check in virtfs backend test harness

crates/test-programs/tests/wasm_tests/runtime/mod.rs

@@ -0,0 +1,2 @@
+pub mod cap_std_sync;
+pub mod virtfs;

crates/test-programs/tests/wasm_tests/runtime/virtfs.rs

@@ -0,0 +1,71 @@
+use anyhow::Context;
+use std::cell::RefCell;
+use std::path::Path;
+use std::rc::Rc;
+use wasi_common::{
+    pipe::{ReadPipe, WritePipe},
+    table::Table,
+    WasiCtx,
+};
+use wasmtime::{Linker, Module, Store};
+
+pub fn instantiate(data: &[u8], bin_name: &str, workspace: Option<&Path>) -> anyhow::Result<()> {
+    let stdout = WritePipe::new_in_memory();
+    let stderr = WritePipe::new_in_memory();
+
+    let r = {
+        let store = Store::default();
+
+        // Create our wasi context.
+        let mut builder = WasiCtx::builder(
+            wasi_cap_std_sync::random_ctx(),
+            wasi_cap_std_sync::clocks_ctx(),
+            wasi_cap_std_sync::sched_ctx(), // We shouldnt actually use this, but we will until we make a virtual scheduler
+            Rc::new(RefCell::new(Table::new())),
+        );
+
+        builder = builder
+            .arg(bin_name)?
+            .arg(".")?
+            .stdin(Box::new(ReadPipe::from(Vec::new())))
+            .stdout(Box::new(stdout.clone()))
+            .stderr(Box::new(stderr.clone()));
+
+        if workspace.is_some() {
+            let fs = wasi_virtfs::Filesystem::new(wasi_cap_std_sync::clocks_ctx().system, 420); // XXX this is duplicated - should be reference counted so I can use the same in the builder...
+            builder = builder.preopened_dir(fs.root(), ".")?;
+        }
+        let wasi = wasmtime_wasi::Wasi::new(&store, builder.build()?);
+
+        let mut linker = Linker::new(&store);
+
+        wasi.add_to_linker(&mut linker)?;
+
+        let module = Module::new(store.engine(), &data).context("failed to create wasm module")?;
+        let instance = linker.instantiate(&module)?;
+        let start = instance.get_func("_start").unwrap();
+        let with_type = start.get0::<()>()?;
+        with_type().map_err(anyhow::Error::from)
+    };
+
+    match r {
+        Ok(()) => Ok(()),
+        Err(trap) => {
+            let stdout = stdout
+                .try_into_inner()
+                .expect("sole ref to stdout")
+                .into_inner();
+            if !stdout.is_empty() {
+                println!("guest stdout:\n{}\n===", String::from_utf8_lossy(&stdout));
+            }
+            let stderr = stderr
+                .try_into_inner()
+                .expect("sole ref to stderr")
+                .into_inner();
+            if !stderr.is_empty() {
+                println!("guest stderr:\n{}\n===", String::from_utf8_lossy(&stderr));
+            }
+            Err(trap.context(format!("error while testing Wasm module '{}'", bin_name,)))
+        }
+    }
+}