feat(auth): accept optional features in prefetch()

prefetch() relied on this.options.features which is only set by show().
Callers that prefetch before show() (e.g. folder hover prefetch) had no
way to pass features into the viewer, so featureEnabled() checks in
viewer prefetch() methods always read defaults.

Add an optional features param to prefetch() and merge it into per-call
viewer options without mutating this.options.

Author: Jose Gaston

src/lib/Preview.js

@@ -693,6 +693,7 @@ class Preview extends EventEmitter {
      * @param {string} options.sharedLink - Shared link
      * @param {string} options.sharedLinkPassword - Shared link password
      * @param {boolean} options.preload - Is this prefetch for a preload
+     * @param {Object} [options.features] - Feature flags to merge into viewer options for this prefetch
      * @param {string} token - Access token
      * @return {void}
      */
@@ -705,6 +706,7 @@ class Preview extends EventEmitter {
         preload = false,
         isDocFirstPrefetchEnabled = false,
         docFirstPagesConfig = null,
+        features,
     }) {
         let file;
         let loader;
@@ -747,6 +749,13 @@ class Preview extends EventEmitter {
             options.docFirstPagesConfig = docFirstPagesConfig;
         }
 
+        // If features are passed in for this prefetch call (e.g. from callers that
+        // invoke prefetch() before show() has set this.options.features), merge them
+        // into the viewer options for this call without mutating this.options.
+        if (features) {
+            options.features = { ...this.options.features, ...features };
+        }
+
         const viewerInstance = new viewer.CONSTRUCTOR(this.createViewerOptions(options));
         if (typeof viewerInstance.prefetch === 'function') {
             viewerInstance.prefetch({

src/lib/__tests__/Preview-test.js

@@ -798,6 +798,51 @@ describe('lib/Preview', () => {
 
             preview.prefetch({ fileId, token, sharedLink, sharedLinkPassword, preload: true });
         });
+
+        test('should merge per-call features into viewer options when features are passed', () => {
+            jest.spyOn(loader, 'determineViewer').mockReturnValue(viewer);
+            jest.spyOn(preview, 'createViewerOptions');
+            preview.options.features = { existingFeature: true };
+
+            preview.prefetch({
+                fileId,
+                token,
+                sharedLink,
+                sharedLinkPassword,
+                features: { migrateAccessTokenToHeader: true },
+            });
+
+            expect(preview.createViewerOptions).toHaveBeenCalledWith(
+                expect.objectContaining({
+                    features: { existingFeature: true, migrateAccessTokenToHeader: true },
+                }),
+            );
+        });
+
+        test('should not set features on viewer options when features are omitted', () => {
+            jest.spyOn(loader, 'determineViewer').mockReturnValue(viewer);
+            jest.spyOn(preview, 'createViewerOptions');
+
+            preview.prefetch({ fileId, token, sharedLink, sharedLinkPassword });
+
+            const callArgs = preview.createViewerOptions.mock.calls[0][0];
+            expect(callArgs).not.toHaveProperty('features');
+        });
+
+        test('should not mutate this.options.features when per-call features are passed', () => {
+            jest.spyOn(loader, 'determineViewer').mockReturnValue(viewer);
+            preview.options.features = { existingFeature: true };
+
+            preview.prefetch({
+                fileId,
+                token,
+                sharedLink,
+                sharedLinkPassword,
+                features: { migrateAccessTokenToHeader: true },
+            });
+
+            expect(preview.options.features).toEqual({ existingFeature: true });
+        });
     });
 
     describe('prefetchViewers()', () => {