feat: add maxProperties object sampler support (#158)

* feat: add maxProperties object sampler support

* chore: refactor naming and use const when possible

src/samplers/object.js

@@ -4,15 +4,18 @@ export function sampleObject(schema, options = {}, spec, context) {
   const depth = (context && context.depth || 1);
 
   if (schema && typeof schema.properties === 'object') {
-    let requiredKeys = (Array.isArray(schema.required) ? schema.required : []);
-    let requiredKeyDict = requiredKeys.reduce((dict, key) => {
-      dict[key] = true;
-      return dict;
-    }, {});
+
+    // Prepare for skipNonRequired option
+    const requiredProperties = Array.isArray(schema.required) ? schema.required : [];
+    const requiredPropertiesMap = {};
+
+    for (const requiredProperty of requiredProperties) {
+        requiredPropertiesMap[requiredProperty] = true;
+    }
 
     Object.keys(schema.properties).forEach(propertyName => {
       // skip before traverse that could be costly
-      if (options.skipNonRequired && !requiredKeyDict.hasOwnProperty(propertyName)) {
+      if (options.skipNonRequired && !requiredPropertiesMap.hasOwnProperty(propertyName)) {
         return;
       }
 
@@ -33,5 +36,31 @@ export function sampleObject(schema, options = {}, spec, context) {
     res[`${String(propertyName)}1`] = traverse(schema.additionalProperties, options, spec, {depth: depth + 1 }).value;
     res[`${String(propertyName)}2`] = traverse(schema.additionalProperties, options, spec, {depth: depth + 1 }).value;
   }
+
+  // Strictly enforce maxProperties constraint
+  if (schema && typeof schema.properties === 'object' && schema.maxProperties !== undefined && Object.keys(res).length > schema.maxProperties) {
+    const filteredResult = {};
+    let propertiesAdded = 0;
+
+    // Always include required properties first, if present
+    const requiredProperties = Array.isArray(schema.required) ? schema.required : [];
+    requiredProperties.forEach(propName => {
+        if (res[propName] !== undefined) {
+            filteredResult[propName] = res[propName];
+            propertiesAdded++;
+        }
+    });
+
+    // Add other properties until maxProperties is reached
+    Object.keys(res).forEach(propName => {
+        if (propertiesAdded < schema.maxProperties && !filteredResult.hasOwnProperty(propName)) {
+            filteredResult[propName] = res[propName];
+            propertiesAdded++;
+        }
+    });
+
+    res = filteredResult;
+  }
+
   return res;
 }

test/unit/object.spec.js

@@ -182,5 +182,28 @@ describe('sampleObject', () => {
       fooId: 'fb4274c7-4fcd-4035-8958-a680548957ff',
       barId: '3c966637-4898-4972-9a9d-baefa6cd6c89'
     });
-  })
+  });
+
+  it('respects maxProperties by including no more than 2 properties in the sampled object', () => {
+    // Define a schema with four properties and a maxProperties limit of two
+    const schema = {
+      type: 'object',
+      properties: {
+        name: { type: 'string' },
+        email: { type: 'string', format: 'email' },
+        age: { type: 'integer', minimum: 0 },
+        phone: { type: 'string' }
+      },
+      required: ['name', 'email'], // 'name' and 'email' are required
+      maxProperties: 2
+    };
+
+    const result = sampleObject(schema);
+
+    expect(Object.keys(result).length).to.be.at.most(2);
+
+    // Assert that if 'name' and 'email' are required, they are included
+    expect(result).to.have.property('name');
+    expect(result).to.have.property('email');
+  });
 });