Allow to fetch("file://")

[Nemo64]

The title says it all. I'd like if fetch could also open local files, just like the browser can if the origin ist file://.

There is even a test that checks that this does not work here:

deno/cli/tests/unit/fetch_test.ts

Lines 14 to 20 in e568ddf

	await assertThrowsAsync(
	async (): Promise<void> => {
	await fetch("file:///");
	},
	TypeError,
	"not supported",
	);

Allowing file:// could profit any library or script that really just needs the contents of a file and doesn't really care where it is.... just like deno run in fact.

At this moment, you'd have to implement some kind of wrapper.

async function readTextFile(url: URL): Promise<string> {
    if (url.protocol === 'file:' && typeof Deno.readTextFile !== 'undefined') {
        return await Deno.readTextFile(url.pathname)
    } else {
        const response = await fetch(url)
        return await response.text()
    }
}

There are a few things interesting points to look out for:

• Error code mapping aka: 404 = not found/file does not exist, 403 = unauthorized/--allow-read-missing/filemod
• Partial request?
• Post/Put request?

[lucacasonato]

Duplicate of #2150