feat(core): customize meta & attributes merges for deepmerge function

packages/apidom-core/README.md

@@ -391,6 +391,42 @@ const output = deepmerge(alex, tony, { customMerge });
 // output.get('pets'); // => ArrayElement(['Cat', 'Parrot', 'Dog'])
 ```
 
+#### customMetaMerge
+
+Specifies a function which can be used to override the default metadata merge behavior.
+The `customMetaMerge` function will be passed target and source metadata. If not specified,
+the default behavior is to deep copy metadata from target to new merged element.
+
+```js
+import { deepmerge, ObjectElement } from '@swagger-api/apidom-core';
+
+const alex = new ObjectElement({ name: { first: 'Alex' } }, { metaKey: true });
+const tony = new ObjectElement({ name: { first: 'Tony' } }, { metaKey: false });
+
+const customMetaMerge = (targetMeta, sourceMeta) => deepmerge(targetMeta, sourceMeta);
+
+const output = deepmerge(alex, tony, { customMetaMerge });
+// output.meta.get('metaKey') // => BooleanElement(false)
+```
+
+#### customAttributesMerge
+
+Specifies a function which can be used to override the default attributes merge behavior.
+The `customAttributesMerge` function will be passed target and source attributes. If not specified,
+the default behavior is to deep copy attributes from target to new merged element.
+
+```js
+import { deepmerge, ObjectElement } from '@swagger-api/apidom-core';
+
+const alex = new ObjectElement({ name: { first: 'Alex' } }, undefined, { attributeKey: true });
+const tony = new ObjectElement({ name: { first: 'Tony' } }, undefined, { attributeKey: false });
+
+const customAttributesMerge = (targetMeta, sourceMeta) => deepmerge(targetMeta, sourceMeta);
+
+const output = deepmerge(alex, tony, { customAttributesMerge });
+// output.attributs.get('attributeKey') // => BooleanElement(false)
+```
+
 #### clone
 
 Defaults to `true`.

packages/apidom-core/src/merge/deepmerge.ts

@@ -14,6 +14,14 @@ type DeepMerge = (
   options?: DeepMergeOptions,
 ) => AnyElement;
 type CustomMerge = (keyElement: Element, options: DeepMergeOptions) => DeepMerge;
+type CustomMetaMerge = (
+  targetElementMeta: ObjectElement,
+  sourceElementMeta: ObjectElement,
+) => ObjectElement;
+type CustomAttributesMerge = (
+  targetElementAttributes: ObjectElement,
+  sourceElementAttributes: ObjectElement,
+) => ObjectElement;
 type ArrayElementMerge = (
   targetElement: ArrayElement,
   sourceElement: ArrayElement,
@@ -30,6 +38,8 @@ export type DeepMergeUserOptions = {
   arrayElementMerge?: ArrayElementMerge;
   objectElementMerge?: ObjectElementMerge;
   customMerge?: CustomMerge;
+  customMetaMerge?: CustomMetaMerge;
+  customAttributesMerge?: CustomAttributesMerge;
 };
 
 type DeepMergeOptions = DeepMergeUserOptions & {
@@ -38,11 +48,13 @@ type DeepMergeOptions = DeepMergeUserOptions & {
   arrayElementMerge: ArrayElementMerge;
   objectElementMerge: ObjectElementMerge;
   customMerge: CustomMerge | undefined;
+  customMetaMerge: CustomMetaMerge | undefined;
+  customAttributesMerge: CustomAttributesMerge | undefined;
 };
 
 export const emptyElement = (element: ObjectElement | ArrayElement) => {
-  const meta = cloneDeep(element.meta);
-  const attributes = cloneDeep(element.attributes);
+  const meta = element.meta.length > 0 ? cloneDeep(element.meta) : undefined;
+  const attributes = element.attributes.length > 0 ? cloneDeep(element.attributes) : undefined;
 
   // @ts-ignore
   return new element.constructor(undefined, meta, attributes);
@@ -68,6 +80,20 @@ const getMergeFunction = (keyElement: Element, options: DeepMergeOptions): DeepM
   return typeof customMerge === 'function' ? customMerge : deepmerge;
 };
 
+const getMetaMergeFunction = (options: DeepMergeOptions): CustomMetaMerge => {
+  if (typeof options.customMetaMerge !== 'function') {
+    return (targetMeta) => cloneDeep(targetMeta);
+  }
+  return options.customMetaMerge;
+};
+
+const getAttributesMergeFunction = (options: DeepMergeOptions): CustomAttributesMerge => {
+  if (typeof options.customAttributesMerge !== 'function') {
+    return (targetAttributes) => cloneDeep(targetAttributes);
+  }
+  return options.customAttributesMerge;
+};
+
 const mergeArrayElement: ArrayElementMerge = (targetElement, sourceElement, options) =>
   targetElement
