Add assets filewatcher to reload on assets changes.

Author: T4rk1n

dash/_utils.py

@@ -1,3 +1,6 @@
+import uuid
+
+
 def interpolate_str(template, **data):
     s = template
     for k, v in data.items():
@@ -20,6 +23,10 @@ def format_tag(tag_name, attributes, inner='', closed=False, opened=False):
             '{}="{}"'.format(k, v) for k, v in attributes.items()]))
 
 
+def generate_hash():
+    return str(uuid.uuid4().hex).strip('-')
+
+
 def get_asset_path(requests_pathname, routes_pathname, asset_path):
     i = requests_pathname.rfind(routes_pathname)
     req = requests_pathname[:i]

dash/_watch.py

@@ -0,0 +1,26 @@
+import collections
+import os
+import re
+import time
+
+
+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 walk():
+        for folder in folders:
+            for current, _, files, in os.walk(folder):
+                for f in files:
+                    if pattern and not pattern.search(f):
+                        continue
+                    path = os.path.join(current, f)
+                    info = os.stat(path)
+                    new_time = info.st_mtime
+                    if new_time > watched[path] > 0:
+                        on_change(path)
+                    watched[path] = new_time
+
+    while True:
+        walk()
+        time.sleep(sleep_time)

dash/dash.py

@@ -6,7 +6,7 @@
 import importlib
 import json
 import pkgutil
-import uuid
+import threading
 import warnings
 import re
 
@@ -25,6 +25,8 @@
 from ._utils import AttributeDict as _AttributeDict
 from ._utils import interpolate_str as _interpolate
 from ._utils import format_tag as _format_tag
+from ._utils import generate_hash as _generate_hash
+from . import _watch
 from ._utils import get_asset_path as _get_asset_path
 from . import _configs
 
@@ -105,10 +107,6 @@ def __init__(
             flask.helpers.get_root_path(name), 'assets'
         )
 
-        self._reload_hash = str(uuid.uuid4().hex).strip('-')\
-            if hot_reload else ''
-        self._reload_interval = hot_reload_interval
-
         # allow users to supply their own flask server
         self.server = server or Flask(name, static_folder=static_folder)
 
@@ -227,6 +225,20 @@ def add_url(name, view_func, methods=('GET',)):
         self._cached_layout = None
         self.routes = []
 
+        # hot reload
+        self._reload_hash = _generate_hash() \
+            if hot_reload else ''
+        self._reload_interval = hot_reload_interval
+        self._hard_reload = False
+        self._lock = threading.RLock()
+        self._watch_thread = None
+        if hot_reload:
+            self._watch_thread = threading.Thread(
+                target=lambda: _watch.watch([self._assets_folder],
+                                            self._on_assets_change,
+                                            sleep_time=0.5))
+            self._watch_thread.start()
+
     @property
     def layout(self):
         return self._layout
@@ -298,7 +310,10 @@ def _config(self):
         return config
 
     def serve_reload_hash(self):
-        return flask.jsonify({'reloadHash': self._reload_hash})
+        return flask.jsonify({
+            'reloadHash': self._reload_hash,
+            'hard': self._hard_reload
+        })
 
     def serve_routes(self):
         return flask.Response(
@@ -968,6 +983,12 @@ def get_asset_url(self, path):
             self.config.routes_pathname_prefix,
             path)
 
+    def _on_assets_change(self, _):
+        self._lock.acquire()
+        self._hard_reload = True
+        self._reload_hash = _generate_hash()
+        self._lock.release()
+
     def run_server(self,
                    port=8050,
                    debug=False,

dev-requirements-py37.txt

@@ -1,5 +1,5 @@
 dash_core_components>=0.27.2
-dash_html_components>=0.12.0rc3
+dash_html_components>=0.13.0rc2
 dash-flow-example==0.0.3
 dash-dangerously-set-inner-html
 dash_renderer