fix: struct ordering

Before objects were either inserted before already inserted objects that
reference them or at the end of the list. This algorithm fails when
structs are reference structs that reference other structs. Now
dependent objects are always inserted first. To implement quickly it
naively iterates over the object list N times to insert all of the
remaining objects.

Author: G4Vi

src/index.ts

@@ -6,18 +6,6 @@ function cppIdentifer(s: string) {
   return helpers.snakeToPascalCase(s);
 }
 
-function objectReferencesObject(existing: ObjectType, name: string) {
-  for (const prop of existing.properties) {
-    if (prop.kind === 'object') {
-      const object = prop as ObjectType
-      if (object.name === name) {
-        return true
-      }
-    }
-  }
-  return false
-}
-
 function v2ToCppTypeXInner(type: XtpNormalizedType, refnamespace: string): string {
   switch (type.kind) {
     case 'string':
@@ -328,29 +316,89 @@ function isTypeUntypedObject(type: XtpNormalizedType) {
   return false
 }
 
+function addObject(objects: Schema[], schema: Schema) {
+  // find the object's direct dependencies
+  const names = new Set();
+  const object = schema.xtpType as ObjectType
+  for (const prop of object.properties) {
+    if (prop.kind === 'object') {
+      const object = prop as ObjectType
+      if (object.name) {
+        names.add(object.name)
+      }
+    } else if (prop.kind === 'array') {
+      const arrayType = prop as ArrayType
+      if (arrayType.elementType.kind === 'object') {
+        const object = arrayType.elementType as ObjectType
+        if (object.name) {
+          names.add(object.name)
+        }
+      }
+    } else if (prop.kind === 'map') {
+      const { keyType, valueType } = prop as MapType
+      if (valueType.kind === 'object') {
+        const object = valueType as ObjectType
+        if (object.name) {
+          names.add(object.name)
+        }
+      }
+    }
+  }
+  // loop until after the dependencies or end of objects
+  let i = 0;
+  for (; i < objects.length; i++) {
+    if (names.size === 0) {
+      break
+    }
+    const existing = objects[i]
+    const existingObject = existing.xtpType as ObjectType;
+    names.delete(existingObject.name)
+  }
+  // not all deps found, can't add yet
+  if (names.size) {
+    return false
+  }
+  // add
+  objects.splice(i, 0, schema);
+  return true
+}
+
 export function render() {
   const tmpl = Host.inputString();
   const prevctx = getContext();
 
   const enums: Schema[] = [];
+  const todoObjects: Schema[] = [];
   const objects: Schema[] = [];
-  Object.values(prevctx.schema.schemas).forEach(schema => {
+  for (const schema of Object.values(prevctx.schema.schemas)) {
     if (helpers.isEnum(schema)) {
       enums.push(schema);
     } else if (helpers.isObject(schema)) {
-      const object = schema.xtpType as ObjectType;
-      // insertion sort objects ahead of objects that use them
-      let i = 0;
-      for (; i < objects.length; i++) {
-        if (objectReferencesObject(objects[i].xtpType as ObjectType, object.name)) {
-          break;
-        }
+      // insertion sort add object after its dependencies
+      // if it's dependencies aren't in objects, defer
+      if (!addObject(objects, schema)) {
+        todoObjects.push(schema)
       }
-      objects.splice(i, 0, schema); // we need Schema as it has the required attribute
     } else {
       throw new Error("unhandled schema type " + schema.xtpType.kind)
     }
-  });
+  }
+  // add the remaining objects
+  // rather than doing dependency analysis
+  // each iteration loop through all the objects until we add an object
+  const maxIterations = todoObjects.length
+  for (let iter = 0; iter < maxIterations; iter++) {
+    for (let i = 0; i < todoObjects.length; i++) {
+      if (addObject(objects, todoObjects[i])) {
+        todoObjects.splice(i, 1)
+        break
+      }
+    }
+  }
+  if (todoObjects.length) {
+    throw new Error("Failed to add remaning objects")
+  }
+
   // sort the properties for efficient struct layout
   for (const object of objects) {
     object.properties.sort((a: Property, b: Property) => {