fix: cache compiled validators in AjvJsonSchemaValidator to prevent memory leak

src/validation/ajv-provider.ts

@@ -35,6 +35,7 @@ function createDefaultAjvInstance(): Ajv {
  */
 export class AjvJsonSchemaValidator implements jsonSchemaValidator {
     private _ajv: Ajv;
+    private _compiledCache: Map<string, ReturnType<Ajv['compile']>>
 
     /**
      * Create an AJV validator
@@ -58,6 +59,7 @@ export class AjvJsonSchemaValidator implements jsonSchemaValidator {
      */
     constructor(ajv?: Ajv) {
         this._ajv = ajv ?? createDefaultAjvInstance();
+        this._compiledCache = new Map();
     }
 
     /**
@@ -70,11 +72,7 @@ export class AjvJsonSchemaValidator implements jsonSchemaValidator {
      * @returns A validator function that validates input data
      */
     getValidator<T>(schema: JsonSchemaType): JsonSchemaValidator<T> {
-        // Check if schema has $id and is already compiled/cached
-        const ajvValidator =
-            '$id' in schema && typeof schema.$id === 'string'
-                ? (this._ajv.getSchema(schema.$id) ?? this._ajv.compile(schema))
-                : this._ajv.compile(schema);
+        const ajvValidator = this._getCompiled(schema);
 
         return (input: unknown): JsonSchemaValidatorResult<T> => {
             const valid = ajvValidator(input);
@@ -94,4 +92,22 @@ export class AjvJsonSchemaValidator implements jsonSchemaValidator {
             }
         };
     }
+
+    private _getCompiled(schema: JsonSchemaType) {
+        if ('$id' in schema && typeof schema.$id === 'string') {
+            return this._ajv.getSchema(schema.$id) ?? this._ajv.compile(schema);
+        }
+        let key: string;
+        try {
+            key = JSON.stringify(schema);
+        } catch {
+            return this._ajv.compile(schema);
+        }
+        let cached = this._compiledCache.get(key);
+        if (cached === undefined) {
+            cached = this._ajv.compile(JSON.parse(key));
+            this._compiledCache.set(key, cached);
+        }
+        return cached;
+    }
 }

test/validation/validation.test.ts

@@ -531,6 +531,62 @@ describe('JSON Schema Validators', () => {
     });
 });
 
+describe('AJV caching', () => {
+    it('caches compiled validators for identical schemas without $id', () => {
+        const validator = new AjvJsonSchemaValidator();
+        const schema: JsonSchemaType = {
+            type: 'object',
+            properties: { name: { type: 'string' } },
+            required: ['name']
+        };
+
+        // Get validator multiple times for the same schema
+        const v1 = validator.getValidator(schema);
+        const v2 = validator.getValidator(schema);
+
+        // Both should produce the same results
+        expect(v1({ name: 'test' })).toEqual(v2({ name: 'test' }));
+        expect(v1({})).toEqual(v2({}));
+    });
+
+    it('caches validators for schemas with same content but different references', () => {
+        const validator = new AjvJsonSchemaValidator();
+        const schema1: JsonSchemaType = { type: 'string' };
+        const schema2: JsonSchemaType = { type: 'string' };
+
+        const v1 = validator.getValidator(schema1);
+        const v2 = validator.getValidator(schema2);
+
+        expect(v1('test')).toEqual(v2('test'));
+        expect(v1(42)).toEqual(v2(42));
+    });
+
+    it('returns different validators for different schemas', () => {
+        const validator = new AjvJsonSchemaValidator();
+        const schema1: JsonSchemaType = { type: 'string' };
+        const schema2: JsonSchemaType = { type: 'number' };
+
+        const v1 = validator.getValidator(schema1);
+        const v2 = validator.getValidator(schema2);
+
+        expect(v1('test').valid).toBe(true);
+        expect(v2('test').valid).toBe(false);
+    });
+
+    it('compiles each unique schema only once', () => {
+        const validator = new AjvJsonSchemaValidator();
+        const schema: JsonSchemaType = { type: 'string' };
+
+        // Call getValidator 5 times with same schema
+        for (let i = 0; i < 5; i++) {
+            validator.getValidator(schema)(i === 0 ? 'test' : 'other');
+        }
+
+        // The cache should have exactly 1 entry
+        expect((validator as any)._compiledCache.size).toBe(1);
+    });
+});
+
 describe('Missing dependencies', () => {
     describe('AJV not installed but CfWorker is', () => {
         beforeEach(() => {