`cargo tree -i --workspace` doesn't work even if you specify a package

[jyn514]

Problem

cargo tree -i can't be used in a workspace.

Steps

$ cargo tree --workspace -p winapi -i
error: The `-i` flag requires a package name.

The `-i` flag is used to inspect the reverse dependencies of a specific
package. It will invert the tree and display the packages that depend on the
given package.

Note that in a workspace, by default it will only display the package's
reverse dependencies inside the tree of the workspace member in the current
directory. The --workspace flag can be used to extend it so that it will show
the package's reverse dependencies across the entire workspace. The -p flag
can be used to display the package's reverse dependencies only with the
subtree of the package given to -p.

Note that both cargo tree -i -p winapi and cargo tree --workspace work fine individually.

Notes

Output of cargo version: cargo 1.49.0-nightly (d5556aeb8 2020-11-04)

[ehuss]

I'm not sure what your trying to view specifically, but I think the command you are looking for is cargo tree --workspace -i winapi. The first line lets you know that the -i flag requires a package name. Perhaps the error message could be clarified to say something like error: The argument `-i <SPEC>` requires a package name, but none was supplied. to match the clap style?

[jyn514]

@ehuss I'm confused - if -i requires a package, then why does it work without --workspace?

(-bash@build-server) ~/.../src/librustdoc ▶️ cargo tree -i -p serde_json
serde_json v1.0.59
└── rustdoc v0.0.0 (/home/joshua/rustc/src/librustdoc)
(-bash@build-server) ~/.../src/librustdoc ▶️ cargo tree -i -p serde_json --workspace
error: The `-i` flag requires a package name.

[ehuss]

Backwards compatibility. That was the old way of specifying a package with -i. There is an ambiguity of which packages are the roots (those passed to -i) and what the "context" is (those passed to -p), so it was changed so that -i takes a package name. If no package name is given to -i, it treats the -p flags as-if they were passed to -i to retain backwards compatibility.

[jyn514]

Would it be possible to extend that compatibility to --workspace as well? Or maybe add a warning to -i -p without --workspace that says the old behavior is deprecated?

[ehuss]

I'm a little concerned that a warning would be a little noisy, since in most cases it just works, but it would probably be ok.

The error message definitely could stand some clarification, though.