IncrementalTaskInputs (Gradle API 2.14.1)
Date: 2016-07-18

Package: org.gradle.api.tasks.incremental

## [Java] Interface IncrementalTaskInputs

- Provides access to any input files that need to be processed by an incremental task.

  An incremental task action is one that accepts a single IncrementalTaskInputs parameter. The task can then provide an action to execute for all input files that are out of date with respect to the previous execution of the task, and a separate action for all input files that have been removed since the previous execution.

       class IncrementalReverseTask extends DefaultTask {
            @InputDirectory
            def File inputDir

            @OutputDirectory
            def File outputDir

            @TaskAction
            void execute(IncrementalTaskInputs inputs) {
                if (!inputs.incremental)
                    project.delete(outputDir.listFiles())

                inputs.outOfDate { change ->
                    def targetFile = project.file("$outputDir/${change.file.name}")
                    targetFile.text = change.file.text.reverse()
                }

                inputs.removed { change ->
                    def targetFile = project.file("$outputDir/${change.file.name}")
                    if (targetFile.exists()) {
                        targetFile.delete()
                    }
                }
            }
        }

  In the case where Gradle is unable to determine which input files need to be reprocessed, then all of the input files will be reported as outOfDate. Cases where this occurs include:

  - There is no history available from a previous execution.
  - An TaskOutputs.upToDateWhen criteria added to the task returns `false`.
  - An Input property has changed since the previous execution.
  - One or more output files have changed since the previous execution.
  Note that this is a stateful API:
  - outOfDate and removed can each only be executed a single time per IncrementalTaskInputs instance.
  - outOfDate must be executed before removed is called.

- - ### Methods Summary

    Methods
    Type | Name and description
    --- | ---
    `boolean` | `isIncremental()` Indicates if it was possible for Gradle to determine which exactly input files were out of date compared to a previous execution.
    `void` | `outOfDate(Action<? super InputFileDetails> outOfDateAction)` Executes the action for all of the input files that are out-of-date since the previous task execution.
    `void` | `removed(Action<? super InputFileDetails> removedAction)` Executes the action for all of the input files that were removed since the previous task execution.

- - ### Method Detail

    - #### public boolean isIncremental()

      Indicates if it was possible for Gradle to determine which exactly input files were out of date compared to a previous execution. This is not possible in the case of no previous execution, changed input properties, output files, etc.

      When `true`:

      - Any input file that has been added or modified since previous execution will be considered 'out-of-date' and reported to outOfDate.
      - Any input files that has been removed since previous execution will be reported to removed.

      When `false`:

      - Every input file will be considered to be 'out-of-date' and will be reported to outOfDate.
      - No input files will be reported to removed.

    - #### public void outOfDate(Action<? super InputFileDetails> outOfDateAction)

      Executes the action for all of the input files that are out-of-date since the previous task execution. The action may also be supplied as a groovy.lang.Closure.

      - When isIncremental() == `true`, the action will be executed for any added or modified input file.
      - When isIncremental() == `false`, the action will be executed for every input file for the task.

      This method may only be called a single time for a single IncrementalTaskInputs instance.

      throws:
        IllegalStateException on second and subsequent invocations.

    - #### public void removed(Action<? super InputFileDetails> removedAction)

      Executes the action for all of the input files that were removed since the previous task execution. The action may also be supplied as a groovy.lang.Closure.

      - When isIncremental() == `true`, the action will be executed for any removed input file.
      - When isIncremental() == `false`, the action will not be executed.

      This method may only be called a single time for a single IncrementalTaskInputs instance.

      This method may only be called after outOfDate has been called.

      throws:
        IllegalStateException if invoked prior to outOfDate, or if invoked more than once.