ntl dev won't start without index.html

[ghost]

Describe the bug

Similar to #4845, Netlify CLI won't start on port 8888, gets stuck waiting for framework.

◈ Starting Netlify Dev with Eleventy

> [email protected] start
> eleventy --serve

[11ty] Writing _site/page/index.html from ./page.md (liquid)
[11ty] Wrote 1 file in 0.07 seconds (v1.0.1)
[11ty] Watching…
[Browsersync] Access URLs:
 -----------------------------------
    Local: http://localhost:8080
 External: http://192.168.0.137:8080
 -----------------------------------
[Browsersync] Serving files from: _site
⠴ Waiting for framework port 8080. This can be configured using the 'targetPort' property in the netlify.toml

Through testing, this is due to the lack of an index file. If page.md (see demo repository) is renamed to index.md then ntl dev starts on port 8888.

◈ Starting Netlify Dev with Eleventy

> [email protected] start
> eleventy --serve

[11ty] Writing _site/index.html from ./index.md (liquid)
[11ty] Wrote 1 file in 0.10 seconds (v1.0.1)
[11ty] Watching…
[Browsersync] Access URLs:
 -----------------------------------
    Local: http://localhost:8080
 External: http://192.168.0.137:8080
 -----------------------------------
[Browsersync] Serving files from: _site
✔ Waiting for framework port 8080. This can be configured using the 'targetPort' property in the netlify.toml

   ┌─────────────────────────────────────────────────┐
   │                                                 │
   │   ◈ Server now ready on http://localhost:8888   │
   │                                                 │
   └─────────────────────────────────────────────────┘

[11ty] File changed: .netlify/edge-functions-import-map.json
[11ty] Writing _site/index.html from ./index.md (liquid)
[11ty] Wrote 1 file in 0.01 seconds (v1.0.1)
[11ty] Watching…
[Browsersync] Reloading Browsers...

Note: Renaming index.md back to page.md after this results in ntl dev starting as there is (now) an index.html file in _site.

The only option (that I have found if not wanting a root index.html) is to configure ntl dev with a custom framework (see netlify.toml in demo repository or below) in which case it will start without the presence of index.html.

Steps to reproduce

Configure a basic Eleventy project (or clone https://github.com/jasiqli/11ty-test)

Run ntl dev *(or ntl dev -o)

Configuration

##
## If there is no `index.html` in the build output, a custom framework needs
## setting so that `netlify dev` will start.
##

# [dev]
#   framework = "#custom"
#   command = "eleventy --serve"
#   targetPort = 8080

Environment

  System:
    OS: macOS 12.5
    CPU: (12) x64 Intel(R) Core(TM) i5-10600 CPU @ 3.30GHz
    Memory: 33.07 MB / 16.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 16.16.0 - /usr/local/bin/node
    npm: 8.11.0 - /usr/local/bin/npm
  npmGlobalPackages:
    netlify-cli: 10.17.4

[ghost]

Closing as not important to me any more.