From 02f7264008e0333d7c4df183d3bcfbda8a6d930f Mon Sep 17 00:00:00 2001
From: Taiki Endo <te316e89@gmail.com>
Date: Fri, 1 Nov 2019 13:09:32 +0900
Subject: [PATCH] chore: check each feature works properly (#1695)

It is hard to maintain features list manually, so use cargo-hack's
`--each-feature` flag. And cargo-hack provides a workaround for an issue
that dev-dependencies leaking into normal build (`--no-dev-deps` flag),
so removed own ci tool.

Also, compared to running tests on all features, there is not much
advantage in running tests on each feature, so only the default features
and all features are tested.
If the behavior changes depending on the feature, we need to test it as
another job in CI.
---
 Cargo.toml                                    |  1 -
 azure-pipelines.yml                           | 43 ++----------
 ci/azure-test-stable.yml                      | 67 +++++++++++++------
 tests-build/Cargo.toml                        | 25 -------
 tests-build/README.md                         |  2 -
 tests-build/src/lib.rs                        |  8 ---
 .../fail/executor_without_current_thread.rs   |  3 -
 .../executor_without_current_thread.stderr    |  7 --
 .../tests/fail/macros_invalid_input.rs        | 25 -------
 .../tests/fail/macros_invalid_input.stderr    | 41 ------------
 .../tests/fail/net_without_tcp_missing_tcp.rs |  4 --
 .../fail/net_without_tcp_missing_tcp.stderr   |  7 --
 .../tests/fail/net_without_udp_missing_udp.rs |  4 --
 .../fail/net_without_udp_missing_udp.stderr   |  7 --
 .../tests/fail/net_without_uds_missing_uds.rs |  4 --
 .../fail/net_without_uds_missing_uds.stderr   |  7 --
 .../fail/tokio_without_net_missing_net.rs     |  3 -
 .../fail/tokio_without_net_missing_net.stderr |  7 --
 tests-build/tests/features.rs                 | 62 -----------------
 tokio/Cargo.toml                              | 17 +++--
 tokio/src/executor/current_thread/mod.rs      |  2 +-
 tokio/src/executor/thread_pool/pool.rs        |  7 +-
 tokio/src/lib.rs                              |  6 +-
 23 files changed, 75 insertions(+), 284 deletions(-)
 delete mode 100644 tests-build/Cargo.toml
 delete mode 100644 tests-build/README.md
 delete mode 100644 tests-build/src/lib.rs
 delete mode 100644 tests-build/tests/fail/executor_without_current_thread.rs
 delete mode 100644 tests-build/tests/fail/executor_without_current_thread.stderr
 delete mode 100644 tests-build/tests/fail/macros_invalid_input.rs
 delete mode 100644 tests-build/tests/fail/macros_invalid_input.stderr
 delete mode 100644 tests-build/tests/fail/net_without_tcp_missing_tcp.rs
 delete mode 100644 tests-build/tests/fail/net_without_tcp_missing_tcp.stderr
 delete mode 100644 tests-build/tests/fail/net_without_udp_missing_udp.rs
 delete mode 100644 tests-build/tests/fail/net_without_udp_missing_udp.stderr
 delete mode 100644 tests-build/tests/fail/net_without_uds_missing_uds.rs
 delete mode 100644 tests-build/tests/fail/net_without_uds_missing_uds.stderr
 delete mode 100644 tests-build/tests/fail/tokio_without_net_missing_net.rs
 delete mode 100644 tests-build/tests/fail/tokio_without_net_missing_net.stderr
 delete mode 100644 tests-build/tests/features.rs

diff --git a/Cargo.toml b/Cargo.toml
index 4a2a71ba8..9c0250f19 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,6 +9,5 @@ members = [
 
   # Internal
   "examples",
-  "tests-build",
   "tests-integration",
 ]
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index ae2bd1bb1..e60090f7e 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -25,20 +25,8 @@ jobs:
     displayName: Test tokio
     cross: true
     crates:
-      tokio:
-        - fs
-        - io
-        - io-util
-        - net-driver
-        - process
-        - rt-full
-        - signal
-        - sync
-        - tcp
-        - timer
-        - udp
-        - uds
-      tests-integration: []
+      - tokio
+      - tests-integration
 
