[web_server] Shorten the offline hint

esphome/components/web_server/__init__.py

@@ -2,7 +2,6 @@ from __future__ import annotations
 
 import base64
 import gzip
-from html import escape as html_escape
 import logging
 import re
 
@@ -349,17 +348,13 @@ def build_index_html(config: ConfigType, offline_hint: bool = True) -> str:
     if js_url and offline_hint:
         # The interface is downloaded from the internet. Show a hint instead of a blank
         # page when the browser cannot reach it, which is common in WiFi AP mode.
+        # Kept short: this string lives in flash on every build without captive_portal.
         hint = (
-            f"Could not load the web interface from {js_url}. This browser needs internet "
-            "access to download it. To serve it from the device instead (for example in "
-            "WiFi access point mode), set local: true under web_server: in the YAML "
-            "configuration and install the firmware again."
+            "Could not download the web interface. This browser needs internet access, "
+            "or set local: true under web_server: in the YAML and reinstall so the "
+            "device serves it."
         )
-        # Escape for a JS single quoted string inside a double quoted HTML attribute.
-        hint_js = html_escape(
-            hint.replace("\\", "\\\\").replace("'", "\\'"), quote=True
-        )
-        html += f'<script src="{js_url}" onerror="document.body.innerText=\'{hint_js}\'"></script>'
+        html += f'<script src="{js_url}" onerror="document.body.innerText=\'{hint}\'"></script>'
     elif js_url:
         html += f'<script src="{js_url}"></script>'
     html += "</body></html>"

tests/unit_tests/components/test_web_server.py

@@ -10,15 +10,8 @@ def test_build_index_html_has_offline_hint() -> None:
         {CONF_JS_URL: "https://oi.esphome.io/v2/www.js", CONF_CSS_URL: ""}
     )
     assert '<script src="https://oi.esphome.io/v2/www.js" onerror="' in html
+    assert "document.body.innerText='Could not download the web interface." in html
     assert "local: true" in html
-    assert "https://oi.esphome.io/v2/www.js. This browser needs internet" in html
-
-
-def test_build_index_html_escapes_hint() -> None:
-    """Quotes in the script URL cannot break out of the onerror attribute."""
-    html = build_index_html({CONF_JS_URL: "http://x/a'b\"c.js", CONF_CSS_URL: ""})
-    assert "onerror=\"document.body.innerText='" in html
-    assert "a\\&#x27;b&quot;c.js" in html
 
 
 def test_build_index_html_hint_disabled() -> None: