[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"skill-jetbrains-mps-aspect-dataflow":3,"mdc--4es1q0-key":29,"related-repo-jetbrains-mps-aspect-dataflow":923,"related-org-jetbrains-mps-aspect-dataflow":996},{"slug":4,"name":4,"fn":5,"description":6,"org":7,"tags":11,"stars":16,"repoUrl":17,"updatedAt":18,"license":19,"forks":20,"topics":21,"repo":24,"sourceUrl":27,"mdContent":28},"mps-aspect-dataflow","define and debug MPS dataflow builders","Use when defining or debugging MPS dataflow builders for a concept — control\u002Fdata flow declarations that drive reachability analysis and variable-use checking. Covers DataFlowBuilderDeclaration, BuilderBlock, emit instructions (code for, jump, ifjump, label, read, write, ret, mayBeUnreachable), positions (AfterPosition, BeforePosition, LabelPosition), the jetbrains.mps.lang.dataFlow language, the NodeParameter implicit, BL+smodel usage inside builder bodies, and IBuilderMode for advanced analyses such as nullable\u002Fnon-null tracking.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},"jetbrains","JetBrains","https:\u002F\u002Fpexgzepcugksgbtrxkhf.supabase.co\u002Fstorage\u002Fv1\u002Fobject\u002Fpublic\u002Forg-logos\u002Fjetbrains.png",[12],{"name":13,"slug":14,"type":15},"Data Analysis","data-analysis","tag",1650,"https:\u002F\u002Fgithub.com\u002FJetBrains\u002FMPS","2026-07-13T06:45:19.114674",null,311,[22,23],"domain-specific-language","dsl",{"repoUrl":17,"stars":16,"forks":20,"topics":25,"description":26},[22,23],"JetBrains Meta programming System","https:\u002F\u002Fgithub.com\u002FJetBrains\u002FMPS\u002Ftree\u002FHEAD\u002Fplugins\u002Fmcp-tools\u002Fresources\u002Fjetbrains\u002Fmps\u002Fagents\u002Fmcp\u002Fskills\u002Fmps-aspect-dataflow","---\nname: mps-aspect-dataflow\ndescription: Use when defining or debugging MPS dataflow builders for a concept — control\u002Fdata flow declarations that drive reachability analysis and variable-use checking. Covers DataFlowBuilderDeclaration, BuilderBlock, emit instructions (code for, jump, ifjump, label, read, write, ret, mayBeUnreachable), positions (AfterPosition, BeforePosition, LabelPosition), the jetbrains.mps.lang.dataFlow language, the NodeParameter implicit, BL+smodel usage inside builder bodies, and IBuilderMode for advanced analyses such as nullable\u002Fnon-null tracking.\ntype: reference\n---\n\n# MPS Dataflow Aspect\n\nThe dataflow aspect (`jetbrains.mps.lang.dataFlow`, `l:7fa12e9c-b949-4976-b4fa-19accbc320b4`) lets a language describe how control and data flow through nodes of a concept. MPS uses that information for reachability analysis, uninitialised-variable checks, and (via `IBuilderMode`) richer flow analyses such as nullable tracking.\n\n## Mental Model\n\nEach `DataFlowBuilderDeclaration` answers: *given a node of concept X, in what order might execution visit its children, and which variables are read or written?*\n\nThe builder body is a **BL `StatementList`** (inside a `BuilderBlock`). You use normal BL control flow (`if`, `foreach`, local variables) to compute which **emit instructions** to output at runtime. The `node` implicit parameter (concept `NodeParameter`) is always in scope — its type is the concept referenced by `conceptDeclaration`, giving smodel-typed access to children and references.\n\nThe MPS dataflow engine builds a control-flow graph from the emitted instructions, then runs analyses (unreachable code, uninitialised variable reads) on that graph. The engine only traces the paths you declare; if no builder exists for a concept, MPS falls back to delegating all children in declaration order.\n\n## Critical Directives\n\n- **`code for` is delegation, not a call.** Never use `jump` for child delegation. Use `EmitCodeForStatement` to inline a child's own builder at this point.\n- **`ifjump` semantics: the jump is taken when the condition is FALSE.** Use it after `code for node.condition` to model branching.\n- **Labels are node references, not string lookups.** `EmitLabelStatement.name` is display-only; jumps reference the label node via `LabelPosition.label`. Two labels with the same string are still distinct targets.\n- **Always null-guard `0..1` children** with BL `if (node.child != null)` before emitting `code for node.child`.\n- **`write node` vs `write node.link`:** use `write node` (just `NodeParameter` as the variable expression) when the concept node **is** the variable being declared. Use `write node.link` (via `SLinkAccess`) when the node merely references the variable being written.\n- **Leaf concepts need no builder.** The engine treats unbuilt concepts as no-ops, or for ordinary parents delegates to children in declaration order.\n- **Do not hand-edit serialized `.mps` dataflow files.** Use MPS MCP node tools.\n\n## Common-Path Workflow\n\n1. Create the dataflow model with `mps_mcp_create_model` and `modelName: \"\u003Clang>.dataFlow\"` if absent. **The aspect ID is `dataFlow` — camelCase, case-sensitive, no `@` suffix**; spelling it `dataflow` (lowercase) produces a utility model that MPS will not recognise. See [aspect-model-stereotypes.md](..\u002Fmps-mcp-workflow\u002Freferences\u002Faspect-model-stereotypes.md). Add `jetbrains.mps.lang.dataFlow` (and transitively `jetbrains.mps.baseLanguage`) as used languages on the model.\n2. Create a `DataFlowBuilderDeclaration` root node; set `conceptDeclaration` to the concept being described; give it a `name`.\n3. Add a `BuilderBlock` child with a `body` (BL `StatementList`).\n4. Emit instructions: delegate to children with `EmitCodeForStatement`; model branches with `EmitIfJumpStatement` + `EmitLabelStatement`; record variable use with `EmitReadStatement` \u002F `EmitWriteStatement`; mark exits with `EmitRetStatement`.\n5. For loops, use `BeforePosition`\u002F`AfterPosition` to encode loop-back\u002Fexit edges; wrap potentially-unreachable instructions in `EmitMayBeUnreachable`.\n6. Validate with `mps_mcp_check_root_node_problems`. For tricky cases, inspect an existing baseLanguage builder via `mps_mcp_print_node` with `deep: true`.\n\n## Related Skills\n\n- `mps-model-manipulation` — BL + smodel code inside builder bodies (`DotExpression`, `SLinkAccess`, `NodeParameter`, behavior method calls).\n- `mps-aspect-behavior` — for behavior methods called from builders to compute target nodes (e.g. `getLoopOrSwitch`, `getReturnJumpTarget`).\n- `mps-aspect-typesystem` — when the dataflow you emit must agree with type checks.\n- `mps-node-editing` — generic JSON-blueprint node creation\u002Freplacement workflow.\n\n## Reference Index\n\n- Concept catalog — open when you need exact concept names, properties, children, cardinalities, or abstract bases for `DataFlowBuilderDeclaration`, `BuilderBlock`, every emit statement, every position type, and the abstract bases. See [references\u002Fconcept-catalog.md](references\u002Fconcept-catalog.md).\n- Verified JSON patterns — open when constructing or editing a builder as JSON for `mps_mcp_*` tools. Includes variable read, single-child delegation, return-with-finally, if\u002Felsif\u002Felse, while loop, assignment, variable declaration, break to ancestor, and a custom inverted-condition statement. See [references\u002Fjson-patterns.md](references\u002Fjson-patterns.md).\n- Rules and pitfalls — open when a builder validates but the engine reports surprising reachability or variable-use results, when choosing between `AfterPosition` and `LabelPosition`, or before using `modes`\u002F`IBuilderMode`. See [references\u002Frules-and-pitfalls.md](references\u002Frules-and-pitfalls.md).\n- Language setup and engine invocation — open when wiring a new dataflow model, or when debugging \"why is my builder not being called\". See [references\u002Fsetup-and-engine.md](references\u002Fsetup-and-engine.md).\n- BaseLanguage builder index — open when you want to study a known-good builder for `IfStatement`, `WhileStatement`, `ReturnStatement`, `BreakStatement`, `VariableDeclaration`, `TryFinallyStatement`, `SwitchStatement`, `ForStatement`, etc. Lists builder names and persistent nodeReferences in `r:00000000-0000-4000-0000-011c895902c2`. See [references\u002Fbaselanguage-builder-index.md](references\u002Fbaselanguage-builder-index.md).\n- Sample language reference — open when looking for a minimal complete builder for a custom language (`UnlessStatement_DataFlow`). See [references\u002Fsample-language-reference.md](references\u002Fsample-language-reference.md).\n",{"data":30,"body":32},{"name":4,"description":6,"type":31},"reference",{"type":33,"children":34},"root",[35,44,75,82,101,174,179,185,394,400,640,646,727,733],{"type":36,"tag":37,"props":38,"children":40},"element","h1",{"id":39},"mps-dataflow-aspect",[41],{"type":42,"value":43},"text","MPS Dataflow Aspect",{"type":36,"tag":45,"props":46,"children":47},"p",{},[48,50,57,59,65,67,73],{"type":42,"value":49},"The dataflow aspect (",{"type":36,"tag":51,"props":52,"children":54},"code",{"className":53},[],[55],{"type":42,"value":56},"jetbrains.mps.lang.dataFlow",{"type":42,"value":58},", ",{"type":36,"tag":51,"props":60,"children":62},{"className":61},[],[63],{"type":42,"value":64},"l:7fa12e9c-b949-4976-b4fa-19accbc320b4",{"type":42,"value":66},") lets a language describe how control and data flow through nodes of a concept. MPS uses that information for reachability analysis, uninitialised-variable checks, and (via ",{"type":36,"tag":51,"props":68,"children":70},{"className":69},[],[71],{"type":42,"value":72},"IBuilderMode",{"type":42,"value":74},") richer flow analyses such as nullable tracking.",{"type":36,"tag":76,"props":77,"children":79},"h2",{"id":78},"mental-model",[80],{"type":42,"value":81},"Mental Model",{"type":36,"tag":45,"props":83,"children":84},{},[85,87,93,95],{"type":42,"value":86},"Each ",{"type":36,"tag":51,"props":88,"children":90},{"className":89},[],[91],{"type":42,"value":92},"DataFlowBuilderDeclaration",{"type":42,"value":94}," answers: ",{"type":36,"tag":96,"props":97,"children":98},"em",{},[99],{"type":42,"value":100},"given a node of concept X, in what order might execution visit its children, and which variables are read or written?",{"type":36,"tag":45,"props":102,"children":103},{},[104,106,118,120,126,128,134,135,141,143,148,150,156,158,164,166,172],{"type":42,"value":105},"The builder body is a ",{"type":36,"tag":107,"props":108,"children":109},"strong",{},[110,112],{"type":42,"value":111},"BL ",{"type":36,"tag":51,"props":113,"children":115},{"className":114},[],[116],{"type":42,"value":117},"StatementList",{"type":42,"value":119}," (inside a ",{"type":36,"tag":51,"props":121,"children":123},{"className":122},[],[124],{"type":42,"value":125},"BuilderBlock",{"type":42,"value":127},"). You use normal BL control flow (",{"type":36,"tag":51,"props":129,"children":131},{"className":130},[],[132],{"type":42,"value":133},"if",{"type":42,"value":58},{"type":36,"tag":51,"props":136,"children":138},{"className":137},[],[139],{"type":42,"value":140},"foreach",{"type":42,"value":142},", local variables) to compute which ",{"type":36,"tag":107,"props":144,"children":145},{},[146],{"type":42,"value":147},"emit instructions",{"type":42,"value":149}," to output at runtime. The ",{"type":36,"tag":51,"props":151,"children":153},{"className":152},[],[154],{"type":42,"value":155},"node",{"type":42,"value":157}," implicit parameter (concept ",{"type":36,"tag":51,"props":159,"children":161},{"className":160},[],[162],{"type":42,"value":163},"NodeParameter",{"type":42,"value":165},") is always in scope — its type is the concept referenced by ",{"type":36,"tag":51,"props":167,"children":169},{"className":168},[],[170],{"type":42,"value":171},"conceptDeclaration",{"type":42,"value":173},", giving smodel-typed access to children and references.",{"type":36,"tag":45,"props":175,"children":176},{},[177],{"type":42,"value":178},"The MPS dataflow engine builds a control-flow graph from the emitted instructions, then runs analyses (unreachable code, uninitialised variable reads) on that graph. The engine only traces the paths you declare; if no builder exists for a concept, MPS falls back to delegating all children in declaration order.",{"type":36,"tag":76,"props":180,"children":182},{"id":181},"critical-directives",[183],{"type":42,"value":184},"Critical Directives",{"type":36,"tag":186,"props":187,"children":188},"ul",{},[189,222,246,272,306,366,376],{"type":36,"tag":190,"props":191,"children":192},"li",{},[193,204,206,212,214,220],{"type":36,"tag":107,"props":194,"children":195},{},[196,202],{"type":36,"tag":51,"props":197,"children":199},{"className":198},[],[200],{"type":42,"value":201},"code for",{"type":42,"value":203}," is delegation, not a call.",{"type":42,"value":205}," Never use ",{"type":36,"tag":51,"props":207,"children":209},{"className":208},[],[210],{"type":42,"value":211},"jump",{"type":42,"value":213}," for child delegation. Use ",{"type":36,"tag":51,"props":215,"children":217},{"className":216},[],[218],{"type":42,"value":219},"EmitCodeForStatement",{"type":42,"value":221}," to inline a child's own builder at this point.",{"type":36,"tag":190,"props":223,"children":224},{},[225,236,238,244],{"type":36,"tag":107,"props":226,"children":227},{},[228,234],{"type":36,"tag":51,"props":229,"children":231},{"className":230},[],[232],{"type":42,"value":233},"ifjump",{"type":42,"value":235}," semantics: the jump is taken when the condition is FALSE.",{"type":42,"value":237}," Use it after ",{"type":36,"tag":51,"props":239,"children":241},{"className":240},[],[242],{"type":42,"value":243},"code for node.condition",{"type":42,"value":245}," to model branching.",{"type":36,"tag":190,"props":247,"children":248},{},[249,254,256,262,264,270],{"type":36,"tag":107,"props":250,"children":251},{},[252],{"type":42,"value":253},"Labels are node references, not string lookups.",{"type":42,"value":255}," ",{"type":36,"tag":51,"props":257,"children":259},{"className":258},[],[260],{"type":42,"value":261},"EmitLabelStatement.name",{"type":42,"value":263}," is display-only; jumps reference the label node via ",{"type":36,"tag":51,"props":265,"children":267},{"className":266},[],[268],{"type":42,"value":269},"LabelPosition.label",{"type":42,"value":271},". Two labels with the same string are still distinct targets.",{"type":36,"tag":190,"props":273,"children":274},{},[275,288,290,296,298,304],{"type":36,"tag":107,"props":276,"children":277},{},[278,280,286],{"type":42,"value":279},"Always null-guard ",{"type":36,"tag":51,"props":281,"children":283},{"className":282},[],[284],{"type":42,"value":285},"0..1",{"type":42,"value":287}," children",{"type":42,"value":289}," with BL ",{"type":36,"tag":51,"props":291,"children":293},{"className":292},[],[294],{"type":42,"value":295},"if (node.child != null)",{"type":42,"value":297}," before emitting ",{"type":36,"tag":51,"props":299,"children":301},{"className":300},[],[302],{"type":42,"value":303},"code for node.child",{"type":42,"value":305},".",{"type":36,"tag":190,"props":307,"children":308},{},[309,328,330,335,337,342,344,349,351,356,358,364],{"type":36,"tag":107,"props":310,"children":311},{},[312,318,320,326],{"type":36,"tag":51,"props":313,"children":315},{"className":314},[],[316],{"type":42,"value":317},"write node",{"type":42,"value":319}," vs ",{"type":36,"tag":51,"props":321,"children":323},{"className":322},[],[324],{"type":42,"value":325},"write node.link",{"type":42,"value":327},":",{"type":42,"value":329}," use ",{"type":36,"tag":51,"props":331,"children":333},{"className":332},[],[334],{"type":42,"value":317},{"type":42,"value":336}," (just ",{"type":36,"tag":51,"props":338,"children":340},{"className":339},[],[341],{"type":42,"value":163},{"type":42,"value":343}," as the variable expression) when the concept node ",{"type":36,"tag":107,"props":345,"children":346},{},[347],{"type":42,"value":348},"is",{"type":42,"value":350}," the