MPS IDE Plugin Language

This skill covers IDE plugins: code that integrates with the MPS/IntelliJ host IDE — menu actions, tool windows, shortcuts, settings panels. Plugin code lives in a regular Solution module (compilation mode: "Regular MPS module contributing extensions to MPS") with model(s) using jetbrains.mps.lang.plugin and jetbrains.mps.lang.plugin.standalone. The canonical model name is <solution_name>.plugin — MPS auto-registers it on that convention.

Official documentation: https://www.jetbrains.com/help/mps/plugin.html

Critical Directives

• Disambiguate the overloaded vocabulary first. "Plugin", "tool", "action group" each mean two or three different things. See references/terminology.md before naming anything.
• A plugin solution is NOT an IntelliJ plugin jar. The solution contains MPS models; the jar is what the MPS Build Language packages from it. Don't conflate.
• A Tool is a tool window — a dockable panel — not a CLI tool or an action.
• Use MPS MCP tools for edits. mps_mcp_insert_root_node_from_json, mps_mcp_update_node, mps_mcp_print_node. Resolve concept names with mps_mcp_search_concepts / mps_mcp_get_concept_details; never guess.
• ModificationStatement.modifiedGroup is a node reference (r:...), not a concept reference (c:...). Look up the target group via mps_mcp_search_root_node_by_name to obtain the node ref.
• Add a model dependency on jetbrains.mps.ide.actions before referencing built-in groups (MainMenu, EditorPopup, NodeActions, ModelActions, ModuleActions, MainToolbar, ProjectViewPopupMenu).
• Pick requiredAccess deliberately: none (no model touch), read (safe traversal), command (mutates with undo + write lock — never open modal dialogs from here), editorCommand (correct undo scope for editor-driven edits).
• Don't call project.tool<…> from dispose. The lookup can fail during teardown.
• Mac keymap trap: with Keymap = Default, MPS translates ctrl → cmd on macOS. If you specifically want ctrl on Mac, add a separate Mac_OS_X KeymapChangesDeclaration.
• After edits, rebuild the module (mps_mcp_alter_nodes MAKE) so generated Java is current, then Reload All in MPS for hot-load.
• Validate every new root with mps_mcp_check_root_node_problems.

Required Used Languages (on the Model)

• jetbrains.mps.lang.plugin — core concepts (Action, Group, Tool, …).
• jetbrains.mps.lang.plugin.standalone — ApplicationPlugin / ProjectPlugin, project.tool<...>, project.preferenceComponent<...>, StandalonePluginDescriptor.
• jetbrains.mps.baseLanguage (+ .classifiers, .collections, .closures) — for code bodies.
• jetbrains.mps.lang.smodel if you touch nodes/models.
• jetbrains.mps.lang.resources for icons.

Common-Path Workflow

For a typical "add a menu item that does X on the selected node":

1. Identify the context — which IDE menu/toolbar should it appear in? (MainMenu, EditorPopup, NodeActions, ProjectViewPopupMenu, …).
2. Locate the target group. mps_mcp_search_root_node_by_name for the group name. Inspect with mps_mcp_print_node to discover the GroupAnchors you can target.
3. Decide plugin solution location. Reuse an existing *.pluginSolution module if one fits; otherwise create a new solution and a <name>.plugin model with the used languages above.
4. Author an ActionDeclaration — see references/actions.md. Set name, caption, parameters (MPSCommonDataKeys.MPS_PROJECT / .NODE etc.), requiredAccess, isApplicable, execute body.
5. Author an ActionGroupDeclaration — see references/action-groups.md. Owns your action(s) via ElementListContents → ActionInstance. Add a ModificationStatement under modifier targeting the existing group + an anchor.
6. Add a keybinding (optional) — new KeymapChangesDeclaration referencing the action — see references/keymaps.md.
7. Rebuild the solution via mps_mcp_alter_nodes MAKE; reload MPS.
8. Validate with mps_mcp_check_root_node_problems on each new root.

For other task families: tool window → references/tools.md; settings page → references/preferences.md; editor tabs → references/editor-tabs.md; bespoke startup → references/lifecycle-plugins.md.