     .concat(sourceElement)
@@ -119,6 +145,8 @@ export const defaultOptions: DeepMergeOptions = {
   arrayElementMerge: mergeArrayElement,
   objectElementMerge: mergeObjectElement,
   customMerge: undefined,
+  customMetaMerge: undefined,
+  customAttributesMerge: undefined,
 };
 
 export default function deepmerge(
@@ -142,19 +170,28 @@ export default function deepmerge(
     return cloneUnlessOtherwiseSpecified(sourceElement, mergedOptions);
   }
 
-  if (sourceIsArrayElement && typeof mergedOptions.arrayElementMerge === 'function') {
-    return mergedOptions.arrayElementMerge(
-      targetElement as ArrayElement,
-      sourceElement as ArrayElement,
-      mergedOptions,
-    );
-  }
-
-  return mergedOptions.objectElementMerge(
-    targetElement as ObjectElement,
-    sourceElement as ObjectElement,
-    mergedOptions,
+  // merging two elements
+  const mergedElement =
+    sourceIsArrayElement && typeof mergedOptions.arrayElementMerge === 'function'
+      ? mergedOptions.arrayElementMerge(
+          targetElement as ArrayElement,
+          sourceElement as ArrayElement,
+          mergedOptions,
+        )
+      : mergedOptions.objectElementMerge(
+          targetElement as ObjectElement,
+          sourceElement as ObjectElement,
+          mergedOptions,
+        );
+
+  // merging meta & attributes
+  mergedElement.meta = getMetaMergeFunction(mergedOptions)(targetElement.meta, sourceElement.meta);
+  mergedElement.attributes = getAttributesMergeFunction(mergedOptions)(
+    targetElement.attributes,
+    sourceElement.attributes,
   );
+
+  return mergedElement;
 }
 
 deepmerge.all = (list: ObjectOrArrayElement[], options?: DeepMergeUserOptions) => {

packages/apidom-core/test/merge/deepmerge.ts

@@ -349,6 +349,17 @@ describe('deepmerge', function () {
     assert.strictEqual(merged.get(2), source.get(0), 'should not clone');
   });
 
+  it('should deep copy meta & attributes from target', function () {
+    const target = new ObjectElement({}, { metaKey: true }, { attributeKey: true });
+    const source = new ObjectElement({}, { metaKey: false }, { attributeKey: false });
+    const merged = deepmerge(target, source);
+
+    assert.deepEqual(toValue(merged.meta), { metaKey: true });
+    assert.deepEqual(toValue(merged.attributes), { attributeKey: true });
+    assert.notStrictEqual(merged.meta, target.meta);
+    assert.notStrictEqual(merged.attributes, target.attributes);
+  });
+
   specify('deepmerge.all', function () {
     const source = new ObjectElement({ key1: 'changed', key2: 'value2' });
     const target = new ObjectElement({ key1: 'value1', key3: 'value3' });
@@ -367,6 +378,36 @@ describe('deepmerge', function () {
     assert.deepEqual(toValue(merged), expected);
   });
 
+  context('given customMetaMerge option', function () {
+    specify('should allow custom merging of meta', function () {
+      const customMetaMerge = (
+        targetMeta: ObjectElement,
+        sourceMeta: ObjectElement,
+      ): ObjectElement => deepmerge(targetMeta, sourceMeta) as ObjectElement;
+      const target = new ObjectElement({}, { metaKey: true });
+      const source = new ObjectElement({}, { metaKey: false });
+
+      const merged = deepmerge(target, source, { customMetaMerge });
+
+      assert.deepEqual(toValue(merged.meta), { metaKey: false });
+    });
+  });
+
+  context('given customAttributesMerge option', function () {
+    specify('should allow custom merging of meta', function () {
+      const customAttributesMerge = (
+        targetAttributes: ObjectElement,
+        sourceAttributes: ObjectElement,
+      ): ObjectElement => deepmerge(targetAttributes, sourceAttributes) as ObjectElement;
+      const target = new ObjectElement({}, undefined, { attributeKey: true });
+      const source = new ObjectElement({}, undefined, { attributeKey: false });
+
+      const merged = deepmerge(target, source, { customAttributesMerge });
+
+      assert.deepEqual(toValue(merged.attributes), { attributeKey: false });
+    });
+  });
+
   context('given arrayElementMerge option', function () {
     specify('should allow custom merging of ArrayElements', function () {
       const arrayElementMerge = (destination: ArrayElement, source: ArrayElement) => source;