add an option to pass an arbitrary set of arguments to cargo build

[torkve]

Fixes #455.
Example: wasm-pack build -- --features "feature-a feature-b"

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[ashleygwilliams]

@torkve thanks so much for this! would you mind adding a test? and potentially an example to the documention? thanks so much!

[torkve]

I've added a test and a bit of docs, however English is not my native language, so feel free to fix it.

[torkve]

Are there any news with this PR? :-)

[ashleygwilliams]

hey @torkve - thank you for this and sorry for the lack of and delay of reply. i'm currently a little blocked on getting 0.6.0 out. my only concern with this PR is that we may also want to pass extra unsupported arguments to wasm-bindgen and this interface poses a bit of a conflict with that. if it were gated by a flag (perhaps --cargo-args) that might work better? i need to perhaps think on exactly what that interface should be. does that concern make any sense? if you have thoughts i'd be happy to hear them!

[torkve]

I suppose you are correct from the POV that options should be similar. --cargo-args and --wasm-bindgen-args would be more intuitive than my implementation.
The reason I wrote it this very way, is the special additional quotation required otherwise. For example, two ways to specify feature set:

$ wasm-pack ... -- --features "feature-a feature-b"
$ wasm-pack ... --cargo-args "--features 'feature-a feature-b'"

Second variant is not pretty enough. And if one would need to escape some characters, it'll become even more complicated.

While currently I do not see any possible complex values in wasm-bindgen arguments, I think it would not be the best option to make it look just like wasm-pack ... --wasm-bindgen-args "..." -- --cargo-args...

May be every wasm-bindgen option just should be exposed in wasm-pack?

[danwilhelm]

Would setting env vars to pass arguments possibly be a solution? That might make it somewhat consistent with cargo, since RUSTFLAGS could be set as well to send some flags to rustc.

Perhaps @alexcrichton might have ideas? I believe he contributed to passing arguments to rustc from cargo.

[alexcrichton]

I'd personally advocate for a design that:

• Like this PR, accepts arbitrary arguments after -- to pass to Cargo
• Adds most first-class options from Cargo to wasm-pack build, like --features, --test, etc.
• Also accepts arbitrary arguments to wasm-bindgen, but as first-class options to wasm-pack. The wasm-bindgen tool is basically an internal implementation detail of wasm-pack, whereas cargo is a first-class feature. I'd much rather prominently support Cargo than wasm-bindgen

[ashleygwilliams]

after thinking about it- i'm inclined to agree with @alexcrichton! i think this looks great- i'll work to get it into 0.6.0