Allow stringFormats to transform value

Author: SamyPesse

src/compileValidateRequest.ts

@@ -10,7 +10,7 @@ import { annotateWithJSDocComment } from './comments';
 const COMMENT = `
 Validate a request against the OpenAPI spec
 @param {{ method: string; path: string; body?: any; query: Record<string, string | string[]>; headers: Record<string, string>; }} request - Input request to validate
-@param {{ stringFormats?: { [format: string]: (value: string, path: string[]) => ValidationError | null } }} [context] - Context object to pass to validation functions
+@param {{ stringFormats?: { [format: string]: (value: string, path: string[]) => ValidationError | string | null } }} [context] - Context object to pass to validation functions
 @returns {{ operationId?: string; params: Record<string, string>; query: Record<string, string | string[]>; body?: any; headers: Record<string, string>; }}
 `;
 

src/compileValueSchema.ts

@@ -814,6 +814,20 @@ function compileStringSchema(compiler: Compiler, schema: OpenAPIStringSchema) {
                     builders.blockStatement([builders.returnStatement(formatResult)]),
                 ),
             );
+            nodes.push(
+                builders.ifStatement(
+                    builders.binaryExpression(
+                        '===',
+                        builders.unaryExpression('typeof', formatResult),
+                        builders.literal('string'),
+                    ),
+                    builders.blockStatement([
+                        builders.expressionStatement(
+                            builders.assignmentExpression('=', value, formatResult),
+                        ),
+                    ]),
+                ),
+            );
         }
 
         if (schema.minLength) {