ts4023-effect-errors

name	ts4023-effect-errors
description	Fix TS4023 errors when exporting Effect-based functions. Use when TypeScript reports "has or is using name 'X' from external module but cannot be named" for Effect error types, or when knip flags error type exports as unused.
review	never

TS4023 with Effect Error Types

Problem

Exporting function returning Effect → TypeScript generates .d.ts → error types in Effect's error channel not exported from source package → TS4023.

TS4023 message is misleading: mentions internal Effect types (Channel, Sink, Stream from effect/Cause), not actual missing errors.

Solution

Export ALL error types that appear in any Effect's error channel - including non-exported class definitions.

1. Find ALL TaggedError classes (not just exported ones)

# Find Data.TaggedError and Schema.TaggedError (both used in codebase)
rg "class \w+Error extends (Data|Schema)\.TaggedError" packages/salesforcedx-vscode-services/src

Critical: Include classes WITHOUT export keyword. Example:

// This ALSO needs to be exported if used in any Effect's error channel
class EmptyComponentSetError extends Schema.TaggedError<EmptyComponentSetError>()('EmptyComponentSetError', {...}) {}

2. For non-exported errors, add export to source file first

// Before
class EmptyComponentSetError extends Schema.TaggedError<EmptyComponentSetError>()('EmptyComponentSetError', {...}) {}

// After
export class EmptyComponentSetError extends Schema.TaggedError<EmptyComponentSetError>()('EmptyComponentSetError', {...}) {}

3. Then export from index.ts

export type { EmptyComponentSetError } from './core/componentSetService';

4. Verify

npm run compile -w packages/salesforcedx-vscode-metadata

Why non-exported errors matter

If a service method like ensureNonEmptyComponentSet can fail with EmptyComponentSetError, that error type appears in the Effect's error channel. Any exported function calling that method inherits the error in its type signature. TypeScript needs to name it in .d.ts.

Knip false positives

Knip flags these as "unused exports" when the error class is defined and used within the same file but exported for TS4023 reasons. Fix by adding /** @ExportTaggedError */ JSDoc to the export:

/** @ExportTaggedError */
export class NoFilesRetrievedError extends Schema.TaggedError<NoFilesRetrievedError>()('NoFilesRetrievedError', {
  message: Schema.String
}) {}

Do NOT add @ExportTaggedError to errors exported from salesforcedx-vscode-services — those are consumed by other packages and knip correctly sees them as used.

Checklist

• rg "class.*TaggedError" - find ALL errors (with AND without export)
• Add export to any non-exported error classes used in Effect chains
• Add export type { ErrorName } to services index.ts
• npm run compile -w <package> passes
• Add /** @ExportTaggedError */ JSDoc to suppress knip false positives (for errors that are only used within the same package, not consumed by other packages)