Reference Examples in This Repository

Seed mps_mcp_print_node / mps_mcp_query_nodes (FIND_USAGES) with these:

Concept	Example nodes	Model
ActionDeclaration	ShowHelpForNode, ShowDefaultHelp, ShowHelpForRoot, ShowHelpForAspect	jetbrains.mps.lang.structure.pluginSolution.plugin
ActionGroupDeclaration	ShowHelp (contributes to Structure and ModelActions)	jetbrains.mps.lang.structure.pluginSolution.plugin
ToolDeclaration	TodoViewer	jetbrains.mps.ide.tools.todo
PreferencesComponentDeclaration	BehaviorDialogsPersistentOptions	jetbrains.mps.ide.actions
InterfaceGroup	IDEAWindows, IDEAGoTo, IDEAEdit, IDEAFile, IDEAView, IDEATools, IDEAVCS	jetbrains.mps.ide.actions
EditorTab	Actions, Behavior, Constraints, Data Flow, Editor, Feedback, Find Usages, Generator, Intentions, Refactorings, Structure, Textgen, Typesystem	jetbrains.mps.ide.devkit.editor
EditorTab (alt)	Run Configuration, Executor, Producer	jetbrains.mps.execution.configurations.pluginSolution.plugin
Order (editor tabs)	Order root	jetbrains.mps.ide.devkit.editor

Related Skills

• mps-aspect-actions — node factories, unrelated to IDE actions despite the name.
• mps-aspect-intentions — Alt+Enter context actions inside the projectional editor.
• mps-aspect-editor-menus-and-keymaps — editor cell actions, substitute menus, side transforms (a different layer from the IDE shell).
• mps-build-language — packaging a plugin solution into a distributable MPS/IDEA plugin (the build script must copy startup.properties from the solution's resources).
• mps-quotations / mps-model-manipulation — writing the base-language bodies inside execute/isApplicable/init/dispose blocks.
• mps-baselanguage — mechanics of building BaseLanguage JSON.

