[Regression] beta.40 breaks TypeScript decorator support by removing jscConfig from applySwcTransform

[technopahadi]

Description:

• In 4.0.1-beta.40, the jscConfig parameter was removed from applySwcTransform() in @workflow/builders
• This breaks projects using TypeScript decorators (TypeORM, NestJS, etc.)
• The tsconfig.json settings like experimentalDecorators are no longer passed to SWC
• beta.39 works, beta.40 fails with "Unexpected token @" errors

Files changed:

• packages/builders/src/apply-swc-transform.ts - removed jscConfig parameter
• packages/builders/src/swc-esbuild-plugin.ts - removed jscConfig argument from call

[technopahadi]

  Updated Root Cause

  The regression isn't about jscConfig - it's about the discovery phase changes.

  In beta.39, Next.js builds skip the discovery esbuild step entirely:
  if (this.config.buildTarget === 'next') {
    return {
      discoveredWorkflows: inputs,
      discoveredSteps: inputs,
    };
  }

  In beta.40, this early return was removed, causing all imported files (including those with decorators) to be processed through SWC during
  discovery.

  The fix is either:
  1. Restore the early return for Next.js builds, OR
  2. Add decorator support to SWC config (my original fix) so it can handle decorator files

  Option 2 (adding decorators: true) is a more robust fix since it allows decorator files to be processed correctly regardless of build target.

  ---
  So my original PR fix is still valid - adding decorators: true is the right approach. It's just that the cause was the removal of the
  early-return, not the removal of jscConfig.

[technopahadi]

Another error I kept getting with beta 4x (44 specifically) was this when starting the workflow:

ReferenceError while running "wrun_01KEHGGM1W35GRPD517DP378XC" workflow:

workflows/copilot/index.ts:21260
var import_api = require("@opentelemetry/api");
                 ^

ReferenceError: require is not defined
    at anonymous (../../node_modules/ai/src/telemetry/get-base-telemetry-attributes.ts:6:2)
    at Script.runInContext (node:vm:149:12)
    at runInContext (node:vm:301:6)
    at /Users/rishabh/www/morphic/platform-backend/apps/orcrust/.next/dev/server/chunks/node_modules_@workflow_core_dist_ce134487._.js:2927:158
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
    at async /Users/rishabh/www/morphic/platform-backend/apps/orcrust/.next/dev/server/chunks/node_modules_@workflow_core_dist_ce134487._.js:343:28
    at async /Users/rishabh/www/morphic/platform-backend/apps/orcrust/.next/dev/server/chunks/node_modules_@workflow_core_dist_ce134487._.js:3762:36
    at async /Users/rishabh/www/morphic/platform-backend/apps/orcrust/.next/dev/server/chunks/node_modules_@workflow_core_dist_ce134487._.js:343:28
    at async /Users/rishabh/www/morphic/platform-backend/apps/orcrust/.next/dev/server/chunks/node_modules_@workflow_core_dist_ce134487._.js:310:58
    at async /Users/rishabh/www/morphic/platform-backend/apps/orcrust/.next/dev/server/chunks/node_modules_@workflow_core_dist_ce134487._.js:3695:16
 POST /.well-known/workflow/v1/flow 200 in 574ms (compile: 337ms, render: 237ms)
^C POST /api/workflows/copilot 200 in 16.6s (compile: 1119ms, render: 15.5s)
ResponseAborted: 
    at ignore-listed frames
 ⨯ unhandledRejection: ResponseAborted: 
    at ignore-listed frames
 ⨯ unhandledRejection:  ResponseAborted: 
    at ignore-listed frames

The bundled workflow code had this piece coming from ai package I think var import_api = require("@opentelemetry/api"); - attempted fixing but failed. Maybe something you guys can look into as it was working fine till 39.

[TooTallNate]

@technopahadi Could you provide a small repro with the decorators setup that's started failing for you?

[ijjk]

Closed by #757