fix(storybook): do not duplicate cacheable operations #27866 (#27951)

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## Current Behavior
<!-- This is the behavior we have today -->
`build-storybook` is being added to cacheable operations multiple times
when the `@nx/storybook:init` generator is being invoked.


## Expected Behavior
<!-- This is the behavior we should expect with the changes in this PR
-->
Do not add `build-storybook` multiple times

## Related Issue(s)
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merged. -->

Fixes #27866

packages/storybook/src/generators/init/init.spec.ts

@@ -3,6 +3,8 @@ import {
   type NxJsonConfiguration,
   type Tree,
   ProjectGraph,
+  updateNxJson,
+  readNxJson,
 } from '@nx/devkit';
 import { createTreeWithEmptyWorkspace } from '@nx/devkit/testing';
 import { initGenerator } from './init';
@@ -56,4 +58,30 @@ describe('@nx/storybook:init', () => {
     });
     expect(tree.read('.gitignore', 'utf-8')).toMatchSnapshot();
   });
+
+  it('should not duplicate cacheable operations in nx.json', async () => {
+    // ARRANGE
+    const nxJson = readNxJson(tree);
+    nxJson.tasksRunnerOptions ??= {};
+    nxJson.tasksRunnerOptions.default ??= {};
+    nxJson.tasksRunnerOptions.default.options ??= {};
+    nxJson.tasksRunnerOptions.default.options.cacheableOperations = [
+      'build-storybook',
+    ];
+    updateNxJson(tree, nxJson);
+
+    // ACT
+    await initGenerator(tree, {
+      addPlugin: false,
+    });
+
+    // ASSERT
+    const updatedNxJson = readNxJson(tree);
+    expect(updatedNxJson.tasksRunnerOptions.default.options.cacheableOperations)
+      .toMatchInlineSnapshot(`
+      [
+        "build-storybook",
+      ]
+    `);
+  });
 });

packages/storybook/src/generators/init/init.ts

@@ -57,7 +57,7 @@ function addCacheableOperation(tree: Tree) {
   const cacheableOperations: string[] | null =
     nxJson.tasksRunnerOptions?.default?.options?.cacheableOperations;
 
-  if (cacheableOperations && cacheableOperations.includes('build-storybook')) {
+  if (cacheableOperations && !cacheableOperations.includes('build-storybook')) {
     nxJson.tasksRunnerOptions.default.options.cacheableOperations.push(
       'build-storybook'
     );