[OPT-39999] Mep-xlg-tags.json issues

[AdobeLinhart]

Adds a check to prevent getXLGListURL() from firing multiple times by utilizing promises. It should only perform the call once.

Behavior

• Do not execute network call for mep-xlg-tags if signed out.
• Execute a single network call for mep-xlg-tags if signed in.

Instructions

• Open test URL
• Open the network panel
• Filter for mep-xlg-tags
• Observe the amount of times called
• Test both as a logged in and logged out user.

Before:

After:

Resolves: OPT-39999

Test URLs:

• Before: https://main--da-bacom--adobecom.aem.live/solutions/cmo
• After: https://main--da-bacom--adobecom.aem.live/solutions/cmo?milolibs=OPT-39999
• Psi: https://OPT-39999--milo--adobecom.aem.page/?martech=off

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Commits

• 449cf5c ✅ (latest)
• 2795684 ✅
• 5855ac8 ✅
• 1f04d4c ✅
• 21ba8c8 ✅
• 8bacb6d ✅
• 6a5a3d9 ✅

[jpratt2]

Approved.
Verified: Only one call is seen in the network tab when logged in. (see attached) The content of the network call appears unharmed.

Verified: there is no network call when logged out

[markpadbe]

I tested this locally and wanted to share a few things I noticed — mostly around how the caching and fetch flow interact. I think the intent makes sense, but a couple of edge cases seem to cause unexpected behavior:

1. Undefined fetch case
   On the second call to getXLGListURL (from getEntitlementMap), the function returns undefined because config.mepXlgTagsURL is already truthy from the first call. That ends up calling fetchData(undefined), which results in a fetch("undefined") request (you can see it fail in the network/perf waterfall). So instead of skipping the duplicate download, we end up with an erroneous request, and the preloaded XLG data never actually gets consumed since getEntitlementMap never receives a valid URL.

2. Cache getting reset
   After that second call, config.mepXlgTagsURL is set back to undefined, which means the “already fetched” guard wouldn’t hold if a third call were to happen.

3. Promise wrapper
   isSignedInUser() looks to be synchronous, so wrapping it in new Promise(resolve => …) adds a microtask delay without really buying us anything.

One alternative that seems to avoid those issues is: kick off the fetch early and cache the Promise itself, so getEntitlementMap can reuse the same in‑flight/resolved response rather than re-deriving the URL each time:

export const getXLGListURL = (config) => {
  if (config.mepXlgTagsURL) return config.mepXlgTagsURL;
  if (!window.adobeIMS?.isSignedInUser()) return undefined;
  const sheet = config.env?.name === 'prod' ? 'prod' : 'stage';
  const rawUrl = `https://www.adobe.com/federal/assets/data/mep-xlg-tags.json?sheet=${sheet}`;
  config.mepXlgTagsURL = normalizePath(rawUrl);
  return config.mepXlgTagsURL;
};

export function prefetchXLGTags(config) {
  const url = getXLGListURL(config);
  if (!url) return;
  config.mepXlgTagsPromise = fetchData(url, DATA_TYPE.JSON);
}

Then in getEntitlementMap, reuse the cached promise:

const fetchedData = config.mepXlgTagsPromise  ? await config.mepXlgTagsPromise  : await fetchData(getXLGListURL(config), DATA_TYPE.JSON);

And in init, replace the loadLink preload with:

if (pzn || pznroc) prefetchXLGTags(config);

That should give us one fetch, no wasted preload, no undefined request, and the data actually gets consumed. And again — the isSignedInUser() guard to skip signed‑out users is great; I’d definitely keep that.

[AdobeLinhart]

Thanks. I haven't really used promises since Angular. It was something Viv suggested. Updated to work as per your specifications.

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