Intermittent CDN Fetch Failures from `jspm.dev` for `immutable@4.0.0-rc.12!cjs`

[rickmcgeer]

Reported by: Aiko (via Rick McGeer)

Summary:
Lively intermittently fails to fetch immutable@4.0.0-rc.12!cjs from jspm.dev during the freezing process. This affects packaging Lively applications into standalone artifacts, leading to unreliable builds unless manually retried.

Symptoms:

[lively.freezer]: Error fetching https://jspm.dev/npm:immutable@4.0.0-rc.12!cjs. Retrying...

The error occurs sporadically, and retrying almost always resolves it, but introduces unnecessary friction in automated or CI-based workflows.

Suggested Improvements:

• Add retry logic with exponential backoff to the freezer
• Support fallback CDNs like esm.sh or skypack.dev
• Optionally allow pinning alternate URLs via import maps for known-flaky packages
• Consider caching flaky modules locally after the first successful freeze

Workaround:
Switching to:

import { Map } from "https://esm.sh/immutable@4.0.0-rc.12";

...appears to avoid the issue entirely.

Reproduce Steps:

• Freeze a Lively world that imports immutable
• Observe intermittent fetch failure from jspm.dev
• Retry manually to recover

Let us know if a patch to the freezer would be welcome — we're happy to contribute.

Observed on c725a77, Windows/Linux, but this occurs everywhere.

[merryman]

This is an issue with #1640. I am sure the server is not properly maintained any more, since its going to be shut down in 6 months. I am working on a fix for that right, now, will be launching, hopefully next month.

[merryman]

We are almost ready to fix this issue with #1765, however there are still some bugs I found with the new esm cdn that is supposed to replace jspm.dev. Once these are resolved, we should be able to merge.