From 8860540e9f274144d03552a0719c6cb5f853418c Mon Sep 17 00:00:00 2001
From: Jakob Hellermann <jakob.hellermann@protonmail.com>
Date: Sun, 20 Mar 2022 11:39:56 +0100
Subject: [PATCH] inline now_or_never to get rid of futures-util dependency

---
 crates/bevy_render/Cargo.toml                 |  1 -
 .../src/render_resource/pipeline_cache.rs     | 37 ++++++++++++++++++-
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/crates/bevy_render/Cargo.toml b/crates/bevy_render/Cargo.toml
index 7b7e40436b978d..14ba909fb3c5b7 100644
--- a/crates/bevy_render/Cargo.toml
+++ b/crates/bevy_render/Cargo.toml
@@ -66,4 +66,3 @@ flate2 = { version = "1.0.22", optional = true }
 ruzstd = { version = "0.2.4", optional = true }
 # For transcoding of UASTC/ETC1S universal formats, and for .basis file support
 basis-universal = { version = "0.2.0", optional = true }
-futures-util = "0.3"
diff --git a/crates/bevy_render/src/render_resource/pipeline_cache.rs b/crates/bevy_render/src/render_resource/pipeline_cache.rs
index aa1efe87cce52f..cd0dbc9a61c488 100644
--- a/crates/bevy_render/src/render_resource/pipeline_cache.rs
+++ b/crates/bevy_render/src/render_resource/pipeline_cache.rs
@@ -90,10 +90,9 @@ impl ShaderCache {
                     .wgpu_device()
                     .push_error_scope(wgpu::ErrorFilter::Validation);
                 let shader_module = render_device.create_shader_module(&module_descriptor);
-                use futures_util::future::FutureExt;
                 let error = render_device.wgpu_device().pop_error_scope();
                 if let Some(Some(wgpu::Error::Validation { description, .. })) =
-                    error.now_or_never()
+                    futures_helper::now_or_never(error)
                 {
                     return Err(RenderPipelineError::CreateShaderModule(description));
                 }
@@ -541,3 +540,37 @@ impl<'a> Iterator for ErrorSources<'a> {
         current
     }
 }
+
+mod futures_helper {
+    use std::{
+        future::Future,
+        task::{Context, Poll, RawWaker, RawWakerVTable, Waker},
+    };
+
+    pub fn now_or_never<F: Future>(future: F) -> Option<F::Output> {
+        let noop_waker = noop_waker();
+        let mut cx = Context::from_waker(&noop_waker);
+
+        futures_lite::pin!(future);
+        match future.poll(&mut cx) {
+            Poll::Ready(x) => Some(x),
+            _ => None,
+        }
+    }
+
+    unsafe fn noop_clone(_data: *const ()) -> RawWaker {
+        noop_raw_waker()
+    }
+
+    unsafe fn noop(_data: *const ()) {}
+
+    const NOOP_WAKER_VTABLE: RawWakerVTable = RawWakerVTable::new(noop_clone, noop, noop, noop);
+
+    fn noop_raw_waker() -> RawWaker {
+        RawWaker::new(std::ptr::null(), &NOOP_WAKER_VTABLE)
+    }
+
+    fn noop_waker() -> Waker {
+        unsafe { Waker::from_raw(noop_raw_waker()) }
+    }
+}