DEV: Refactor uppy s3 mulipart mixin to not use self = this (#14960)

We no longer use this pattern, so we can replace with function
binding instead.

app/assets/javascripts/discourse/app/mixins/uppy-s3-multipart.js

@@ -1,13 +1,13 @@
 import Mixin from "@ember/object/mixin";
+import { bind } from "discourse-common/utils/decorators";
 import { Promise } from "rsvp";
 import { ajax } from "discourse/lib/ajax";
 import AwsS3Multipart from "@uppy/aws-s3-multipart";
+const RETRY_DELAYS = [0, 1000, 3000, 5000];
 
 export default Mixin.create({
   _useS3MultipartUploads() {
     this.set("usingS3MultipartUploads", true);
-    const self = this;
-    const retryDelays = [0, 1000, 3000, 5000];
 
     this._uppyInstance.use(AwsS3Multipart, {
       // controls how many simultaneous _chunks_ are uploaded, not files,
@@ -18,10 +18,22 @@ export default Mixin.create({
       // chunk size via getChunkSize(file), so we may want to increase
       // the chunk size for larger files
       limit: 10,
-      retryDelays,
+      retryDelays: RETRY_DELAYS,
 
-      createMultipartUpload(file) {
-        self._uppyInstance.emit("create-multipart", file.id);
+      createMultipartUpload: this._createMultipartUpload,
+      prepareUploadParts: this._prepareUploadParts,
+      completeMultipartUpload: this._completeMultipartUpload,
+      abortMultipartUpload: this._abortMultipartUpload,
+
+      // we will need a listParts function at some point when we want to
+      // resume multipart uploads; this is used by uppy to figure out
+      // what parts are uploaded and which still need to be
+    });
+  },
+
+  @bind
+  _createMultipartUpload(file) {
+    this._uppyInstance.emit("create-multipart", file.id);
 
     const data = {
       file_name: file.name,
@@ -43,7 +55,7 @@ export default Mixin.create({
       data,
       // uppy is inconsistent, an error here fires the upload-error event
     }).then((responseData) => {
-          self._uppyInstance.emit("create-multipart-success", file.id);
+      this._uppyInstance.emit("create-multipart-success", file.id);
 
       file.meta.unique_identifier = responseData.unique_identifier;
       return {
@@ -53,7 +65,8 @@ export default Mixin.create({
     });
   },
 
-      prepareUploadParts(file, partData) {
+  @bind
+  _prepareUploadParts(file, partData) {
     if (file.preparePartsRetryAttempts === undefined) {
       file.preparePartsRetryAttempts = 0;
     }
@@ -67,7 +80,7 @@ export default Mixin.create({
       .then((data) => {
         if (file.preparePartsRetryAttempts) {
           delete file.preparePartsRetryAttempts;
-              self._consoleDebug(
+          this._consoleDebug(
             `[uppy] Retrying batch fetch for ${file.id} was successful, continuing.`
           );
         }
@@ -85,26 +98,27 @@ export default Mixin.create({
         // if we exceed the attempts then there is no way that uppy will
         // retry the upload once again, so in that case the alert can
         // be safely shown to the user that their upload has failed.
-            if (file.preparePartsRetryAttempts < retryDelays.length) {
+        if (file.preparePartsRetryAttempts < RETRY_DELAYS.length) {
           file.preparePartsRetryAttempts += 1;
           const attemptsLeft =
-                retryDelays.length - file.preparePartsRetryAttempts + 1;
-              self._consoleDebug(
+            RETRY_DELAYS.length - file.preparePartsRetryAttempts + 1;
+          this._consoleDebug(
             `[uppy] Fetching a batch of upload part URLs for ${file.id} failed with status ${status}, retrying ${attemptsLeft} more times...`
           );
           return Promise.reject({ source: { status } });
         } else {
-              self._consoleDebug(
+          this._consoleDebug(
             `[uppy] Fetching a batch of upload part URLs for ${file.id} failed too many times, throwing error.`
           );
           // uppy is inconsistent, an error here does not fire the upload-error event
-              self._handleUploadError(file, err);
+          this._handleUploadError(file, err);
         }
       });
   },
 
-      completeMultipartUpload(file, data) {
-        self._uppyInstance.emit("complete-multipart", file.id);
+  @bind
+  _completeMultipartUpload(file, data) {
+    this._uppyInstance.emit("complete-multipart", file.id);
     const parts = data.parts.map((part) => {
       return { part_number: part.PartNumber, etag: part.ETag };
     });
@@ -119,12 +133,13 @@ export default Mixin.create({
       }),
       // uppy is inconsistent, an error here fires the upload-error event
     }).then((responseData) => {
-          self._uppyInstance.emit("complete-multipart-success", file.id);
+      this._uppyInstance.emit("complete-multipart-success", file.id);
       return responseData;
     });
   },
 
-      abortMultipartUpload(file, { key, uploadId }) {
+  @bind
+  _abortMultipartUpload(file, { key, uploadId }) {
     // if the user cancels the upload before the key and uploadId
     // are stored from the createMultipartUpload response then they
     // will not be set, and we don't have to abort the upload because
@@ -136,7 +151,7 @@ export default Mixin.create({
     // this gives us a chance to inspect the upload stub before
     // it is deleted from external storage by aborting the multipart
     // upload; see also ExternalUploadManager
-        if (file.meta.error && self.siteSettings.enable_upload_debug_mode) {
+    if (file.meta.error && this.siteSettings.enable_upload_debug_mode) {
       return;
     }
 
@@ -147,13 +162,7 @@ export default Mixin.create({
       },
       // uppy is inconsistent, an error here does not fire the upload-error event
     }).catch((err) => {
-          self._handleUploadError(file, err);
-        });
-      },
-
-      // we will need a listParts function at some point when we want to
-      // resume multipart uploads; this is used by uppy to figure out
-      // what parts are uploaded and which still need to be
+      this._handleUploadError(file, err);
     });
   },
 });