chore: fitness quality gate to only allow TS & TSX files in app directory (#9723)

## **Description**

This PR adds a fitness function to fail if a .js or .jsx file is added
to the app/ directory.

## **Related issues**

Fixes:
https://github.com/orgs/MetaMask/projects/60/views/3?pane=issue&itemId=59597337

## **Manual testing steps**

1. Attempt to push a .js or .jsx file  in the app directory
2. See the fitness function fail
3.

## **Screenshots/Recordings**

NA See unit tests

### **Before**

<!-- [screenshots/recordings] -->

### **After**

- Commit [outside of app
directory](https://github.com/MetaMask/metamask-mobile/actions/runs/9353695806/job/25744808362)
- Commit [inside of app
directory](https://github.com/MetaMask/metamask-mobile/actions/runs/9455916396/job/26046720818?pr=9723)

## **Pre-merge author checklist**

- [ ] I’ve followed [MetaMask Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

---------

Co-authored-by: Cal Leung <cleun007@gmail.com>

Author: sethkfman

.github/scripts/fitness-functions/common/constants.ts

@@ -7,4 +7,7 @@ enum AUTOMATION_TYPE {
   PRE_PUSH_HOOK = 'pre-push-hook',
 }
 
-export { EXCLUDE_REGEX, AUTOMATION_TYPE };
+// only allow TS and TSX files in the app directory only
+const APP_FOLDER_JS_REGEX = /^(app).*\.(js|jsx)$/;
+
+export { EXCLUDE_REGEX, APP_FOLDER_JS_REGEX, AUTOMATION_TYPE };

.github/scripts/fitness-functions/common/shared.ts

@@ -33,6 +33,34 @@ function filterDiffByFilePath(diff: string, regex: RegExp): string {
   return filteredDiff;
 }
 
+function restrictedFilePresent(diff: string, regex: RegExp): boolean {
+  // split by `diff --git` and remove the first element which is empty
+  const diffBlocks = diff.split(`diff --git`).slice(1);
+  let jsOrJsxFilePresent = false;
+  diffBlocks
+    .map((block) => block.trim())
+    .filter((block) => {
+      block
+        // get the first line of the block which has the paths
+        .split('\n')[0]
+        .trim()
+        // split the two paths
+        .split(' ')
+        // remove `a/` and `b/` from the paths
+        .map((path) => path.substring(2))
+        // if at least one of the two paths matches the regex, filter the
+        // corresponding diff block in
+        .forEach((path) => {
+          if (regex.test(path)) {
+            // Not excluded, include in check
+            jsOrJsxFilePresent = true;
+          }
+        });
+      return jsOrJsxFilePresent;
+    })
+  return jsOrJsxFilePresent;
+}
+
 // This function returns all lines that are additions to files that are being
 // modified but that previously already existed. Example:
 // diff --git a/test.js b/test.js
@@ -111,6 +139,7 @@ function hasNumberOfCodeBlocksIncreased(
 
 export {
   filterDiffByFilePath,
+  restrictedFilePresent,
   filterDiffFileCreations,
   filterDiffLineAdditions,
   hasNumberOfCodeBlocksIncreased,

.github/scripts/fitness-functions/rules/index.ts

@@ -1,3 +1,4 @@
+import { preventJavaScriptFileAdditions } from './javascript-additions';
 import { preventCodeBlocksRule } from './prevent-code-blocks';
 
 const RULES: IRule[] = [
@@ -6,6 +7,11 @@ const RULES: IRule[] = [
     fn: preventCodeBlocksRule,
     docURL: '[WIP] No documentation exists for this rule yet.',
   },
+  {
+    name: 'Check for js or jsx file being added',
+    fn: preventJavaScriptFileAdditions,
+    docURL: '[WIP] No documentation exists for this rule yet.',
+  },
 ];
 
 interface IRule {
@@ -32,5 +38,5 @@ function runFitnessFunctionRule(rule: IRule, diff: string): void {
   }
 }
 
-export { RULES, runFitnessFunctionRule };
+export { RULES, runFitnessFunctionRule, preventJavaScriptFileAdditions };
 export type { IRule };

.github/scripts/fitness-functions/rules/javascript-additions.test.ts

@@ -0,0 +1,51 @@
+import {
+  generateModifyFilesDiff,
+  generateCreateFileDiff,
+} from '../common/test-data';
+import { preventJavaScriptFileAdditions } from './javascript-additions';
+
+describe('preventJavaScriptFileAdditions()', (): void => {
+  it('should pass when receiving an empty diff', (): void => {
+    const testDiff = '';
+
+    const hasRulePassed = preventJavaScriptFileAdditions(testDiff);
+
+    expect(hasRulePassed).toBe(true);
+  });
+
+  it('should pass when receiving a diff with a new TS file on the shared folder', (): void => {
+    const testDiff = [
+      generateModifyFilesDiff('new-file.ts', 'foo', 'bar'),
+      generateModifyFilesDiff('old-file.js', undefined, 'pong'),
+      generateCreateFileDiff('app/test.ts', 'yada yada yada yada'),
+    ].join('');
+
+    const hasRulePassed = preventJavaScriptFileAdditions(testDiff);
+
+    expect(hasRulePassed).toBe(true);
+  });
+
+  it('should not pass when receiving a diff with a new JS file on the shared folder', (): void => {
+    const testDiff = [
+      generateModifyFilesDiff('new-file.ts', 'foo', 'bar'),
+      generateModifyFilesDiff('old-file.js', undefined, 'pong'),
+      generateCreateFileDiff('app/test.js', 'yada yada yada yada'),
+    ].join('');
+
+    const hasRulePassed = preventJavaScriptFileAdditions(testDiff);
+
+    expect(hasRulePassed).toBe(false);
+  });
+
+  it('should not pass when receiving a diff with a new JSX file on the shared folder', (): void => {
+    const testDiff = [
+      generateModifyFilesDiff('new-file.ts', 'foo', 'bar'),
+      generateModifyFilesDiff('old-file.js', undefined, 'pong'),
+      generateCreateFileDiff('app/test.jsx', 'yada yada yada yada'),
+    ].join('');
+
+    const hasRulePassed = preventJavaScriptFileAdditions(testDiff);
+
+    expect(hasRulePassed).toBe(false);
+  });
+});

.github/scripts/fitness-functions/rules/javascript-additions.ts

@@ -0,0 +1,11 @@
+import { APP_FOLDER_JS_REGEX } from '../common/constants';
+import { restrictedFilePresent } from '../common/shared';
+
+function preventJavaScriptFileAdditions(diff: string): boolean {
+  if (restrictedFilePresent(diff, APP_FOLDER_JS_REGEX)) {
+    return false;
+  }
+  return true;
+}
+
+export { preventJavaScriptFileAdditions };