feat(cloudflare): experimental config redirection support

[pi0]

Nitro has introduced an experimental (opt-in) way to generate/extend wrangler.toml for cloudflare deployments (#2353, #2355).

The end goal is to leverage Cloudflare platform features such as Node compat v2 (hybrid) and Async Context with zero-config and ensure we can reliably enable these features.

However, overwriting the user config is not ideal or recommended.

Thanks to the huge huge efforts and collab with the Cloudflare team and @petebacondarwin, a new solution (~> cloudflare/workers-sdk#7442) is coming to allow frameworks like Nitro to generate a merged wrangler.toml in dist and config that redirects/points wrangler CLI and pages CI to it.

This PR is to experiment this new feature e2e from both sides.

Remarks

• As before, this feature is only effective when there is extra cloudflare.wrangler: {} config is provided
• New mode is opt-in via EXPERIMENTAL_WRANGLER_CONFIG env variable
• Old method is to be removed as soon as feat: add support for redirecting Wrangler to a generated config when running deploy commands cloudflare/workers-sdk#7442 is globally availble
• We currently resolve configs from rootDir, it might need to be changed to cwd() later for monorepo support (pending more tests)
• New support is added for reading wrangler.json from user
• Merging strategy is to be improved, however we always respect explicit user config in wrangler.toml|json over

Local testing

• pnpm build --stub
• EXPERIMENTAL_WRANGLER_CONFIG=1 p nitro build playground --preset cloudflare_pages

ℹ Generated playground/dist/_routes.json                                                                                        
ℹ Generated playground/dist/_headers                                                                                             
ℹ Generated playground/dist/_redirects                                                                                           
ℹ Generated playground/.wrangler/deploy/config.json                                                                              
ℹ Generated playground/dist/_worker.js/wrangler.json 

.wrangler/deploy/config.json:

{"configPath":"../../dist/_worker.js/wrangler.json"}

wrangler.toml (user)

compatibility_flags = [ "nodejs_als" ]
name = "nitro-test"
compatibility_date = "2024-09-19"

[assets]
directory = "./.output/public/"
binding = "ASSETS"

[durable_objects]
[[durable_objects.bindings]]
name = "$DurableObject"
class_name = "$DurableObject"

[[migrations]]
tag = "v1"
new_classes = [ "$DurableObject" ]

dist/_worker.js/wrangler.json

{
  "compatibility_flags": [
    "nodejs_als",
    "nodejs_als"
  ],
  "name": "nitro-test",
  "compatibility_date": "2024-09-19",
  "assets": {
    "directory": "./.output/public/",
    "binding": "ASSETS"
  },
  "durable_objects": {
    "bindings": [
      {
        "name": "$DurableObject",
        "class_name": "$DurableObject"
      }
    ]
  },
  "migrations": [
    {
      "tag": "v1",
      "new_classes": [
        "$DurableObject"
      ]
    }
  ]
}

[petebacondarwin]

Given this is using the cloudflare_pages plugin, this should not have an assets section in the user's wrangler.toml.
Nor should it have Durable Objects defined, since these are not valid in Pages projects.

This is likely to break the Pages CI.

Not a problem in real life because the user wouldn't have that. But in terms of testing, I will remove that from the wrangler.toml

[petebacondarwin]

For Pages projects that have a wrangler.toml it is required to have a pages_build_output_dir field in order that the config is considered for deployment. Otherwise it is completely ignored.

Depending on what you want the DX, you could either require the user to add that field themselves, or you could add it as part of the generation of wrangler.json. I think the latter is better, since I believe you want to generate a wrangler.json even if there is no user wrangler.toml.

[petebacondarwin]

Oh I see that you actively do not want the user to set this.
OK. But in that case you need to provide it automatically.

[petebacondarwin]

Perhaps add after the check?

    mergedConfig.pages_build_output_dir = nitro.options.output.publicDir;