cli-support: Make default_module_path optional

[realtimetodie]

Adds a new CLI flag --omit-default-module-path, to control the default_module_path generated JavaScript code.

The default_module_path generated JavaScript code is enabled by default, users need to explicitly disable it by setting the --omit-default-module-path CLI flag

$ wasm-bindgen --omit-default-module-path

Documentation

$ wasm-bindgen --help

Options:

...

--omit-default-module-path       Don't add WebAssembly fallback imports in generated JavaScript

Affected JavaScript code

$ wasm-bindgen --target web

async function init(input) {
    if (typeof input === 'undefined') {
        input = import.meta.url.replace(/\.js$/, '_bg.wasm');
    }
    ...

$ wasm-bindgen --target no-modules

async function init(input) {
    if (typeof input === 'undefined') {
        let src;
        if (typeof document === 'undefined') {
            src = location.href;
        } else {
            src = document.currentScript.src;
        }
        input = src.replace(/\\.js$/, '_bg.wasm');
    }
    ...

[realtimetodie]

@alexcrichton

[alexcrichton]

Thanks for this! I think though due to docopt the default is still false? Can a test be added for this as well?

[realtimetodie]

I changed the CLI option to the flag --omit-default-module-path and added tests to the CLI test suite.

[realtimetodie]

The Windows tests are flaky, I had to force-push it multiple times.

[alexcrichton]

Ok thanks again for the PR!