and

apps/website/docs/contracts/cookbook/custom_matchers.md

@@ -7,9 +7,9 @@ Let us write a custom matcher that checks if an age of a user is within a certai
 ```ts
 import { type Contract } from '@withease/contracts';
 
-function age(min, max): Contract<unknown, number> {
+function age(min, max): Contract<number, number> {
   return {
-    isData: (data) => typeof data === 'number' && data >= min && data <= max,
+    isData: (data) => data >= min && data <= max,
     getErrorMessages: (data) =>
       `Expected a number between ${min} and ${max}, but got ${data}`,
   };
@@ -19,10 +19,10 @@ function age(min, max): Contract<unknown, number> {
 Now you can use this matcher in your schema:
 
 ```ts
-import { rec, str } from '@withease/contracts';
+import { rec, str, and, num } from '@withease/contracts';
 
 const User = rec({
   name: str,
-  age: age(18, 100),
+  age: and(num, age(18, 100)),
 });
 ```

packages/contracts/src/contracts.test.ts

@@ -1,6 +1,6 @@
 import { describe, it, test, expect } from 'vitest';
 
-import { bool, num, str, rec, or, val, arr } from './index';
+import { bool, num, str, rec, or, val, arr, and, Contract } from './index';
 
 describe('bool', () => {
   it('valid', () => {
@@ -240,6 +240,47 @@ describe('str', () => {
     });
   });
 
+  describe('and', () => {
+    const len = (l: number): Contract<string, string> => {
+      return {
+        isData: (x: string): x is string => x.length >= l,
+        getErrorMessages: (x) =>
+          x.length >= l ? [] : [`expected length >= ${l}, got ${x.length}`],
+      };
+    };
+
+    const cntrct = and(str, len(10));
+
+    it('valid all', () => {
+      const str10 = '1234567890';
+
+      expect(cntrct.isData(str10)).toBeTruthy();
+      expect(cntrct.getErrorMessages(str10)).toEqual([]);
+    });
+
+    it('invalid first', () => {
+      const number = 1234567890;
+
+      expect(cntrct.isData(number)).toBeFalsy();
+      expect(cntrct.getErrorMessages(number)).toMatchInlineSnapshot(`
+        [
+          "expected string, got number",
+        ]
+      `);
+    });
+
+    it('invalid second', () => {
+      const str9 = '123456789';
+
+      expect(cntrct.isData(str9)).toBeFalsy();
+      expect(cntrct.getErrorMessages(str9)).toMatchInlineSnapshot(`
+        [
+          "expected length >= 10, got 9",
+        ]
+      `);
+    });
+  });
+
   describe('or', () => {
     const cntrct = or(bool, val(0));
     it('valid', () => {

packages/contracts/src/index.ts

@@ -1,3 +1,5 @@
+import { func } from 'superstruct';
+
 /**
  * A type that allows to extract the result type of a _Contract_.
  *
@@ -123,12 +125,48 @@ export function or<T extends Array<Contract<unknown, any>>>(
   };
 }
 
+/**
+ * Function that creates a _Contract_ that checks if a value is conform to all of the given _Contracts_.
+ *
+ * @example
+ * function age(min, max): Contract<number, number> {
+ *   return {
+ *     isData: (data) => data >= min && data <= max,
+ *     getErrorMessages: (data) =>
+ *       `Expected a number between ${min} and ${max}, but got ${data}`,
+ *   };
+ * }
+ *
+ * const User = rec({
+ *   name: str,
+ *   age: and(num, age(18, 100)),
+ * });
+ */
+export function and<T>(
+  first: Contract<unknown, T>,
+  ...rest: Array<Contract<T, T>>
+): Contract<unknown, T> {
+  const all = [first, ...rest];
+  return {
+    isData: (x): x is T => all.every((c) => c.isData(x as any)),
+    getErrorMessages: (x) => {
+      for (const c of all) {
+        if (!c.isData(x as any)) {
+          return c.getErrorMessages(x as any);
+        }
+      }
+
+      return [];
+    },
+  };
+}
+
 /**
  * Function that creates a _Contract_ that checks if a value is object and every property is conform to the given _Contract_.
- * 
+ *
  * @example
  * const Ids = rec(str, num);
- * 
+ *
  * Ids.isData({ id1: 1, id2: 2 }) === true;
  * Ids.isData({ id1: 1, id2: '2' }) === false;
  */