`@ApiProperty({ type: Boolean, enum: [true] })` generates a value of type number in the OpenApi doc

[thomaslule]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

When describing a property like this:

@ApiProperty({ type: Boolean, enum: [true] })
hello = true;

The generated openapi property looks like this:

{ "hello": { "type": "number", "enum": [true] } }

Notice the number type where it should be boolean.

Minimum reproduction code

https://github.com/thomaslule/nestjs-boolean-enum

Steps to reproduce

1. npm i
2. npm run start:dev
3. navigate to http://localhost:3000/api-json
4. notice that the type of hello is number instead of boolean

Expected behavior

I expect this generated openapi property:

{ "hello": { "type": "boolean", "enum": [true] } }

Package version

11.2.6

NestJS version

11.0.1

Node.js version

24.2.0

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

I also tried to write @ApiProperty({ type: 'boolean', enum: [false] }) and obtained the same result.

[SupunGeethanjana]

Fix Bug #3772: @ApiProperty({ type: Boolean, enum: [true] }) generates type: number

The getEnumType utility in lib/utils/enum.utils.ts incorrectly defaults to 'number' if an enum doesn't contain strings, which fails for boolean enums.

Proposed Changes

[Component: Utilities]

[MODIFY] enum.utils.ts

• Update getEnumValues return type to include boolean[].
• Update getEnumType to check for booleans and return 'boolean' when appropriate.
• Update getEnumType return type to include 'boolean'.

Verification Plan

Automated Tests

• Run the reproduction test created earlier:

  npx jest test/reproduce_issue_3772.spec.ts

• Run all unit tests to ensure no regressions:

  npm test

• Run e2e tests to ensure schema validation still passes:

  npm run test:e2e

[SupunGeethanjana]

#3774