Parse .wat files in the run subcommand

WasmKit already supports parsing of WAT (WebAssembly Text format), but its command-line interface does not act accordingly for files with `.wat` file extension. This change conditionally parses the text format on matching file extension instead of assuming that all given files are in binary format.

Author: MaxDesiatov

Package.swift

@@ -28,6 +28,7 @@ let package = Package(
         .executableTarget(
             name: "CLI",
             dependencies: [
+                "WAT",
                 "WasmKit",
                 "WasmKitWASI",
                 .product(name: "ArgumentParser", package: "swift-argument-parser"),

Sources/CLI/CMakeLists.txt

@@ -5,7 +5,7 @@ add_executable(wasmkit-cli
 )
 
 target_link_wasmkit_libraries(wasmkit-cli PUBLIC
-  ArgumentParser WasmKitWASI)
+  ArgumentParser WAT WasmKitWASI)
 
 install(TARGETS wasmkit-cli
   RUNTIME DESTINATION bin)

Sources/CLI/Commands/Run.swift

@@ -1,5 +1,6 @@
 import ArgumentParser
 import SystemPackage
+import WAT
 import WasmKit
 import WasmKitWASI
 
@@ -119,12 +120,12 @@ struct Run: ParsableCommand {
         let module: Module
         if verbose, #available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *) {
             let (parsedModule, parseTime) = try measure {
-                try parseWasm(filePath: FilePath(path))
+                try self.parseWasm(filePath: FilePath(path))
             }
             log("Finished parsing module: \(parseTime)", verbose: true)
             module = parsedModule
         } else {
-            module = try parseWasm(filePath: FilePath(path))
+            module = try self.parseWasm(filePath: FilePath(path))
         }
 
         let (interceptor, finalize) = try deriveInterceptor()
@@ -148,6 +149,23 @@ struct Run: ParsableCommand {
         }
     }
 
+    /// Parses a `.wasm` or `.wat` module.
+    func parseWasm(filePath: FilePath) throws -> Module {
+        if filePath.extension == "wat", #available(macOS 11.0, iOS 14.0, macCatalyst 14.0, tvOS 14.0, visionOS 1.0, watchOS 7.0, *) {
+            let fileHandle = try FileDescriptor.open(filePath, .readOnly)
+            defer { try? fileHandle.close() }
+
+            let size = try fileHandle.seek(offset: 0, from: .end)
+
+            let wat = try String(unsafeUninitializedCapacity: Int(size)) {
+                try fileHandle.read(fromAbsoluteOffset: 0, into: .init($0))
+            }
+            return try WasmKit.parseWasm(bytes: wat2wasm(wat))
+        } else {
+            return try WasmKit.parseWasm(filePath: filePath)
+        }
+    }
+
     /// Derives the runtime interceptor based on the command line arguments
     func deriveInterceptor() throws -> (interceptor: EngineInterceptor?, finalize: () -> Void) {
         var interceptors: [EngineInterceptor] = []