From 80f668b04cd8bce518afc318f73da6dc9a1eb94c Mon Sep 17 00:00:00 2001
From: Divyessh Maheshwari <divyesshm@gmail.com>
Date: Fri, 28 Oct 2022 17:41:32 +0530
Subject: [PATCH 1/3] fix custom 404 page error in multi page application

---
 dash/dash.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/dash/dash.py b/dash/dash.py
index 11855ce584..98cd13509b 100644
--- a/dash/dash.py
+++ b/dash/dash.py
@@ -2064,7 +2064,14 @@ def update(pathname, search):
                 # get layout
                 if page == {}:
                     module_404 = (
-                        ".".join([self.pages_folder, "not_found_404"])
+                        ".".join(
+                            [
+                                self.pages_folder.replace("\\", "/")
+                                .lstrip("/")
+                                .replace("/", "."),
+                                "not_found_404",
+                            ]
+                        )
                         if self.pages_folder
                         else "not_found_404"
                     )

From bd7cbce4009c46e7749f2d9b0c54930f8fa82547 Mon Sep 17 00:00:00 2001
From: Divyessh Maheshwari <divyesshm@gmail.com>
Date: Wed, 2 Nov 2022 06:32:03 +0530
Subject: [PATCH 2/3] Add suggested modification

---
 dash/dash.py | 21 +++++----------------
 1 file changed, 5 insertions(+), 16 deletions(-)

diff --git a/dash/dash.py b/dash/dash.py
index 98cd13509b..239d59e773 100644
--- a/dash/dash.py
+++ b/dash/dash.py
@@ -2063,22 +2063,11 @@ def update(pathname, search):
 
                 # get layout
                 if page == {}:
-                    module_404 = (
-                        ".".join(
-                            [
-                                self.pages_folder.replace("\\", "/")
-                                .lstrip("/")
-                                .replace("/", "."),
-                                "not_found_404",
-                            ]
-                        )
-                        if self.pages_folder
-                        else "not_found_404"
-                    )
-                    not_found_404 = _pages.PAGE_REGISTRY.get(module_404)
-                    if not_found_404:
-                        layout = not_found_404["layout"]
-                        title = not_found_404["title"]
+                    for module, page in _pages.PAGE_REGISTRY.items():
+                        if module.split(".")[-1] == "not_found_404":
+                            layout = page["layout"]
+                            title = page["title"]
+                            break
                     else:
                         layout = html.H1("404 - Page not found")
                         title = self.title

From 93c9de19551755753929e1f2af26ef33ef9fc431 Mon Sep 17 00:00:00 2001
From: alexcjohnson <alex@plot.ly>
Date: Wed, 2 Nov 2022 11:14:27 -0400
Subject: [PATCH 3/3] changelog for pages 404 fix

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2894d0ecf5..907e3ba438 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 ### Fixed
 
+- [#2292](https://github.com/plotly/dash/pull/2292) Pages: find the 404 page even if `pages_folder` is nested, or the 404 page is nested inside `pages_folder`.
 - [#2265](https://github.com/plotly/dash/pull/2265) Removed deprecated `before_first_request` as reported in [#2177](https://github.com/plotly/dash/issues/2177).
 - [#2257](https://github.com/plotly/dash/pull/2257) Fix tuple types in the TypeScript component generator.