EdgeType

An explicit edge is one that was specified in the build description.

The explicit specification of an edge from a task to a resource should be considered a contract that must be fulfilled by the task. If the task does not report that resource as an output, the task is marked as failed.

An implicit edge is one that is reported by a task.

The set of implicit edges should always be a superset of the set of explicit edges. If this is not the case, it implies one of two problems:

1. A superfluous dependency is specified in the build description. 2. The task is not reporting all dependencies.

Case (1) causes no harm except over-building. However, case (2) should be considered an error because explicit edges are a contract that the task must fulfill. It is not possible to differentiate between these two cases. Thus, the more conservative approach is taken to always consider it an error if the set of explicit edges is not a subset of the set of implicit edges.

An edge is both explicit and implicit if it is in the build description and reported by a task.