Import tracer

[kriskowal]

What is the Problem Being Solved?

Bundles tend to get big and we notice when they can’t be posted to an Agoric blockchain with a message size limit, for example. They get big because modules get entrained by import and we need a way to investigate why they got entrained and how many bytes they (shallowly, transitively, differentially) contributed to the bundle. So, a tool like yarn why, but for modules instead of packages would be in order.

Description of the Design

A CLI tool, tentatively bundle-why would take bundle-why <entry.js> <contributor.js> would make a report starting at contributor.js that shows how many bytes it is, how many bytes it transitively imports, and how many bytes it transitively imports that were not accounted for by previous entries, then indent (maybe) and make the same report for each of its shallow imports from largest differential weight to least.

The tool will need to take the same -C,condition as bundle-source.

Security Considerations

None.

Scaling Considerations

None.

Test Plan

None.

Compatibility Considerations

None.

Upgrade Considerations

None.

[kriskowal]

Maybe trace-imports

[erights]

See also Agoric/agoric-sdk#9900 and the nice collections of links it cites