buildexportdepend

Buildexportdepend is a directive used in some multi-package build systems to control how a target’s build-time dependencies are propagated to downstream packages. When enabled, the build system exports the dependency graph of a target so that consumers can reason about what they must build, even if they do not directly depend on the original source. This can improve correctness and efficiency in complex hierarchies and support more reliable incremental builds.

In practice, buildexportdepend is implemented as a boolean flag or attribute on a build rule or package recipe. It influences the metadata emitted by the build, such as a dependency manifest or package metadata, and is consulted by the dependency resolver used by downstream packages. The exported information typically includes transitive build-time dependencies that are necessary to build the target in downstream contexts.

Example usage in a hypothetical package definition:

buildexportdepend = true

target: libfoo

With this flag set, any package depending on libfoo can receive the full set of libfoo’s build-time dependencies in its own graph, ensuring proper rebuild behavior when those dependencies change.

Considerations and limitations: enabling buildexportdepend can increase the size of dependency metadata and the work required to compute it. Not all build systems support it, and it may introduce complexity or potential for stale metadata if not maintained correctly. It is most beneficial in large, multi-package environments where accurate transitive build information improves incremental builds and correctness.

See also: dependency graph, build system, dependencies, transitive dependencies, export metadata.