feat(cli): Improve error handling around grain run (#1913)

Co-authored-by: Blaine Bublitz <[email protected]>
Co-authored-by: Oscar Spencer <[email protected]>

cli/bin/grainrun.js

@@ -30,12 +30,37 @@ const wasi = new WASI({
 const importObject = { wasi_snapshot_preview1: wasi.wasiImport };
 
 async function run(filename) {
+  let bytes;
   try {
-    const wasm = await WebAssembly.compile(await readFile(filename));
-    const instance = await WebAssembly.instantiate(wasm, importObject);
+    bytes = await readFile(filename);
+  } catch (err) {
+    console.error(`Unable to read file: ${filename}`);
+    process.exit(1);
+  }
 
+  let wasm;
+  try {
+    wasm = await WebAssembly.compile(bytes);
+  } catch (err) {
+    if (filename.endsWith(".gr")) {
+      console.error(
+        `The \`grain run\` command is used on compiled \`.wasm\` files.`
+      );
+      console.error(
+        `To compile and run your \`.gr\` file, use \`grain ${filename}\``
+      );
+    } else {
+      console.error(`Unable to compile WebAssembly module.`);
+      console.error(err.statck);
+    }
+    process.exit(1);
+  }
+
+  try {
+    const instance = await WebAssembly.instantiate(wasm, importObject);
     wasi.start(instance);
   } catch (err) {
+    console.error(`Unable to instantiate WebAssembly module.`);
     console.error(err.stack);
     process.exit(1);
   }