confusion: does `colcon` or `rosdep` install packages from `package.xml`?

[VladimirFokow]

I know rosdep uses package.xml to install packages. But does colcon also use it?

Reading the "Beginner" tutorials, this quote (in section "6 Customize package.xml") is confusing to me. It says that "colcon" is searching package.xml:

This is where your package.xml would list its dependencies on other packages, for colcon to search for

Maybe replace "colcon" with "rosdep"? Or does colcon also use it - in which case, replace "colcon" with "rosdep and colcon"?

[clalancette]

I believe it is correct as-is.

rosdep is the tool that indeed walks the package.xml files and installs dependencies.

colcon is the tool that builds a workspace full of packages. In order to do this, it has to know the topological ordering between them, so it also looks at the dependencies listed in package.xml to figure out that ordering.

If you have suggestions on how to improve the wording, we are of course happy to entertain them.

[VladimirFokow]

Thank you for clarification!

I would replace "colcon" with "rosdep and colcon", just to be more clear. But if there are reasons not to, I'm okay with closing this issue

[MichaelOrlov]

@cottsay A friendly ping to follow up on this issue.