vercel__workflow/packages/builders

@workflow/builders

Shared builder infrastructure for Workflow SDK. This package provides the base builder class and utilities used by framework-specific integrations.

Overview

This package contains the core build logic for transforming workflow source files into deployable bundles. It is used by:

• @workflow/cli - For standalone/basic builds
• @workflow/next - For Next.js integration
• @workflow/nitro - For Nitro/Nuxt integration

Key components

• BaseBuilder: Abstract base class providing common build logic
• Build plugins: esbuild plugins for workflow transformations
• SWC integration: Compiler plugin integration for workflow directives

Usage

This package is typically not used directly. Instead, use one of the framework-specific packages that extend BaseBuilder:

import { BaseBuilder } from '@workflow/builders';

class MyBuilder extends BaseBuilder {
  async build(): Promise<void> {
    // Implement builder-specific logic
  }
}

Observing transforms

Builder configurations can provide an optional onAfterTransform observer for tooling that derives metadata from the exact SWC output used by a build:

import type { WorkflowAfterTransformHook } from '@workflow/builders';

// Pass as `onAfterTransform` in the builder configuration.
const onAfterTransform: WorkflowAfterTransformHook = async ({
  mode,
  filename,
  absolutePath,
  source,
  code,
  workflowManifest,
}) => {
  // Observe the accepted transform result.
};

The observer is awaited after the transform's manifest entries have been accepted. It cannot replace the generated code, and throwing aborts the build. A source file may be observed multiple times across transform modes, bundles, and watch rebuilds, so consumers should deduplicate results when necessary.

Architecture

The builder system uses:

1. esbuild for bundling and tree-shaking
2. SWC for transforming workflow directives ("use workflow", "use step")
3. Enhanced resolve for TypeScript path mapping

License

MIT