Wasm-pack: Make debug builds the default

[fitzgen]

cargo does dev builds by default and we should match that behavior.

We should also match the terminology: dev instead of debug.

[alexcrichton]

I think there's a strong point in favor of this to match what Cargo does, having as little deviation from Cargo as possible in wasm-pack makes it more familiar to Rust developers and also makes general information about Cargo applicable to wasm-pack as well.

I also think, though, that this is arguably a good point to diverge from Cargo. A fair number of users have popped up on our channels asking why code is so slow, and it often comes back to manual wasm-bindgen usage without --release when building in Cargo. Most users of wasm-pack are probably brand new to Rust (and maybe wasm too!) and having our best foot forward by default may not be a bad idea.

I think I could personally go either way on this!

[fitzgen]

Yeah me too honestly.

I do feel more stronly about matching terminology, though.

[ashleygwilliams]

i personally think that diverging is the right choice here, but am open to being convinced otherwise. i'm glad that we switched to match terminology- do you feel like we can close this for now and revisit closer to 1.0?

[alexcrichton]

I think it's fine to take care of more pressing issues and revisit this possibly after 1.0

[chinedufn]

i personally think that diverging is the right choice here, but am open to being convinced otherwise.

Migrated a project to wasm-pack a few days ago and I'm just now realizing that I've been using release builds the entire time.

Noticed certain things that used to work (mostly things behind cfg(debug_assertions) not work lately but didn't link it to using wasm-pack since I made a bunch of other changes before I noticed.

I'm very used to dev builds being the default so it caught be my surprise that release builds are the default.

In some ways I can understand that for people new to Rust and coming in through WASM --release might save them some performance confusion, but even so they'll be getting slower builds as they try to iterate (like silly me was.. can't believe I didn't notice.. ha!) before they realize that they can speed things up with a debug build.

So.. for me it makes sense to be consistent with the rest of the Rust toolchain, but I can of course see that the flood of "why is my code slow!" is a concern.

---

Potential Solution

1. By default wasm-pack build prints a very loud very noticeable message letting you know that you are running a debug or release build (whatever is decided to be best)

2. This message also lets you know that you can silence this message with some --quiet flag or something..

3. No more performance confusion or inconsistency-with-cargo confusion (unless you just don't notice the loud message)

Any downsides / challenges here? Anything that I've overlooked? Mainly just don't want someone else to feel the same confusion that I just felt to the point where I was looking up if cfg(debug_assertions) still worked ha!

[chinedufn]

Potential Solution 2

Don't default to any profile and make passing in --dev/release/profile required.

Upside being not relying on people reading stdout / downside being one extra thing that's required to get started.

[chinedufn]

Sorry one other thing that comes to mind!

I just went to go to all of the places that I use wasm-pack test to set it to use a debug build, but it looks like wasm-pack test already defaults to debug builds.

So whether or not build/test should be consistent is yet another consideration here.

Ok I think I'm done... cheers!

[ibaryshnikov]

+1 for making --dev builds by default. Release builds confuse me too. @chinedufn offered a great solution with logging.
Here are the current messages

cargo build:

Finished dev [unoptimized + debuginfo]

cargo build --release:

Finished release [optimized]

wasm-pack build:

.
.
Finished release [optimized]
.
.
📦   Your wasm pkg is ready to publish

wasm-pack build --debug:

.
.
Finished dev [unoptimized + debuginfo]
.
.
📦   Your wasm pkg is ready to publish

Why is the last message pkg is ready to publish when it's unoptimized + debuginfo?