"src.subarray is not a function" in blitBuffer

[tmcw]

My previous bug report in #20616 around blitBuffer was fixed, but this surfaced a bug a few lines below the old one (both bugs were surfaced with this testcase that tries to use web-push).

The error is src.subarray is not a function, and can be replicated with the same code sample as in the previous bug report:

➜  val.town git:(v3) ✗ deno
Deno 1.37.1
exit using ctrl+d, ctrl+c, or close()
REPL is running with all permissions allowed.
To specify permissions, run `deno repl` with allow flags.
> import { Buffer } from "node:buffer"
undefined
> Buffer.from('ZmRzYWZkYWZkc2E', 'base64url')
Uncaught TypeError: src.subarray is not a function
    at blitBuffer (ext:deno_node/internal/buffer.mjs:1779:15)
    at Uint8Array.base64urlWrite (ext:deno_node/internal/buffer.mjs:691:10)
    at Object.write (ext:deno_node/internal/buffer.mjs:2195:11)
    at Uint8Array.write (ext:deno_node/internal/buffer.mjs:794:14)
    at fromString (ext:deno_node/internal/buffer.mjs:214:22)
    at _from (ext:deno_node/internal/buffer.mjs:119:12)
    at Function.from (ext:deno_node/internal/buffer.mjs:157:10)
    at <anonymous>:2:8

As far as I can tell, the blitBuffer method is usually passed an Array as its first argment:

deno/ext/node/polyfills/internal/buffer.mjs

Line 748 in d5b6c63

utf8ToBytes(string, this.length - offset),

But the subarray method only exists on TypedArray instances. It seems like this file - buffer.mjs - has neither tests nor types. Maybe this could get some test coverage?

[bartlomieju]

CC @aapoalas could you take a look?

[aapoalas]

I opened a fix PR. This file is tested by the Node tests but apparently either some of them are disabled or Node's test coverage isn't too great?