool, str] = None
+) -> Optional[Union[bool, str]]:
     """Consolidate the config with priority from high to low provided init
     value > OS environ > default."""
 
@@ -55,8 +58,10 @@ def get_combined_config(name, val, default=None):
 
 
 def pathname_configs(
-    url_base_pathname=None, routes_pathname_prefix=None, requests_pathname_prefix=None
-):
+    url_base_pathname: str = None,
+    routes_pathname_prefix: str = None,
+    requests_pathname_prefix: str = None,
+) -> Tuple[str, str, str]:
     _pathname_config_error_message = """
     {} This is ambiguous.
     To fix this, set `routes_pathname_prefix` instead of `url_base_pathname`.

dash/_grouping.py

@@ -46,7 +46,7 @@ def flatten_grouping(grouping, schema=None):
     return [grouping]
 
 
-def grouping_len(grouping):
+def grouping_len(grouping) -> int:
     """
     Get the length of a grouping. The length equal to the number of scalar values
     contained in the grouping, which is equivalent to the length of the list that would

dash/_utils.py

@@ -9,6 +9,8 @@
 import io
 import json
 from functools import wraps
+from typing import Dict
+
 from . import exceptions
 
 logger = logging.getLogger()
@@ -21,15 +23,21 @@ def to_json(value):
     return to_json_plotly(value)
 
 
-def interpolate_str(template, **data):
+def interpolate_str(template, **data) -> str:
     s = template
     for k, v in data.items():
         key = "{%" + k + "%}"
         s = s.replace(key, v)
     return s
 
 
-def format_tag(tag_name, attributes, inner="", closed=False, opened=False):
+def format_tag(
+    tag_name: str,
+    attributes: Dict[str, str],
+    inner: str = "",
+    closed: bool = False,
+    opened: bool = False,
+) -> str:
     tag = "<{tag} {attributes}"
     if closed:
         tag += "/>"

dash/_watch.py

@@ -2,18 +2,24 @@
 import os
 import re
 import time
+from typing import List, Callable, DefaultDict
 
 
-def watch(folders, on_change, pattern=None, sleep_time=0.1):
-    pattern = re.compile(pattern) if pattern else None
-    watched = collections.defaultdict(lambda: -1)
+def watch(
+    folders: List[str],
+    on_change: Callable,
+    pattern: str = None,
+    sleep_time: float = 0.1,
+) -> None:
+    compiled_pattern = re.compile(pattern) if pattern else None
+    watched: DefaultDict[str, float] = collections.defaultdict(lambda: -1)
 
-    def walk():
+    def walk() -> None:
         walked = []
         for folder in folders:
             for current, _, files in os.walk(folder):
                 for f in files:
-                    if pattern and not pattern.search(f):
+                    if compiled_pattern and not compiled_pattern.search(f):
                         continue
                     path = os.path.join(current, f)