use byte array instead of string for code fetch (#1307)

2 files changed, 9 insertions, 3 deletions

diff --git a/js/compiler.ts b/js/compiler.ts
index e0bfb77bb..5031fb0bf 100644
--- a/js/compiler.ts
+++ b/js/compiler.ts
@@ -233,6 +233,7 @@ export class Compiler
       // We query Rust with a CodeFetch message. It will load the sourceCode,
       // and if there is any outputCode cached, will return that as well.
       const fetchResponse = this._os.codeFetch(moduleSpecifier, containingFile);
+      assert(fetchResponse != null, "fetchResponse is null");
       moduleId = fetchResponse.moduleName;
       fileName = fetchResponse.filename;
       mediaType = fetchResponse.mediaType;
diff --git a/js/os.ts b/js/os.ts
index e56aab574..7fc37e46a 100644
--- a/js/os.ts
+++ b/js/os.ts
@@ -4,6 +4,7 @@ import { assert } from "./util";
 import * as util from "./util";
 import * as flatbuffers from "./flatbuffers";
 import { sendSync } from "./dispatch";
+import { TextDecoder } from "./text_encoding";
 
 interface CodeInfo {
   moduleName: string | undefined;
@@ -45,13 +46,17 @@ export function codeFetch(specifier: string, referrer: string): CodeInfo {
   assert(baseRes!.inner(codeFetchRes) != null);
   // flatbuffers returns `null` for an empty value, this does not fit well with
   // idiomatic TypeScript under strict null checks, so converting to `undefined`
+  const sourceCode = codeFetchRes.sourceCodeArray() || undefined;
+  const outputCode = codeFetchRes.outputCodeArray() || undefined;
+  const sourceMap = codeFetchRes.sourceMapArray() || undefined;
+  const decoder = new TextDecoder();
   return {
     moduleName: codeFetchRes.moduleName() || undefined,
     filename: codeFetchRes.filename() || undefined,
     mediaType: codeFetchRes.mediaType(),
-    sourceCode: codeFetchRes.sourceCode() || undefined,
-    outputCode: codeFetchRes.outputCode() || undefined,
-    sourceMap: codeFetchRes.sourceMap() || undefined
+    sourceCode: sourceCode && decoder.decode(sourceCode),
+    outputCode: outputCode && decoder.decode(outputCode),
+    sourceMap: sourceMap && decoder.decode(sourceMap)
   };
 }