Only create tokio runtime once for block_on

Author: udoprog

Cargo.lock

@@ -34,9 +34,10 @@ async-std = { version = "1.4.0", default-features = false, optional = true }
 tokio = { version = "0.2", optional = true }
 once_cell = { version = "1.3", optional = true }
 dotenv = { version = "0.15.0", default-features = false }
-futures = { version = "0.3.1", default-features = false }
+futures = { version = "0.3.1", default-features = false, features = ["executor"] }
 proc-macro2 = { version = "1.0.6", default-features = false }
 sqlx = { version = "0.2.0", default-features = false, path = "../sqlx-core", package = "sqlx-core" }
 syn = { version = "1.0.11", default-features = false, features = [ "full" ] }
 quote = { version = "1.0.2", default-features = false }
 url = { version = "2.1.0", default-features = false }
+lazy_static = "1.4.0"

sqlx-macros/Cargo.toml

@@ -25,10 +25,16 @@ mod query_macros;
 
 use query_macros::*;
 
+#[cfg(feature = "runtime-tokio")]
+lazy_static::lazy_static! {
+    static ref BASIC_RUNTIME: tokio::runtime::Runtime = {
+        tokio::runtime::Builder::new().basic_scheduler().enable_all().build().expect("failed to build tokio runtime")
+    };
+}
+
 #[cfg(feature = "runtime-tokio")]
 fn block_on<F: std::future::Future>(future: F) -> F::Output {
-    // TODO: Someone think of something better for async proc macros + tokio
-    tokio::runtime::Runtime::new().unwrap().block_on(future)
+    BASIC_RUNTIME.enter(|| futures::executor::block_on(future))
 }
 
 fn macro_result(tokens: proc_macro2::TokenStream) -> TokenStream {