Remove faulty location.href fallback and disable --split-linked-modules by default

[daxpedda]

This removes the faulty fallback to location.href on the no-modules target.

The problem is that if you are in a worker and using importScripts(), location.href can never return the path to the imported script, the shim, which is what we want, instead location.href will return the path to the script that starts the worker, which is not useful in this context and in fact will break any path created for linked modules.

Additionally it disables --split-linked-modules by default when using wasm-bindgen-cli-support, which was probably an oversight. In return I added a new environment variable WASM_BINDGEN_SPLIT_LINKED_MODULES for wasm-bindgen-test-runner to enable it for whomever requires it.

Fixes #3277.

[lukaslihotzki]

I'm sorry for the trouble my PR caused.

Can script_src simply be set to a relative path instead? Like ./filename.js (with the filename wasm-bindgen uses). Then, link_to! would also just return relative paths. (Relative paths break web pages using the history API to change the current URL, but this isn't applicable to workers.)

Edit: This may not work if relative paths are still resolved to the original URL and not the importScripts-URL. However, can we use this: https://github.com/chemicstry/wasm_thread/blob/main/src/script_path.js

[Liamolucko]

Can script_src simply be set to a relative path instead? Like ./filename.js (with the filename wasm-bindgen uses). Then, link_to! would also just return relative paths. (Relative paths break web pages using the history API to change the current URL, but this isn't applicable to workers.)

No, because relative paths get resolved by fetch, new Worker etc. relative to location.href, not to the path of the current file. So, it runs into the the same problems as setting script_src to location.href.

[lukaslihotzki]

Maybe I should not have hidden this in an edit, but have you seen my suggestion to use https://github.com/chemicstry/wasm_thread/blob/main/src/script_path.js?

[daxpedda]

Edit: This may not work if relative paths are still resolved to the original URL and not the importScripts-URL. However, can we use this: https://github.com/chemicstry/wasm_thread/blob/main/src/script_path.js

Just tried it and it does work indeed, but I don't think wasm-bindgen should use this, it isn't exactly stable or standardized, to say the least, it's a pretty hacky workaround.

[lukaslihotzki]

I looked it up and Error.stack is indeed undefined by the ES standard.