Return empty feed instead of 204 from the DiscoJuice feeds endpoint

[Kasinhou]

Problem

The login and register pages throw an uncaught JS error on load, which fails the Playwright consoleErrors.spec.ts checks (2 pages × chromium/firefox/webkit = 6 failing tests):

TypeError: Cannot read properties of undefined (reading 'length')
    at n.merge (jquery-2.1.4.min.js)
    at Object.success (aai/discojuice/discojuice.js:62)

Root cause

The DiscoJuice IdP-discovery widget on those pages loads /server/api/discojuice/feeds?callback=dj_md_1 via JSONP and passes the response body straight to jQuery.merge().

ClarinDiscoJuiceFeedsController returned 204 No Content whenever the feed cache was blank:

if (StringUtils.isBlank(feedsContent)) {
    response.sendError(HttpServletResponse.SC_NO_CONTENT);
    return null;
}

That cache is populated only by ClarinDiscoJuiceFeedsUpdateScheduler, which downloads feeds only when shibboleth.discofeed.allowed is true — and that property defaults to false. So on a default deployment the endpoint always returns 204, the JSONP script tag executes with no body, the dj_md_1(...) callback never receives its argument, and jQuery.merge(list, undefined) reads undefined.length and throws.

A 204 fundamentally breaks the JSONP contract: the response body must be executable JS that calls the callback, so an empty body can never be consumed safely.

Fix

When there is no feed content, return an empty but valid feed instead of a 204:

• with a callback → dj_md_1([])
• without a callback → []

The callback now always fires with a well-formed (possibly empty) array, so the widget degrades gracefully (no extra IdPs listed) instead of crashing. Deployments that have shibboleth.discofeed.allowed enabled and real feed content are unaffected — that path is unchanged.

The now-unused HttpServletResponse parameter and its imports were removed along with the sendError branch.

Test

Added getDiscoFeedsWithoutContentReturnsEmptyFeed to ClarinDiscoJuiceFeedsControllerIT, which forces the empty-cache state and asserts 200 with dj_md_1([]) (with callback) and [] (without), instead of a 204. The existing getDiscoFeeds test (populated feed) still covers the normal path.

Verification

Reproduced live on dev-6.pc:8603: the error fires on /repository/login and /repository/register (both mount the widget) and not on /repository/home (no widget). The failing network call is GET /server/api/discojuice/feeds?callback=dj_md_1 → 204.

Note: the widget also makes external calls to store.discojuice.org that fail with ERR_NAME_NOT_RESOLVED in the sandboxed test env. That is unrelated environment noise — the 204 is what triggers the console error the tests assert on.

🤖 Generated with Claude Code

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