convert svelte worker to ts

Should make it easier to maintain, and ironically it also fixes
the issue with .mjs files from this morning.

ts/svelte/BUILD.bazel

@@ -1,16 +1,24 @@
 load("@build_bazel_rules_nodejs//:index.bzl", "nodejs_binary")
+load("@npm//@bazel/typescript:index.bzl", "ts_library")
+
+_deps = [
+    "@npm//@bazel/worker",
+    "@npm//sass",
+    "@npm//svelte",
+    "@npm//svelte-preprocess",
+    "@npm//svelte2tsx",
+    "@npm//typescript",
+]
+
+ts_library(
+    name = "svelte_bin_ts",
+    srcs = ["svelte.ts"],
+    deps = _deps,
+)
 
 nodejs_binary(
     name = "svelte_bin",
-    data = [
-        ":svelte.js",
-        "@npm//@bazel/worker",
-        "@npm//sass",
-        "@npm//svelte",
-        "@npm//svelte-preprocess",
-        "@npm//svelte2tsx",
-        "@npm//typescript",
-    ],
-    entry_point = ":svelte.js",
+    data = ["svelte_bin_ts"] + _deps,
+    entry_point = ":svelte.ts",
     visibility = ["//visibility:public"],
 )

ts/svelte/svelte.ts

@@ -1,14 +1,12 @@
 const fs = require("fs");
-const process = require("process");
-const path = require("path");
 const worker = require("@bazel/worker");
-const svelte = require("svelte/compiler.js");
 const svelte2tsx = require("svelte2tsx");
 const preprocess = require("svelte-preprocess");
-const ts = require("typescript");
+import * as ts from "typescript";
+import * as svelte from "svelte/compiler";
 
 const tsOptions = {
-    jsx: "preserve",
+    jsx: ts.JsxEmit.Preserve,
     declaration: true,
     emitDeclarationOnly: true,
     skipLibCheck: true,
@@ -73,7 +71,7 @@ async function writeJs(source, inputFilename, outputPath) {
 
     try {
         const processed = await svelte.preprocess(source, preprocessOptions);
-        const result = svelte.compile(processed.toString(), {
+        const result = svelte.compile(processed.toString!(), {
             format: "esm",
             generate: "dom",
             filename: outputPath,