Return original read closer if no extension factories are supplied (#3784)

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As title

---

#### Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No

#### Type of change

<!--- Please check the type of change your PR introduces: --->
- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [x] 🧹 Tech Debt/Cleanup

#### Issue(s)

<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
* #<issue>

#### Test Plan

<!-- How will this be tested prior to merging.-->
- [ ] 💪 Manual
- [x] ⚡ Unit test
- [x] 💚 E2E

src/internal/m365/onedrive/collection.go

@@ -539,29 +539,23 @@ func (oc *Collection) populateDriveItem(
 				return nil, err
 			}
 
-			itemData := rc
-
-			// Add per item extensions if available
-			if len(itemExtensionFactory) > 0 {
-				extRc, extData, err := extensions.AddItemExtensions(
-					ctx,
-					rc,
-					itemInfo,
-					itemExtensionFactory)
-				if err != nil {
-					err := clues.Wrap(err, "adding extensions").Label(fault.LabelForceNoBackupCreation)
-					el.AddRecoverable(ctx, err)
-					return nil, err
-				}
-
-				itemData = extRc
-				itemInfo.Extension.Data = extData.Data
+			extRc, extData, err := extensions.AddItemExtensions(
+				ctx,
+				rc,
+				itemInfo,
+				itemExtensionFactory)
+			if err != nil {
+				err := clues.Wrap(err, "adding extensions").Label(fault.LabelForceNoBackupCreation)
+				el.AddRecoverable(ctx, err)
+				return nil, err
 			}
 
+			itemInfo.Extension.Data = extData.Data
+
 			// display/log the item download
 			progReader, _ := observe.ItemProgress(
 				ctx,
-				itemData,
+				extRc,
 				observe.ItemBackupMsg,
 				clues.Hide(itemName+dataSuffix),
 				itemSize)

src/internal/m365/onedrive/collection_test.go

@@ -936,7 +936,10 @@ func (suite *CollectionUnitTestSuite) TestItemExtensions() {
 			mbh.GI = mock.GetsItem{Err: assert.AnError}
 			mbh.GIP = mock.GetsItemPermission{Perm: models.NewPermissionCollectionResponse()}
 			mbh.GetResps = []*http.Response{
-				{StatusCode: http.StatusOK, Body: io.NopCloser(strings.NewReader(string(test.payload)))},
+				{
+					StatusCode: http.StatusOK,
+					Body:       io.NopCloser(strings.NewReader(string(test.payload))),
+				},
 			}
 			mbh.GetErrs = []error{
 				nil,

src/pkg/extensions/extensions.go

@@ -21,7 +21,8 @@ type CreateItemExtensioner interface {
 
 // AddItemExtensions wraps provided readcloser with extensions
 // supplied via factory, with the first extension in slice being
-// the innermost one.
+// the innermost one. If no extensions are provided, the original
+// readcloser is returned.
 func AddItemExtensions(
 	ctx context.Context,
 	rc io.ReadCloser,
@@ -32,12 +33,14 @@ func AddItemExtensions(
 		return nil, nil, clues.New("nil readcloser")
 	}
 
+	// If no extensions were supplied, return the original readcloser
 	if len(factories) == 0 {
-		return nil, nil, clues.New("no extensions supplied")
+		return rc, &details.ExtensionData{}, nil
 	}
 
 	ctx = clues.Add(ctx, "num_extensions", len(factories))
 
+	// Create extension data store to be passed to extensions
 	extData := &details.ExtensionData{
 		Data: make(map[string]any),
 	}

src/pkg/extensions/extensions_test.go

@@ -85,7 +85,7 @@ func (suite *ExtensionsUnitSuite) TestAddItemExtensions() {
 				extData *details.ExtensionData,
 				err error,
 			) bool {
-				return err != nil && extRc == nil && extData == nil
+				return err == nil && extRc == testRc && extData != nil && extData.Data == nil
 			},
 		},
 		{