MPS Generation Plans

A generation plan (Plan) is an ordered script that controls which generators run, in what sequence, and with what synchronization points. Without a plan, MPS determines order from mutual generator priorities and dependencies. A plan lets language designers specify that ordering once, in a single place, without requiring all involved languages to know about each other.

Language: jetbrains.mps.lang.generator.plan (id 7ab1a6fa-0a11-4b95-9e48-75f363d6cb00, version 3) Also requires: jetbrains.mps.lang.smodel (for LanguageId / LanguageIdentity nodes)

When to use a generation plan

• You need a guaranteed ordering of generators across languages that must not depend on each other.
• You are doing cross-model generation and need mapping labels from one model to be available when generating another (requires checkpoints).
• You want to fork the generation of certain models into a separate branch (e.g., generate both .java files and XML descriptors from the same input).
• You want a conditional contribution added to a base plan without modifying it (PlanContribution).

Critical Directives

• Genplan models use the genplan stereotype. File name pattern: <name>@genplan.mps. Pass modelName: "<name>@genplan" to mps_mcp_create_model. See aspect-model-stereotypes.md for all model identifiers. Set doNotGenerate=true (MPS adds this automatically).
• Only one DevKit per model may carry a genplan. Assigning multiple genplan-bearing DevKits to the same model is unsupported.
• Plan.steps is 1..n. A plan with no steps is invalid.
• LanguageEntry.language (LanguageId) and GeneratorModulePointer.module (ModulePointer) are each cardinality 1 — missing them is a validation error.
• Checkpoints persist transient state. Cross-phase reference resolution works only when phases share a plan AND a Checkpoint sits between them.
• Do not hand-edit serialized .mps genplan files. Use MPS MCP node tools.

Common-Path Workflow

1. Create a solution; add a model with stereotype genplan (file like MyPlan@genplan.mps).
2. Add used languages jetbrains.mps.lang.generator.plan and jetbrains.mps.lang.smodel.
3. Create a Plan root node with a descriptive name.
4. Add Transform steps in order (one per phase); group parallel-safe languages in one Transform with multiple LanguageEntry children.
5. Insert Checkpoint steps wherever downstream generators must resolve cross-model references.
6. Add Fork steps for any output variant requiring its own branch (e.g. XML alongside Java); or add a separate PlanContribution root for conditional activation.
7. Attach the plan to models via a DevKit (production) or the Custom generation facet (prototyping).
8. Verify with MPS UI Show generation plan and mps_mcp_check_root_node_problems.

Related Skills

• mps-aspect-generator — for the generator rules and templates that the plan orchestrates.
• mps-aspect-textgen — for the text serialization that consumes generated models.
• mps-aspect-accessories — for DevKit setup, used languages, and runtime solutions that ship with a plan.
• mps-node-editing — generic JSON-blueprint node creation workflow.

Reference Index

• Plan setup and DevKit attachment — open when creating a new genplan model, wiring it into a DevKit, or switching between DevKit and Custom generation facet attachment. See references/plan-setup.md.
• Step concept catalog — open when you need exact concept names, properties, cardinalities, and the meanings of Transform, ApplyGenerators, Checkpoint, IncludePlan, Fork, CheckpointDeclaration, CheckpointSynchronization, DocumentationStep. See references/step-catalog.md.
• Transform and ApplyGenerators — open when wiring languages by identity (LanguageEntry.kind = Transform / TargetAt / Extend) or naming specific generator modules. Includes the verified "the plan" and "WithCompiledGenerator" JSON examples. See references/transform-and-applygenerators.md.
• Checkpoints and cross-model resolution — open when phases need to share mapping labels, when a downstream plan must read another plan's checkpoint, or when picking among InPlaceCheckpointSpec, DeclaredCheckpointSpec, InPlaceCheckpointRefSpec. See references/checkpoints.md.
• IncludePlan, Fork, and PlanContribution — open when composing plans from smaller pieces, splitting branches, or activating a conditional contribution without modifying the base plan. Includes "GenPlanWithFork", "LangConstraintsPlan", and "DocumentationPlan" JSON examples. See references/composition-and-fork.md.
• Fork selectors and parameters — open when conditionally activating forks via ParameterEquals or ConceptListSelector, or defining a ParameterDeclaration. See references/fork-selectors.md.
• Model attributes (InitModelAttributes, targetFacet) — open when routing the output of a branch to a specific facet such as documentation generation. Includes the verified ModelAttributeAssignment blueprint. See references/model-attributes.md.
• Concept quick reference — open when assembling JSON that requires conceptReference strings or qualified concept names. See references/concept-quick-reference.md.
• Verification and discovery — open to find existing plans (FIND_INSTANCES, search by name) or to validate a plan using MPS UI and MCP tools. See references/verification-and-discovery.md.
• Authoring checklist — open at the end of an authoring session for a final scan before merging. See references/authoring-checklist.md.