feat(core): add ai rule files to gitignore (#31238)

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## Current Behavior
<!-- This is the behavior we have today -->
Rule files are created by Nx Console, and gitignore updates are done
there.

## Expected Behavior
<!-- This is the behavior we should expect with the changes in this PR
-->
Rule files are still created by Nx Console, but there is now a migration
to add those files to the gitignore rules on migration and new
workspaces.

## Related Issue(s)
<!-- Please link the issue being fixed so it gets closed when this is
merged. -->

Fixes #

docs/generated/manifests/nx-api.json

@@ -3414,6 +3414,16 @@
       }
     },
     "migrations": {
+      "/nx-api/nx/migrations/21-1-0-add-ignore-entries-for-nx-rule-files": {
+        "description": "Adds **/nx-rules.mdc and **/nx.instructions.md to .gitignore if not present",
+        "file": "generated/packages/nx/migrations/21-1-0-add-ignore-entries-for-nx-rule-files.json",
+        "hidden": false,
+        "name": "21-1-0-add-ignore-entries-for-nx-rule-files",
+        "version": "21.1.0-beta.2",
+        "originalFilePath": "/packages/nx",
+        "path": "/nx-api/nx/migrations/21-1-0-add-ignore-entries-for-nx-rule-files",
+        "type": "migration"
+      },
       "/nx-api/nx/migrations/release-version-config-changes": {
         "description": "Updates release version config based on the breaking changes in Nx v21",
         "file": "generated/packages/nx/migrations/release-version-config-changes.json",

docs/generated/packages-metadata.json

@@ -3390,6 +3390,16 @@
       }
     ],
     "migrations": [
+      {
+        "description": "Adds **/nx-rules.mdc and **/nx.instructions.md to .gitignore if not present",
+        "file": "generated/packages/nx/migrations/21-1-0-add-ignore-entries-for-nx-rule-files.json",
+        "hidden": false,
+        "name": "21-1-0-add-ignore-entries-for-nx-rule-files",
+        "version": "21.1.0-beta.2",
+        "originalFilePath": "/packages/nx",
+        "path": "nx/migrations/21-1-0-add-ignore-entries-for-nx-rule-files",
+        "type": "migration"
+      },
       {
         "description": "Updates release version config based on the breaking changes in Nx v21",
         "file": "generated/packages/nx/migrations/release-version-config-changes.json",

docs/generated/packages/nx/migrations/21-1-0-add-ignore-entries-for-nx-rule-files.json

@@ -0,0 +1,12 @@
+{
+  "name": "21-1-0-add-ignore-entries-for-nx-rule-files",
+  "version": "21.1.0-beta.2",
+  "description": "Adds **/nx-rules.mdc and **/nx.instructions.md to .gitignore if not present",
+  "implementation": "/packages/nx/src/migrations/update-21-1-0/add-gitignore-entry.ts",
+  "aliases": [],
+  "hidden": false,
+  "path": "/packages/nx",
+  "schema": null,
+  "type": "migration",
+  "examplesFile": ""
+}

packages/nx/migrations.json

@@ -83,6 +83,11 @@
       "version": "21.0.0-beta.11",
       "description": "Updates release changelog config based on the breaking changes in Nx v21",
       "implementation": "./src/migrations/update-21-0-0/release-changelog-config-changes"
+    },
+    "21-1-0-add-ignore-entries-for-nx-rule-files": {
+      "version": "21.1.0-beta.2",
+      "description": "Adds **/nx-rules.mdc and **/nx.instructions.md to .gitignore if not present",
+      "implementation": "./src/migrations/update-21-1-0/add-gitignore-entry"
     }
   }
 }

