feat: createStructWithAdditionalProperties superstruct factory (#334)

packages/starknet-snap/src/utils/superstruct.test.ts

@@ -1,5 +1,5 @@
 import { constants } from 'starknet';
-import { StructError, assert } from 'superstruct';
+import { StructError, assert, object, number, string } from 'superstruct';
 
 import transactionExample from '../__tests__/fixture/transactionExample.json';
 import typedDataExample from '../__tests__/fixture/typedDataExample.json';
@@ -11,6 +11,7 @@ import {
   CairoVersionStruct,
   CallDataStruct,
   ChainIdStruct,
+  createStructWithAdditionalProperties,
   TxVersionStruct,
   TypeDataStruct,
 } from './superstruct';
@@ -174,3 +175,52 @@ describe('CallDataStruct', () => {
     );
   });
 });
+
+describe('createStructWithAdditionalProperties', () => {
+  const predefinedProperties = object({
+    name: string(),
+    age: number(),
+  });
+
+  const additionalPropertyTypes = string(); // Additional properties should be strings
+  const ExtendedPropStruct = createStructWithAdditionalProperties(
+    predefinedProperties,
+    additionalPropertyTypes,
+  );
+  it('should validate predefined properties correctly', () => {
+    const validData = {
+      name: 'John',
+      age: 30,
+    };
+    const [error, result] = ExtendedPropStruct.validate(validData);
+
+    expect(error).toBeUndefined();
+    expect(result).toStrictEqual(validData);
+  });
+
+  it('should validate additional properties correctly', () => {
+    const validDataWithExtra = {
+      name: 'John',
+      age: 30,
+      nickname: 'Johnny',
+    };
+
+    const [error, result] = ExtendedPropStruct.validate(validDataWithExtra);
+
+    expect(error).toBeUndefined();
+    expect(result).toStrictEqual(validDataWithExtra);
+  });
+
+  it('should fail validation if additional properties are of the wrong type', () => {
+    const invalidData = {
+      name: 'John',
+      age: 30,
+      nickname: 12345, // Invalid type for additional property
+    };
+
+    const [error] = ExtendedPropStruct.validate(invalidData);
+
+    expect(error).toBeDefined();
+    expect(error?.message).toContain('Expected a string, but received');
+  });
+});

packages/starknet-snap/src/utils/superstruct.ts

@@ -1,5 +1,6 @@
 import { union } from '@metamask/snaps-sdk';
 import { constants, validateAndParseAddress } from 'starknet';
+import type { Struct } from 'superstruct';
 import {
   boolean,
   enums,
@@ -11,6 +12,8 @@ import {
   any,
   number,
   array,
+  dynamic,
+  assign,
 } from 'superstruct';
 
 import { CAIRO_VERSION_LEGACY, CAIRO_VERSION } from './constants';
@@ -91,3 +94,38 @@ export const CairoVersionStruct = enums([CAIRO_VERSION, CAIRO_VERSION_LEGACY]);
 export const TxVersionStruct = enums(
   Object.values(constants.TRANSACTION_VERSION),
 );
+
+/**
+ * Creates a struct that combines predefined properties with additional dynamic properties.
+ *
+ * This function generates a Superstruct schema that includes both the predefined properties
+ * and any additional properties found in the input. The additional properties are validated
+ * according to the specified `additionalPropertyTypes`, or `any` if not provided.
+ *
+ * @param predefinedProperties - A Superstruct schema defining the base set of properties that are expected.
+ * @param additionalPropertyTypes - A Superstruct schema that defines the types for any additional properties.
+ * Defaults to `any`, allowing any additional properties.
+ * @returns A dynamic struct that first validates against the predefined properties and then
+ * includes any additional properties that match the `additionalPropertyTypes` schema.
+ */
+export const createStructWithAdditionalProperties = (
+  predefinedProperties: Struct<any, any>,
+  additionalPropertyTypes: Struct<any, any> = any(),
+) => {
+  return dynamic((value) => {
+    if (typeof value !== 'object' || value === null) {
+      return predefinedProperties;
+    }
+
+    const additionalProperties = Object.keys(value).reduce<
+      Record<string, Struct>
+    >((schema, key) => {
+      if (!(key in predefinedProperties.schema)) {
+        schema[key] = additionalPropertyTypes;
+      }
+      return schema;
+    }, {});
+
+    return assign(predefinedProperties, object(additionalProperties));
+  });
+};