ESBuild define option can break adapter-node assetsMiddleware #2581

Describe the bug

I switched from another adapter to use node adapter and had esbuild options with define. That basically overwrites esbuild_app_dir defined by the adapter breaking assetsMiddleware. A symptom is rather odd as all assets are responding to status code 500 with no clue why.

Maybe the adapter should warn the user if they overwrite the esbuild_app_dir property from define or the documentation could mention it. Now you can figure it out but it's not that obvious.

Reproduction

In svelte.config.js configure node adapter like:

adapterNode({
  esbuild(defaultOptions) {
    return {
      ...defaultOptions,
      define: {
        foo: 'bar'
      }
    };
  }
});

Build, run node build and check broken http://localhost:3000 site.

Fix is to do configuration e.g.:

adapterNode({
  esbuild(defaultOptions) {
    defaultOptions.define = {
      ...defaultOptions.define,
      foo: 'bar'
    }
    return defaultOptions;
  }
});

Logs

No response

System Info

System:
    OS: macOS 11.5.2
    CPU: (4) x64 Intel(R) Core(TM) i5-6267U CPU @ 2.90GHz
    Memory: 63.46 MB / 8.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 14.16.1 - /usr/local/bin/node
    Yarn: 1.22.4 - /usr/local/bin/yarn
    npm: 6.14.12 - /usr/local/bin/npm
  Browsers:
    Chrome: 94.0.4606.71
    Safari: 14.1.2
  npmPackages:
    @sveltejs/adapter-node: ^1.0.0-next.53 => 1.0.0-next.53
    @sveltejs/adapter-static: ^1.0.0-next.13 => 1.0.0-next.20
    @sveltejs/kit: 1.0.0-next.180 => 1.0.0-next.180
    svelte: ^3.34.0 => 3.43.1

Severity

annoyance

Additional Information

No response