 # Test crates that are NOT platform specific
 - template: ci/azure-test-stable.yml
@@ -47,29 +35,10 @@ jobs:
     displayName: Test sub crates -
     rust: beta
     crates:
-      tokio-macros: []
-      tokio-test: []
-      tokio-util: []
-      examples: []
-
-# Test compilation failure
-# Disable pending: https://github.com/tokio-rs/tokio/pull/1695#issuecomment-547045383
-# - template: ci/azure-test-stable.yml
-#   parameters:
-#     name: test_features
-#     displayName: Test feature flags
-#     rust: beta
-#     crates:
-#       tests-build:
-#         # - tokio-executor
-#         # - executor-without-current-thread
-#         # - macros-invalid-input
-#         # - net-no-features
-#         # - net-with-tcp
-#         # - net-with-udp
-#         # - net-with-uds
-#         # - tokio-no-features
-#         # - tokio-with-net
+      - tokio-macros
+      - tokio-test
+      - tokio-util
+      - examples
 
 # Run loom tests
 - template: ci/azure-loom.yml
diff --git a/ci/azure-test-stable.yml b/ci/azure-test-stable.yml
index f0ff7a7c1..93e9ee138 100644
--- a/ci/azure-test-stable.yml
+++ b/ci/azure-test-stable.yml
@@ -20,6 +20,11 @@ jobs:
       # rust_version: stable
       rust_version: ${{ parameters.rust }}
 
+  - script: cargo install cargo-hack
+    displayName: Install cargo-hack
+    # FIXME(taiki-e): many features of current cargo-hack are not available on windows: https://github.com/taiki-e/cargo-hack/issues/3
+    condition: not(eq(variables['Agent.OS'], 'Windows_NT'))
+
   - template: azure-is-release.yml
 
   - ${{ each crate in parameters.crates }}:
@@ -28,17 +33,28 @@ jobs:
       env:
         LOOM_MAX_PREEMPTIONS: 2
         CI: 'True'
-      displayName: ${{ crate.key }} - cargo test
-      workingDirectory: $(Build.SourcesDirectory)/${{ crate.key }}
+      displayName: ${{ crate }} - cargo test
+      workingDirectory: $(Build.SourcesDirectory)/${{ crate }}
 
-    # Run with each specified feature
-    - ${{ each feature in crate.value }}:
-      - script: cargo test --no-default-features --features ${{ feature }}
-        env:
-          LOOM_MAX_PREEMPTIONS: 2
-          CI: 'True'
-        displayName: ${{ crate.key }} - cargo test --features ${{ feature }}
-        workingDirectory: $(Build.SourcesDirectory)/${{ crate.key }}
+    # Run with all crate features
+    - script: cargo test --all-features
+      env:
+        LOOM_MAX_PREEMPTIONS: 2
+        CI: 'True'
+      displayName: ${{ crate }} - cargo test --all-features
+      workingDirectory: $(Build.SourcesDirectory)/${{ crate }}
+
+    # Check each specified feature works properly
+    # * --each-feature - run for each feature which includes --no-default-features and default features of package
+    # * --no-dev-deps - build without dev-dependencies to avoid https://github.com/rust-lang/cargo/issues/4866
+    - script: cargo hack check --each-feature --no-dev-deps
+      env:
+        LOOM_MAX_PREEMPTIONS: 2
+        CI: 'True'
+      displayName: ${{ crate }} - cargo hack check --each-feature
+      workingDirectory: $(Build.SourcesDirectory)/${{ crate }}
+      # FIXME(taiki-e): many features of current cargo-hack are not available on windows: https://github.com/taiki-e/cargo-hack/issues/3
+      condition: not(eq(variables['Agent.OS'], 'Windows_NT'))
 
   - template: azure-patch-crates.yml
 
@@ -48,14 +64,25 @@ jobs:
       env:
         LOOM_MAX_PREEMPTIONS: 2
         CI: 'True'
-      displayName: ${{ crate.key }} - cargo test
-      workingDirectory: $(Build.SourcesDirectory)/${{ crate.key }}
+      displayName: ${{ crate }} - cargo test
+      workingDirectory: $(Build.SourcesDirectory)/${{ crate }}
 
-    # Run with each specified feature
-    - ${{ each feature in crate.value }}:
-      - script: cargo test --no-default-features --features ${{ feature }}
-        env:
-          LOOM_MAX_PREEMPTIONS: 2
-          CI: 'True'
-        displayName: ${{ crate.key }} - cargo test --features ${{ feature }}
-        workingDirectory: $(Build.SourcesDirectory)/${{ crate.key }}
+    # Run with all crate features
+    - script: cargo test --all-features
+      env:
+        LOOM_MAX_PREEMPTIONS: 2
+        CI: 'True'
+      displayName: ${{ crate }} - cargo test --all-features
+      workingDirectory: $(Build.SourcesDirectory)/${{ crate }}
+
+    # Check each specified feature works properly
+    # * --each-feature - run for each feature which includes --no-default-features and default features of package
+    # * --no-dev-deps - build without dev-dependencies to avoid https://github.com/rust-lang/cargo/issues/4866
+    - script: cargo hack check --each-feature --no-dev-deps
+      env:
+        LOOM_MAX_PREEMPTIONS: 2
+        CI: 'True'
+      displayName: ${{ crate }} - cargo hack check --each-feature
+      workingDirectory: $(Build.SourcesDirectory)/${{ crate }}
+      # FIXME(taiki-e): many features of current cargo-hack are not available on windows: https://github.com/taiki-e/cargo-hack/issues/3
+      condition: not(eq(variables['Agent.OS'], 'Windows_NT'))
diff --git a/tests-build/Cargo.toml b/tests-build/Cargo.toml
deleted file mode 100644
index 36dbc883c..000000000
--- a/tests-build/Cargo.toml
+++ /dev/null
@@ -1,25 +0,0 @@
-[package]
-name = "tests-build"
-version = "0.1.0"
-authors = ["Tokio Contributors <team@tokio.rs>"]
-edition = "2018"
-publish = false
-
-[features]
-# executor-without-current-thread = ["tokio-executor"]
-# macros-invalid-input = ["tokio/rt-full"]
-# net-no-features = ["tokio-net"]
-# net-with-tcp = ["tokio-net/tcp"]
-# net-with-udp = ["tokio-net/udp"]
-# net-with-uds = ["tokio-net/uds"]
-# net-with-process = ["tokio-net/process"]
-# tokio-no-features = ["tokio"]
-# tokio-with-net = ["tokio/net-full"]
-
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
-[dependencies]
-# tokio = { path = "../tokio", optional = true, default-features = false }
-
-[dev-dependencies]
-trybuild = "1.0"
diff --git a/tests-build/README.md b/tests-build/README.md
deleted file mode 100644
index f491e2bc3..000000000
--- a/tests-build/README.md
+++ /dev/null
@@ -1,2 +0,0 @@
-Tests the various combination of feature flags. This is broken out to a separate
-crate to work around limitations with cargo features.
diff --git a/tests-build/src/lib.rs b/tests-build/src/lib.rs
deleted file mode 100644
index 7f38a4406..000000000
--- a/tests-build/src/lib.rs
+++ /dev/null
@@ -1,8 +0,0 @@
-#[cfg(feature = "tokio-executor")]
-pub use tokio_executor;
-
-#[cfg(feature = "tokio-net")]
-pub use tokio_net;
-
-#[cfg(feature = "tokio")]
-pub use tokio;
diff --git a/tests-build/tests/fail/executor_without_current_thread.rs b/tests-build/tests/fail/executor_without_current_thread.rs
deleted file mode 100644
index 205ce7e42..000000000
--- a/tests-build/tests/fail/executor_without_current_thread.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-use tests_build::tokio_executor::current_thread;
-
-fn main() {}
diff --git a/tests-build/tests/fail/executor_without_current_thread.stderr b/tests-build/tests/fail/executor_without_current_thread.stderr
deleted file mode 100644
index f2287c3fc..000000000
--- a/tests-build/tests/fail/executor_without_current_thread.stderr
+++ /dev/null
@@ -1,7 +0,0 @@
-error[E0432]: unresolved import `tests_build::tokio_executor::current_thread`
- --> $DIR/executor_without_current_thread.rs:1:5
-  |
-1 | use tests_build::tokio_executor::current_thread;
-  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `current_thread` in `tokio_executor`
-
-For more information about this error, try `rustc --explain E0432`.
diff --git a/tests-build/tests/fail/macros_invalid_input.rs b/tests-build/tests/fail/macros_invalid_input.rs
deleted file mode 100644
index 5b1a8adc0..000000000
--- a/tests-build/tests/fail/macros_invalid_input.rs
+++ /dev/null
@@ -1,25 +0,0 @@
-use tests_build::tokio;
-
-#[tokio::main]
-fn main_is_not_async() {}
-
-#[tokio::main(foo)]
-async fn main_attr_has_unknown_args() {}
-
-#[tokio::main(threadpool::bar)]
-async fn main_attr_has_path_args() {}
-
-#[tokio::test]
-fn test_is_not_async() {}
-
-#[tokio::test]
-async fn test_fn_has_args(_x: u8) {}
-
-#[tokio::test(foo)]
-async fn test_attr_has_args() {}
-
-#[tokio::test]
-#[test]
-async fn test_has_second_test_attr() {}
-
-fn main() {}
diff --git a/tests-build/tests/fail/macros_invalid_input.stderr b/tests-build/tests/fail/macros_invalid_input.stderr
deleted file mode 100644
index 123734864..000000000
--- a/tests-build/tests/fail/macros_invalid_input.stderr
+++ /dev/null
@@ -1,41 +0,0 @@
-error: the async keyword is missing from the function declaration
- --> $DIR/macros_invalid_input.rs:4:1
-  |
-4 | fn main_is_not_async() {}
-  | ^^
-
-error: Unknown attribute foo is specified; expected `current_thread` or `threadpool`
- --> $DIR/macros_invalid_input.rs:6:15
-  |
-6 | #[tokio::main(foo)]
-  |               ^^^
-
-error: Must have specified ident
- --> $DIR/macros_invalid_input.rs:9:15
-  |
-9 | #[tokio::main(threadpool::bar)]
-  |               ^^^^^^^^^^^^^^^
-
-error: the async keyword is missing from the function declaration
-  --> $DIR/macros_invalid_input.rs:13:1
-   |
-13 | fn test_is_not_async() {}
-   | ^^
-
-error: the test function cannot accept arguments
-  --> $DIR/macros_invalid_input.rs:16:27
-   |
-16 | async fn test_fn_has_args(_x: u8) {}
-   |                           ^^^^^^
-
