feat(wasi) Add the “floating” WasiVersion::Latest version.

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## **[Unreleased]**
 
+- [#1029](https://github.com/wasmerio/wasmer/pull/1029) Add the “floating” `WasiVersion::Latest` version.
 - [#1006](https://github.com/wasmerio/wasmer/pull/1006) Fix minor panic issue when `wasmer::compile_with` called with llvm backend
 - [#1009](https://github.com/wasmerio/wasmer/pull/1009) Enable LLVM verifier for all tests, add new llvm-backend-tests crate.
 - [#1022](https://github.com/wasmerio/wasmer/pull/1022) Add caching support for Singlepass backend.

lib/wasi/src/lib.rs

@@ -142,7 +142,9 @@ pub fn generate_import_object_for_version(
         WasiVersion::Snapshot0 => {
             generate_import_object_snapshot0(args, envs, preopened_files, mapped_dirs)
         }
-        WasiVersion::Snapshot1 => generate_import_object(args, envs, preopened_files, mapped_dirs),
+        WasiVersion::Snapshot1 | WasiVersion::Latest => {
+            generate_import_object(args, envs, preopened_files, mapped_dirs)
+        }
     }
 }
 

lib/wasi/src/utils.rs

@@ -7,13 +7,26 @@ pub fn is_wasi_module(module: &Module) -> bool {
     get_wasi_version(module).is_some()
 }
 
-/// The version of WASI.  This is determined by the namespace string
+/// The version of WASI. This is determined by the imports namespace
+/// string.
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub enum WasiVersion {
-    /// "wasi_unstable"
+    /// `wasi_unstable`.
     Snapshot0,
-    /// "wasi_snapshot_preview1"
+    /// `wasi_snapshot_preview1`.
     Snapshot1,
+
+    /// Latest version.
+    ///
+    /// It's a “floating” version, i.e. it's an alias to the latest
+    /// version (for the moment, `Snapshot1`). Using this version is a
+    /// way to ensure that modules will run only if they come with the
+    /// latest WASI version (in case of security issues for instance),
+    /// by just updating the runtime.
+    ///
+    /// Note that this version is never returned by an API. It is
+    /// provided only by the user.
+    Latest,
 }
 
 /// Detect the version of WASI being used from the namespace