com.facebook.buck.core.graph.transformation

Interface GraphComputation<Key extends ComputeKey<Result>,Result extends ComputeResult>

Type Parameters:

Key - The types of Keys used to query for the result on the graph computation

Result - The result of the computation given a specific key.

All Known Subinterfaces:

ComposedComputation<BaseKey,Result2>

All Known Implementing Classes:

BuildPackagePathToBuildFileManifestComputation, BuildPackagePathToUnconfiguredTargetNodePackageComputation, BuildTargetPatternToBuildPackagePathComputation, BuildTargetToUnconfiguredTargetNodeComputation, DirectoryListComputation, FileTreeComputation, LeftComposingComputation, LegacyCompatibleRuleAnalysisComputation, RightComposingComputation, RuleAnalysisComputation, UnconfiguredTargetNodeToUnconfiguredTargetNodeWithDepsComputation, WatchmanBuildPackageComputation

public interface GraphComputation<Key extends ComputeKey<Result>,Result extends ComputeResult>

Interface for transformations with the GraphTransformationEngine.

The transformation is guaranteed the following conditions:

• 1. transform(ComputeKey, ComputationEnvironment) is only called once per key if caching is enabled.
• 2. transform(ComputeKey, ComputationEnvironment) is only called after all keys in discoverDeps(ComputeKey, ComputationEnvironment) has been computed.
• 3. discoverDeps(ComputeKey, ComputationEnvironment) is only called after all keys in discoverPreliminaryDeps(ComputeKey) has been computed

Note that dependencies can be keys of other GraphComputations.

Method Summary

Modifier and Type	Method and Description
com.google.common.collect.ImmutableSet<? extends ComputeKey<? extends ComputeResult>>	discoverDeps(Key key, ComputationEnvironment env) Compute dependent keys required to compute given key, and a set of dependencies as listed by discoverPreliminaryDeps(ComputeKey).
com.google.common.collect.ImmutableSet<? extends ComputeKey<? extends ComputeResult>>	discoverPreliminaryDeps(Key key) Compute dependent keys required to compute given the current key.
ComputationIdentifier<Result>	getIdentifier()
Result	transform(Key key, ComputationEnvironment env) Perform a transformation identified by key Key into a final type Result.

Method Detail

getIdentifier

ComputationIdentifier<Result> getIdentifier()

Returns:

the identifier of the key for this transformation. This should match ComputeKey.getIdentifier()

transform

Result transform(Key key,
                 ComputationEnvironment env)
          throws Exception

Perform a transformation identified by key Key into a final type Result. This transformation should be performed synchronously.

Parameters:

key - The Key of the requested result

env - The execution environment containing results of keys from discoverDeps(ComputeKey, ComputationEnvironment) and discoverPreliminaryDeps(ComputeKey)

Returns:

The result of the transformation

Throws:

Exception

discoverDeps

com.google.common.collect.ImmutableSet<? extends ComputeKey<? extends ComputeResult>> discoverDeps(Key key,
                                                                                                   ComputationEnvironment env)
                                                                                            throws Exception

Compute dependent keys required to compute given key, and a set of dependencies as listed by discoverPreliminaryDeps(ComputeKey). The results of those computations will be available in transform(ComputeKey, ComputationEnvironment) as a part of ComputationEnvironment

Parameters:

key - the current key to transform

env - The execution environment containing results of keys from discoverPreliminaryDeps(ComputeKey)

Returns:

a set of keys that the transformation of the current key depends on

Throws:

Exception

discoverPreliminaryDeps

com.google.common.collect.ImmutableSet<? extends ComputeKey<? extends ComputeResult>> discoverPreliminaryDeps(Key key)
                                                                                                       throws Exception

Compute dependent keys required to compute given the current key. The results of those computations will be available in discoverDeps(ComputeKey, ComputationEnvironment) as a part of ComputationEnvironment, and transform(ComputeKey, ComputationEnvironment)

Parameters:

key - the current key to transform

Returns:

a set of keys that the discoverDeps(ComputeKey, ComputationEnvironment) and transform(ComputeKey, ComputationEnvironment) of the current key depends on

Throws:

Exception