save dep and timestamp as tuple

src/cache.js

@@ -69,28 +69,27 @@ const handleExternalDepedencies = async function (
   externalDependencies,
   getFileTimestamp,
 ) {
-  const result = [];
-  for (const dep of externalDependencies) {
+  for (const depAndEmptyTimestamp of externalDependencies) {
     try {
+      const [dep] = depAndEmptyTimestamp;
       const { timestamp } = await getFileTimestamp(dep);
-      result.push(dep + "\0" + timestamp);
+      depAndEmptyTimestamp.push(timestamp);
     } catch {
-      result.push(dep);
+      // ignore errors if timestamp is not available
     }
   }
-  result.sort();
-  return result;
+  return externalDependencies;
 };
 
 const areExternalDependenciesModified = async function (
   externalDepsWithTimestamp,
   getFileTimestamp,
 ) {
   for (const depAndTimestamp of externalDepsWithTimestamp) {
-    const [dep, timestamp] = depAndTimestamp.split("\0");
+    const [dep, timestamp] = depAndTimestamp;
     let newTimestamp;
     try {
-      newTimestamp = (await getFileTimestamp(dep)).timestamp + "";
+      newTimestamp = (await getFileTimestamp(dep)).timestamp;
     } catch {
       return true;
     }

src/index.js

@@ -212,8 +212,7 @@ async function loader(source, inputSourceMap, overrides) {
 
       const { code, map, metadata, externalDependencies } = result;
 
-      externalDependencies?.forEach(depAndTimestamp => {
-        const dep = depAndTimestamp.split("\0")[0];
+      externalDependencies?.forEach(([dep]) => {
         this.addDependency(dep);
       });
       metadataSubscribers.forEach(subscriber => {

src/transform.js

@@ -32,7 +32,9 @@ module.exports = async function (source, options) {
     metadata,
     sourceType,
     // Convert it from a Set to an Array to make it JSON-serializable.
-    externalDependencies: Array.from(externalDependencies || []),
+    externalDependencies: Array.from(externalDependencies || [], dep => [
+      dep,
+    ]).sort(),
   };
 };