wasi:filesystem@0.3.0-rc-2025-09-16: Add tests for symbolic links

Author: wingo

tests/rust/wasm32-wasip3/src/bin/filesystem-symbolic-links.json

@@ -0,0 +1,3 @@
+{
+    "dirs": ["fs-tests.dir"]
+}

tests/rust/wasm32-wasip3/src/bin/filesystem-symbolic-links.rs

@@ -0,0 +1,115 @@
+use std::process;
+extern crate wit_bindgen;
+
+wit_bindgen::generate!({
+    inline: r"
+  package test:test;
+
+  world test {
+      include wasi:filesystem/imports@0.3.0-rc-2025-09-16;
+      include wasi:cli/command@0.3.0-rc-2025-09-16;
+  }
+",
+    additional_derives: [PartialEq, Eq, Hash, Clone],
+    // Work around https://github.com/bytecodealliance/wasm-tools/issues/2285.
+    features:["clocks-timezone"],
+    generate_all
+});
+
+use wasi::filesystem::types::Descriptor;
+use wasi::filesystem::types::{DescriptorFlags, ErrorCode, OpenFlags, PathFlags};
+
+async fn test_symbolic_links(dir: &Descriptor) {
+    let ln_s = |from: &str, to: &str| -> _ { dir.symlink_at(from.to_string(), to.to_string()) };
+    let readlink = |path: &str| dir.readlink_at(path.to_string());
+    let stat_with_flags = |flags: PathFlags, path: &str| dir.stat_at(flags, path.to_string());
+    let stat_follow = |path: &str| stat_with_flags(PathFlags::SYMLINK_FOLLOW, path);
+    let open_r_follow = |path: &str| -> _ {
+        dir.open_at(
+            PathFlags::SYMLINK_FOLLOW,
+            path.to_string(),
+            OpenFlags::empty(),
+            DescriptorFlags::READ,
+        )
+    };
+    let open_r = |path: &str| -> _ {
+        dir.open_at(
+            PathFlags::empty(),
+            path.to_string(),
+            OpenFlags::empty(),
+            DescriptorFlags::READ,
+        )
+    };
+    let rm = |path: &str| dir.unlink_file_at(path.to_string());
+
+    // readlink-at: async func(path: string) -> result<string, error-code>;
+    assert_eq!(readlink("").await, Err(ErrorCode::NoEntry));
+    assert_eq!(readlink(".").await, Err(ErrorCode::Invalid));
+    assert_eq!(readlink("a.txt").await, Err(ErrorCode::Invalid));
+    assert_eq!(readlink("z.txt").await, Err(ErrorCode::NoEntry));
+    assert_eq!(readlink("./../").await, Err(ErrorCode::NotPermitted));
+    assert_eq!(readlink("..").await, Err(ErrorCode::NotPermitted));
+    assert_eq!(readlink("/").await, Err(ErrorCode::NotPermitted));
+    assert_eq!(readlink("parent").await, Ok("..".to_string()));
+
+    let afd = open_r("a.txt").await.unwrap();
+    assert_eq!(
+        afd.readlink_at(".".to_string()).await,
+        Err(ErrorCode::NotDirectory)
+    );
+
+    // https://github.com/WebAssembly/wasi-filesystem/issues/186
+    assert_eq!(
+        open_r("parent")
+            .await
+            .expect_err("open symlink with NOFOLLOW"),
+        ErrorCode::Loop
+    );
+
+    ln_s("parent", "parent-link").await.unwrap();
+    assert_eq!(open_r("parent-link").await.unwrap_err(), ErrorCode::Loop);
+    assert_eq!(
+        open_r_follow("parent-link").await.unwrap_err(),
+        ErrorCode::NotPermitted
+    );
+    assert_eq!(
+        stat_follow("parent-link").await.unwrap_err(),
+        ErrorCode::NotPermitted
+    );
+    assert_eq!(open_r("parent-link").await.unwrap_err(), ErrorCode::Loop);
+    assert_eq!(
+        ln_s("a.txt", "parent-link/a.txt").await,
+        Err(ErrorCode::NotPermitted)
+    );
+    rm("parent-link").await.unwrap();
+
+    ln_s("self", "self").await.unwrap();
+    assert_eq!(open_r_follow("self").await.unwrap_err(), ErrorCode::Loop);
+    assert_eq!(stat_follow("self").await.unwrap_err(), ErrorCode::Loop);
+    rm("self").await.unwrap();
+
+    assert_eq!(ln_s("whatever", "").await, Err(ErrorCode::NoEntry));
+    assert_eq!(ln_s("", "whatever").await, Err(ErrorCode::NoEntry));
+    // symlink-at: async func(old-path: string, new-path: string) -> result<_, error-code>;
+}
+
+struct Component;
+export!(Component);
+impl exports::wasi::cli::run::Guest for Component {
+    async fn run() -> Result<(), ()> {
+        match &wasi::filesystem::preopens::get_directories()[..] {
+            [(dir, dirname)] if dirname == "fs-tests.dir" => {
+                test_symbolic_links(dir).await;
+            }
+            [..] => {
+                eprintln!("usage: run with one open dir named 'fs-tests.dir'");
+                process::exit(1)
+            }
+        };
+        Ok(())
+    }
+}
+
+fn main() {
+    unreachable!("main is a stub");
+}