feat(ajv): add returnsCoercedValues option to keep the coerced value by ajv

docs/docs/model.md

@@ -129,6 +129,66 @@ The @@Nullable@@ decorator is used allow a null value on a field while preservin
   </Tab>
 </Tabs>
 
+::: warning
+
+Since the v7.43.0, `ajv.returnsCoercedValues` is available to solve the following issue: [#2355](https://github.com/tsedio/tsed/issues/2355)
+If `returnsCoercedValues` is true, AjvService will return the coerced value instead of the original value. In this case, `@Nullable()` will be mandatory to
+allow the coercion of the value to `null`.
+
+For example if `returnsCoercedValues` is `false` (default behavior), Ts.ED will allow null value on a field without `@Nullable()` decorator:
+
+```typescript
+class NullableModel {
+  @Proprety()
+  propString: string; // null => null
+
+  @Proprety()
+  propNumber: number; // null => null
+
+  @Property()
+  propBool: boolean; // null => null
+}
+```
+
+Ajv won't emit validation error if the value is null due to his coercion behavior. AjvService will return the original value and not the Ajv coerced value.
+Another problem is, the typings of the model doesn't reflect the real coerced value.
+
+Using the `returnsCoercedValues` option, AjvService will return the coerced type. In this case, our previous model will have the following behavior:
+
+```typescript
+class NullableModel {
+  @Proprety()
+  propString: string; // null => ''
+
+  @Proprety()
+  propNumber: number; // null => 0
+
+  @Property()
+  propBool: boolean; // null => false
+}
+```
+
+Now `@Nullable` usage is mandatory to allow `null` value on properties:
+
+```typescript
+class NullableModel {
+  @Nullable(String)
+  propString: string | null; // null => null
+
+  @Nullable(Number)
+  propNumber: number | null; // null => null
+
+  @Nullable(Boolean)
+  propBool: boolean | null; // null => null
+}
+```
+
+:::
+
+::: warning
+`returnsCoercedValue` will become true by default in the next major version of Ts.ED.
+:::
+
 ## Any
 
 The @@Any@@ decorator is used to allow any types:
@@ -677,7 +737,7 @@ So by using the @@deserialize@@ function with the extra groups options, we can m
 <Tab label="Creation">
 
 ```typescript
-import { deserialize } from '@tsed/json-mapper';
+import {deserialize} from "@tsed/json-mapper";
 
 const result = deserialize<User>(
   {
@@ -697,7 +757,7 @@ console.log(result); // User {firstName, lastName, email, password}
 <Tab label="With group">
 
 ```typescript
-import { deserialize } from '@tsed/json-mapper';
+import {deserialize} from "@tsed/json-mapper";
 
