@tus/s3-store: Fix incorrect part retreival procedure (#507)

* @tus/s3-store: Fix incorrect part retreival procedure

* change that function always returns an array

Author: mitjap

packages/s3-store/index.ts

@@ -378,38 +378,26 @@ export class S3Store extends DataStore {
   private async retrieveParts(
     id: string,
     partNumberMarker?: string
-  ): Promise<Array<AWS.Part> | undefined> {
+  ): Promise<Array<AWS.Part>> {
     const params: AWS.ListPartsCommandInput = {
       Bucket: this.bucket,
       Key: id,
       UploadId: this.cache.get(id)?.['upload-id'],
-    }
-    if (partNumberMarker) {
-      params.PartNumberMarker = partNumberMarker
+      PartNumberMarker: partNumberMarker,
     }
 
     const data = await this.client.listParts(params)
 
-    // INFO: NextPartNumberMarker should be undefined when there are no more parts to retrieve,
-    // instead it keeps giving `0` so to prevent an infinite loop we check the number.
-    if (data.NextPartNumberMarker && Number(data.NextPartNumberMarker) > 0) {
-      return this.retrieveParts(id, data.NextPartNumberMarker).then((parts) => {
-        if (parts && data.Parts) {
-          return [...data.Parts, ...parts]
-        }
-        return data.Parts
-      })
-    }
+    let parts = data.Parts ?? []
 
-    const parts = data.Parts
+    if (data.IsTruncated) {
+      const rest = await this.retrieveParts(id, data.NextPartNumberMarker)
+      parts = [...parts, ...rest]
+    }
 
-    if (parts && !partNumberMarker) {
-      return (
-        parts
-          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-          .sort((a, b) => a.PartNumber! - b.PartNumber!)
-          .filter((value, index) => value.PartNumber === index + 1)
-      )
+    if (!partNumberMarker) {
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      parts.sort((a, b) => a.PartNumber! - b.PartNumber!)
     }
 
     return parts
@@ -490,7 +478,8 @@ export class S3Store extends DataStore {
     // Metadata request needs to happen first
     const metadata = await this.getMetadata(id)
     const parts = await this.retrieveParts(id)
-    const partNumber = parts?.length ?? 0
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    const partNumber: number = parts.length > 0 ? parts[parts.length - 1].PartNumber! : 0
     const nextPartNumber = partNumber + 1
 
     const bytesUploaded = await this.processUpload(
@@ -505,7 +494,7 @@ export class S3Store extends DataStore {
     if (metadata.file.size === newOffset) {
       try {
         const parts = await this.retrieveParts(id)
-        await this.finishMultipartUpload(metadata, parts as Array<AWS.Part>)
+        await this.finishMultipartUpload(metadata, parts)
         this.clearCache(id)
       } catch (error) {
         log(`[${id}] failed to finish upload`, error)