Class DependencyAggregation

  • All Implemented Interfaces:
    BuildEngineAction, AllowsNonAnnotatedFields, HasRuntimeDeps, BuildRule, HasNameAndType, Comparable<BuildRule>

    public final class DependencyAggregation
    extends AbstractBuildRule
    implements HasRuntimeDeps
    A noop build rule used to aggregate dependencies shared amongst many rules.

    In cases where many rules require largely the same sets of dependencies, such as cxx compilation of files in a target, explicitly copying the dependencies to every such rule imposes slow down and memory usage proportional to the number of rules that share a dependency set. This class curtails the copying of all shared dependencies between rules, and instead allow each rule to depend on this single rule, which captures the shared dependencies.

    This class is distinct from NoopBuildRuleWithDeclaredAndExtraDeps to make clear the requirements for its operation, namely, that it cannot be cached. This rule must not be cached in order for its dependencies to always be evaluated in different build strategies (in particular, top-down).

    • Method Detail

      • getBuildDeps

        public SortedSet<BuildRule> getBuildDeps()
        Specified by:
        getBuildDeps in interface BuildRule
        the set of rules that must be built before this rule. Normally, this matches the value of the deps argument for this build rule in the build file in which it was defined.

        However, there are special cases where other arguments pull in implicit dependencies (e.g., the keystore argument in android_binary). In these cases, the implicit dependencies are also included in the set returned by this method. The value of the original deps argument, as defined in the build file, must be accessed via a custom getter provided by the build rule.

      • isCacheable

        public boolean isCacheable()
        Description copied from interface: BuildRule
        Whether this BuildRule can be cached.

        Uncached build rules are never written out to cache, never read from cache, and does not count in cache statistics. This rule is useful for artifacts which cannot be easily normalized.

        Uncached rules are not always rebuilt, however, as long as the existing on-disk representation is up to date. This means that these rules can take advantage of SupportsInputBasedRuleKey to prevent rebuilding.

        Specified by:
        isCacheable in interface BuildEngineAction
        Specified by:
        isCacheable in interface BuildRule
        isCacheable in class AbstractBuildRule