Work around bad implementation of service-worker rendered pages in Microsoft SharePoint #226
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
There was a problem hiding this comment.
Pull Request Overview
This PR centralizes JSON-detection logic into a shared module and adds a special case to ignore SharePoint service-worker responses that wrongly claim to be JSON.
- Extracted common background logic (detection, storage, messaging) into
background-common.ts - Updated Firefox and Chrome background scripts to use
isEventJSONandinstallMessageListener - Special-cased detection of SharePoint pages by checking for the
MicrosoftSharePointTeamServicesheader
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/content.ts | Added trailing comma on errorPage invocation to align arguments |
| src/background-firefox.ts | Switched to isEventJSON for header inspection; removed redundant listener and storage code |
| src/background-common.ts | New shared module with isEventJSON, storage helpers (addJsonUrl, hasJsonUrl), and installMessageListener |
| src/background-chrome.ts | Replaced inline detection and messaging with calls to shared isEventJSON and installMessageListener |
Comments suppressed due to low confidence (3)
src/background-firefox.ts:13
- [nitpick] The indentation level of this line appears inconsistent with the surrounding block. Aligning it with the
if (header) {braces will improve readability.
addJsonUrl(event.url);
src/background-chrome.ts:13
- [nitpick] Since this listener does not specify the "blocking" extraInfoSpec, returning the headers is unnecessary and could be removed to simplify the code.
return { responseHeaders: event.responseHeaders };
src/background-common.ts:7
- Consider adding unit tests for
isEventJSON, especially covering the case where aMicrosoftSharePointTeamServicesheader is present so it correctly returnsundefined.
export function isEventJSON(
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Apparently Microsoft SharePoint will render pages from its service worker after the first load. The service worker downloads a JSON document and then processes it into HTML to return to the browser. However, they fail to change the content type header of the response, so they are effectively stating "This is JSON". And of course if you say it's JSON, JSONView will display it as JSON.
This fixes it by specifically looking for a header that indicates we're getting a response from SharePoint, rather than trying to second-guess responses generically.
Fixes #210