Return contentType in transformRequest

[nitedani]

Description

I would like to use transformRequest for retrieving assets through an rpc connection between a worker and the Vite dev server.
My issue is that transformRequest doesn't return the content-type of the result. I need to set the right content-type in the response sent to the browser.

An alternative would be to support passing a standard Request to the vite middlewares, returning a standard Response. #15389

This is not a blocker. I can always just proxy the requests through http between browser<->worker<->vite.

Suggested solution

Add contentType to the transformRequest return type.

Alternative

Support passing a standard Request to the vite middlewares, returning a standard Response.
#15389

Additional context

No response

Validations

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• Read the Contributing Guidelines.
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• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[hi-ogawa]

I think ViteDevServer.transformRequest is meant to return javascript for most of the cases?

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

Lines 201 to 217 in 8b11fea

	// resolve, load and transform using the plugin container
	const result = await transformRequest(url, server, {
	html: req.headers.accept?.includes('text/html'),
	})
	if (result) {
	const depsOptimizer = getDepsOptimizer(server.config, false) // non-ssr
	const type = isDirectCSSRequest(url) ? 'css' : 'js'
	const isDep =
	DEP_VERSION_RE.test(url) || depsOptimizer?.isOptimizedDepUrl(url)
	return send(req, res, result.code, type, {
	etag: result.etag,
	// allow browser to cache npm deps!
	cacheControl: isDep ? 'max-age=31536000,immutable' : 'no-cache',
	headers: server.config.server.headers,
	map: result.map,
	})
	}

I remember there's .css?direct (which I think vike uses?) but this might be the only odd ball which returns text/css content type. If that's the case, then you could check ?direct on your runtime? If that's not the case, then I wonder what's the other possible content types.