-error: Unknown attribute foo is specified; expected `current_thread` or `threadpool`
-  --> $DIR/macros_invalid_input.rs:18:15
-   |
-18 | #[tokio::test(foo)]
-   |               ^^^
-
-error: second test attribute is supplied
-  --> $DIR/macros_invalid_input.rs:22:1
-   |
-22 | #[test]
-   | ^^^^^^^
diff --git a/tests-build/tests/fail/net_without_tcp_missing_tcp.rs b/tests-build/tests/fail/net_without_tcp_missing_tcp.rs
deleted file mode 100644
index 80010233a..000000000
--- a/tests-build/tests/fail/net_without_tcp_missing_tcp.rs
+++ /dev/null
@@ -1,4 +0,0 @@
-use tests_build::tokio_net::tcp;
-
-fn main() {}
-
diff --git a/tests-build/tests/fail/net_without_tcp_missing_tcp.stderr b/tests-build/tests/fail/net_without_tcp_missing_tcp.stderr
deleted file mode 100644
index 83ff59fb4..000000000
--- a/tests-build/tests/fail/net_without_tcp_missing_tcp.stderr
+++ /dev/null
@@ -1,7 +0,0 @@
-error[E0432]: unresolved import `tests_build::tokio_net::tcp`
- --> $DIR/net_without_tcp_missing_tcp.rs:1:5
-  |
-1 | use tests_build::tokio_net::tcp;
-  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `tcp` in `tokio_net`
-
-For more information about this error, try `rustc --explain E0432`.
diff --git a/tests-build/tests/fail/net_without_udp_missing_udp.rs b/tests-build/tests/fail/net_without_udp_missing_udp.rs
deleted file mode 100644
index 6731af93f..000000000
--- a/tests-build/tests/fail/net_without_udp_missing_udp.rs
+++ /dev/null
@@ -1,4 +0,0 @@
-use tests_build::tokio_net::udp;
-
-fn main() {}
-
diff --git a/tests-build/tests/fail/net_without_udp_missing_udp.stderr b/tests-build/tests/fail/net_without_udp_missing_udp.stderr
deleted file mode 100644
index e3471a792..000000000
--- a/tests-build/tests/fail/net_without_udp_missing_udp.stderr
+++ /dev/null
@@ -1,7 +0,0 @@
-error[E0432]: unresolved import `tests_build::tokio_net::udp`
- --> $DIR/net_without_udp_missing_udp.rs:1:5
-  |
-1 | use tests_build::tokio_net::udp;
-  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `udp` in `tokio_net`
-
-For more information about this error, try `rustc --explain E0432`.
diff --git a/tests-build/tests/fail/net_without_uds_missing_uds.rs b/tests-build/tests/fail/net_without_uds_missing_uds.rs
deleted file mode 100644
index d48a5eb40..000000000
--- a/tests-build/tests/fail/net_without_uds_missing_uds.rs
+++ /dev/null
@@ -1,4 +0,0 @@
-use tests_build::tokio_net::uds;
-
-fn main() {}
-
diff --git a/tests-build/tests/fail/net_without_uds_missing_uds.stderr b/tests-build/tests/fail/net_without_uds_missing_uds.stderr
deleted file mode 100644
index ad79fe183..000000000
--- a/tests-build/tests/fail/net_without_uds_missing_uds.stderr
+++ /dev/null
@@ -1,7 +0,0 @@
-error[E0432]: unresolved import `tests_build::tokio_net::uds`
- --> $DIR/net_without_uds_missing_uds.rs:1:5
-  |
-1 | use tests_build::tokio_net::uds;
-  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `uds` in `tokio_net`
-
-For more information about this error, try `rustc --explain E0432`.
diff --git a/tests-build/tests/fail/tokio_without_net_missing_net.rs b/tests-build/tests/fail/tokio_without_net_missing_net.rs
deleted file mode 100644
index f2e278364..000000000
--- a/tests-build/tests/fail/tokio_without_net_missing_net.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-use tests_build::tokio::net;
-
-fn main() {}
diff --git a/tests-build/tests/fail/tokio_without_net_missing_net.stderr b/tests-build/tests/fail/tokio_without_net_missing_net.stderr
deleted file mode 100644
index 4435b0a66..000000000
--- a/tests-build/tests/fail/tokio_without_net_missing_net.stderr
+++ /dev/null
@@ -1,7 +0,0 @@
-error[E0432]: unresolved import `tests_build::tokio::net`
- --> $DIR/tokio_without_net_missing_net.rs:1:5
-  |
-1 | use tests_build::tokio::net;
-  |     ^^^^^^^^^^^^^^^^^^^^^^^ no `net` in `tokio`
-
-For more information about this error, try `rustc --explain E0432`.
diff --git a/tests-build/tests/features.rs b/tests-build/tests/features.rs
deleted file mode 100644
index b40e44ed6..000000000
--- a/tests-build/tests/features.rs
+++ /dev/null
@@ -1,62 +0,0 @@
-#![allow(unused_imports)]
-
-#[test]
-#[cfg(feature = "tokio-net")]
-fn net_default() {
-    use tests_build::tokio_net::driver::{set_default, Handle, Reactor, Registration};
-    use tests_build::tokio_net::util::PollEvented;
-}
-
-#[test]
-#[cfg(feature = "net-with-tcp")]
-fn net_with_tcp() {
-    use tests_build::tokio_net::tcp;
-}
-
-#[test]
-#[cfg(feature = "net-with-udp")]
-fn net_with_udp() {
-    use tests_build::tokio_net::udp;
-}
-
-#[test]
-#[cfg(feature = "net-with-uds")]
-fn net_with_uds() {
-    use tests_build::tokio_net::uds;
-}
-
-#[test]
-#[cfg(feature = "net-with-process")]
-fn net_with_process() {
-    use tests_build::tokio_net::process;
-}
-
-#[test]
-#[cfg(feature = "tokio-with-net")]
-fn tokio_with_net() {
-    // net is present
-    use tests_build::tokio::net;
-}
-
-#[test]
-fn compile_fail() {
-    let t = trybuild::TestCases::new();
-
-    #[cfg(feature = "executor-without-current-thread")]
-    t.compile_fail("tests/fail/executor_without_current_thread.rs");
-
-    #[cfg(feature = "macros-invalid-input")]
-    t.compile_fail("tests/fail/macros_invalid_input.rs");
-
-    #[cfg(feature = "net-no-features")]
-    {
-        t.compile_fail("tests/fail/net_without_tcp_missing_tcp.rs");
-        t.compile_fail("tests/fail/net_without_udp_missing_udp.rs");
-        t.compile_fail("tests/fail/net_without_uds_missing_uds.rs");
-    }
-
-    #[cfg(feature = "tokio-no-features")]
-    t.compile_fail("tests/fail/tokio_without_net_missing_net.rs");
-
-    drop(t);
-}
diff --git a/tokio/Cargo.toml b/tokio/Cargo.toml
index 057055e26..48b27a398 100644
--- a/tokio/Cargo.toml
+++ b/tokio/Cargo.toml
@@ -36,19 +36,24 @@ default = [
   "timer",
 ]
 
