Put stdweb dependency behind a target feature

.travis.yml

@@ -47,7 +47,7 @@ matrix:
         # Cargo has errors with sub-commands so ignore updating for now:
         - cargo --list | egrep "^\s*web$" -q || cargo install cargo-web
       script:
-        - cargo web test --target wasm32-unknown-unknown --nodejs
+        - cargo web test --target wasm32-unknown-unknown --nodejs --features=wasm-stdweb
 
     # Trust cross-built/emulated targets. We must repeat all non-default values.
     - rust: stable

CHANGELOG.md

@@ -17,6 +17,7 @@ You may also find the [Update Guide](UPDATING.md) useful.
 - Deprecate `rand_derive`. (#256)
 - Add `log` feature. Logging is now available in `JitterRng`, `OsRng`, `EntropyRng` and `ReseedingRng`. (#246)
 - Add `serde-1` feature for some PRNGs. (#189)
+- `wasm-stdweb` feature for `OsRng` support on WASM via stdweb. (#272, #336)
 
 ### `Rng` trait
 - Split `Rng` in `RngCore` and `Rng` extension trait.
@@ -68,7 +69,7 @@ You may also find the [Update Guide](UPDATING.md) useful.
 ### Platform support and `OsRng`
 - Add support for CloudABI. (#224)
 - Remove support for NaCl. (#225)
-- Replace stubs with proper WASM support in `OsRng`. (#272)
+- WASM support for `OsRng` via stdweb, behind the `wasm-stdweb` feature. (#272, #336)
 - On systems that do not have a syscall interface, only keep a single file descriptor open for `OsRng`. (#239)
 - Better error handling and reporting in `OsRng` (using new error type). (#225)
 - `OsRng` now uses non-blocking when available. (#225)

Cargo.toml

@@ -23,6 +23,7 @@ alloc = ["rand_core/alloc"]  # enables Vec and Box support without std
 i128_support = [] # enables i128 and u128 support
 
 serde-1 = ["serde", "serde_derive"]
+wasm-stdweb = ["stdweb"]
 
 
 [target.'cfg(unix)'.dependencies]
@@ -35,9 +36,10 @@ winapi = { version = "0.3", features = ["minwindef", "ntsecapi", "profileapi", "
 rand_core = { path = 'rand_core', default-features = false }
 
 log = { version = "0.4", optional = true }
-
-serde = {version="1",optional=true}
+serde = {version="1", optional=true}
 serde_derive = {version="1", optional=true}
+stdweb = {version="0.4", optional=true}
+
 
 [workspace]
 members = ["rand_core"]
@@ -53,6 +55,3 @@ cloudabi = "0.0.3"
 
 [target.'cfg(target_os = "fuchsia")'.dependencies]
 fuchsia-zircon = "0.3.2"
-
-[target.wasm32-unknown-unknown.dependencies]
-stdweb = "0.4"

README.md

@@ -88,6 +88,7 @@ optional features are available:
 -   `log` enables some logging via the `log` crate
 -   `nightly` enables all unstable features (`i128_support`)
 -   `serde-1` enables serialisation for some types, via Serde version 1
+-   `wasm-stdweb` enables support for `OsRng` on WASM via stdweb.
 -   `std` enabled by default; by setting "default-features = false" `no_std`
     mode is activated; this removes features depending on `std` functionality:
     -   `OsRng` is entirely unavailable

src/lib.rs

@@ -179,7 +179,7 @@
 #![cfg_attr(not(feature="std"), no_std)]
 #![cfg_attr(all(feature="alloc", not(feature="std")), feature(alloc))]
 #![cfg_attr(feature = "i128_support", feature(i128_type, i128))]
-#![cfg_attr(all(target_arch = "wasm32", not(target_os = "emscripten")), recursion_limit="128")]
+#![cfg_attr(feature = "wasm-stdweb", recursion_limit="128")]
 
 #[cfg(feature="std")] extern crate std as core;
 #[cfg(all(feature = "alloc", not(feature="std")))] extern crate alloc;
@@ -188,7 +188,7 @@
 #[cfg(feature="serde-1")] extern crate serde;
 #[cfg(feature="serde-1")] #[macro_use] extern crate serde_derive;
 
-#[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
+#[cfg(feature = "wasm-stdweb")]
 #[macro_use]
 extern crate stdweb;
 

src/os.rs

@@ -613,7 +613,31 @@ mod imp {
     }
 }
 
-#[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
+#[cfg(all(target_arch = "wasm32",
+          not(target_os = "emscripten"),
+          not(feature = "wasm-stdweb")))]
+mod imp {
+    use {Error, ErrorKind};
+
+    #[derive(Debug)]
+    pub struct OsRng;
+
+    impl OsRng {
+        pub fn new() -> Result<OsRng, Error> {
+            Err(Error::new(ErrorKind::Unavailable,
+                           "not supported on WASM without stdweb"))
+        }
+
+        pub fn try_fill_bytes(&mut self, _v: &mut [u8]) -> Result<(), Error> {
+            Err(Error::new(ErrorKind::Unavailable,
+                           "not supported on WASM without stdweb"))
+        }
+    }
+}
+
+#[cfg(all(target_arch = "wasm32",
+          not(target_os = "emscripten"),
+          feature = "wasm-stdweb"))]
 mod imp {
     use std::mem;
     use stdweb::unstable::TryInto;

src/thread_rng.rs

@@ -175,7 +175,7 @@ mod test {
 
     #[test]
     #[cfg(feature="std")]
-    #[cfg(not(all(target_arch = "wasm32", not(target_os = "emscripten"))))]
+    #[cfg(not(feature="wasm-stdweb"))]
     fn test_thread_rng() {
         let mut r = ::thread_rng();
         r.gen::<i32>();