Reference Index

• Open references/terminology.md when starting any plugin task — disambiguates "plugin solution" vs "IntelliJ plugin", ApplicationPlugin/ProjectPlugin vs the deployable jar, Tool (tool window) vs "CLI tool", ActionGroup vs BootstrapGroup/InterfaceGroup, anchor (->), EditorMenu/SubstituteMenu (different aspect), Intention (different aspect), Node Factory (different language).
• Open references/concept-catalog.md when looking up a concept FQN — every rootable concept (ActionDeclaration, ActionGroupDeclaration, InterfaceGroup, ToolDeclaration, TabbedToolDeclaration, KeymapChangesDeclaration, PreferencesComponentDeclaration, EditorTab, Order, NonDumbAwareActions, IdeaConfigurationXml, IdeaInitializerDescriptor, ApplicationPluginDeclaration, ProjectPluginDeclaration, StandalonePluginDescriptor) plus every non-root concept you reference (blocks, parameters, instances, anchors, separators, keystrokes, shortcut changes, preference pages, persistent properties, etc.).
• Open references/actions.md when declaring or modifying an ActionDeclaration — all fields (name, caption, description, mnemonic, ID, overrides, isAlwaysVisible, requiredAccess, outsideCommandExecution, updateInBackground, fillActionContext, nativeLanguage, updateBlock, executeFunction, icon, parameter, constructionParameter, methodDeclaration, places), the two parameter kinds (ActionDataParameterDeclaration simple-from-DataKey vs ActionParameterDeclaration complex-typed), RequiredCondition vs isOptional, how to refer to parameters inside bodies (ActionParameterReferenceOperation / ActionDataParameterReferenceOperation), the ShowHelpForNode blueprint with typical MPSCommonDataKeys.MPS_PROJECT + MPSCommonDataKeys.NODE, and the requiredAccess table (none / read / command / editorCommand) with the dialog-from-command deadlock warning.
• Open references/action-groups.md when assembling menus / toolbars / popups — ActionGroupDeclaration fields (name, caption, mnemonic, isPopup, isInvisibleWhenDisabled, isInternal, isPluginXmlGroup, updateInBackground, modifier, contents), the three contents variants (ElementListContents static / BuildGroupBlock once / UpdateGroupBlock every open), ActionGroupMember interface, ActionInstance with actualParameter for construction parameters, GroupAnchor (named slots), Separator, InterfaceExtentionPoint (bootstrap ->), ModificationStatement to plug into MainMenu / EditorPopup / NodeActions / etc., and the ShowHelp blueprint.
• Open references/tools.md when building a tool window — ToolDeclaration fields (name, caption, position enum, isAvailableOnStartup, number deprecated, icon deprecated, toolIcon, getComponentBlock, toolInitBlock, toolDisposeBlock, fieldDeclaration, methodDeclaration, shortcut), the lifecycle (BaseProjectTool, init once, dispose on close, never call project.tool<…> from dispose), retrieval via project.tool<MyTool> (GetToolInProjectOperation), the TodoViewer blueprint, and TabbedToolDeclaration differences (no getComponentBlock, tabs added from init).
• Open references/keymaps.md when adding shortcuts — KeymapChangesDeclaration fields (name, keymap enum: Default / Mac_OS_X / Mac_OS_X_Plus / XWin / GNOME / KDE, isPluginXmlKeymap, shortcutChange), SimpleShortcutChange with action ref + ordered KeyMapKeystroke sequence (chords), KeyMapKeystroke fields (modifiers space-separated string, keycode Java-style like VK_F9, change enum replace_all / remove), the Default → cmd-on-Mac translation, blueprint for HelpKeymap with Ctrl-F1.
• Open references/preferences.md when creating a Settings dialog page — PreferencesComponentDeclaration fields (name, persistenPropertyDeclaration, afterReadBlock, beforeWriteBlock, preferencePage), PreferencePage fields (name, helpTopic, icon, component, isModifiedBlock, resetBlock, commitBlock), how to retrieve from code (project.preferenceComponent<MyPrefs>), persistence to workspace.xml, the MyPluginPrefs skeleton.
• Open references/editor-tabs.md when adding tabs to a concept editor (e.g. the language-definition editor's Structure/Editor/Behavior tabs) — EditorTab fields (name, shortcutChar, commandOnCreate deprecated, baseNodeConcept, icon, order legacy, listenBlock, baseNodeBlock, isApplicableBlock, nodesBlock, createTabBlock), Order root + EditorTabReference for left-to-right ordering, the Behavior tab blueprint.
• Open references/interface-group.md when targeting an external (IDEA / platform) action group — InterfaceGroup fields (name, groupID, contents, modifier), the groupID expression pattern (IdeActions.GROUP_FILE etc.), the IDEAFile blueprint, and InterfaceExtentionPoint (bootstrap ->) for external extension-point ids inside an ElementListContents.
• Open references/non-dumb-aware.md when opting actions out of dumb mode — NonDumbAwareActions root, one per plugin model, listing actions that must not run while indexing is in progress.
• Open references/idea-configuration-xml.md when the higher-level concepts can't express something — IdeaConfigurationXml (outputPath, actions child of IdeaActionsDescriptor) for emitting raw META-INF/IdeaComponents.xml. Use sparingly.
• Open references/lifecycle-plugins.md when needing bespoke application or project lifecycle hooks — ApplicationPluginDeclaration (app scope) vs ProjectPluginDeclaration (project scope, initBlock/disposeBlock receive project), fieldDeclaration for private state, retrieval via application plugin<Name> / project plugin<Name>, the ProjectPlugin skeleton, when to add StandalonePluginDescriptor (model not following <solution>.plugin convention; needInitConfig UI toggle).
• Open references/common-failures.md when a plugin feature misbehaves — "Group X not found" (missing jetbrains.mps.ide.actions dep); concept-ref-vs-node-ref confusion on modifiedGroup; action doesn't appear (modifier missing / required param unresolved / isAlwaysVisible not set); deadlock when opening dialog from execute (requiredAccess = command holds write lock — compute inputs first, then project.modelAccess.executeCommand { ... }); TabbedTool missing getComponentBlock (by design); ctrl shortcut works on Win but not Mac (Default translates to cmd); constructionParameter without toString() causes generated-ID collisions; IDE doesn't see edits (rebuild + Reload All).