packages/nx/src/command-line/init/implementation/utils.ts

@@ -222,6 +222,21 @@ export function updateGitIgnore(root: string) {
       }
       lines.push('.nx/workspace-data');
     }
+    if (!contents.includes('.cursor/rules/nx-rules.mdc')) {
+      if (!sepIncluded) {
+        lines.push('\n');
+        sepIncluded = true;
+      }
+      lines.push('.cursor/rules/nx-rules.mdc');
+    }
+    if (!contents.includes('.github/instructions/nx.instructions.md')) {
+      if (!sepIncluded) {
+        lines.push('\n');
+        sepIncluded = true;
+      }
+      lines.push('.github/instructions/nx.instructions.md');
+    }
+
     writeFileSync(ignorePath, lines.join('\n'), 'utf-8');
   } catch {}
 }

packages/nx/src/migrations/update-21-1-0/add-gitignore-entry.spec.ts

@@ -0,0 +1,33 @@
+import { createTreeWithEmptyWorkspace } from '../../generators/testing-utils/create-tree-with-empty-workspace';
+import addGitignoreEntry from './add-gitignore-entry';
+
+describe('addGitignoreEntry migration', () => {
+  it('should add .cursor/rules/nx-rules.mdc and .github/instructions/nx.instructions.md to .gitignore if not present', async () => {
+    const tree = createTreeWithEmptyWorkspace();
+    tree.write('.gitignore', 'dist\nnode_modules\n');
+    await addGitignoreEntry(tree);
+    const result = tree.read('.gitignore', 'utf-8');
+    expect(result).toContain('.cursor/rules/nx-rules.mdc');
+    expect(result).toContain('.github/instructions/nx.instructions.md');
+  });
+
+  it('should not add duplicate entries if already present', async () => {
+    const tree = createTreeWithEmptyWorkspace();
+    tree.write(
+      '.gitignore',
+      'dist\n.cursor/rules/nx-rules.mdc\n.github/instructions/nx.instructions.md\n'
+    );
+    await addGitignoreEntry(tree);
+    const result = tree.read('.gitignore', 'utf-8');
+    expect(result.match(/\.cursor\/rules\/nx-rules\.mdc/g)?.length).toBe(1);
+    expect(
+      result.match(/\.github\/instructions\/nx\.instructions\.md/g)?.length
+    ).toBe(1);
+  });
+
+  it('should do nothing if .gitignore does not exist', async () => {
+    const tree = createTreeWithEmptyWorkspace();
+    await addGitignoreEntry(tree);
+    expect(tree.exists('.gitignore')).toBe(false);
+  });
+});

packages/nx/src/migrations/update-21-1-0/add-gitignore-entry.ts

@@ -0,0 +1,24 @@
+import { Tree } from '../../generators/tree';
+import ignore from 'ignore';
+
+export default async function addGitignoreEntry(tree: Tree) {
+  if (!tree.exists('nx.json')) {
+    return;
+  }
+
+  const GITIGNORE_ENTRIES = [
+    '.cursor/rules/nx-rules.mdc',
+    '.github/instructions/nx.instructions.md',
+  ];
+  if (!tree.exists('.gitignore')) {
+    return;
+  }
+  let content = tree.read('.gitignore', 'utf-8') || '';
+  const ig = ignore().add(content);
+  for (const entry of GITIGNORE_ENTRIES) {
+    if (!ig.ignores(entry)) {
+      content = content.trimEnd() + '\n' + entry + '\n';
+    }
+  }
+  tree.write('.gitignore', content);
+}

packages/workspace/src/generators/new/files-integrated-repo/__dot__gitignore

@@ -40,3 +40,5 @@ Thumbs.db
 
 .nx/cache
 .nx/workspace-data
+.cursor/rules/nx-rules.mdc
+.github/instructions/nx.instructions.md

packages/workspace/src/generators/new/files-package-based-repo/__dot__gitignore

@@ -40,3 +40,5 @@ Thumbs.db
 
 .nx/cache
 .nx/workspace-data
+.cursor/rules/nx-rules.mdc
+.github/instructions/nx.instructions.md

packages/workspace/src/generators/new/files-root-app/__dot__gitignore

@@ -40,3 +40,5 @@ Thumbs.db
 
 .nx/cache
 .nx/workspace-data
+.cursor/rules/nx-rules.mdc
+.github/instructions/nx.instructions.md