There are hashes for the images in Leaflet. The leaflet.css file references these images, and if their URLs change, the .map file will break. One solution is to recompile leaflet.css from the .less files; the other solution is to avoid adding the hashes. Commit
2761f78 implements the second choice (no hash).

The code is not very clean:

• the variable names might neither matched their usages nor being harmonized
• there are multiple new imports for example in webapp.py, not sure this is the right place

but this issue aside, it seems to be good enough.

Isn't it simpler/better to use [hash] from roolup.js / e.g.:

index f8d3e6757..45ae8a574 100644
--- a/client/simple/vite.config.js
+++ b/client/simple/vite.config.js
@@ -107,9 +107,9 @@ export default defineConfig({
 
       // file naming conventions / pathnames are relative to outDir (PATH.dist)
       output: {
-        entryFileNames: "[name].js",
-        chunkFileNames: "[name].js",
-        assetFileNames: "[name].[ext]",
+        entryFileNames: "[name].[hash].js",
+        chunkFileNames: "[name].[hash].js",
+        assetFileNames: "[name].[hash].[ext]",
         // Vite does not support "rollupOptions.output.sourcemap".
         // Please use "build.sourcemap" instead.
         // sourcemap: true,

with ./manage vite.simple.build we get a hash values in the file names of JS and CSS files and the manifest (searxng/searx/static/themes/simple/manifest.json) is like this:

{
  "js/searxng.head.js": {
    "file": "js/searxng.head.min.5vbFT7cW.js",
    "name": "js/searxng.head.min",
    "src": "js/searxng.head.js",
    "isEntry": true
  },
  "js/searxng.js": {
    "file": "js/searxng.min.CoHvYy0-.js",
    "name": "js/searxng.min",
    "src": "js/searxng.js",
    "isEntry": true
  },
  "less/rss.less": {
    "file": "css/rss.min.aJKEdM9t.css",
    "src": "less/rss.less",
    "isEntry": true
  },
  "less/style-ltr.less": {
    "file": "css/searxng.min.vfsuff-7.css",
    "src": "less/style-ltr.less",
    "isEntry": true
  },
  "less/style-rtl.less": {
    "file": "css/searxng-rtl.min.DI7zUmR_.css",
    "src": "less/style-rtl.less",
    "isEntry": true
  }
}

The custom code in this PR add a hash for the all the files (with explicite exceptions)
Can roolup do that, including for example leaflet.js, img/searxng.svg ?
How does it handle references between the ressources ? For example

At the moment, this is not possible because we are copying the assets (images).

With the PR:

• migrate web-client development from grunt to vite #4284

we moved to vite, but at the moment we are not using it properly yet, we are currently only doing with it what we did before with grunt.

For example, we currently only use the build process and assets such as images are copied .. the path to real client development is not yet complete (the migration to vite is not finished). As soon all objects are managed by vite at some point, then all this is possible, but in the current state the framework is not aware of the connection between CSS, JS and assets.

Ok, I don't know what you want to prioritize.
The PR is here, feel free to merge / put aside / close / whatever.