Handle class-transformer @Expose decorator (#120)

* feat: enhance validation metadata processing to support class-transformer exposed metadata

* feat: add tests for Expose decorator and improve metadata handling

* Update src/index.ts

Co-authored-by: Aleksi Pekkala <aleksipekkala@gmail.com>

* Update src/index.ts

Co-authored-by: Aleksi Pekkala <aleksipekkala@gmail.com>

* fix: refactor for CI approved

---------

Co-authored-by: Aleksi Pekkala <aleksipekkala@gmail.com>

Author: pedro2s

__tests__/expose.test.ts

@@ -0,0 +1,34 @@
+// tslint:disable:no-submodule-imports
+import { Expose } from 'class-transformer'
+import { IsString } from 'class-validator'
+import { validationMetadatasToSchemas } from '../src'
+const { defaultMetadataStorage } = require('class-transformer/cjs/storage')
+
+// @ts-ignore unused
+class User {
+  @IsString()
+  id: string
+
+  @Expose({ name: 'domain_id' })
+  @IsString()
+  domainId: string
+}
+
+describe('Expose() decorator', () => {
+  it('rename Expose()-decorated properties from output schema', () => {
+    const schema = validationMetadatasToSchemas({
+      classTransformerMetadataStorage: defaultMetadataStorage,
+    })
+
+    expect(schema).toEqual({
+      User: {
+        properties: {
+          id: { type: 'string' },
+          domain_id: { type: 'string' },
+        },
+        type: 'object',
+        required: ['id', 'domain_id'],
+      },
+    })
+  })
+})

src/index.ts

@@ -8,6 +8,7 @@ import type { ReferenceObject, SchemaObject } from 'openapi3-ts'
 import { getMetadataSchema } from './decorators'
 import { defaultConverters } from './defaultConverters'
 import { defaultOptions, IOptions } from './options'
+import { ExposeMetadata } from 'class-transformer'
 
 export { JSONSchema } from './decorators'
 
@@ -64,6 +65,26 @@ export function validationMetadataArrayToSchemas(
             isExcluded({ ...propMeta, target }, options)
           )
       )
+      .map((propMeta) => {
+        /**
+         * Retrieves all properties that have the Expose decorator from class-transformer
+         * and remaps the property names to the names exposed by the Expose decorator.
+         */
+        const exposeMetadata =
+          userOptions?.classTransformerMetadataStorage?.getExposedMetadatas(
+            propMeta.target as any
+          )
+
+        const ctMetaForField = exposeMetadata?.find(
+          (meta: ExposeMetadata) => meta.propertyName === propMeta.propertyName
+        )
+
+        if (ctMetaForField?.options.name) {
+          propMeta.propertyName = ctMetaForField.options.name
+        }
+
+        return propMeta
+      })
 
     const properties: { [name: string]: ReferenceObject | SchemaObject } = {}