Merge #351

351: Feature/wasm r=Dylan-DPC a=zrzka

# Description

This PR adds two new features:

* `stdweb`
* `wasm-bindgen`

These features are kind of _passthrough_ features, because they do nothing in the `uuid` crate itself. They're just passed to the `rand` crate to make the `uuid` crate working for the `wasm32-unknown-unknown` target.

# Motivation

I'm unable to generate random UUID (v4) when this crate is compiled for the `wasm32-unknown-unknown` target.

# Tests

I just added these features ...

```
- cargo test --features "v3"
- cargo test --features "v3 stdweb"
- cargo test --features "v3 wasm-bindgen"
```

... for all `v3` & `v4` & `v5` (`rand` crate is used in all these features) to the `script` section in the `.travis.yml`.

Not sure if it makes sense, but it can demonstrate that it's buildable at least.

I don't think that more tests are required unless you'd like to bring the whole `wasm-bindgen`, `wasm-pack`, ... machinery here. And it has no sense to do it, because goal of this PR is not to publish `uuid-rs` NPM package, just add the ability to compile & use it from the `wasm32-unknown-unknown` target.

# Related Issue(s)

* #350
* [now() doesn't work](balena-io-modules/balena-temen#37)

# Manual tests

My Cargo.toml:

```
[dependencies]
uuid = { features = ["v4"], git = "https://github.com/zrzka/uuid.git", branch = "feature/wasm" }

[target.wasm32-unknown-unknown.dependencies]
uuid = { features = ["wasm-bindgen"], git = "https://github.com/zrzka/uuid.git", branch = "feature/wasm" }
```

My `index.js`:

```
const bt = require('balena-temen');

console.log(
    bt.evaluate({
        "id": {
            "$$eval": "uuidv4()"
        }
    })
);
```

[uuidv4() implementation](https://github.com/balena-io-modules/balena-temen/blob/master/src/builtin/function/uuidv4.rs#L9-L11).

Output:

```
{ id: 'cefa2919-ff48-48ef-a231-e13697e23ed2' }
```


Co-authored-by: Robert Vojta <rvojta@me.com>

.travis.yml

@@ -11,19 +11,37 @@ matrix:
   - rust: nightly
     before_script:
     - rustup component add rustfmt-preview
+    - rustup target add wasm32-unknown-unknown
     script:
     - cargo fmt --all -- --check
     - cargo test --features "serde std v1 v3 v4 v5"
     - cargo bench --features "serde std v1 v3 v4 v5"
+    - cargo build --target wasm32-unknown-unknown --features "v3 stdweb"
+    - cargo build --target wasm32-unknown-unknown --features "v4 stdweb"
+    - cargo build --target wasm32-unknown-unknown --features "v5 stdweb"
+    - cargo build --target wasm32-unknown-unknown --features "v3 wasm-bindgen"
+    - cargo build --target wasm32-unknown-unknown --features "v4 wasm-bindgen"
+    - cargo build --target wasm32-unknown-unknown --features "v5 wasm-bindgen"
   - os: linux
     rust: nightly
     script:
     - cargo test --features "const_fn"
+  - rust: beta
+    before_script:
+      - rustup target add wasm32-unknown-unknown
+    script:
+      - cargo build --target wasm32-unknown-unknown --features "v3 wasm-bindgen"
+      - cargo build --target wasm32-unknown-unknown --features "v4 wasm-bindgen"
+      - cargo build --target wasm32-unknown-unknown --features "v5 wasm-bindgen"
   - rust: stable
     before_script:
     - rustup component add clippy-preview
+    - rustup target add wasm32-unknown-unknown
     script:
     - cargo clippy --features "u128 v1 v3 v4 v5 slog"
+    - cargo build --target wasm32-unknown-unknown --features "v3 wasm-bindgen"
+    - cargo build --target wasm32-unknown-unknown --features "v4 wasm-bindgen"
+    - cargo build --target wasm32-unknown-unknown --features "v5 wasm-bindgen"
   - rust: 1.22.0
     script:
     - cargo test --features "serde std v4"

Cargo.toml

@@ -38,7 +38,7 @@ version = "0.5"
 
 [dependencies.rand]
 optional = true
-version = "0.5"
+version = "0.6"
 
 [dependencies.serde]
 default-features = false
@@ -77,6 +77,8 @@ v1 = []
 v3 = ["md5", "rand"]
 v4 = ["rand"]
 v5 = ["sha1", "rand"]
+stdweb = ["rand/stdweb"]
+wasm-bindgen = ["rand/wasm-bindgen"]
 
 # since rust 1.26.0
 u128 = ["byteorder"]

src/lib.rs

@@ -43,6 +43,14 @@
 //! * `serde` - adds the ability to serialize and deserialize a `Uuid` using the
 //!   `serde` crate.
 //!
+//! You need to enable one of the following Cargo features together with
+//! `v3`, `v4` or `v5` feature if you're targeting `wasm32` architecture:
+//!
+//! * `stdweb` - enables support for `OsRng` on `wasm32-unknown-unknown` via
+//!   `stdweb` combined with `cargo-web`
+//! * `wasm-bindgen` - `wasm-bindgen` enables support for `OsRng` on
+//!   `wasm32-unknown-unknown` via [`wasm-bindgen`]
+//!
 //! By default, `uuid` can be depended on with:
 //!
 //! ```toml
@@ -103,6 +111,8 @@
 //!
 //! * [Wikipedia: Universally Unique Identifier](     http://en.wikipedia.org/wiki/Universally_unique_identifier)
 //! * [RFC4122: A Universally Unique IDentifier (UUID) URN Namespace](     http://tools.ietf.org/html/rfc4122)
+//!
+//! [`wasm-bindgen`]: https://github.com/rustwasm/wasm-bindgen
 
 #![cfg_attr(not(feature = "std"), no_std)]
 #![cfg_attr(feature = "const_fn", feature(const_fn))]
@@ -160,11 +170,38 @@ mod std_support;
 mod test_util;
 #[cfg(feature = "u128")]
 mod u128_support;
-#[cfg(feature = "v3")]
+#[cfg(all(
+    feature = "v3",
+    any(
+        not(target_arch = "wasm32"),
+        all(
+            target_arch = "wasm32",
+            any(feature = "stdweb", feature = "wasm-bindgen")
+        )
+    )
+))]
 mod v3;
-#[cfg(feature = "v4")]
+#[cfg(all(
+    feature = "v4",
+    any(
+        not(target_arch = "wasm32"),
+        all(
+            target_arch = "wasm32",
+            any(feature = "stdweb", feature = "wasm-bindgen")
+        )
+    )
+))]
 mod v4;
-#[cfg(feature = "v5")]
+#[cfg(all(
+    feature = "v5",
+    any(
+        not(target_arch = "wasm32"),
+        all(
+            target_arch = "wasm32",
+            any(feature = "stdweb", feature = "wasm-bindgen")
+        )
+    )
+))]
 mod v5;
 #[cfg(all(windows, feature = "winapi"))]
 mod winapi_support;