Native Vensim MDL parser

doc/simlin-project.schema.json

@@ -125,6 +125,12 @@
           "items": {
             "$ref": "#/$defs/LoopMetadata"
           }
+        },
+        "groups": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ModelGroup"
+          }
         }
       },
       "required": [
@@ -498,6 +504,9 @@
         "zoom": {
           "type": "number",
           "format": "double"
+        },
+        "useLetteredPolarity": {
+          "type": "boolean"
         }
       },
       "required": [
@@ -798,6 +807,12 @@
           "items": {
             "$ref": "#/$defs/LinkPoint"
           }
+        },
+        "polarity": {
+          "type": [
+            "string",
+            "null"
+          ]
         }
       },
       "required": [
@@ -954,6 +969,39 @@
         "name"
       ]
     },
+    "ModelGroup": {
+      "description": "Semantic/organizational group for categorizing model variables.\nThis is distinct from visual diagram groups (ViewElement::Group).",
+      "type": "object",
+      "properties": {
+        "name": {
+          "type": "string"
+        },
+        "doc": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "parent": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "members": {
+          "type": "array",
+          "items": {
+            "type": "string"
+          }
+        },
+        "runEnabled": {
+          "type": "boolean"
+        }
+      },
+      "required": [
+        "name"
+      ]
+    },
     "Dimension": {
       "type": "object",
       "properties": {

src/app/NewProject.tsx

@@ -19,7 +19,6 @@ import ExpandMoreIcon from '@mui/icons-material/ExpandMore';
 import { Project } from './Project';
 import { User } from './User';
 import { Project as ProjectDM } from '@system-dynamics/core/datamodel';
-import { convertMdlToXmile } from '@system-dynamics/xmutil';
 import { Project as Engine2Project } from '@system-dynamics/engine2';
 import type { JsonProject } from '@system-dynamics/engine2';
 
@@ -143,27 +142,12 @@ export class NewProject extends React.Component<NewProjectProps, NewProjectState
     }
     const file = event.target.files[0];
     const contents = await readFile(file);
-    let logs: string | undefined;
-
     try {
       let engine2Project: Engine2Project;
 
       if (file.name.endsWith('.mdl')) {
-        // For Vensim MDL files, try direct import first if available
-        const hasVensim = await Engine2Project.hasVensimSupport();
-        if (hasVensim) {
-          engine2Project = await Engine2Project.openVensim(contents);
-        } else {
-          // Fall back to xmutil conversion when direct Vensim support is not available
-          const [xmileContents, conversionLogs] = await convertMdlToXmile(contents, true);
-          logs = conversionLogs;
-          if (xmileContents.length === 0) {
-            throw new Error('Vensim converter: ' + (logs || 'unknown error'));
-          }
-          engine2Project = await Engine2Project.open(xmileContents);
-        }
+        engine2Project = await Engine2Project.openVensim(contents);
       } else {
-        // XMILE/STMX files open directly
         engine2Project = await Engine2Project.open(contents);
       }
 
@@ -172,12 +156,8 @@ export class NewProject extends React.Component<NewProjectProps, NewProjectState
       const activeProject = ProjectDM.fromJson(json);
       const views = activeProject.models.get('main')?.views;
       if (!views || views.isEmpty()) {
-        let errorMsg = `can't import model with no view at this time.`;
-        if (logs && logs.length !== 0) {
-          errorMsg = logs;
-        }
         this.setState({
-          errorMsg,
+          errorMsg: `can't import model with no view at this time.`,
         });
         return;
       }

src/app/config/rsbuild/shared.config.js

@@ -138,7 +138,6 @@ const sharedConfig = defineConfig({
           '@system-dynamics/core': resolveApp('../core'),
           '@system-dynamics/diagram': resolveApp('../diagram'),
           '@system-dynamics/engine2': resolveApp('../engine2'),
-          '@system-dynamics/xmutil': resolveApp('../xmutil-js'),
         },
       },
     },

src/app/package.json

@@ -9,8 +9,7 @@
   "dependencies": {
     "@system-dynamics/core": "^1.0.0",
     "@system-dynamics/diagram": "^1.0.0",
-    "@system-dynamics/engine2": "^2.0.0",
-    "@system-dynamics/xmutil": "^1.0.0"
+    "@system-dynamics/engine2": "^2.0.0"
   },
   "devDependencies": {
     "@rsbuild/core": "^1.3.22",

src/app/tsconfig.browser.json

@@ -32,7 +32,6 @@
   "references": [
     { "path": "../core/tsconfig.browser.json" },
     { "path": "../diagram/tsconfig.browser.json" },
-    { "path": "../engine2/tsconfig.browser.json" },
-    { "path": "../xmutil-js/tsconfig.browser.json" }
+    { "path": "../engine2/tsconfig.browser.json" }
   ]
 }

src/core/datamodel.ts

@@ -38,6 +38,7 @@ import {
   type JsonFlowPoint,
   type JsonLinkPoint,
   type JsonLoopMetadata,
+  type JsonModelGroup,
   type JsonSource,
 } from '@system-dynamics/engine2';
 
