Core: Resolve builder preset path correctly in pnpm strict mode

[braedenfoster]

What I did

Fixed builder preset path resolution in pnpm monorepos with strict module resolution (shamefully-hoist=false).

Supersedes #33750 (closed due to inactivity). This PR addresses the CI failures that were flagged by the reviewer on the original PR.

Closes #33748

Problem

The current code uses dirname(builderName) to construct the path to the builder's preset file. When builderName is a bare package name like @storybook/builder-vite, dirname() performs string manipulation and returns @storybook, resulting in an invalid path @storybook/preset.js that causes ERR_MODULE_NOT_FOUND in pnpm's strict resolution mode.

Why the original PR (#33750) had CI failures

The original one-line fix (dirname(builderName) → resolvePackageDir(builderName)) broke the *--vitest sandbox integration tests. The root cause: builderName is not always a bare package name. Framework presets resolve it via import.meta.resolve(), producing either:

• A file URL: file:///path/to/node_modules/@storybook/builder-vite/dist/index.js
• An absolute path: /path/to/node_modules/@storybook/builder-vite/dist/index.js

Passing a file URL or absolute path to resolvePackageDir() (which expects a bare package name) produced incorrect results, breaking preset loading in the CI sandbox tests.

The bare package name case only occurs when users specify the builder directly in their config (e.g. core: { builder: '@storybook/builder-vite' }), which is the scenario that fails under pnpm strict mode.

Solution

code/core/src/core-server/load.ts: Detect whether builderName is already resolved (file URL or absolute path) vs a bare package name, and use the appropriate resolution strategy for each:

• Already resolved (file URL / absolute path): use dirname() as before
• Bare package name: use resolvePackageDir() to properly resolve the package directory

code/core/src/shared/utils/module.ts: Added a require.resolve fallback in resolvePackageDir for strict pnpm environments where both import.meta.resolve calls may fail. Uses createRequire (already imported) as a final fallback.

Testing

• Verified the fix resolves the issue in a pnpm monorepo with shamefully-hoist=false
• Tested with @storybook/builder-vite and vitest browser mode
• Ran the full core-server test suite (255 tests pass, 0 regressions)
• Ran all preset-related tests that mock resolvePackageDir (30 tests pass)
• Reproduction: https://github.com/braedenfoster/storybook-pnpm-repro

Summary by CodeRabbit

• Bug Fixes
  • More robust package resolution to correctly distinguish resolved paths from bare package names when loading presets.
  • Added an additional fallback for module resolution to improve reliability in strict package manager environments (e.g., pnpm), reducing resolution failures across runtimes.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a048c4b4-099d-487a-8f8b-1f9c207701c9

📥 Commits

Reviewing files that changed from the base of the PR and between b8fb9c0 and 370e8d9.

📒 Files selected for processing (1)

• code/core/src/shared/utils/module.ts

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📝 Walkthrough

Walkthrough

Distinguishes resolved (absolute/file URL) vs bare builder package names when assembling presets, and adds a require.resolve fallback in package-directory resolution after importMetaResolve to handle stricter environments like pnpm.

Changes

Cohort / File(s)	Summary
Builder Path Resolution code/core/src/core-server/load.ts	Use isAbsolute to detect resolved builderName; if resolved use dirname(builderName), otherwise call resolvePackageDir and push the appropriate preset.js path into corePresets.
Module Resolution Fallback code/core/src/shared/utils/module.ts	Enhance resolvePackageDir fallback chain: keep Bun-style importMetaResolve(join(pkg, 'package.json')) fallback, and add a final fallback using require.resolve via createRequire(parent ?? import.meta.url) to locate package.json and return its dirname.

Sequence Diagram(s)

(omitted)

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• Core: Use exsolve resolveModulePath for safeResolveModule #32477: Updates module-resolution fallback logic in core/src/shared/utils/module.ts for unresolved package paths.
• Core: Join framework preset path with slash #32838: Adjusts package/preset path resolution patterns related to builder/preset resolution.

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[coderabbitai]

🧹 Nitpick comments (1)

code/core/src/shared/utils/module.ts (1)

35-42: The require.resolve fallback ignores the parent parameter.

The function signature accepts an optional parent parameter for resolution context, but the new fallback on line 40-41 creates a require from import.meta.url (this module's location) rather than from parent. If a caller passes parent expecting it to affect resolution, the fallback won't honor it.

