Merge pull request #1 from arizworld/feat/customize_error_messages

Feat - implemented customizing error messages at the time of validation

Author: aritradevelops

src/decorator/ValidationOptions.ts

@@ -29,6 +29,11 @@ export interface ValidationOptions {
    * A transient set of data passed through to the validation result for response mapping
    */
   context?: any;
+
+  /**
+   * While using transformFunction if provided then the transformFunction will be called with this.
+   */
+  transformKey?: string
 }
 
 export function isValidationOptions(val: any): val is ValidationOptions {

src/metadata/ValidationMetadata.ts

@@ -44,6 +44,10 @@ export class ValidationMetadata {
    */
   message: string | ((args: ValidationArguments) => string);
 
+  /**
+   * While using transformFunction to customize error messages the transformFunction will be called with this key.
+   */
+  transformKey?: string
   /**
    * Validation groups used for this validation.
    */
@@ -87,6 +91,7 @@ export class ValidationMetadata {
       this.always = args.validationOptions.always;
       this.each = args.validationOptions.each;
       this.context = args.validationOptions.context;
+      this.transformKey = args.validationOptions.transformKey;
     }
   }
 }

src/validation/ValidationExecutor.ts

@@ -30,7 +30,7 @@ export class ValidationExecutor {
   // Constructor
   // -------------------------------------------------------------------------
 
-  constructor(private validator: Validator, private validatorOptions?: ValidatorOptions) {}
+  constructor(private validator: Validator, private validatorOptions?: ValidatorOptions) { }
 
   // -------------------------------------------------------------------------
   // Public Methods
@@ -46,8 +46,8 @@ export class ValidationExecutor {
     if (!this.metadataStorage.hasValidationMetaData && this.validatorOptions?.enableDebugMessages === true) {
       console.warn(
         `No validation metadata found. No validation will be  performed. There are multiple possible reasons:\n` +
-          `  - There may be multiple class-validator versions installed. You will need to flatten your dependencies to fix the issue.\n` +
-          `  - This validation runs before any file with validation decorator was parsed by NodeJS.`
+        `  - There may be multiple class-validator versions installed. You will need to flatten your dependencies to fix the issue.\n` +
+        `  - This validation runs before any file with validation decorator was parsed by NodeJS.`
       );
     }
 
@@ -67,6 +67,18 @@ export class ValidationExecutor {
     );
     const groupedMetadatas = this.metadataStorage.groupByPropertyName(targetMetadatas);
 
+    /**if transformationFunction is provided then overwrite the message with the transformationFunction */
+    if (this.validatorOptions?.validationError?.transformFunction && typeof this.validatorOptions?.validationError?.transformFunction === 'function') {
+      targetMetadatas.forEach(e => {
+        e.message = () => (this.validatorOptions?.validationError?.transformFunction as Function)(e.transformKey || e.name || e.type || 'This validation does not have an name or type associated with it, please add one.')
+      });
+      Object.keys(groupedMetadatas).forEach(prop => {
+        groupedMetadatas[prop].forEach(e => {
+          e.message = () => (this.validatorOptions?.validationError?.transformFunction as Function)(e.transformKey || e.name || e.type || 'This validation does not have an name or type associated with it, please add one.')
+        });
+      })
+    }
+
     if (forbidUnknownValues && !targetMetadatas.length) {
       const validationError = new ValidationError();
 

src/validation/ValidatorOptions.ts

@@ -69,6 +69,13 @@ export interface ValidatorOptions {
      * Indicates if validated value should be exposed in ValidationError.
      */
     value?: boolean;
+
+    /**
+     * A function to modify the error message.The function will be called with the transformKey or the name of the validation.
+     * @param key the name of the error.
+     * @returns string. it will be shown instead of the default error message.
+     */
+    transformFunction?: (key: string) => string
   };
 
   /**