Vite dev server crashes with appType mpa on root URI

[wolfgangwalther]

Describe the bug

Using appType: mpa without a <root>/index.html file will crash when requesting / instead of returning 404.

See #10336 (comment) for the change that introduced this.

Reproduction

https://stackblitz.com/edit/vitejs-vite-t9a2jr?file=vite.config.js

Steps to reproduce

Run the dev server and request /.

System Info

System:
    OS: Linux 5.15 Alpine Linux
    CPU: (32) x64 AMD Ryzen 9 3950X 16-Core Processor
    Memory: 104.02 GB / 125.75 GB
    Container: Yes
    Shell: 1.35.0 - /bin/ash
  Binaries:
    Node: 19.0.1 - /usr/local/bin/node
    Yarn: 3.2.4 - /usr/local/bin/yarn
    npm: 8.19.2 - /usr/local/bin/npm
  npmPackages:
    @vitejs/plugin-vue2: 2.0.1 => 2.0.1
    vite: 3.2.3 => 3.2.3

Used Package Manager

yarn

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[sun0day]

For a quick solution, maybe we should allow mpa mode fallback to index.html as spa does.

[bluwy]

Error:

21:36:21 [vite] Internal server error: Cannot read properties of undefined (reading 'charAt')

Looks like it's failing at:

	        if(rewriteTarget.charAt(0) !== '/') {
	          logger(
	            'We recommend using an absolute path for the rewrite target.',
	            'Received a non-absolute rewrite target',
	            rewriteTarget,
	            'for URL',
	            req.url
	          );
	        }

	        logger('Rewriting', req.method, req.url, 'to', rewriteTarget);
	        req.url = rewriteTarget;
	        return next();

We could return req.url here so it's a no-op to fix it:

vite/packages/vite/src/node/server/middlewares/htmlFallback.ts

Lines 24 to 26 in 0d73473

	if (spaFallback) {
	return `/index.html`
	}

[github-actions]

Hello @wolfgangwalther. We like your proposal/feedback and would appreciate a contribution via a Pull Request by you or another community member. We thank you in advance for your contribution and are looking forward to reviewing it!