slight now pre-opens the . dir to allow filesystem access (#343)

* slight now pre-opens . to allow filesystem ops

Signed-off-by: danbugs <danilochiarlone@gmail.com>

* .gitignored test.txt file

Signed-off-by: danbugs <danilochiarlone@gmail.com>

---------

Signed-off-by: danbugs <danilochiarlone@gmail.com>

Author: danbugs

.gitignore

@@ -3,4 +3,5 @@ target/
 bindings.rs
 .idea
 .DS_Store
-**.tar.gz
+**.tar.gz
+tests/test.txt

crates/runtime/src/lib.rs

@@ -8,7 +8,7 @@ use async_trait::async_trait;
 use ctx::SlightCtxBuilder;
 use resource::{get_host_state, HttpData};
 use slight_common::{CapabilityBuilder, WasmtimeBuildable, WasmtimeLinkable};
-use wasi_cap_std_sync::WasiCtxBuilder;
+use wasi_cap_std_sync::{ambient_authority, Dir, WasiCtxBuilder};
 use wasi_common::WasiCtx;
 use wasmtime::{Config, Engine, Instance, Linker, Module, Store};
 
@@ -132,7 +132,10 @@ pub fn default_config() -> Result<Config> {
 
 // TODO (Joe): expose the wasmtime wasi context as a capability?
 pub fn default_wasi() -> Result<WasiCtx> {
-    let ctx: WasiCtxBuilder = WasiCtxBuilder::new().inherit_stdio().inherit_args()?;
+    let ctx: WasiCtxBuilder = WasiCtxBuilder::new()
+        .preopened_dir(Dir::open_ambient_dir(".", ambient_authority())?, ".")?
+        .inherit_stdio()
+        .inherit_args()?;
     Ok(ctx.build())
 }
 

tests/build.rs

@@ -7,13 +7,15 @@ const WIT_DIRECTORY: &str = "wit/*";
 const KEYVALUE_TEST_PATH: &str = "./keyvalue-test";
 const HTTP_TEST_PATH: &str = "./http-test";
 const CONFIGS_TEST_PATH: &str = "./configs-test";
+const FILESYSTEM_ACCESS_TEST_PATH: &str = "./filesystem-access-test";
 
 fn main() {
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rerun-if-changed={WIT_DIRECTORY}");
     println!("cargo:rerun-if-changed={KEYVALUE_TEST_PATH}/src/main.rs");
     println!("cargo:rerun-if-changed={HTTP_TEST_PATH}/src/main.rs");
     println!("cargo:rerun-if-changed={CONFIGS_TEST_PATH}/src/main.rs");
+    println!("cargo:rerun-if-changed={FILESYSTEM_ACCESS_TEST_PATH}/src/main.rs");
 
     // Check if wasm32-wasi target is installed
 
@@ -31,6 +33,7 @@ fn main() {
         cargo_wasi_build(KEYVALUE_TEST_PATH);
         cargo_wasi_build(HTTP_TEST_PATH);
         cargo_wasi_build(CONFIGS_TEST_PATH);
+        cargo_wasi_build(FILESYSTEM_ACCESS_TEST_PATH);
     }
 }
 

tests/filesystem-access-test/Cargo.lock

@@ -0,0 +1,14 @@
+[package]
+name = "filesystem-access-test"
+version = "0.1.0"
+edition = "2021"
+authors = [ "DeisLabs Engineering Team" ]
+
+[[bin]]
+name = "filesystem-access-test"
+test = false
+
+[dependencies]
+anyhow = "1"
+
+[workspace]

tests/filesystem-access-test/Cargo.toml

@@ -0,0 +1,6 @@
+specversion = "0.2"
+
+[[capability]]
+resource = "keyvalue.filesystem"
+name = "rand"
+    # This capability does not require any configs

tests/filesystem-access-test/slightfile.toml

@@ -0,0 +1,16 @@
+use std::fs::OpenOptions;
+use std::io::Write;
+
+fn main() -> anyhow::Result<()> {
+    // Open the file in append mode
+    let mut file = OpenOptions::new()
+        .write(true)
+        .append(true)
+        .create(true)
+        .open("./test.txt")?;
+
+    // Write the string to the file
+    writeln!(file, "\nHello, World!")?;
+
+    Ok(())
+}

tests/filesystem-access-test/src/main.rs

@@ -36,6 +36,21 @@ mod integration_tests {
         use crate::{run, slight_path};
         use anyhow::Result;
 
+        #[test]
+        fn filesystem_access_test() -> Result<()> {
+            let out_dir = PathBuf::from(format!("{}/target/wasms", env!("CARGO_MANIFEST_DIR")));
+            let out_dir = out_dir.join("wasm32-wasi/debug/filesystem-access-test.wasm");
+            let file_config = &format!(
+                "{}/filesystem-access-test/slightfile.toml",
+                env!("CARGO_MANIFEST_DIR")
+            );
+            run(
+                &slight_path(),
+                vec!["-c", file_config, "run", out_dir.to_str().unwrap()],
+            );
+            Ok(())
+        }
+
         #[test]
         fn envvars_test() -> Result<()> {
             let out_dir = PathBuf::from(format!("{}/target/wasms", env!("CARGO_MANIFEST_DIR")));