fix(masthead-search): react searchNoRedirect prop doesn't work on ent…

…er (#8516)

### Related Ticket(s)

#8334

### Description

people using the `searchNoRedirect` prop and press enter within the search box are still being redirected. The `onKeyDown` was removed in this [PR](#7365), but it is actually necessary when the `searchNoRedirect` is used

### Changelog

**New**

- added back the `onKeyDown` function

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packages/react/src/__tests__/__snapshots__/storyshots.test.js.snap

@@ -52871,6 +52871,7 @@ exports[`Storyshots Components|Dotcom shell Search open 1`] = `
                                     "aria-label": "Search all of IBM",
                                     "className": "bx--header__search--input",
                                     "onChange": [Function],
+                                    "onKeyDown": [Function],
                                     "placeholder": "Search all of IBM",
                                     "role": "combobox",
                                     "value": "",
@@ -123771,6 +123772,7 @@ exports[`Storyshots Components|Masthead Search open onload 1`] = `
                                 "aria-label": "Search all of IBM",
                                 "className": "bx--header__search--input",
                                 "onChange": [Function],
+                                "onKeyDown": [Function],
                                 "placeholder": "Search all of IBM",
                                 "role": "combobox",
                                 "value": "",

packages/react/src/components/Masthead/MastheadSearch.js

@@ -270,6 +270,27 @@ const MastheadSearch = forwardRef(
       event.currentTarget.dispatchEvent(onSearchNoRedirect);
     }
 
+    /**
+     * Custom onKeyDown event handlers
+     *
+     * @param {event} event The callback event
+     */
+    function onKeyDown(event) {
+      switch (event.key) {
+        case 'Enter': {
+          // Disables Enter key if searchNoRirect is true
+          if (rest.searchNoRedirect) {
+            onSearchNoRedirect(event, state.val);
+            event.preventDefault();
+          }
+          // Disable search on enter key if the search field is empty
+          if (!state.val) {
+            event.preventDefault();
+          }
+        }
+      }
+    }
+
     /**
      * When the input field changes, we set the new val to our state
      *
@@ -296,6 +317,7 @@ const MastheadSearch = forwardRef(
       placeholder: placeHolderText,
       value: state.val,
       onChange,
+      onKeyDown,
       className: `${prefix}--header__search--input`,
       'aria-label': placeHolderText,
       role: 'combobox',