Default all async support to std::future (#1741)

This commit defaults all crates in-tree to use `std::future` by default
and none of them support the crates.io `futures` 0.1 crate any more.
This is a breaking change for `wasm-bindgen-futures` and
`wasm-bindgen-test` so they've both received a major version bump to
reflect the new defaults. Historical versions of these crates should
continue to work if necessary, but they won't receive any more
maintenance after this is merged.

The movement here liberally uses `async`/`await` to remove the need for
using any combinators on the `Future` trait. As a result many of the
crates now rely on a much more recent version of the compiler,
especially to run tests.

The `wasm-bindgen-futures` crate was updated to remove all of its
futures-related dependencies and purely use `std::future`, hopefully
improving its compatibility by not having any version compat
considerations over time. The implementations of the executors here are
relatively simple and only delve slightly into the `RawWaker` business
since there are no other stable APIs in `std::task` for wrapping these.

This commit also adds support for:

    #[wasm_bindgen_test]
    async fn foo() {
        // ...
    }

where previously you needed to pass `(async)` now that's inferred
because it's an `async fn`.

Closes #1558
Closes #1695

Cargo.toml

@@ -43,7 +43,7 @@ cfg-if = "0.1.9"
 
 [target.'cfg(target_arch = "wasm32")'.dev-dependencies]
 js-sys = { path = 'crates/js-sys', version = '0.3.27' }
-wasm-bindgen-test = { path = 'crates/test', version = '=0.2.50' }
+wasm-bindgen-test = { path = 'crates/test', version = '=0.3.0' }
 serde_derive = "1.0"
 wasm-bindgen-test-crate-a = { path = 'tests/crates/a', version = '0.1' }
 wasm-bindgen-test-crate-b = { path = 'tests/crates/b', version = '0.1' }

azure-pipelines.yml

@@ -9,6 +9,9 @@ jobs:
     displayName: "Run wasm-bindgen crate tests (unix)"
     steps:
       - template: ci/azure-install-rust.yml
+        # TODO: switch this back to `stable` when async/await is stable
+        parameters:
+          toolchain: nightly
       - template: ci/azure-install-node.yml
       - template: ci/azure-install-geckodriver.yml
       - template: ci/azure-install-sccache.yml
@@ -48,6 +51,9 @@ jobs:
       vmImage: vs2017-win2016
     steps:
       - template: ci/azure-install-rust.yml
+        # TODO: switch this back to `stable` when async/await is stable
+        parameters:
+          toolchain: nightly
       - template: ci/azure-install-node.yml
       - template: ci/azure-install-geckodriver.yml
       - template: ci/azure-install-sccache.yml
@@ -91,6 +97,9 @@ jobs:
     displayName: "Run web-sys crate tests"
     steps:
       - template: ci/azure-install-rust.yml
+        # TODO: switch this back to `stable` when async/await is stable
+        parameters:
+          toolchain: nightly
       - template: ci/azure-install-node.yml
       - template: ci/azure-install-geckodriver.yml
       - template: ci/azure-install-sccache.yml
@@ -104,6 +113,9 @@ jobs:
     displayName: "Run js-sys crate tests"
     steps:
       - template: ci/azure-install-rust.yml
+        # TODO: switch this back to `stable` when async/await is stable
+        parameters:
+          toolchain: nightly
       - template: ci/azure-install-node.yml
       - template: ci/azure-install-geckodriver.yml
       - template: ci/azure-install-sccache.yml
@@ -113,6 +125,9 @@ jobs:
     displayName: "Run wasm-bindgen-webidl crate tests"
     steps:
       - template: ci/azure-install-rust.yml
+        # TODO: switch this back to `stable` when async/await is stable
+        parameters:
+          toolchain: nightly
       - template: ci/azure-install-node.yml
         #- template: ci/azure-install-sccache.yml
       - script: cargo test -p wasm-bindgen-webidl
@@ -124,8 +139,9 @@ jobs:
     displayName: "Run UI tests"
     steps:
       - template: ci/azure-install-rust.yml
+        # TODO: switch this back to `stable` when async/await is stable
         parameters:
-          toolchain: beta
+          toolchain: nightly
       - template: ci/azure-install-node.yml
       - template: ci/azure-install-sccache.yml
       - script: cargo test -p wasm-bindgen-macro
@@ -156,6 +172,9 @@ jobs:
     displayName: "Build almost all examples"
     steps:
       - template: ci/azure-install-rust.yml
+        # TODO: switch this back to `stable` when async/await is stable
+        parameters:
+          toolchain: nightly
       - template: ci/azure-install-sccache.yml
       - template: ci/azure-install-wasm-pack.yml
       - script: mv _package.json package.json && npm install && rm package.json
@@ -177,7 +196,7 @@ jobs:
     steps:
       - template: ci/azure-install-rust.yml
         parameters:
-          toolchain: nightly-2019-07-30
+          toolchain: nightly-2019-08-27
       - template: ci/azure-install-sccache.yml
       - script: rustup component add rust-src
         displayName: "install rust-src"
@@ -198,6 +217,9 @@ jobs:
     displayName: "Build benchmarks"
     steps:
       - template: ci/azure-install-rust.yml
+        # TODO: switch this back to `stable` when async/await is stable
+        parameters:
+          toolchain: nightly
       - template: ci/azure-install-sccache.yml
       - template: ci/azure-install-wasm-pack.yml
       - script: wasm-pack build --target web benchmarks
@@ -263,7 +285,6 @@ jobs:
   - job: doc_book
     displayName: "Doc - build the book"
     steps:
-      - template: ci/azure-install-rust.yml
       - script: |
           set -e
           curl -L https://github.com/rust-lang-nursery/mdBook/releases/download/v0.3.0/mdbook-v0.3.0-x86_64-unknown-linux-gnu.tar.gz | tar xzf -
@@ -279,6 +300,9 @@ jobs:
     displayName: "Doc - build the API documentation"
     steps:
       - template: ci/azure-install-rust.yml
+        # TODO: switch this back to `stable` when async/await is stable
+        parameters:
+          toolchain: nightly
       # Install rustfmt so we can format the web-sys bindings
       - script: rustup component add rustfmt
         displayName: "Install rustfmt"

crates/futures/Cargo.toml

@@ -7,17 +7,13 @@ license = "MIT/Apache-2.0"
 name = "wasm-bindgen-futures"
 repository = "https://github.com/rustwasm/wasm-bindgen/tree/master/crates/futures"
 readme = "./README.md"
-version = "0.3.27"
+version = "0.4.0"
 edition = "2018"
 
 [dependencies]
 cfg-if = "0.1.9"
-futures = "0.1.20"
 js-sys = { path = "../js-sys", version = '0.3.27' }
 wasm-bindgen = { path = "../..", version = '0.2.50' }
-futures-util-preview = { version = "0.3.0-alpha.18", optional = true }
-futures-channel-preview = { version = "0.3.0-alpha.18", optional = true }
-lazy_static = { version = "1.3.0", optional = true }
 
 [target.'cfg(target_feature = "atomics")'.dependencies.web-sys]
 path = "../web-sys"
@@ -28,7 +24,5 @@ features = [
 ]
 
 [target.'cfg(target_arch = "wasm32")'.dev-dependencies]
-wasm-bindgen-test = { path = '../test', version = '0.2.50' }
-
-[features]
-futures_0_3 = ["futures-util-preview", "futures-channel-preview", "lazy_static"]
+wasm-bindgen-test = { path = '../test', version = '0.3.0' }
+futures-channel-preview = { version = "0.3.0-alpha.18" }