For the immediate fix (builder preset resolution in load.ts), parent is not passed, so this works. However, for consistency and correctness, consider using the parent parameter when available:

Proposed fix to respect parent in fallback

     } catch {
       // Fallback using require.resolve for strict pnpm environments where import.meta.resolve may fail
-      const require = createRequire(import.meta.url);
+      const require = createRequire(parent ?? import.meta.url);
       return dirname(require.resolve(join(pkg, 'package.json')));
     }

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@code/core/src/shared/utils/module.ts` around lines 35 - 42, The fallback
branch in module resolution ignores the optional parent parameter: update the
catch block in the function that uses dirname/fileURLToPath/importMetaResolve to
create the Require from parent when provided (use createRequire(parent) if
parent is a file URL/string), and only fall back to
createRequire(import.meta.url) when parent is not passed; then call
require.resolve(join(pkg, 'package.json')) via that parent-scoped require so the
resolution honors the parent context (refer to the catch block where
createRequire and require.resolve are used).

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@code/core/src/shared/utils/module.ts`:
- Around line 35-42: The fallback branch in module resolution ignores the
optional parent parameter: update the catch block in the function that uses
dirname/fileURLToPath/importMetaResolve to create the Require from parent when
provided (use createRequire(parent) if parent is a file URL/string), and only
fall back to createRequire(import.meta.url) when parent is not passed; then call
require.resolve(join(pkg, 'package.json')) via that parent-scoped require so the
resolution honors the parent context (refer to the catch block where
createRequire and require.resolve are used).

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 083c6ed3-2eb7-4485-9130-de945105eb83

📥 Commits

Reviewing files that changed from the base of the PR and between bb7e528 and b8fb9c0.

📒 Files selected for processing (2)

• code/core/src/core-server/load.ts
• code/core/src/shared/utils/module.ts

[storybook-app-bot]

Package Benchmarks

^{Commit: 370e8d9, ran on 6 March 2026 at 08:07:59 UTC}

The following packages have significant changes to their size or dependencies:

@storybook/builder-webpack5

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@storybook/angular

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Bundle Size Analyzer	Link	Link

@storybook/ember

	Before	After	Difference
Dependency count	189	189	0
Self size	15 KB	15 KB	🚨 +18 B 🚨
Dependency size	28.90 MB	28.88 MB	🎉 -19 KB 🎉
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@storybook/nextjs

	Before	After	Difference
Dependency count	534	534	0
Self size	648 KB	648 KB	🚨 +87 B 🚨
Dependency size	59.86 MB	59.84 MB	🎉 -19 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/nextjs-vite

	Before	After	Difference
Dependency count	92	92	0
Self size	1.12 MB	1.12 MB	🚨 +262 B 🚨
Dependency size	22.47 MB	22.45 MB	🎉 -19 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/react-native-web-vite

	Before	After	Difference
Dependency count	124	124	0
Self size	30 KB	30 KB	🚨 +18 B 🚨
Dependency size	23.76 MB	23.74 MB	🎉 -19 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/react-vite

	Before	After	Difference
Dependency count	82	82	0
Self size	35 KB	35 KB	0 B
Dependency size	20.25 MB	20.24 MB	🎉 -19 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/react-webpack5

	Before	After	Difference
Dependency count	271	271	0
Self size	24 KB	24 KB	🚨 +12 B 🚨
Dependency size	44.53 MB	44.51 MB	🎉 -19 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/server-webpack5

	Before	After	Difference
Dependency count	197	197	0
Self size	16 KB	16 KB	🎉 -12 B 🎉
Dependency size	33.44 MB	33.42 MB	🎉 -19 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/cli

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Dependency count	183	183	0
Self size	779 KB	779 KB	0 B
Dependency size	67.35 MB	67.33 MB	🎉 -18 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/codemod

	Before	After	Difference
Dependency count	176	176	0
Self size	32 KB	32 KB	0 B
Dependency size	65.87 MB	65.86 MB	🎉 -18 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/preset-react-webpack

	Before	After	Difference
Dependency count	167	167	0
Self size	18 KB	18 KB	0 B
Dependency size	31.40 MB	31.38 MB	🎉 -19 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/react

	Before	After	Difference
Dependency count	58	58	0
Self size	1.19 MB	1.19 MB	🚨 +215 B 🚨
Dependency size	13.21 MB	13.19 MB	🎉 -19 KB 🎉
Bundle Size Analyzer	Link	Link