@@ -859,13 +860,9 @@ const linkViewElementDefaults = {
   arc: undefined as number | undefined,
   isStraight: false,
   multiPoint: undefined as List<Point> | undefined,
+  polarity: undefined as string | undefined,
 };
 export class LinkViewElement extends Record(linkViewElementDefaults) implements ViewElement {
-  // this isn't useless, as it ensures we specify the full object
-
-  constructor(props: typeof linkViewElementDefaults) {
-    super(props);
-  }
   static fromJson(json: JsonLinkViewElement): LinkViewElement {
     let arc: number | undefined = undefined;
     let isStraight = false;
@@ -886,6 +883,7 @@ export class LinkViewElement extends Record(linkViewElementDefaults) implements
       arc,
       isStraight,
       multiPoint,
+      polarity: json.polarity,
     });
   }
   toJson(): JsonLinkViewElement {
@@ -900,6 +898,9 @@ export class LinkViewElement extends Record(linkViewElementDefaults) implements
     } else if (this.multiPoint) {
       result.multiPoints = this.multiPoint.map((p) => ({ x: p.x, y: p.y })).toArray();
     }
+    if (this.polarity !== undefined) {
+      result.polarity = this.polarity;
+    }
     return result;
   }
   get cx(): number {
@@ -1162,13 +1163,9 @@ const stockFlowViewDefaults = {
   elements: List<ViewElement>(),
   viewBox: Rect.default(),
   zoom: -1,
+  useLetteredPolarity: false,
 };
 export class StockFlowView extends Record(stockFlowViewDefaults) {
-  // this isn't useless, as it ensures we specify the full object
-
-  constructor(props: typeof stockFlowViewDefaults) {
-    super(props);
-  }
   static fromJson(json: JsonView, variables: Map<string, Variable>): StockFlowView {
     let maxUid = -1;
     let namedElements = Map<string, UID>();
@@ -1243,6 +1240,7 @@ export class StockFlowView extends Record(stockFlowViewDefaults) {
       nextUid,
       viewBox,
       zoom: json.zoom ?? 1,
+      useLetteredPolarity: json.useLetteredPolarity ?? false,
     });
   }
   toJson(): JsonView {
@@ -1282,6 +1280,10 @@ export class StockFlowView extends Record(stockFlowViewDefaults) {
       result.zoom = this.zoom;
     }
 
+    if (this.useLetteredPolarity) {
+      result.useLetteredPolarity = true;
+    }
+
     return result;
   }
 }
@@ -1343,11 +1345,55 @@ export class LoopMetadata extends Record(loopMetadataDefaults) {
   }
 }
 
+const modelGroupDefaults = {
+  name: '',
+  doc: undefined as string | undefined,
+  parent: undefined as string | undefined,
+  members: List<string>(),
+  runEnabled: false,
+};
+
+/**
+ * Semantic/organizational group for categorizing model variables.
+ * This is distinct from visual diagram groups (GroupViewElement).
+ */
+export class ModelGroup extends Record(modelGroupDefaults) {
+  constructor(props: typeof modelGroupDefaults) {
+    super(props);
+  }
+  static fromJson(json: JsonModelGroup): ModelGroup {
+    return new ModelGroup({
+      name: json.name,
+      doc: json.doc,
+      parent: json.parent,
+      members: List(json.members ?? []),
+      runEnabled: json.runEnabled ?? false,
+    });
+  }
+  toJson(): JsonModelGroup {
+    const result: JsonModelGroup = {
+      name: this.name,
+      members: this.members.toArray(),
+    };
+    if (this.doc) {
+      result.doc = this.doc;
+    }
+    if (this.parent) {
+      result.parent = this.parent;
+    }
+    if (this.runEnabled) {
+      result.runEnabled = this.runEnabled;
+    }
+    return result;
+  }
+}
+
 const modelDefaults = {
   name: '',
   variables: Map<string, Variable>(),
   views: List<StockFlowView>(),
   loopMetadata: List<LoopMetadata>(),
+  groups: List<ModelGroup>(),
 };
 export class Model extends Record(modelDefaults) {
   // this isn't useless, as it ensures we specify the full object
@@ -1370,6 +1416,7 @@ export class Model extends Record(modelDefaults) {
       variables,
       views: List((json.views ?? []).map((view: JsonView) => StockFlowView.fromJson(view, variables))),
       loopMetadata: List((json.loopMetadata ?? []).map((lm: JsonLoopMetadata) => LoopMetadata.fromJson(lm))),
+      groups: List((json.groups ?? []).map((g: JsonModelGroup) => ModelGroup.fromJson(g))),
     });
   }
   toJson(): JsonModel {
@@ -1406,6 +1453,9 @@ export class Model extends Record(modelDefaults) {
     if (this.loopMetadata.size > 0) {
       result.loopMetadata = this.loopMetadata.map((lm: LoopMetadata) => lm.toJson()).toArray();
     }
+    if (this.groups.size > 0) {
+      result.groups = this.groups.map((g: ModelGroup) => g.toJson()).toArray();
+    }
 
     return result;
   }
@@ -1439,7 +1489,7 @@ export class Dt extends Record(dtDefaults) {
   }
 }
 
-export type SimMethod = 'euler' | 'rk4';
+export type SimMethod = 'euler' | 'rk2' | 'rk4';
 
 const simSpecsDefaults = {
   start: 0,