variable being declared. Use ",{"type":36,"tag":51,"props":352,"children":354},{"className":353},[],[355],{"type":42,"value":325},{"type":42,"value":357}," (via ",{"type":36,"tag":51,"props":359,"children":361},{"className":360},[],[362],{"type":42,"value":363},"SLinkAccess",{"type":42,"value":365},") when the node merely references the variable being written.",{"type":36,"tag":190,"props":367,"children":368},{},[369,374],{"type":36,"tag":107,"props":370,"children":371},{},[372],{"type":42,"value":373},"Leaf concepts need no builder.",{"type":42,"value":375}," The engine treats unbuilt concepts as no-ops, or for ordinary parents delegates to children in declaration order.",{"type":36,"tag":190,"props":377,"children":378},{},[379,392],{"type":36,"tag":107,"props":380,"children":381},{},[382,384,390],{"type":42,"value":383},"Do not hand-edit serialized ",{"type":36,"tag":51,"props":385,"children":387},{"className":386},[],[388],{"type":42,"value":389},".mps",{"type":42,"value":391}," dataflow files.",{"type":42,"value":393}," Use MPS MCP node tools.",{"type":36,"tag":76,"props":395,"children":397},{"id":396},"common-path-workflow",[398],{"type":42,"value":399},"Common-Path Workflow",{"type":36,"tag":401,"props":402,"children":403},"ol",{},[404,480,506,533,584,612],{"type":36,"tag":190,"props":405,"children":406},{},[407,409,415,417,423,425,446,448,454,456,463,465,470,472,478],{"type":42,"value":408},"Create the dataflow model with ",{"type":36,"tag":51,"props":410,"children":412},{"className":411},[],[413],{"type":42,"value":414},"mps_mcp_create_model",{"type":42,"value":416}," and ",{"type":36,"tag":51,"props":418,"children":420},{"className":419},[],[421],{"type":42,"value":422},"modelName: \"\u003Clang>.dataFlow\"",{"type":42,"value":424}," if absent. ",{"type":36,"tag":107,"props":426,"children":427},{},[428,430,436,438,444],{"type":42,"value":429},"The aspect ID is ",{"type":36,"tag":51,"props":431,"children":433},{"className":432},[],[434],{"type":42,"value":435},"dataFlow",{"type":42,"value":437}," — camelCase, case-sensitive, no ",{"type":36,"tag":51,"props":439,"children":441},{"className":440},[],[442],{"type":42,"value":443},"@",{"type":42,"value":445}," suffix",{"type":42,"value":447},"; spelling it ",{"type":36,"tag":51,"props":449,"children":451},{"className":450},[],[452],{"type":42,"value":453},"dataflow",{"type":42,"value":455}," (lowercase) produces a utility model that MPS will not recognise. See ",{"type":36,"tag":457,"props":458,"children":460},"a",{"href":459},"..\u002Fmps-mcp-workflow\u002Freferences\u002Faspect-model-stereotypes.md",[461],{"type":42,"value":462},"aspect-model-stereotypes.md",{"type":42,"value":464},". Add ",{"type":36,"tag":51,"props":466,"children":468},{"className":467},[],[469],{"type":42,"value":56},{"type":42,"value":471}," (and transitively ",{"type":36,"tag":51,"props":473,"children":475},{"className":474},[],[476],{"type":42,"value":477},"jetbrains.mps.baseLanguage",{"type":42,"value":479},") as used languages on the model.",{"type":36,"tag":190,"props":481,"children":482},{},[483,485,490,492,497,499,505],{"type":42,"value":484},"Create a ",{"type":36,"tag":51,"props":486,"children":488},{"className":487},[],[489],{"type":42,"value":92},{"type":42,"value":491}," root node; set ",{"type":36,"tag":51,"props":493,"children":495},{"className":494},[],[496],{"type":42,"value":171},{"type":42,"value":498}," to the concept being described; give it a ",{"type":36,"tag":51,"props":500,"children":502},{"className":501},[],[503],{"type":42,"value":504},"name",{"type":42,"value":305},{"type":36,"tag":190,"props":507,"children":508},{},[509,511,516,518,524,526,531],{"type":42,"value":510},"Add a ",{"type":36,"tag":51,"props":512,"children":514},{"className":513},[],[515],{"type":42,"value":125},{"type":42,"value":517}," child with a ",{"type":36,"tag":51,"props":519,"children":521},{"className":520},[],[522],{"type":42,"value":523},"body",{"type":42,"value":525}," (BL ",{"type":36,"tag":51,"props":527,"children":529},{"className":528},[],[530],{"type":42,"value":117},{"type":42,"value":532},").",{"type":36,"tag":190,"props":534,"children":535},{},[536,538,543,545,551,553,559,561,567,569,575,577,583],{"type":42,"value":537},"Emit instructions: delegate to children with ",{"type":36,"tag":51,"props":539,"children":541},{"className":540},[],[542],{"type":42,"value":219},{"type":42,"value":544},"; model branches with ",{"type":36,"tag":51,"props":546,"children":548},{"className":547},[],[549],{"type":42,"value":550},"EmitIfJumpStatement",{"type":42,"value":552}," + ",{"type":36,"tag":51,"props":554,"children":556},{"className":555},[],[557],{"type":42,"value":558},"EmitLabelStatement",{"type":42,"value":560},"; record variable use with ",{"type":36,"tag":51,"props":562,"children":564},{"className":563},[],[565],{"type":42,"value":566},"EmitReadStatement",{"type":42,"value":568}," \u002F ",{"type":36,"tag":51,"props":570,"children":572},{"className":571},[],[573],{"type":42,"value":574},"EmitWriteStatement",{"type":42,"value":576},"; mark exits with ",{"type":36,"tag":51,"props":578,"children":580},{"className":579},[],[581],{"type":42,"value":582},"EmitRetStatement",{"type":42,"value":305},{"type":36,"tag":190,"props":585,"children":586},{},[587,589,595,597,603,605,611],{"type":42,"value":588},"For loops, use ",{"type":36,"tag":51,"props":590,"children":592},{"className":591},[],[593],{"type":42,"value":594},"BeforePosition",{"type":42,"value":596},"\u002F",{"type":36,"tag":51,"props":598,"children":600},{"className":599},[],[601],{"type":42,"value":602},"AfterPosition",{"type":42,"value":604}," to encode loop-back\u002Fexit edges; wrap potentially-unreachable instructions in ",{"type":36,"tag":51,"props":606,"children":608},{"className":607},[],[609],{"type":42,"value":610},"EmitMayBeUnreachable",{"type":42,"value":305},{"type":36,"tag":190,"props":613,"children":614},{},[615,617,623,625,631,633,639],{"type":42,"value":616},"Validate with ",{"type":36,"tag":51,"props":618,"children":620},{"className":619},[],[621],{"type":42,"value":622},"mps_mcp_check_root_node_problems",{"type":42,"value":624},". For tricky cases, inspect an existing baseLanguage builder via ",{"type":36,"tag":51,"props":626,"children":628},{"className":627},[],[629],{"type":42,"value":630},"mps_mcp_print_node",{"type":42,"value":632}," with ",{"type":36,"tag":51,"props":634,"children":636},{"className":635},[],[637],{"type":42,"value":638},"deep: true",{"type":42,"value":305},{"type":36,"tag":76,"props":641,"children":643},{"id":642},"related-skills",[644],{"type":42,"value":645},"Related Skills",{"type":36,"tag":186,"props":647,"children":648},{},[649,680,705,716],{"type":36,"tag":190,"props":650,"children":651},{},[652,658,660,666,667,672,673,678],{"type":36,"tag":51,"props":653,"children":655},{"className":654},[],[656],{"type":42,"value":657},"mps-model-manipulation",{"type":42,"value":659}," — BL + smodel code inside builder bodies (",{"type":36,"tag":51,"props":661,"children":663},{"className":662},[],[664],{"type":42,"value":665},"DotExpression",{"type":42,"value":58},{"type":36,"tag":51,"props":668,"children":670},{"className":669},[],[671],{"type":42,"value":363},{"type":42,"value":58},{"type":36,"tag":51,"props":674,"children":676},{"className":675},[],[677],{"type":42,"value":163},{"type":42,"value":679},", behavior method calls).",{"type":36,"tag":190,"props":681,"children":682},{},[683,689,691,697,698,704],{"type":36,"tag":51,"props":684,"children":686},{"className":685},[],[687],{"type":42,"value":688},"mps-aspect-behavior",{"type":42,"value":690}," — for behavior methods called from builders to compute target nodes (e.g. ",{"type":36,"tag":51,"props":692,"children":694},{"className":693},[],[695],{"type":42,"value":696},"getLoopOrSwitch",{"type":42,"value":58},{"type":36,"tag":51,"props":699,"children":701},{"className":700},[],[702],{"type":42,"value":703},"getReturnJumpTarget",{"type":42,"value":532},{"type":36,"tag":190,"props":706,"children":707},{},[708,714],{"type":36,"tag":51,"props":709,"children":711},{"className":710},[],[712],{"type":42,"value":713},"mps-aspect-typesystem",{"type":42,"value":715}," — when the dataflow you emit must agree with type checks.",{"type":36,"tag":190,"props":717,"children":718},{},[719,725],{"type":36,"tag":51,"props":720,"children":722},{"className":721},[],[723],{"type":42,"value":724},"mps-node-editing",{"type":42,"value":726}," — generic JSON-blueprint node creation\u002Freplacement workflow.",{"type":36,"tag":76,"props":728,"children":730},{"id":729},"reference-index",[731],{"type":42,"value":732},"Reference Index",{"type":36,"tag":186,"props":734,"children":735},{},[736,760,779,818,829,904],{"type":36,"tag":190,"props":737,"children":738},{},[739,741,746,747,752,754,759],{"type":42,"value":740},"Concept catalog — open when you need exact concept names, properties, children, cardinalities, or abstract bases for ",{"type":36,"tag":51,"props":742,"children":744},{"className":743},[],[745],{"type":42,"value":92},{"type":42,"value":58},{"type":36,"tag":51,"props":748,"children":750},{"className":749},[],[751],{"type":42,"value":125},{"type":42,"value":753},", every emit statement, every position type, and the abstract bases. See ",{"type":36,"tag":457,"props":755,"children":757},{"href":756},"references\u002Fconcept-catalog.md",[758],{"type":42,"value":756},{"type":42,"value":305},{"type":36,"tag":190,"props":761,"children":762},{},[763,765,771,773,778],{"type":42,"value":764},"Verified JSON patterns — open when constructing or editing a builder as JSON for ",{"type":36,"tag":51,"props":766,"children":768},{"className":767},[],[769],{"type":42,"value":770},"mps_mcp_*",{"type":42,"value":772}," tools. Includes variable read, single-child delegation, return-with-finally, if\u002Felsif\u002Felse, while loop, assignment, variable declaration, break to ancestor, and a custom inverted-condition statement. See ",{"type":36,"tag":457,"props":774,"children":776},{"href":775},"references\u002Fjson-patterns.md",[777],{"type":42,"value":775},{"type":42,"value":305},{"type":36,"tag":190,"props":780,"children":781},{},[782,784,789,790,796,798,804,805,810,812,817],{"type":42,"value":783},"Rules and pitfalls — open when a builder validates but the engine reports surprising reachability or variable-use results, when choosing between ",{"type":36,"tag":51,"props":785,"children":787},{"className":786},[],[788],{"type":42,"value":602},{"type":42,"value":416},{"type":36,"tag":51,"props":791,"children":793},{"className":792},[],[794],{"type":42,"value":795},"LabelPosition",{"type":42,"value":797},", or before using ",{"type":36,"tag":51,"props":799,"children":801},{"className":800},[],[802],{"type":42,"value":803},"modes",{"type":42,"value":596},{"type":36,"tag":51,"props":806,"children":808},{"className":807},[],[809],{"type":42,"value":72},{"type":42,"value":811},". See ",{"type":36,"tag":457,"props":813,"children":815},{"href":814},"references\u002Frules-and-pitfalls.md",[816],{"type":42,"value":814},{"type":42,"value":305},{"type":36,"tag":190,"props":819,"children":820},{},[821,823,828],{"type":42,"value":822},"Language setup and engine invocation — open when wiring a new dataflow model, or when debugging \"why is my builder not being called\". See ",{"type":36,"tag":457,"props":824,"children":826},{"href":825},"references\u002Fsetup-and-engine.md",[827],{"type":42,"value":825},{"type":42,"value":305},{"type":36,"tag":190,"props":830,"children":831},{},[832,834,840,841,847,848,854,855,861,862,868,869,875,876,882,883,889,891,897,898,903],{"type":42,"value":833},"BaseLanguage builder index — open when you want to study a known-good builder for ",{"type":36,"tag":51,"props":835,"children":837},{"className":836},[],[838],{"type":42,"value":839},"IfStatement",{"type":42,"value":58},{"type":36,"tag":51,"props":842,"children":844},{"className":843},[],[845],{"type":42,"value":846},"WhileStatement",{"type":42,"value":58},{"type":36,"tag":51,"props":849,"children":851},{"className":850},[],[852],{"type":42,"value":853},"ReturnStatement",{"type":42,"value":58},{"type":36,"tag":51,"props":856,"children":858},{"className":857},[],[859],{"type":42,"value":860},"BreakStatement",{"type":42,"value":58},{"type":36,"tag":51,"props":863,"children":865},{"className":864},[],[866],{"type":42,"value":867},"VariableDeclaration",{"type":42,"value":58},{"type":36,"tag":51,"props":870,"children":872},{"className":871},[],[873],{"type":42,"value":874},"TryFinallyStatement",{"type":42,"value":58},{"type":36,"tag":51,"props":877,"children":879},{"className":878},[],[880],{"type":42,"value":881},"SwitchStatement",{"type":42,"value":58},{"type":36,"tag":51,"props":884,"children":886},{"className":885},[],[887],{"type":42,"value":888},"ForStatement",{"type":42,"value":890},", etc. Lists builder names and persistent nodeReferences in ",{"type":36,"tag":51,"props":892,"children":894},{"className":893},[],[895],{"type":42,"value":896},"r:00000000-0000-4000-0000-011c895902c2",{"type":42,"value":811},{"type":36,"tag":457,"props":899,"children":901},{"href":900},"references\u002Fbaselanguage-builder-index.md",[902],{"type":42,"value":900},{"type":42,"value":305},{"type":36,"tag":190,"props":905,"children":906},{},[907,909,915,917,922],{"type":42,"value":908},"Sample language reference — open when looking for a minimal complete builder for a custom language (",{"type":36,"tag":51,"props":910,"children":912},{"className":911},[],[913],{"type":42,"value":914},"UnlessStatement_DataFlow",{"type":42,"value":916},"). See ",{"type":36,"tag":457,"props":918,"children":920},{"href":919},"references\u002Fsample-language-reference.md",[921],{"type":42,"value":919},{"type":42,"value":305},{"items":924,"total":995},[925,941,950,958,969,973,986],{"slug":926,"name":926,"fn":927,"description":928,"org":929,"tags":930,"stars":16,"repoUrl":17,"updatedAt":940},"mps-aspect-accessories","configure JetBrains MPS module dependencies","Wire MPS module and model dependencies, used languages, used devkits, extended languages, runtime solutions, accessory models, and language\u002Fdependency versions. Use when adding\u002Fremoving module dependencies, importing languages or devkits into a model, declaring runtime solutions, or shipping accessory content visible to consumers without explicit import.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[931,934,937],{"name":932,"slug":933,"type":15},"Architecture","architecture",{"name":935,"slug":936,"type":15},"Configuration","configuration",{"name":938,"slug":939,"type":15},"Engineering","engineering","2026-07-17T06:06:57.311661",{"slug":942,"name":942,"fn":943,"description":944,"org":945,"tags":946,"stars":16,"repoUrl":17,"updatedAt":949},"mps-aspect-actions","define and edit MPS node factories","Use when defining or editing MPS node factories (the \"actions\" aspect) — `NodeFactories` roots, per-concept `NodeFactory` setup functions that initialize a freshly created node and optionally copy data from a replaced `sampleNode`, plus the actions aspect's `CopyPasteHandlers` and `PasteWrappers` roots. Reach for this skill when a substitution, side transform, completion replacement, or `add new initialized(...)` should preserve fields from the node it is replacing, or when defaults set in a constructor are not enough.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[947,948],{"name":932,"slug":933,"type":15},{"name":938,"slug":939,"type":15},"2026-07-17T06:04:48.066901",{"slug":688,"name":688,"fn":951,"description":952,"org":953,"tags":954,"stars":16,"repoUrl":17,"updatedAt":957},"define and edit MPS concept behavior","Use when defining or editing MPS `ConceptBehavior` — per-concept methods (non-virtual \u002F virtual \u002F abstract \u002F static \u002F virtual static), constructors, virtual dispatch (MRO), super and interface-default calls (`super\u003CInterface>.method`), overriding methods from `lang.core.behavior` interfaces such as `ScopeProvider.getScope` \u002F `INamedConcept.getName` \u002F `BaseConcept.getPresentation`, calling sibling methods (`LocalBehaviorMethodCall`) and behavior methods from other aspects via `node.method(...)