-blocking = []
-fs = ["blocking"]
+executor-core = []
+blocking = ["executor-core", "sync"]
+fs = ["blocking", "io-traits"]
 io-traits = ["bytes", "iovec"]
 io-util = ["io-traits", "pin-project", "memchr"]
 io = ["io-traits", "io-util"]
 macros = ["tokio-macros"]
 net-full = ["tcp", "udp", "uds"]
-net-driver = ["mio", "blocking", "lazy_static"]
+net-driver = ["io-traits", "mio", "blocking", "lazy_static"]
 rt-current-thread = [
+  "executor-core",
   "crossbeam-channel",
   "timer",
+  "sync",
+  "net-driver",
 ]
 rt-full = [
+  "executor-core",
   "macros",
   "num_cpus",
   "net-full",
@@ -61,11 +66,13 @@ signal = [
   "libc",
   "mio-uds",
   "net-driver",
-  "signal-hook-registry"
+  "signal-hook-registry",
+  "winapi/consoleapi",
+  "winapi/minwindef",
 ]
 sync = ["fnv"]
 tcp = ["io", "net-driver"]
-timer = ["slab"]
+timer = ["executor-core", "sync", "slab"]
 udp = ["io", "net-driver"]
 uds = ["io", "net-driver", "mio-uds", "libc"]
 process = [
diff --git a/tokio/src/executor/current_thread/mod.rs b/tokio/src/executor/current_thread/mod.rs
index dcc9c51ac..62619f2aa 100644
--- a/tokio/src/executor/current_thread/mod.rs
+++ b/tokio/src/executor/current_thread/mod.rs
@@ -18,10 +18,10 @@
 mod scheduler;
 use self::scheduler::{Scheduler, TickArgs};
 
