Add chunks back to prepareUploadParts, indexed by partNumber

packages/@uppy/aws-s3-multipart/src/MultipartUploader.js

@@ -248,6 +248,11 @@ class MultipartUploader {
         key: this.key,
         uploadId: this.uploadId,
         partNumbers: candidates.map((index) => index + 1),
+        chunks: candidates.reduce((chunks, candidate) => ({
+          ...chunks,
+          // Use the part number as the index
+          [candidate + 1]: this.chunks[candidate],
+        }), {}),
       }),
     })
 

packages/@uppy/aws-s3-multipart/src/index.test.js

@@ -143,10 +143,18 @@ describe('AwsS3Multipart', () => {
 
       await core.upload()
 
+      function validatePartData ({ partNumbers, chunks }, expected) {
+        expect(partNumbers).toEqual(expected)
+        partNumbers.forEach(partNumber => {
+          expect(chunks[partNumber]).toBeDefined()
+        })
+      }
+
       expect(awsS3Multipart.opts.prepareUploadParts.mock.calls.length).toEqual(3)
-      expect(awsS3Multipart.opts.prepareUploadParts.mock.calls[0][1].partNumbers).toEqual([1, 2, 3, 4, 5])
-      expect(awsS3Multipart.opts.prepareUploadParts.mock.calls[1][1].partNumbers).toEqual([6, 7, 8])
-      expect(awsS3Multipart.opts.prepareUploadParts.mock.calls[2][1].partNumbers).toEqual([9, 10])
+
+      validatePartData(awsS3Multipart.opts.prepareUploadParts.mock.calls[0][1], [1, 2, 3, 4, 5])
+      validatePartData(awsS3Multipart.opts.prepareUploadParts.mock.calls[1][1], [6, 7, 8])
+      validatePartData(awsS3Multipart.opts.prepareUploadParts.mock.calls[2][1], [9, 10])
 
       const completeCall = awsS3Multipart.opts.completeMultipartUpload.mock.calls[0][1]
 

packages/@uppy/aws-s3-multipart/types/index.d.ts

@@ -21,7 +21,7 @@ interface AwsS3MultipartOptions extends PluginOptions {
     ) => MaybePromise<AwsS3Part[]>
     prepareUploadParts?: (
       file: UppyFile,
-      partData: { uploadId: string; key: string; partNumbers: Array<number> }
+      partData: { uploadId: string; key: string; partNumbers: Array<number>; chunks: { [k: number]: Blob } }
     ) => MaybePromise<{ presignedUrls: { [k: number]: string }, headers?: { [k: string]: string } }>
     abortMultipartUpload?: (
       file: UppyFile,

packages/@uppy/aws-s3-multipart/types/index.test-d.ts

@@ -22,6 +22,7 @@ import type { AwsS3Part } from '..'
       expectType<string>(partData.uploadId)
       expectType<string>(partData.key)
       expectType<Array<number>>(partData.partNumbers)
+      expectType<{ [k: number]: Blob }>(partData.chunks)
       return { presignedUrls: {} }
     },
     abortMultipartUpload (file, opts) {

website/src/docs/aws-s3-multipart.md

@@ -110,6 +110,7 @@ A function that generates a batch of signed URLs for the specified part numbers.
 * `uploadId` - The UploadID of this Multipart upload.
 * `key` - The object key in the S3 bucket.
 * `partNumbers` - An array of indecies of this part in the file (`PartNumber` in S3 terminology). Note that part numbers are _not_ zero-based.
+* `chunks` - A Javascript object with the part numbers as keys and the Blob data for each part as the value.
 
 `prepareUploadParts` should return a `Promise` with an `Object` with keys: