Duplicate <script> tags for the shared chunks

[kristw]

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• I have checked the superset logs for python stacktraces and included it here as text if any
• I have reproduced the issue with at least the latest released version of superset
• I have checked the issue tracker for the same issue and I haven't found one similar

Superset version

Master

Expected results

One <script> tag for each chunk.

Actual results

There are duplicate <script> tags for the shared chunks. If you view page source, there will be multiple vendors-addSlice-common-dashboard-explore-profile-sqllab-theme-welcome.0fe210d7.chunk.js

For example on the top of the page.

<script src="/static/assets/dist/vendors-addSlice-common-dashboard-explore-profile-sqllab-theme-welcome.0fe210d7.chunk.js"></script>
<script src="/static/assets/dist/vendors-dashboard-explore-profile-sqllab-theme-welcome.0fe210d7.chunk.js"></script>
<script src="/static/assets/dist/theme.0fe210d7.entry.js"></script>

<script src="/static/assets/dist/vendors-addSlice-common-dashboard-explore-profile-sqllab-theme-welcome.0fe210d7.chunk.js"></script>
<script src="/static/assets/dist/vendors-addSlice-common-dashboard-explore-profile-sqllab-welcome.0fe210d7.chunk.js"></script>
<script src="/static/assets/dist/addSlice-common-dashboard-explore-profile-sqllab-welcome.0fe210d7.chunk.js"></script>
<script src="/static/assets/dist/common.0fe210d7.entry.js"></script>

Because each entry in the js manifest lists an array of chunks each entry point needs, independent of other entry points. When we render this directly to FAB template, it does not de-dup.

XHR Performance-wise not too bad as browser only fetches and parses once, but for correctness, if the chunk executes something, it executes multiple times.

Steps to reproduce

Open Superset, view source.