*: Drop generic wasm32-unknown-unknown support (#2038)

With `rand` `v0.8.0` platform support changed [1] due to its upgrade to
`getrandom` `v0.2`. With `getrandom` `v0.2` `wasm32-unknown-unknown` is no
longer supported out of the box:

> This crate fully supports the wasm32-wasi and wasm32-unknown-emscripten
> targets. However, the wasm32-unknown-unknown target is not automatically
> supported since, from the target name alone, we cannot deduce which JavaScript
> interface is in use (or if JavaScript is available at all).
>
> Instead, if the "js" Cargo feature is enabled, this crate will assume that you
> are building for an environment containing JavaScript, and will call the
> appropriate methods. Both web browser (main window and Web Workers) and
> Node.js environments are supported, invoking the methods described above using
> the wasm-bindgen toolchain.
>
> This feature has no effect on targets other than wasm32-unknown-unknown.

This commit drops support for wasm32-unknown-unknown in favor of the two more
specific targets wasm32-wasi and wasm32-unknown-emscripten.

Note on `resolver = "2"`: The new resolver is required to prevent features
being mixed, more specifically to prevent libp2p-noise to build with the
`ring-resolver` feature. See [3] for details.

---

[1] https://github.com/rust-random/rand/blob/master/CHANGELOG.md#platform-support
[2] https://docs.rs/getrandom/0.2.2/getrandom/#webassembly-support
[3] https://doc.rust-lang.org/nightly/cargo/reference/features.html#feature-resolver-version-2

.github/workflows/ci.yml

@@ -56,11 +56,18 @@ jobs:
 
     - uses: actions/checkout@v2
 
-    - name: Install Rust
+    - name: Install Rust wasm32-unknown-emscripten
       uses: actions-rs/toolchain@v1
       with:
         toolchain: stable
-        target: wasm32-unknown-unknown
+        target: wasm32-unknown-emscripten
+        override: true
+
+    - name: Install Rust wasm32-wasi
+      uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        target: wasm32-wasi
         override: true
 
     - name: Install a recent version of clang
@@ -85,10 +92,15 @@ jobs:
         path: target
         key: wasm-cargo-build-target-${{ hashFiles('Cargo.toml') }}
 
-    - name: Build on WASM
+    - name: Build on wasm32-unknown-emscripten
+      # TODO: also run `cargo test`
+      # TODO: ideally we would build `--workspace`, but not all crates compile for WASM
+      run: cargo build --target=wasm32-unknown-emscripten
+
+    - name: Build on wasm32-wasi
       # TODO: also run `cargo test`
       # TODO: ideally we would build `--workspace`, but not all crates compile for WASM
-      run: cargo build --target=wasm32-unknown-unknown
+      run: cargo build --target=wasm32-wasi
 
   check-rustdoc-links:
     name: Check rustdoc intra-doc links

CHANGELOG.md

@@ -55,6 +55,10 @@
     - `libp2p-request-response`
     - `libp2p-swarm`
     - `libp2p-wasm-ext`
+
+- Drop support for `wasm32-unknown-unknown` in favor of
+  `wasm32-unknown-emscripten` and `wasm32-wasi` [PR
+  2038](https://github.com/libp2p/rust-libp2p/pull/2038).
 
 ## Version 0.36.0 [2021-03-17]
 

Cargo.toml

@@ -100,6 +100,7 @@ env_logger = "0.8.1"
 tokio = { version = "1.0.1", features = ["io-util", "io-std", "macros", "rt", "rt-multi-thread"] }
 
 [workspace]
+resolver = "2"
 members = [
     "core",
     "misc/multiaddr",