Getting the no-modules TypeScript *.d.ts Files Working

[aaron-human]

Partially based on #693.

The current --target no-modules TypeScript declaration files don't correctly describe what the JS interface looks like:

• The functions exported via extern { and #[wasm_bindgen] are stored in the wasm_bindgen namespace, but the TypeScript declaration files don't put them in any namespace.
• Everything else at the root level of the TypeScript file was exportd. As of TypeScript 3.8.3, that meant it wasn't visible. So those were switched over to declare statements.

This tries to fix the above by adjusting the output for just no-modules. It also removes the bunch of extra spaces at the end of the declaration file.

As an example, the output went from:

/* tslint:disable */
/* eslint-disable */
/**
* @param {number} id
*/
export function call_in(id: number): void;

export type InitInput = RequestInfo | URL | Response | BufferSource | WebAssembly.Module;

export interface InitOutput {
  readonly memory: WebAssembly.Memory;
  readonly call_in: (a: number) => void;
}

/**
* If `module_or_path` is {RequestInfo} or {URL}, makes a request and
* for everything else, calls `WebAssembly.instantiate` directly.
*
* @param {InitInput | Promise<InitInput>} module_or_path
*
* @returns {Promise<InitOutput>}
*/
export default function init (module_or_path?: InitInput | Promise<InitInput>): Promise<InitOutput>;
        

To:

declare namespace wasm_bindgen {
	/* tslint:disable */
	/* eslint-disable */
	/**
	* @param {number} id
	*/
	export function call_in(id: number): void;
	
}

declare type InitInput = RequestInfo | URL | Response | BufferSource | WebAssembly.Module;

declare interface InitOutput {
  readonly memory: WebAssembly.Memory;
  readonly call_in: (a: number) => void;
}

/**
* If `module_or_path` is {RequestInfo} or {URL}, makes a request and
* for everything else, calls `WebAssembly.instantiate` directly.
*
* @param {InitInput | Promise<InitInput>} module_or_path
*
* @returns {Promise<InitOutput>}
*/
declare function wasm_bindgen (module_or_path?: InitInput | Promise<InitInput>): Promise<InitOutput>;

Testing

When I ran cargo test and cargo test --target wasm32-unknown-unknown on my local setup, it reported all passes.

[alexcrichton]

Thanks for this! Would it be possible to add tests for this specifically too? I believe crates/typescript-tests doesn't currently use --no-modules, but perhaps a separate entry point and/or a separate test for --no-modules could be added?

Other than that the changes look great here!

[aaron-human]

Ok, I'll see if I can setup some tests.

[aaron-human]

Ok, the tests should now try to build with no-modules and then verify that TypeScript doesn't reject the built typescript_tests.d.ts. That's at least the file I usually use. Not sure if the *.bg.d.ts files also need to be tested. Or if the files need to be built against something (i.e. to produce an actual JS output file). What's in now was enough to catch when I manually dumped a junk string into typescript_tests.d.ts, so it's at least validating the syntax.

[realtimetodie]

@alexcrichton

[alexcrichton]

Thanks! For the test though it looks like this just asserts that it parses correctly, but could some JS be written which consumes the wasm-bindgen generated JS? That way we can ensure the expected idioms all typecheck and information is all listed as we'd expect.

[aaron-human]

@alexcrichton The tests now build the (no-modules) *.d.ts files against *.ts files very similar to those in src. The exact *.ts files were modified to try and remove the import statements and otherwise switch things away from using JS modules. I was aiming to avoid copying/committing the modified *.ts files in src; didn't want to make future maintainers have to manually keep the two variants in sync.

[aaron-human]

Any chance this will get merged? It should be ready to review.

[alexcrichton]

Er apologies I missed that this was ready!

I'm not sure what the test is doing though, what's with all the sed? I would hope that we wouldn't have to doctor the output, otherwise that seems like a bug that needs fixing in wasm-bindgen.

[aaron-human]

The testing changes try to re-use the existing typescript testing that have been setup for the "--target web" case. The sed and grep calls in the script are to copy TypeScript files from "src" into a new (temporary) "src_no_modules" directory while also renaming things inside the files so they'll work with --target no-modules rather than --target web. I've added more comments so it's clearer that this is going on. Though the overview is that:

• The files have dropped any lines with "import". Since "no-modules" has no modules, imports aren't needed.
• The "wbg" namespace (which is where the tests imported the API to) has been replaced with "wasm_bindgen" (the namespace that "no-modules" exports into).
• I skipped all the TypeScript test files that mentioned importing the "../pkg/typescript_tests_bg.wasm" (by excluding files with "_bg.wasm") as I don't know what that file does.

I was aiming to re-use the existing tests rather than writing up new ones, as I'm not too well versed in all of the binding generation functionality. (The project that got me to set this up really only used "call Rust from JS" and "call JS from Rust" with fairly simple argument/return types.) I also figured it'd be nice to not have separate files for testing "--target web" vs "--target no-modules".

[alexcrichton]

Ah I see, thanks for clarifying! Sounds good to me!