 const result = deserialize<User>(
   {
@@ -718,7 +778,7 @@ console.log(result); // User {id, firstName, lastName, email, password}
 <Tab label="With glob pattern">
 
 ```typescript
-import { deserialize } from '@tsed/json-mapper';
+import {deserialize} from "@tsed/json-mapper";
 
 const result = deserialize<User>(
   {

docs/tutorials/ajv.md

@@ -37,7 +37,9 @@ import {Configuration} from "@tsed/common";
 import "@tsed/ajv"; // import ajv ts.ed module
 
 @Configuration({
-  ajv: {}
+  ajv: {
+    returnsCoercedValues: true // returns coerced value to the next pipe instead of returns original value (See #2355)
+  }
 })
 export class Server {}
 ```
@@ -227,6 +229,10 @@ describe("Product", () => {
 });
 ```
 
+::: warning
+If you planed to create keyword that transform the data, you have to set `returnsCoercedValues` to `true` in your configuration.
+:::
+
 ### With "code" function
 
 Starting from v7 Ajv uses [CodeGen module](https://github.com/ajv-validator/ajv/blob/master/lib/compile/codegen/index.ts) for all pre-defined keywords - see [codegen.md](https://ajv.js.org/codegen.html) for details.

packages/platform/platform-params/src/pipes/ValidationPipe.ts

@@ -72,7 +72,7 @@ export class ValidationPipe implements PipeMethods {
       customKeys: true
     });
 
-    await this.validator.validate(value, {
+    value = await this.validator.validate(value, {
       schema,
       type: metadata.isClass ? metadata.type : undefined,
       collectionType: metadata.collectionType

packages/specs/ajv/jest.config.js

@@ -9,7 +9,7 @@ module.exports = {
   },
   coverageThreshold: {
     global: {
-      branches: 86.88,
+      branches: 87.87,
       functions: 100,
       lines: 99.71,
       statements: 99.71

packages/specs/ajv/src/interfaces/IAjvSettings.ts

@@ -19,4 +19,5 @@ export type ErrorFormatter = (error: AjvErrorObject) => string;
 export interface IAjvSettings extends Options {
   Ajv?: any;
   errorFormatter?: ErrorFormatter;
+  returnsCoercedValues?: boolean;
 }

packages/specs/ajv/src/services/AjvService.spec.ts

@@ -6,6 +6,7 @@ import {AjvService} from "./AjvService";
 describe("AjvService", () => {
   beforeEach(() => PlatformTest.create());
   afterEach(() => PlatformTest.reset());
+
   it("should use the function api as schema", async () => {
     const ajvService = PlatformTest.get<AjvService>(AjvService);
 

packages/specs/ajv/src/services/AjvService.ts

@@ -21,6 +21,9 @@ export class AjvService {
   @Constant("ajv.errorFormatter", defaultErrorFormatter)
   protected errorFormatter: ErrorFormatter;
 
+  @Constant("ajv.returnsCoercedValues")
+  protected returnsCoercedValues: boolean;
+
   @Inject()
   protected ajv: Ajv;
 
@@ -30,7 +33,7 @@ export class AjvService {
     const schema = defaultSchema || getJsonSchema(type, {...additionalOptions, customKeys: true});
 
     if (schema) {
-      const localValue = deepClone(value);
+      const localValue = this.returnsCoercedValues ? value : deepClone(value);
       const validate = this.ajv.compile(schema);
 
       const valid = await validate(localValue);
@@ -44,6 +47,10 @@ export class AjvService {
           value: localValue
         });
       }
+
+      if (this.returnsCoercedValues) {
+        return localValue;
+      }
     }
 
     return value;

packages/specs/ajv/test/integration/nullable.integration.spec.ts

@@ -0,0 +1,187 @@
+import "../../src/index";
+import {BodyParams, ParamTypes, ParamValidationError, PlatformTest, Post, QueryParams, UseParam, ValidationPipe} from "@tsed/common";
+import {BadRequest} from "@tsed/exceptions";
+import {CollectionOf, getJsonSchema, JsonParameterStore, MinLength, Nullable, Property, Required, Schema, string} from "@tsed/schema";
+
+async function validate(value: any, metadata: any) {
+  const pipe: ValidationPipe = await PlatformTest.invoke<ValidationPipe>(ValidationPipe);
+
+  try {
+    return await pipe.transform(value, metadata);
+  } catch (er) {
+    if (er instanceof BadRequest) {
+      return ParamValidationError.from(metadata, er);
+    }
+
+    throw er;
+  }
+}
+
+class NestedModel {
+  @Property()
+  id: string;
+}
+
+class NullModel {
+  @Nullable(String)
+  prop1: string | null;
+
+  @Nullable(Number)
+  prop2: number;
+
+  @Nullable(Date)
+  prop3: Date | null;
+
+  @Nullable(NestedModel)
+  prop4: NestedModel | null;
+
+  @Nullable(Array)
+  prop5: string[] | null;
+}
+
+class NoNullableModel {
+  @Property()
+  prop1: string;
+
+  @Property()
+  prop2: number;
+
+  @Property()
+  prop3: Date;
+
+  @Property()
+  prop4: NestedModel;
+
+  @CollectionOf(String)
+  prop5: string[];
+}
+
+describe("Nullable model", () => {
+  describe("when returnsCoercedValues is false", () => {
+    beforeEach(() =>
+      PlatformTest.create({
+        ajv: {
+          coerceTypes: "array"
+        }
+      })
+    );
+    afterEach(() => PlatformTest.reset());
+    it("should validate object and returns the original value (NullModel)", async () => {
+      class Ctrl {
+        get(@BodyParams() value: NullModel) {}
+      }
+
+      const value = {
+        prop1: null,
+        prop2: null,
+        prop3: null,
+        prop4: null,
+        prop5: null
+      };
+
+      const result = await validate(value, JsonParameterStore.get(Ctrl, "get", 0));
+
+      expect(result).toEqual({
+        prop1: null,
+        prop2: null,
+        prop3: null,
+        prop4: null,
+        prop5: null
+      });
+
+      const result2 = await validate(
+        {
+          prop1: "test",
+          prop2: 1,
+          prop3: "2020-01-01",
+          prop4: {
+            id: "id"
+          },
+          prop5: ["test"]
+        },
+        JsonParameterStore.get(Ctrl, "get", 0)
+      );
+
+      expect(result2).toEqual({
+        prop1: "test",
+        prop2: 1,
+        prop3: "2020-01-01",
+        prop4: {
+          id: "id"
+        },
+        prop5: ["test"]
+      });
+    });
+    it("should validate object and returns the original value (NoNullableModel)", async () => {
+      class Ctrl {
+        get(@BodyParams() value: NoNullableModel) {}
+      }
+
+      const value = {
+        prop1: null,
+        prop2: null,
+        prop3: null,
+        prop5: null
+      };
+
+      const result = await validate(value, JsonParameterStore.get(Ctrl, "get", 0));
+
+      expect(result).toEqual({
+        prop1: null,
+        prop2: null,
+        prop3: null,
+        prop5: null
+      });
+    });
+  });
+  describe("when returnsCoercedValues is true", () => {
+    beforeEach(() =>
+      PlatformTest.create({
+        ajv: {
+          verbose: true,
+          coerceTypes: "array",
+          returnsCoercedValues: true
+        }
+      })
+    );
+    afterEach(() => PlatformTest.reset());
+    it("should validate object and return the coerced value (NullModel)", async () => {
+      class Ctrl {
+        get(@BodyParams() value: NullModel) {}
+      }
+
+      const value = {
+        prop1: null,
+        prop2: null,
+        prop3: null,
+        prop4: null,
+        prop5: null
+      };
+
+      const result = await validate(value, JsonParameterStore.get(Ctrl, "get", 0));
+
+      expect(result).toEqual(value);
+    });
+    it("should validate object and return the coerced value (NoNullableModel)", async () => {
+      class Ctrl {
+        get(@BodyParams() value: NoNullableModel) {}
+      }
+
+      const value = {
+        prop1: null,
+        prop2: null,
+        prop3: null,
+        prop5: null
+      };
+
+      const result = await validate(value, JsonParameterStore.get(Ctrl, "get", 0));
+
+      expect(result).toEqual({
+        prop1: "",
+        prop2: 0,
+        prop3: "",
+        prop5: [""]
+      });
+    });
+  });
+});