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:

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).