refactor: Remove --preload flag

[rschristian]

What kind of change does this PR introduce?

Removal of a feature

Did you add tests for your changes?

Existing cover

Summary

Removes --preload flag from peact build.

Upon writing #1731 I came to notice that our system for creating preload tags was quite unsound. We rely entirely upon the assumption that the user's directory structure matches their router perfectly. If it doesn't, preload tags will not be generated correctly.

For example, assume the following directory structure:

src
--routes
----foo.js

This creates a chunk route-foo and generates a load manifest looking something like the following:

{
    "/foo": {
        "bundle.abcde.css": {
		"type": "style",
		"weight": 1
	},
	"bundle.abcde.js": {
		"type": "script",
		"weight": 1
	},
	"route-foo.chunk.abcde.js": {
		"type": "script",
		"weight": 0.9
	},
	"route-foo.chunk.abcde": {
		"type": "style",
		"weight": 0.9
	}
}

The problem here is that we've just equated routes/foo.js with /foo, without actually acknowledging what the router says of the matter.

import Foo from 'routes/foo.js';

<Router>
    <Foo path="/bar" />
</Router>

In this situation, preload tags will never be created as the chunks are attached to /foo which is never prerendered.

In a more realistic scenario, imagine we have routes/about and /about-us. Preload won't work as the route doesn't match the directory structure perfectly.

Fundamentally this feature is majorly flawed, and as such I'm removing it. I'll try to reimplement it if possible later, but I really don't think it can stay in this state. Even if a user knows exactly how this works (and that's asking a lot), it's way too easy to accidentally break.

Does this PR introduce a breaking change?

Yes.

The --preload flag is removed. There's no migration path at the time of writing, though hopefully that will change in the future.

[changeset-bot]

🦋 Changeset detected

Latest commit: 5e79f26

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
preact-cli	Major

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