External Builder API and Plugins

External Build Process Workflow

When the user invokes an action that involves executing an external build (Make, Build Artifacts, etc.), the following steps happen:

• Before-compile tasks are performed in the IDE process.

• Some source generation tasks that depend on the PSI (e.g., UI designer form to source compilation) are executed in the IDE process.

• BuildTargetScopeProvider extensions are called to calculate the scope of the external build (the set of build targets to compile based on the target module to make and the known set of changes).

• The external build process is spawned (or an existing build process background process is reused).

• The external build process loads the project model (.idea, .iml files, and so on), represented by a JpsModel instance.

• The full tree of targets to build is calculated based on each build target's dependencies to be compiled.

• For each target, the set of builders capable of building this target is calculated.

• For every target and every builder, the build() method is called. This can happen in parallel if the "Compile independent modules in parallel" option is enabled in the settings. For module-level builders, the order of invoking builders for a single target is determined by their category; for other builders, the order is undefined.

• Caches to record the state of the compilation are saved.

• Compilation messages reported through the CompileContext API are transmitted to the IDE process and displayed in the UI (in the Messages view).

• Post-compile tasks are executed in the IDE process.

Incremental Build

To support incremental build, the build process uses several caches which are persisted between build invocations. Even if your compiler doesn't support incremental build, you still need to report correct information so that incremental build works correctly for other compilers.

• SourceToOutputMapping is a many-to-many relationship between source files and output files ("which source files were used to produce the specified output file"). It's filled by calls to BuildOutputConsumer.registerOutputFile() and ModuleLevelBuilder.OutputConsumer.registerOutputFile().

The IDE monitors the project content changes and uses the information from those caches to generate the set of dirty and deleted files for every compilation. (Dirty files need to be recompiled, and deleted files need to have their output deleted). A builder can also report additional files as dirty (e.g., if a method is deleted, the builder can report the classes using this method as dirty.) A module-level builder can add some files to the dirty scope; if this happens, and if the builder returns ADDITIONAL_PASS_REQUIRED from its build() method, another round of builder execution for the same module chunk will be started with the new dirty scope.

A builder may also want to have its custom caches to store additional information to support the partial recompilation of a target (e.g., the dependencies between Java files in a module). To store this data, you can either store arbitrary files in the directory returned from BuildDataManager.getDataPaths().getTargetDataRoot() or use a higher-level API: BuildDataManager.getStorage()

To pass custom data between the invocation of the same builder between multiple targets, you can use CompileContext.getUserData() and CompileContext.putUserData().

Services and Extensions in External Builder

The external builder process uses the standard Java services mechanism to support plugins. There are several service interfaces (e.g. BuilderService which can be implemented in plugins to extend the builder functionality. An implementation of a service needs to be registered by creating the META-INF/services/$service-interface-fqn$ file containing the implementation class's qualified name. E.g. BuilderService implementations are registered in META-INF/services/org.jetbrains.jps.incremental.BuilderService file. These files don't have extensions, so you need to map corresponding patterns to text files in IDE settings.

Registering a Plugin for External Builder

Sources of a plugin for External Builder should be put in a separate module. By convention, such a module has a name '...-jps-plugin', and its sources are placed under the jps-plugin directory in the main plugin directory. Use com.intellij.compileServer.plugin extension point to add the plugin to the classpath of the external build process, the plugin JAR should be named $JPS_module_name$.jar. Build | Prepare Plugin Module for Deployment action will automatically pack the 'jps-plugin' part to a separate JAR accordingly.

See IntelliJ Platform Explorer for samples.

Debugging a Plugin for External Builder

If your test IDE is IntelliJ IDEA 16.0 or newer

Switch on "Debug Build Process" toggle action (available via 'Find Action') in the test IDE. After that, every time compilation is run, the build process will wait for debugger connection on some (random) port and will show the port number in the status bar. In a working copy of IDE, a "Remote" run configuration should be created and pointed to this port. Suppose you often need to debug external builders and want to reuse the created "Remote" run configuration. In that case, you may fix the port number by adding the following VM option to the plugin run configuration:

If your test IDE is IntelliJ IDEA 15.0 or older

Start IDE with your plugin with the following VM option:

After that, every time compilation is run in the test IDE, the build process will wait for debugger connection on this port and then proceed. In a working copy of IDE, a "Remote" run configuration should be created and pointed to this port. Specifying port "-1" will disable debugging mode.

Profiling External Build Process

The build process has built-in self-CPU-profiling capabilities.

After this, every build process run should result in a CPU snapshot stored in $USER_HOME$/Snapshots directory. Snapshots are named like ExternalBuild\-$DATE$.snapshot.

Specifying -Dprofiling.mode=false will turn profiling off. Please capture a couple of snapshots for the situations you believe the build should work much faster than it does.

Please create an issue in the issue tracker and attach generated *.snapshot files to it or upload them as described here and specify links in the issue. Please also provide details about the memory and other VM settings for the build process you were using.

Accessing External Build Process' Logs

The log file is located under the directory:

There, both build-log.log and build-log.properties files can be found. The build-log.properties is a log4j configuration file, where the log level and desired logging categories can be adjusted. This file contains logging from all build sessions, including those from the auto-make.

In IntelliJ Platform versions before version 14.1, log4j configuration was stored in build-log.xml.

Accessing Project Model and Configuration from External Build

The project model in the External Build process is provided by JPS (JetBrains Project System). A project is represented by JpsProject, a module by JpsModule, and so on. Suppose your compiler depends on something that isn't added to the model yet (e.g., some facet settings). In that case, you need to extend the JPS model (use JpsOsmorcModuleExtension as a reference implementation) and provide an implementation of JpsModelSerializerExtension to load the configuration from project files.