mps-quotations

name	mps-quotations
description	Use when writing or debugging MPS quotations and anti-quotations — "node literals" that create SNode trees inline in behavior, typesystem, intentions, generator, and other model code. Covers heavy quotations (`Quotation`, `<...>`), light quotations (`NodeBuilder`, constructor-style for bootstrapping), and the four anti-quotation varieties: child (`%(...)%`), list (`*(...)*`), reference (`^(...)^`), property (`$(...)$`). Reach for this skill whenever the task involves splicing runtime values into quoted node trees or choosing between heavy and light quotations.
type	reference

MPS Quotations and Anti-quotations

A quotation is a node literal — a concise expression that evaluates to an SNode (or tree of SNodes) at runtime. Instead of building nodes manually via the smodel API, you write the desired structure in the target language syntax and let MPS wrap it. Anti-quotations ("antiquotations") are escape holes inside a quotation where a runtime expression is spliced in.

Required used language: jetbrains.mps.lang.quotation (UUID 3a13115c-633c-4c5c-bbcc-75c4219e9555)

Critical Directives

• Quotations do not call behavior constructors. Using <Car()> produces an SNode of concept Car without running its constructor. Use new node<Car>() (smodel API) when you need the constructor to run.
• Use the concept identifier inside a quotation, not an alias. Write <IntegerType>, not <int>.
• All four anti-quotation kinds attach via the inherited smodelAttribute role on any BaseConcept. The anti-quotation node is a sibling attribute of the host node, not a replacement child. The runtime substitution happens during materialisation. See references/antiquotations.md.
• ListAntiquotation constraint: the list role must contain at least one placeholder child before you can activate a list antiquotation. The placeholder is replaced at runtime with zero-or-more nodes.
• PropertyAntiquotation.propertyId and ReferenceAntiquotation.linkId are filled in automatically by MPS when you type $ / ^ in a property/reference cell. Do not construct these encoded ids manually unless you have already verified the exact language-uuid/concept-id/property-or-link-id form against the running MPS. See references/property-and-reference-ids.md.
• Prefer heavy quotation (<...>) for readability; switch to light quotation (NodeBuilder) only for bootstrapping (the target language can't be a used language), for generators-of-generators, or when nesting depth makes embedded syntax unreadable. See references/heavy-vs-light.md.
• The deprecated NodeBuilderInitLink.expression (cardinality 0..1) was removed in 2019.2. Use initValue with a NodeBuilderExpression instead.
• Edit quotation-bearing models through MPS MCP tools (mps_mcp_insert_root_node_from_json, mps_mcp_update_node). Do not hand-edit .mps files.
• Validate with mps_mcp_check_root_node_problems; quotations frequently expose missing used-languages on the host model (the quoted concept's language must be a used language, not just a dependency).

Common-Path Workflow

1. Add jetbrains.mps.lang.quotation to the host model's used languages, plus the language whose concepts will be quoted.
2. In the editor, type < in an expression position to insert a Quotation, then type the desired surface syntax of the quoted node. The quoted concept must be available as a used language; otherwise switch to NodeBuilder.
3. To inject runtime values, place the caret inside the appropriate cell and type:
   • % — child antiquotation (replaces the child node)
   • * — list antiquotation (replaces a list-position node; requires a placeholder child first)
   • ^ — reference antiquotation (replaces a reference target)
   • $ — property antiquotation (replaces a property value)
4. For bootstrapping or deep nesting, use the Convert Quotation to NodeBuilder intention (or insert NodeBuilder directly).
5. Validate with mps_mcp_check_root_node_problems; rebuild the host language if needed.

When To Use Which Form

Situation	Recommended form
Short, readable node literal in behavior / typesystem / intentions code	Heavy quotation
One or more children computed at runtime	Heavy quotation + child/list antiquotation
A property computed at runtime	Heavy quotation + property antiquotation
A reference target resolved at runtime	Heavy quotation + reference antiquotation
Bootstrapping (generating language infrastructure) or concept not importable	Light quotation (NodeBuilder)
More than 3 levels of nesting where embedded syntax is confusing	Light quotation (NodeBuilder)

Related Skills

• mps-aspect-behavior — behavior bodies frequently use quotations to build sub-trees; remember constructors do not fire when materialising a quotation.
• mps-aspect-typesystem — <TypeConcept> literals inside rule bodies are heavy quotations; the typesystem model typically imports jetbrains.mps.lang.quotation as a used language. The :==:/:<=: body shapes are in mps-aspect-typesystem json-blueprints.md.
• mps-aspect-generator — template macros are a different mechanism for building target trees; quotations are used in non-template code (filters, mapping scripts, conditions) within the generator model.
• mps-aspect-migrations — <NewConcept> plus ^(oldNode.target)^ is the canonical shape inside migration rewrite scripts (references/antiquotation-reference.md includes the verbatim example).
• mps-aspect-intentions — the replace_invokeOperation_with_compactInvoke example shipping with the closures language uses <%(...)%> + *(...)* to rebuild an expression tree.
• mps-aspect-structure-concepts — when the quoted concept's link/property metadata is needed; propertyId / linkId encode the persistent form of those declarations.
• mps-model-manipulation — the smodel operations and BaseLanguage expressions used inside antiquotation expression slots.

Reference Index

• Open references/heavy-vs-light.md when deciding between Quotation and NodeBuilder — the surface trade-offs, the bootstrapping rationale, and the recommendation table for typical situations.
• Open references/heavy-quotation.md when authoring a basic Quotation (<...>) — concept structure, the quotedNode/smodelAttribute/modelToCreate roles, JSON blueprint, and the verbatim MoneyType example from the baseLanguage.money generator.
• Open references/antiquotations.md for the full antiquotation catalog — the four kinds at a glance, attachment mechanism via smodelAttribute, syntax (%/*/^/$), the AbstractAntiquotation interface, the Antiquotation (child) shape, and the closures-intention worked example combining child + list antiquotations.
• Open references/antiquotation-list.md when working with ListAntiquotation (*(...)*) — placeholder requirement, expression type (nlist<..> / Iterable), and how it cooperates with multi-cardinality list roles.
• Open references/antiquotation-property.md when writing or debugging a PropertyAntiquotation ($(...)$) — concept structure, propertyId / name_DebugInfo / stringValueMigrated properties, and the full JSON printout from the quotation editor test.
• Open references/antiquotation-reference.md when a runtime reference target must be spliced — ReferenceAntiquotation (^(...)^) shape, linkId / role_DebugInfo properties, and the migration-script example creating a NewComponentRef whose target is computed at runtime.
• Open references/property-and-reference-ids.md for the encoded id formats used by PropertyAntiquotation.propertyId and ReferenceAntiquotation.linkId — language-uuid/concept-id/property-or-link-id — and the rule "let MPS fill these in" when editing in the IDE.
• Open when using — the constructor-style notation, / / / () concept structure, deprecation note on , JSON blueprint, and the verbatim nested-NodeBuilder example from .