Fix aria null values (#5097)

* fix: align aria null behavior between setting methods

* fix: setAttribute string case

* fix: revert missing stringify

* fix: revert deletion

* fix: revert setAttribute 'null' behavior change

packages/@lwc/engine-server/src/__tests__/fixtures/attribute-aria/dynamic/expected.html

@@ -14,7 +14,7 @@
       <template shadowrootmode="open">
         <div>
         </div>
-        <x-grandchild aria-activedescendant="null" aria-atomic="null" aria-autocomplete="null" aria-braillelabel="null" aria-brailleroledescription="null" aria-busy="null" aria-checked="null" aria-colcount="null" aria-colindex="null" aria-colindextext="null" aria-colspan="null" aria-controls="null" aria-current="null" aria-describedby="null" aria-description="null" aria-details="null" aria-disabled="null" aria-errormessage="null" aria-expanded="null" aria-flowto="null" aria-haspopup="null" aria-hidden="null" aria-invalid="null" aria-keyshortcuts="null" aria-label="null" aria-labelledby="null" aria-level="null" aria-live="null" aria-modal="null" aria-multiline="null" aria-multiselectable="null" aria-orientation="null" aria-owns="null" aria-placeholder="null" aria-posinset="null" aria-pressed="null" aria-readonly="null" aria-relevant="null" aria-required="null" aria-roledescription="null" aria-rowcount="null" aria-rowindex="null" aria-rowindextext="null" aria-rowspan="null" aria-selected="null" aria-setsize="null" aria-sort="null" aria-valuemax="null" aria-valuemin="null" aria-valuenow="null" aria-valuetext="null" role="null">
+        <x-grandchild>
           <template shadowrootmode="open">
           </template>
         </x-grandchild>

packages/@lwc/engine-server/src/__tests__/fixtures/attribute-null/expected.html

@@ -1,4 +1,4 @@
-<x-test aria-description="undefined" data-bar="null" data-foo="null" data-lwc-host-mutated="aria-description aria-label data-bar data-foo">
+<x-test aria-describedby="undefined" aria-label="null" aria-labelledby="undefined" data-bar-set-attribute="null" data-foo-set-attribute="null" data-lwc-host-mutated="aria-describedby aria-description aria-label aria-labelledby data-bar-set-attribute data-foo-set-attribute">
   <template shadowrootmode="open">
   </template>
 </x-test>

packages/@lwc/engine-server/src/__tests__/fixtures/attribute-null/modules/x/test/test.js

@@ -1,14 +1,25 @@
 import { LightningElement } from 'lwc';
 
 export default class extends LightningElement {
+    isNull = null;
     connectedCallback() {
-        this.setAttribute('data-foo', 'foo');
-        this.setAttribute('data-foo', null);
-        this.setAttribute('data-bar', null);
+        // Non-aria set attribute should be "null"
+        this.setAttribute('data-foo-set-attribute', 'foo');
+        this.setAttribute('data-foo-set-attribute', null);
+        this.setAttribute('data-bar-set-attribute', null);
 
+        // Aria null (the attribute should be absent)
+        this.ariaDescription = 'awesome description';
+        this.ariaDescription = null;
+
+        // Aria null setAttribute (the attribute should be "null")
         this.setAttribute('aria-label', 'awesome label');
-        this.ariaLabel = null;
-        this.setAttribute('aria-description', 'awesome description');
-        this.ariaDescription = undefined;
+        this.setAttribute('aria-label', null);
+
+        // Aria undefined (the attribute should be "undefined")
+        this.setAttribute('aria-describedby', 'awesome label');
+        this.setAttribute('aria-describedby', undefined);
+        this.ariaLabelledBy = 'id1';
+        this.ariaLabelledBy = undefined;
     }
 }

packages/@lwc/engine-server/src/renderer.ts

@@ -227,8 +227,15 @@ function setProperty(node: N, propName: string, value: any): void {
                 : removeAttribute(node, attrName);
         }
 
-        // Handle global html attributes and AOM.
-        if (REFLECTIVE_GLOBAL_PROPERTY_SET.has(propName) || isAriaAttribute(attrName)) {
+        if (isAriaAttribute(attrName)) {
+            // TODO [#3284]: According to the spec, IDL nullable type values
+            // (null and undefined) should remove the attribute; however, we
+            // only do so in the case of null for historical reasons.
+            return isNull(value)
+                ? removeAttribute(node, attrName)
+                : setAttribute(node, attrName, value);
+        } else if (REFLECTIVE_GLOBAL_PROPERTY_SET.has(propName)) {
+            // Handle global html attributes and AOM.
             return setAttribute(node, attrName, value);
         }
     }

packages/@lwc/ssr-compiler/src/__tests__/utils/expected-failures.ts

@@ -8,7 +8,6 @@
 // We should slowly drive down these test failures or at least document where we expect the failures
 // TODO [#4815]: enable all SSR v2 tests
 export const expectedFailures = new Set([
-    'attribute-aria/dynamic/index.js',
     'attribute-class/with-scoped-styles-only-in-child/dynamic/index.js',
     'attribute-class/with-scoped-styles/dynamic/index.js',
     'attribute-global-html/as-component-prop/undeclared/index.js',