[bug][bender sources] Package with no source files is being dropped from dependency graph

[WRoenninger]

When warning[W04]: Source group in package contains no source files. is being thrown, the manifest is dropped from the dependency tree, regardless if it contains further dependencies.

Was using a Bender.yml to collect a bunch of dependencies together. The aggregate bender file does not contain any source files, but a bunch of dependecies.

Example_structure:

Bender(top) <--- Is showing up in resolved tree
    -> Bender(no_sources_but_has_dependencies) <--- This throws the warning 
         -> Bender(with_some_sources) <--- Not showing up in resolved tree!
         -> Bender(with_more_sources) <--- Not showing up in resolved tree!
    -> Bender(with_different_sources) <--- Is showing up in resolved tree

Seems to be connected with the yml validation or topological sorting. Command which the bug was observed is bender -d <path_to_top> sources -f. The command bender packages has them correctly listed. Seems they are also being dropped from bender script.

Setup:

• All dependencies are inside the same repository and being linked via path.
• A .bender.yml in the repositories root is used as a pseudo registry to specify the concrete paths and avoid duplications.

Bender version 0.31.0

[micprog]

Currently, this functionality is not supported. I started implementing a fix in the fix_no_sources branch, but I am debating if this should be supported by bender. Ideally, a package declares all its dependencies explicitly to ensure the version requirements are properly applied, and to ensure the export_include_dirs are properly propagated, which will not be the case for the transitive dependencies.

[WRoenninger]

In the case of the export_include_dirs I agree, they should stay being not transitive as they are now. In case of a bender manifest only declaring dependencies, would expect the manifest to just be a node in the tree and stop propagation of eventual export_include_dirs.

Target filtering could leave a manifest empty of sources already. Mechanically think this would not differ from specifying no sources at all.

Note: In bender 0.28.1 a manifest node without sources was not removed from the graph. Hence observing this whilst trying out the new version.

Note Note: Great job on that big release btw. Happy to see that it happened. Have been waiting for it for a while :)

[micprog]

I thought this was already an issue previously (#161, #166), but if the behavior changed more investigation is needed. Nonetheless, it seems the functionality is needed, so we should ensure it is functional.

[WRoenninger]

Might now have something to do with the manifest validation, am getting the W04 warning after all.

Is a manifest being discarded if the validation fails? Would explain the missing dependencies if the failing manifest is the only link to the child manifests.

[WRoenninger]

Thinking now with the new target specific dependencies, having support for empty sources would make a neat dependency selector. Use case might be some implementation platform selection top-level, tech-abstraction and the like.