Allow "use step" functions to be defined outside of the app directory #708
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🦋 Changeset detectedLatest commit: def292b The changes in this PR will be included in the next version bump. This PR includes changesets to release 10 packages
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🧪 E2E Test Results❌ Some tests failed Summary
❌ Failed Tests💻 Local Development (28 failed)nuxt-stable (28 failed):
🌍 Community Worlds (12 failed)mongodb (1 failed):
redis (1 failed):
starter (9 failed):
turso (1 failed):
Details by Category✅ ▲ Vercel Production
❌ 💻 Local Development
✅ 📦 Local Production
✅ 🐘 Local Postgres
✅ 🪟 Windows
❌ 🌍 Community Worlds
❌ Some E2E test jobs failed:
Check the workflow run for details. |
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December 31, 2025 09:00
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📊 Benchmark Results
workflow with no steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) | Nitro | Express workflow with 1 step💻 Local Development
▲ Production (Vercel)
🔍 Observability: Nitro | Next.js (Turbopack) | Express workflow with 10 sequential steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) | Nitro Promise.all with 10 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) | Nitro Promise.all with 25 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Nitro | Next.js (Turbopack) Promise.race with 10 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Nitro | Next.js (Turbopack) | Express Promise.race with 25 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) | Nitro | Express Stream Benchmarks (includes TTFB metrics)workflow with stream💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) | Nitro SummaryFastest Framework by WorldWinner determined by most benchmark wins
Fastest World by FrameworkWinner determined by most benchmark wins
Column Definitions
Worlds:
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![vercel[bot]](https://avatars.githubusercontent.com/in/8329?s=60&v=4){kind=small}
Comment on lines
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| // Get output content if not writing to file | ||
| const outputContent = | ||
| !writeToFile && stepsResult.outputFiles?.[0] | ||
| ? stepsResult.outputFiles[0].text | ||
| : undefined; |
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Missing error check for esbuild output when creating steps bundle in-memory. The TypeScript overload promises a non-optional outputContent: string, but the implementation can return undefined, which will cause runtime errors in the second build pass.
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📝 Patch Details
diff --git a/packages/builders/src/base-builder.ts b/packages/builders/src/base-builder.ts
index 0b37f3f..be5939a 100644
--- a/packages/builders/src/base-builder.ts
+++ b/packages/builders/src/base-builder.ts
@@ -391,6 +391,13 @@ export abstract class BaseBuilder {
// Create .gitignore in .swc directory
await this.createSwcGitignore();
+ // Ensure output files exist when not writing to disk
+ if (!writeToFile) {
+ if (!stepsResult.outputFiles || stepsResult.outputFiles.length === 0) {
+ throw new Error('No output files generated from esbuild');
+ }
+ }
+
// Get output content if not writing to file
const outputContent =
!writeToFile && stepsResult.outputFiles?.[0]
Analysis
Missing error check for esbuild output in createStepsBundle
What fails: The createStepsBundle() method in base-builder.ts has TypeScript overloads that promise a non-optional outputContent: string when the outfile parameter is omitted, but the implementation can return undefined, violating the type contract. This causes the callers in standalone.ts and vercel-build-output-api.ts to use the outputContent directly in esbuild's stdin.contents without null-checking, creating a type-safety issue.
How to reproduce:
- Call
createStepsBundle()without theoutfileparameter (as done instandalone.tsline 54 andvercel-build-output-api.tsline 59) - The TypeScript overload guarantees
outputContent: string - The implementation uses:
!writeToFile && stepsResult.outputFiles?.[0] ? stepsResult.outputFiles[0].text : undefined - If
stepsResult.outputFilesis empty or falsy,outputContentbecomesundefined, violating the contract
Result: TypeScript incorrectly allows undefined to be passed where string is required by the overload contract. While esbuild should always populate outputFiles when write: false succeeds, the lack of explicit error checking creates a defensive programming gap.
Expected: The code should validate that outputFiles exists and is non-empty before extracting content, similar to the error check in createWorkflowsBundle() at line 548-550:
if (!interimBundle.outputFiles || interimBundle.outputFiles.length === 0) {
throw new Error('No output files generated from esbuild');
}Fix: Added explicit error check in createStepsBundle() at line 393-397 to ensure outputFiles exists when writeToFile is false, making the type contract enforceable.
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TL;DR
Enable "use step" functions to be defined outside of the app directory with proper path alias resolution.
What changed?
pathsAliasHelperto a proper step function calledpathsAliasStepthat can be imported directlypathsAliasWorkflowto call the external step function directly instead of using a wrapper stepHow to test?
Run the
pathsAliasWorkflowtest which imports a step function from outside the workbench directory using a TypeScript path alias. The workflow should complete successfully and return "pathsAliasStep".Why make this change?
This enhancement provides more flexibility in organizing step functions by allowing them to be defined anywhere in the codebase, not just within the app directory. It enables better code organization and reuse of step functions across different parts of the application while maintaining proper path alias resolution.