Allow plugins to overwrite built-in loaders

[marvinhagemeister]

With this change default loaders are only added if no other prefix is present already in the path id.

I've tried a few other alternatives to the changes here, but they all end up working around limitations in rollup's plugin system and make user plugins pretty verbose to write. The gist of the problem is that with custom plugins we'll have to deal with recursive resolution early on.

The way that this usually occurs is that a custom plugin strips their prefix and passes the stripped id on to this.resolve. The plugins resolved by that have no knowledge about the original path and just see ./foo.json and add their prefix, because they assume that this is the full import specifier. This leads to errors like the one outlined in #449 where my-json:./foo.json will be turned into my-json:json:./foo.json. The changes in this PR ensure that my-json:./foo.json stays that way.

We essentially split up resolution and applying default loaders into two distinctive concerns. The plugins itself should only match when their prefix is present. The defaultLoader plugin ensures that "raw" specifiers like ./foo.json are turned into json:./foo.json from where we can just reused the existing resolution semantics.

Fixes #449

[changeset-bot]

🦋 Changeset detected

Latest commit: 31c83e7

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

This PR includes changesets to release 1 package

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wmr	Patch

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[github-actions]

Size Change: -47 B (0%)

Total Size: 733 kB

Filename	Size	Change
packages/wmr/wmr.cjs	700 kB	-47 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
examples/demo/dist/about/index.html	667 B	0 B
examples/demo/dist/assets/Calendar.********.css	702 B	0 B
examples/demo/dist/assets/style.********.css	386 B	0 B
examples/demo/dist/chunks/class-fields.********.js	200 B	0 B
examples/demo/dist/chunks/compat.********.js	15.3 kB	0 B
examples/demo/dist/chunks/index.********.js	199 B	0 B
examples/demo/dist/chunks/json.********.js	235 B	0 B
examples/demo/dist/chunks/prerender.********.js	2.41 kB	0 B
examples/demo/dist/class-fields/index.html	646 B	0 B
examples/demo/dist/compat/index.html	1.5 kB	0 B
examples/demo/dist/env/index.html	722 B	0 B
examples/demo/dist/error/index.html	656 B	0 B
examples/demo/dist/files/index.html	688 B	0 B
examples/demo/dist/index.********.js	7.23 kB	0 B
examples/demo/dist/index.html	714 B	0 B
examples/demo/dist/json/index.html	666 B	0 B
examples/demo/dist/lazy-and-late/index.html	668 B	0 B

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[danielweck]

I am getting uncaught errors ERR_HTTP_HEADERS_SENT Cannot set headers after they are sent to the client since around the time this PR was merge into the main branch. I am not 100% this PR is responsible though. Investigating...

(node:59869) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:558:11)
    at ServerResponse.c.writeHead (/PATH_TO/node_modules/wmr/wmr.cjs:2:2663686)
    at WZe (/PATH_TO/node_modules/wmr/wmr.cjs:2:2660743)
    at Array.<anonymous> (/PATH_TO/node_modules/wmr/wmr.cjs:2:2662442)
    at u (/PATH_TO/node_modules/wmr/wmr.cjs:2:2648010)
    at l (/PATH_TO/node_modules/wmr/wmr.cjs:2:2647978)
    at Array.<anonymous> (/PATH_TO/node_modules/wmr/wmr.cjs:2:2662478)
    at u (/PATH_TO/node_modules/wmr/wmr.cjs:2:2648010)
    at l (/PATH_TO/node_modules/wmr/wmr.cjs:2:2647978)
    at Array.<anonymous> (/PATH_TO/node_modules/wmr/wmr.cjs:2:2801453)
(node:59869) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 30)

[danielweck]

Okay, the above exception is thrown whenever I hard-refresh the page with CMD+R (any route, lazy included).

[danielweck]

I tested this PR. The main goal is indeed achieved, and as demonstrated by your integration tests, this closes #449
Well done 👍 :)

However, this PR breaks "nested absolute path import" as described here:
#449 (comment)

...I will be searching for a workaround for this, as it is an important feature in a codebase where relative paths such as ../../../stuff.js are a pain. I will let you know ;)

[danielweck]

Ah, interesting: the "nested absolute path import" only occurs with JSON files, not SVG. I will post a new issue once I've narrowed this down.

  wmr:middleware  /~/pages/test.json -> json:~/pages/test.json file: json:/PATH_TO/public/~/pages/test.json
  middleware:npm  "preact-iso/hydrate"
404 /@json/~/pages/test.json - File not found
  at  (:-1:-1)

[danielweck]

Okay, I found a workaround for JSON files, using the same trick I used before for SVG files :)

In the text: plugin's resolveId(id, importer):

if (config.mode === 'start') id = `${id}${'\0'}`;

..and in load(id):

if (config.mode === 'start') id = id.replace(/\0$/, '');

I am filing a new issue.

[marvinhagemeister]

@danielweck thanks for giving the fix a go 👍 The path aliasing thing is next on my list and I think I have an idea of where things get weird.

[danielweck]

I filed this issue: #524