`. Reach for this skill whenever the task involves authoring or modifying `\u003Clang>\u002FlanguageModels\u002Fbehavior.mps`.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[955,956],{"name":932,"slug":933,"type":15},{"name":938,"slug":939,"type":15},"2026-07-13T06:45:21.757084",{"slug":959,"name":959,"fn":960,"description":961,"org":962,"tags":963,"stars":16,"repoUrl":17,"updatedAt":968},"mps-aspect-constraints","define JetBrains MPS language constraints","Use when defining or editing MPS language constraints — property validators \u002F setters \u002F getters, referent search scopes (imperative or inherited via `ScopeProvider.getScope`), `referentSetHandler` side effects, default-scope blocks, `canBeChild` \u002F `canBeParent` \u002F `canBeAncestor` \u002F `canBeRoot` placement rules, `defaultConcreteConcept` for abstract concepts, `set \u003Cread-only>` and `{name}` aliasing, and scope helpers (`SimpleRoleScope`, `ListScope`, `CompositeScope`, `HidingByNameScope`). Reach for this skill whenever the task involves authoring or modifying `\u003Clang>\u002FlanguageModels\u002Fconstraints.mps`.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[964,965],{"name":932,"slug":933,"type":15},{"name":966,"slug":967,"type":15},"Code Analysis","code-analysis","2026-07-23T05:41:33.639365",{"slug":4,"name":4,"fn":5,"description":6,"org":970,"tags":971,"stars":16,"repoUrl":17,"updatedAt":18},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[972],{"name":13,"slug":14,"type":15},{"slug":974,"name":974,"fn":975,"description":976,"org":977,"tags":978,"stars":16,"repoUrl":17,"updatedAt":985},"mps-aspect-editor","define MPS editor layouts","Use when creating or changing MPS editor definitions — the overall workflow from scaffolding a `ConceptEditorDeclaration` through componentizing reusable `EditorComponentDeclaration`s, refining cell models and cell layouts, applying style sheets and indent-layout style items, wiring smart references, leveraging inheritance via super-concepts and interfaces, inspecting (`print_node_json`, `show_node_representation`) and validating (`check_root_node_problems`). Covers `jetbrains.mps.lang.editor` cell models (`CellModel_RefNode`\u002F`CellModel_RefNodeList`\u002F`CellModel_RefCell`\u002F`CellModel_Property`\u002F`CellModel_Constant`), layout choices, and JSON blueprints for common editor shapes. For the non-layout side (action maps, keymaps, transformation\u002Fsubstitute menus) use `mps-aspect-editor-menus-and-keymaps`.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[979,982],{"name":980,"slug":981,"type":15},"Design","design",{"name":983,"slug":984,"type":15},"UI Components","ui-components","2026-07-23T05:41:56.638151",{"slug":987,"name":987,"fn":988,"description":989,"org":990,"tags":991,"stars":16,"repoUrl":17,"updatedAt":994},"mps-aspect-editor-menus-and-keymaps","author MPS editor menus and keymaps","Use when authoring the **non-layout** parts of the MPS editor aspect — what happens when the user types, presses a key, triggers completion, pastes, or invokes a context action. Covers action maps (`CellActionMapDeclaration`), cell keymaps (`CellKeyMapDeclaration`), transformation menus (`TransformationMenu_Default` \u002F `_Named` \u002F `_Contribution`), substitute menus (`SubstituteMenu_Default` \u002F `SubstituteMenu` \u002F contributions), side transforms (LEFT\u002FRIGHT), legacy cell menus, paste wrappers and copy-paste handlers (in the actions language), completion styling, reference presentation, two-step deletion, and the editor selection API. Trigger terms: `actionMap`, `keyMap`, `delete_action_id`, `transformationMenu`, `substituteMenu`, `Ctrl+Space`, `Ctrl+Alt+B`, side transform, paste wrapper, completion styling, `PasteWrappers`, `CopyPasteHandlers`. For the **layout** side (cells, layouts, style sheets) use `mps-aspect-editor` instead.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[992,993],{"name":938,"slug":939,"type":15},{"name":983,"slug":984,"type":15},"2026-07-23T05:41:49.666535",31,{"items":997,"total":1084},[998,1004,1009,1014,1019,1023,1028,1033,1042,1052,1061,1074],{"slug":926,"name":926,"fn":927,"description":928,"org":999,"tags":1000,"stars":16,"repoUrl":17,"updatedAt":940},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1001,1002,1003],{"name":932,"slug":933,"type":15},{"name":935,"slug":936,"type":15},{"name":938,"slug":939,"type":15},{"slug":942,"name":942,"fn":943,"description":944,"org":1005,"tags":1006,"stars":16,"repoUrl":17,"updatedAt":949},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1007,1008],{"name":932,"slug":933,"type":15},{"name":938,"slug":939,"type":15},{"slug":688,"name":688,"fn":951,"description":952,"org":1010,"tags":1011,"stars":16,"repoUrl":17,"updatedAt":957},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1012,1013],{"name":932,"slug":933,"type":15},{"name":938,"slug":939,"type":15},{"slug":959,"name":959,"fn":960,"description":961,"org":1015,"tags":1016,"stars":16,"repoUrl":17,"updatedAt":968},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1017,1018],{"name":932,"slug":933,"type":15},{"name":966,"slug":967,"type":15},{"slug":4,"name":4,"fn":5,"description":6,"org":1020,"tags":1021,"stars":16,"repoUrl":17,"updatedAt":18},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1022],{"name":13,"slug":14,"type":15},{"slug":974,"name":974,"fn":975,"description":976,"org":1024,"tags":1025,"stars":16,"repoUrl":17,"updatedAt":985},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1026,1027],{"name":980,"slug":981,"type":15},{"name":983,"slug":984,"type":15},{"slug":987,"name":987,"fn":988,"description":989,"org":1029,"tags":1030,"stars":16,"repoUrl":17,"updatedAt":994},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1031,1032],{"name":938,"slug":939,"type":15},{"name":983,"slug":984,"type":15},{"slug":1034,"name":1034,"fn":1035,"description":1036,"org":1037,"tags":1038,"stars":16,"repoUrl":17,"updatedAt":1041},"mps-aspect-generation-plan","modify MPS generation plans","Use when defining or modifying an MPS generation plan — explicit ordering of generators, checkpoints for cross-model reference resolution, forks for parallel branches, IncludePlan composition, conditional PlanContribution activation, ParameterEquals\u002FConceptListSelector fork selectors, and InitModelAttributes for targetFacet routing. Apply when working with @genplan models, the jetbrains.mps.lang.generator.plan language, attaching plans via DevKits or the Custom generation facet, or debugging cross-model mapping label resolution.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1039,1040],{"name":932,"slug":933,"type":15},{"name":938,"slug":939,"type":15},"2026-07-13T06:44:59.507855",{"slug":1043,"name":1043,"fn":1044,"description":1045,"org":1046,"tags":1047,"stars":16,"repoUrl":17,"updatedAt":1051},"mps-aspect-generator","define JetBrains MPS generator rules","Use when defining or modifying MPS generators — author a generator module, add or edit root\u002Freduction\u002Fweaving\u002Fpattern mapping rules, attach template macros ($COPY_SRC, $LOOP, $IF, $PROPERTY, $REF, $SWITCH, $MAP_SRC, $WEAVE, $INSERT, $LABEL, $TRACE, $VAR), wire mapping labels, build template switches, write pre\u002Fpost mapping scripts, navigate `genContext`, or debug \"rule didn't fire\", missing references, empty output, infinite reduction loops, and generated-Java compile failures.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1048,1049,1050],{"name":932,"slug":933,"type":15},{"name":966,"slug":967,"type":15},{"name":938,"slug":939,"type":15},"2026-07-17T06:06:58.042999",{"slug":1053,"name":1053,"fn":1054,"description":1055,"org":1056,"tags":1057,"stars":16,"repoUrl":17,"updatedAt":1060},"mps-aspect-intentions","define and edit MPS intentions","Use when defining or editing MPS intentions (the Alt+Enter context-action aspect) — adding `IntentionDeclaration` roots, parameterized or surround-with variants, description\u002FisApplicable\u002Fexecute blocks, child-filter functions, factory-initialized AST splicing, or debugging why an intention is not offered. Lives in the language's `intentions` model and uses `jetbrains.mps.lang.intentions`.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1058,1059],{"name":932,"slug":933,"type":15},{"name":938,"slug":939,"type":15},"2026-07-23T05:41:48.692899",{"slug":1062,"name":1062,"fn":1063,"description":1064,"org":1065,"tags":1066,"stars":16,"repoUrl":17,"updatedAt":1073},"mps-aspect-migrations","author and debug MPS migration scripts","Use when authoring or debugging MPS migration scripts that upgrade user models after a language definition changes — covers jetbrains.mps.lang.migration (MigrationScript class-based, PureMigrationScript declarative, MoveConcept\u002FMoveContainmentLink\u002FMoveReferenceLink\u002FMoveProperty, ordering via OrderDependency, data exchange via putData\u002FgetData, RefactoringLog, ConceptMigrationReference) and jetbrains.mps.lang.script Enhancement Scripts (MigrationScript with MigrationScriptPart_Instance, ExtractInterfaceMigration, FactoryMigrationScriptPart, CommentMigrationScriptPart) — when a model needs version-gated upgrade, concept rename or removal, link or property rename, instance-level transformation, or composition of migration steps.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1067,1070],{"name":1068,"slug":1069,"type":15},"Debugging","debugging",{"name":1071,"slug":1072,"type":15},"Migration","migration","2026-07-13T06:45:20.372122",{"slug":1075,"name":1075,"fn":1076,"description":1077,"org":1078,"tags":1079,"stars":16,"repoUrl":17,"updatedAt":1083},"mps-aspect-structure-concepts","define concepts in MPS structure aspect","Define concepts, interface concepts, enumerations, and constrained data types in an MPS language's `structure` aspect. Covers smart-reference detection, alias rules, cardinality, INamedConcept usage, bulk creation, and the full `mps_mcp_alter_structure` \u002F `mps_mcp_query_structure` reference. Use when authoring or modifying a language's structure model.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1080],{"name":1081,"slug":1082,"type":15},"Data Modeling","data-modeling","2026-07-23T05:41:30.705975",188]