how does a packager find version requirements for indirect dependencies?

[davidsarah]

The method of finding Tahoe's indirect requirements documented at ​http://tahoe-lafs.org/trac/tahoe-lafs/wiki/AdvancedInstall#Dependencies,

• requires a built copy of Tahoe, and
• only prints the versions being used by that copy, not the requirements.

The indirect dependencies are pyutil, zbase32, and argparse. It might be easier just to document that (with minimum version requirements if any) and update the documentation manually.

[dstufft]

This is actually a pretty hard problem to solve. The issue is that indirect dependencies are not a concrete thing and can depend on what version of direct dependencies get installed (or are already installed).

For instance:

tahoe-lafs depends on foo, foo 1.0 depends on bar, foo 2.0 depends on wat

In the above example there isn't a single set of requirements, it's a tree where the final set depends on what version of foo ends up being selected for installation. It *can* be expressed of course but it can be a very confusing representation if the version specifiers of anything but the root of the tree varies. If they are static then you can collapse the branches into a single branch and you may (in a simple case) get a single set because every combination of dependencies ends up having the same requirement specifiers.