add comments, make everything scheduler-related private to crate

crates/wasi/src/preview2/ctx.rs

@@ -1,9 +1,7 @@
 use crate::preview2::{
     clocks::{self, WasiClocks},
     filesystem::{Dir, TableFsExt},
-    pipe, random,
-    sched::{self, WasiSched},
-    stdio,
+    pipe, random, stdio,
     stream::{InputStream, OutputStream, TableStreamExt},
     DirPerms, FilePerms, Table,
 };
@@ -20,14 +18,11 @@ pub struct WasiCtxBuilder {
 
     random: Option<Box<dyn RngCore + Send + Sync>>,
     clocks: Option<WasiClocks>,
-
-    sched: Option<Box<dyn WasiSched>>,
 }
 
 impl WasiCtxBuilder {
     pub fn new() -> Self {
         Self::default()
-            .set_sched(sched::sync::SyncSched)
             .set_clocks(clocks::host::clocks_ctx())
             .set_random(random::thread_rng())
             .set_stdin(pipe::ReadPipe::new(std::io::empty()))
@@ -102,11 +97,6 @@ impl WasiCtxBuilder {
         self
     }
 
-    pub fn set_sched(mut self, sched: impl WasiSched + 'static) -> Self {
-        self.sched = Some(Box::new(sched));
-        self
-    }
-
     pub fn build(self, table: &mut Table) -> Result<WasiCtx, anyhow::Error> {
         use anyhow::Context;
 
@@ -131,7 +121,6 @@ impl WasiCtxBuilder {
         Ok(WasiCtx {
             random: self.random.context("required member random")?,
             clocks: self.clocks.context("required member clocks")?,
-            sched: self.sched.context("required member sched")?,
             env: self.env,
             args: self.args,
             preopens,
@@ -152,7 +141,6 @@ pub trait WasiView: Send {
 pub struct WasiCtx {
     pub random: Box<dyn RngCore + Send + Sync>,
     pub clocks: WasiClocks,
-    pub sched: Box<dyn WasiSched>,
     pub env: Vec<(String, String)>,
     pub args: Vec<String>,
     pub preopens: Vec<(u32, String)>,

crates/wasi/src/preview2/mod.rs

@@ -1,3 +1,24 @@
+///! # Wasmtime's WASI Preview 2 Implementation
+///!
+///! Welcome to the (new!) WASI implementation from the Wasmtime team. The goal
+///! of this implementation is to support WASI Preview 2 via the Component
+///! Model, as well as to provide legacy Preview 1 host support with an adapter
+///! that is implemented in terms of the Preview 2 interfaces.
+///!
+///! Presently, this crate is experimental. We don't yet recommend you use it
+///! in production. Specifically:
+///! * it does not yet support a synchronous rust embedding
+///! * polling and streams need a redesign. IO that currently shoudl be
+///! non-blocking may be blocking. poll probably doesnt work at all.
+///! * its internal organization could use some love
+///! * the Preview 1 host support is in its infancy
+///! * the wit files in tree describing preview 2 are not faithful to the
+///! standards repos
+///!
+///! Once these issues are resolved, we expect to move this namespace up to the
+///! root of the wasmtime-wasi crate, and move its other exports underneath a
+///! `pub mod legacy` with an off-by-default feature flag, and after 2
+///! releases, retire and remove that code from our tree.
 pub mod clocks;
 mod ctx;
 mod error;
@@ -7,7 +28,7 @@ pub mod pipe;
 pub mod preview1;
 pub mod preview2;
 pub mod random;
-pub mod sched;
+mod sched;
 pub mod stdio;
 pub mod stream;
 pub mod table;
@@ -19,6 +40,5 @@ pub use clocks::{WasiClocks, WasiMonotonicClock, WasiWallClock};
 pub use ctx::{WasiCtx, WasiCtxBuilder, WasiView};
 pub use error::I32Exit;
 pub use filesystem::{DirPerms, FilePerms};
-pub use sched::{Poll, WasiSched};
 pub use stream::{InputStream, OutputStream};
 pub use table::{Table, TableError};

crates/wasi/src/preview2/preview2/poll.rs

@@ -36,7 +36,7 @@ impl<T: WasiView> wasi::poll::Host for T {
     }
 
     async fn poll_oneoff(&mut self, futures: Vec<Pollable>) -> anyhow::Result<Vec<u8>> {
-        use crate::preview2::sched::{Poll, Userdata};
+        use crate::preview2::sched::{sync::SyncSched, Poll, Userdata, WasiSched};
 
         // Convert `futures` into `Poll` subscriptions.
         let mut poll = Poll::new();
@@ -72,9 +72,8 @@ impl<T: WasiView> wasi::poll::Host for T {
             }
         }
 
-        let ctx = self.ctx();
         // Do the poll.
-        ctx.sched.poll_oneoff(&mut poll).await?;
+        SyncSched.poll_oneoff(&mut poll).await?;
 
         // Convert the results into a list of `u8` to return.
         let mut results = vec![0_u8; len];

crates/wasi/src/preview2/sched.rs

@@ -1,25 +1,26 @@
+#![allow(dead_code)]
 use crate::preview2::{
     clocks::WasiMonotonicClock,
     stream::{InputStream, OutputStream},
 };
 use anyhow::Error;
-pub mod subscription;
-pub mod sync;
+pub(crate) mod subscription;
+pub(crate) mod sync;
 pub use cap_std::time::Duration;
 
-pub use subscription::{
-    MonotonicClockSubscription, RwEventFlags, RwSubscription, Subscription, SubscriptionResult,
+pub(crate) use subscription::{
+    MonotonicClockSubscription, RwSubscription, Subscription, SubscriptionResult,
 };
 
 #[async_trait::async_trait]
-pub trait WasiSched: Send + Sync {
+pub(crate) trait WasiSched: Send + Sync {
     async fn poll_oneoff<'a>(&self, poll: &mut Poll<'a>) -> Result<(), Error>;
     async fn sched_yield(&self) -> Result<(), Error>;
     async fn sleep(&self, duration: Duration) -> Result<(), Error>;
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
-pub struct Userdata(u64);
+pub(crate) struct Userdata(u64);
 impl From<u64> for Userdata {
     fn from(u: u64) -> Userdata {
         Userdata(u)
@@ -32,9 +33,7 @@ impl From<Userdata> for u64 {
     }
 }
 
-pub type PollResults = Vec<(SubscriptionResult, Userdata)>;
-
-pub struct Poll<'a> {
+pub(crate) struct Poll<'a> {
     subs: Vec<(Subscription<'a>, Userdata)>,
 }
 

crates/wasi/src/preview2/sched/sync.rs

@@ -8,7 +8,7 @@ use std::time::Duration;
 
 use anyhow::Error;
 
-pub async fn poll_oneoff<'a>(poll: &mut Poll<'a>) -> Result<(), Error> {
+pub(crate) async fn poll_oneoff<'a>(poll: &mut Poll<'a>) -> Result<(), Error> {
     // Collect all stream I/O subscriptions. Clock subscriptions are handled
     // separately below.
     let mut ready = false;
@@ -139,7 +139,7 @@ pub async fn poll_oneoff<'a>(poll: &mut Poll<'a>) -> Result<(), Error> {
 
     Ok(())
 }
-pub struct SyncSched;
+pub(crate) struct SyncSched;
 #[async_trait::async_trait]
 impl WasiSched for SyncSched {
     async fn poll_oneoff<'a>(&self, poll: &mut Poll<'a>) -> Result<(), Error> {