-use crate::executor::{EnterError, Executor, SpawnError, TypedExecutor};
 #[cfg(feature = "blocking")]
 use crate::executor::blocking::{Pool, PoolWaiter};
 use crate::executor::park::{Park, ParkThread, Unpark};
+use crate::executor::{EnterError, Executor, SpawnError, TypedExecutor};
 
 use std::cell::Cell;
 use std::error::Error;
diff --git a/tokio/src/executor/thread_pool/pool.rs b/tokio/src/executor/thread_pool/pool.rs
index 1da4239be..6a83e97dd 100644
--- a/tokio/src/executor/thread_pool/pool.rs
+++ b/tokio/src/executor/thread_pool/pool.rs
@@ -68,8 +68,11 @@ impl ThreadPool {
         F: Future,
     {
         crate::executor::global::with_threadpool(self, || {
-            let mut enter = crate::executor::enter().expect("attempting to block while on a Tokio executor");
-            crate::executor::blocking::with_pool(self.spawner.blocking_pool(), || enter.block_on(future))
+            let mut enter =
+                crate::executor::enter().expect("attempting to block while on a Tokio executor");
+            crate::executor::blocking::with_pool(self.spawner.blocking_pool(), || {
+                enter.block_on(future)
+            })
         })
     }
 
diff --git a/tokio/src/lib.rs b/tokio/src/lib.rs
index 94eb3072e..f42a8a1e9 100644
--- a/tokio/src/lib.rs
+++ b/tokio/src/lib.rs
@@ -95,7 +95,7 @@ pub mod fs;
 
 pub mod future;
 
-#[cfg(feature = "io")]
+#[cfg(feature = "io-traits")]
 pub mod io;
 
 #[cfg(feature = "net-driver")]
@@ -121,8 +121,10 @@ pub mod sync;
 #[cfg(feature = "timer")]
 pub mod timer;
 
+#[cfg(feature = "executor-core")]
+pub mod executor;
+
 if_runtime! {
-    pub mod executor;
     pub mod runtime;
 
     #[doc(inline)]