Multi project build order

When you build a bnd project in ant the dependencies are built first. This explains how the ordered set of dependencies is computed.

First of all, you can explicitly specify projects to build with

-depends:project1,project2,...

Second, you can supply one or more DependencyContributor bnd plugins to modify this set, for instance

-plugin:org.foo.MyDependencyContributor;prop1=value1,prop2=value2

The DependencyContributor is given the current project and the depends set (modified by previous DependencyContributors)

For instance, it's easy to write a DependencyContributor that adds all projects in the workspace, for a "build-all" project.

Third, you have specified the bundles your project depends on with the

-buildPath:bsn1,bsn2,...

When a bsn is from a project in the workspace, it is added.

Now we know the direct dependencies for the "current" project. The set of ordered transitive dependencies is calculated by a simple tree traversal of these projects, skipping duplicates. This results in an ordered set of projects in a suitable order to build in.

The code for this is in Project.prepare (computing the direct dependencies) and Project.traverse (computing the transitive dependencies).