Add fallback traceback formatting.

Author: T4rk1n

dash/_utils.py

@@ -8,6 +8,8 @@
 import logging
 import io
 import json
+import secrets
+import string
 from functools import wraps
 
 logger = logging.getLogger()
@@ -206,3 +208,9 @@ def _wrapper(*args, **kwargs):
         return _wrapper
 
     return wrapper
+
+
+def gen_salt(chars):
+    return "".join(
+        secrets.choice(string.ascii_letters + string.digits) for _ in range(chars)
+    )

dash/dash.py

@@ -11,14 +11,12 @@
 import mimetypes
 import hashlib
 import base64
+import traceback
 from urllib.parse import urlparse
 
 import flask
 from flask_compress import Compress
 
-from werkzeug.debug import tbtools
-from werkzeug.security import gen_salt
-
 from pkg_resources import get_distribution, parse_version
 from dash import dcc
 from dash import html
@@ -51,6 +49,7 @@
     patch_collections_abc,
     split_callback_id,
     to_json,
+    gen_salt,
 )
 from . import _callback
 from . import _get_paths
@@ -105,28 +104,40 @@
 _re_renderer_scripts_id = 'id="_dash-renderer', "new DashRenderer"
 
 
-def _get_traceback(secret, error):
-    def _get_skip(text):
+def _get_traceback(secret, error: Exception):
+
+    try:
+        # pylint: disable=import-outside-toplevel
+        from werkzeug.debug import tbtools
+    except ImportError:
+        tbtools = None
+
+    def _get_skip(text, divider=2):
         skip = 0
-        for i, line in enumerate(text.splitlines()):
+        for i, line in enumerate(text):
             if "%% callback invoked %%" in line:
-                skip = int((i + 1) / 2)
+                skip = int((i + 1) / divider)
                 break
         return skip
 
     # werkzeug<2.1.0
     if hasattr(tbtools, "get_current_traceback"):
         tb = tbtools.get_current_traceback()
-        skip = _get_skip(tb.plaintext)
+        skip = _get_skip(tb.plaintext.splitlines())
         return tbtools.get_current_traceback(skip=skip).render_full()
 
-    tb = tbtools.DebugTraceback(error)  # pylint: disable=no-member
-    skip = _get_skip(tb.render_traceback_text())
+    if hasattr(tbtools, "DebugTraceback"):
+        tb = tbtools.DebugTraceback(error)  # pylint: disable=no-member
+        skip = _get_skip(tb.render_traceback_text().splitlines())
+
+        # pylint: disable=no-member
+        return tbtools.DebugTraceback(error, skip=skip).render_debugger_html(
+            True, secret, True
+        )
 
-    # pylint: disable=no-member
-    return tbtools.DebugTraceback(error, skip=skip).render_debugger_html(
-        True, secret, True
-    )
+    tb = traceback.format_exception(type(error), error, error.__traceback__)
+    skip = _get_skip(tb, 1)
+    return tb[0] + "".join(tb[skip:])
 
 
 class _NoUpdate: