feat: Add requiredWhen support

__tests__/validator.test.ts

@@ -127,6 +127,63 @@ describe("Validator - Required Validation", () => {
   });
 });
 
+describe("Validator - Required When Validation", () => {
+  it("should validate requiredWhen fields", () => {
+    const validator = new Validator(
+      {
+        name: { type: "string", requiredWhen: { field: "age", value: 18 } },
+        age: { type: "number" },
+      },
+      {
+        name: {
+          type: "Name must be a string",
+          requiredWhen: "Name is required",
+        },
+        age: {
+          type: "Age must be a number",
+        },
+      }
+    );
+
+    expect(validator.validate({ name: "John Doe", age: 18 })).resolves.toBe(
+      true
+    );
+    expect(validator.validate({ age: 18 })).resolves.toBe(false);
+  });
+
+  it("should validate requiredWhen fields with multiple values", () => {
+    const validator = new Validator(
+      {
+        name: {
+          type: "string",
+          requiredWhen: {
+            field: "age",
+            value: [18, 20],
+          },
+        },
+        age: { type: "number" },
+      },
+      {
+        name: {
+          type: "Name must be a string",
+          requiredWhen: "Name is required",
+        },
+        age: {
+          type: "Age must be a number",
+        },
+      }
+    );
+
+    expect(validator.validate({ name: "John Doe", age: 18 })).resolves.toBe(
+      true
+    );
+    expect(validator.validate({ name: "John Doe", age: 20 })).resolves.toBe(
+      true
+    );
+    expect(validator.validate({ age: 18 })).resolves.toBe(false);
+  });
+});
+
 describe("Validator - Min/Max Validation", () => {
   it("should validate number fields against a minimum value", () => {
     const validator = new Validator(

package.json

@@ -30,17 +30,18 @@
     "@semantic-release/changelog": "^6.0.3",
     "@semantic-release/git": "^10.0.1",
     "@types/jest": "^29.5.10",
+    "@types/mocha": "^10.0.6",
     "@typescript-eslint/eslint-plugin": "^6.13.1",
     "@typescript-eslint/parser": "^6.13.1",
     "conventional-changelog-conventionalcommits": "^7.0.2",
     "eslint": "^8.54.0",
+    "fix-tsup-cjs": "^1.2.0",
     "jest": "^29.7.0",
     "jest-sonar-reporter": "^2.0.0",
     "semantic-release": "^22.0.12",
     "ts-jest": "^29.1.1",
     "ts-node": "^10.9.1",
     "tsup": "^8.0.1",
-    "typescript": "^5.3.2",
-    "fix-tsup-cjs": "^1.2.0"
+    "typescript": "^5.3.2"
   }
-}
+}

src/index.ts

@@ -42,6 +42,10 @@ interface Rule {
    * Enumeration of valid values.
    */
   enum?: Array<string | number | boolean>;
+  /**
+   * Field is required when another field matches a specific value.
+   */
+  requiredWhen?: { field: string; value: any | any[] };
 }
 
 /**
@@ -84,6 +88,10 @@ interface Message {
    * The error message for invalid enum value.
    */
   enum?: string;
+  /**
+   * The error message for requiredWhen validation failure.
+   */
+  requiredWhen?: string;
 }
 
 /**
@@ -255,6 +263,34 @@ class Validator {
         continue; // Skip further checks if the field is missing
       }
 
+      // Handle requiredWhen condition
+      if (rule.requiredWhen) {
+        const conditionField = rule.requiredWhen.field;
+        const conditionValue = rule.requiredWhen.value;
+        let conditionMet = false;
+
+        // Check if conditionValue is an array and if it includes the input value
+        if (Array.isArray(conditionValue)) {
+          conditionMet = conditionValue.includes(input[conditionField]);
+        } else {
+          // If conditionValue is not an array, proceed with the normal equality check
+          conditionMet = input[conditionField] === conditionValue;
+        }
+
+        // If the condition is met and the field is required but not present or empty
+        if (conditionMet && (value === "" || value === undefined)) {
+          this.errors[key] =
+            this.messages[key].required ??
+            `"${key}" is required when "${conditionField}" is set to ${
+              Array.isArray(conditionValue)
+                ? conditionValue.join(" or ")
+                : conditionValue
+            }.`;
+          isValid = false;
+          continue; // Skip further checks for this field
+        }
+      }
+
       // If the value is not present, no need to check further rules
       if (value === undefined) continue;