feat: added useNullAsOptional option (#1017)

Changes:
- with this flag, undefined types will be replaced with null.
- fields with optional label in proto files, will implicitly accept
undefined too.

this feature is needed when we wanna have better type alignment with
ORMs ( drizzle, typeorm, prisma ) or other services such as Firestore,
since they mostly ignore `undefined` in their types.

Note:

@stephenh as you wanted I made simple, small changes, this works well
for my `nestjs` project, I'm not very familiar with other
implementations and frameworks, please check it out and let me know what
you think. if any changes are required please let me know, I will work
them out.

thanks for this amazing library 🙏 

closes #869

README.markdown

@@ -547,6 +547,58 @@ Generated code will be placed in the Gradle build directory.
 
 - With `--ts_proto_opt=comments=false`, comments won't be copied from the proto files to the generated code.
 
+- With `--ts_proto_opt=useNullAsOptional=true`, `undefined` values will be converted to `null`, and if you use `optional` label in your `.proto` file, the field will have `undefined` type as well. for example:
+
+```protobuf
+message ProfileInfo {
+    int32 id = 1;
+    string bio = 2;
+    string phone = 3;
+}
+
+message Department {
+    int32 id = 1;
+    string name = 2;
+}
+
+message User {
+    int32 id = 1;
+    string username = 2;
+    /*
+     ProfileInfo will be optional in typescript, the type will be ProfileInfo | null | undefined
+     this is needed in cases where you don't wanna provide any value for the profile.
+    */
+    optional ProfileInfo profile = 3;
+
+    /*
+      Department only accepts a Department type or null, so this means you have to pass it null if there is no value available.
+    */
+    Department  department = 4;
+}
+```
+
+the generated interfaces will be:
+
+```typescript
+export interface ProfileInfo {
+  id: number;
+  bio: string;
+  phone: string;
+}
+
+export interface Department {
+  id: number;
+  name: string;
+}
+
+export interface User {
+  id: number;
+  username: string;
+  profile?: ProfileInfo | null | undefined; // check this one
+  department: Department | null; // check this one
+}
+```
+
 ### NestJS Support
 
 We have a great way of working together with [nestjs](https://docs.nestjs.com/microservices/grpc). `ts-proto` generates `interfaces` and `decorators` for you controller, client. For more information see the [nestjs readme](NESTJS.markdown).

integration/use-null-as-optional/parameters.txt

@@ -0,0 +1 @@
+useNullAsOptional=true

integration/use-null-as-optional/use-null-as-optional.proto

@@ -0,0 +1,23 @@
+syntax = "proto3";
+
+package useNullAsOptional;
+
+message ProfileInfo {
+  int32 id = 1;
+  string bio = 2;
+  string phone = 3;
+}
+
+message User {
+  int32 id = 1;
+  string username = 2;
+  optional ProfileInfo profile = 3;
+}
+
+message UserById {
+  int32 id = 1;
+}
+
+service HeroService {
+    rpc FindOneHero (UserById) returns (User) {}
+}

integration/use-null-as-optional/use-null-as-optional.ts

@@ -0,0 +1,297 @@
+/* eslint-disable */
+import * as _m0 from "protobufjs/minimal";
+
+export const protobufPackage = "useNullAsOptional";
+
+export interface ProfileInfo {
+  id: number;
+  bio: string;
+  phone: string;
+}
+
+export interface User {
+  id: number;
+  username: string;
+  profile?: ProfileInfo | null | undefined;
+}
+
+export interface UserById {
+  id: number;
+}
+
+function createBaseProfileInfo(): ProfileInfo {
+  return { id: 0, bio: "", phone: "" };
+}
+
+export const ProfileInfo = {
+  encode(message: ProfileInfo, writer: _m0.Writer = _m0.Writer.create()): _m0.Writer {
+    if (message.id !== 0) {
+      writer.uint32(8).int32(message.id);
+    }
+    if (message.bio !== "") {
+      writer.uint32(18).string(message.bio);
+    }
+    if (message.phone !== "") {
+      writer.uint32(26).string(message.phone);
+    }
+    return writer;
+  },
+
+  decode(input: _m0.Reader | Uint8Array, length?: number): ProfileInfo {
+    const reader = input instanceof _m0.Reader ? input : _m0.Reader.create(input);
+    let end = length === undefined ? reader.len : reader.pos + length;
+    const message = createBaseProfileInfo();
+    while (reader.pos < end) {
+      const tag = reader.uint32();
+      switch (tag >>> 3) {
+        case 1:
+          if (tag !== 8) {
+            break;
+          }
+
+          message.id = reader.int32();
+          continue;
+        case 2:
+          if (tag !== 18) {
+            break;
+          }
+
+          message.bio = reader.string();
+          continue;
+        case 3:
+          if (tag !== 26) {
+            break;
+          }
+
+          message.phone = reader.string();
+          continue;
+      }
+      if ((tag & 7) === 4 || tag === 0) {
+        break;
+      }
+      reader.skipType(tag & 7);
+    }
+    return message;
+  },
+
+  fromJSON(object: any): ProfileInfo {
+    return {
+      id: isSet(object.id) ? globalThis.Number(object.id) : 0,
+      bio: isSet(object.bio) ? globalThis.String(object.bio) : "",
+      phone: isSet(object.phone) ? globalThis.String(object.phone) : "",
+    };
+  },
+
+  toJSON(message: ProfileInfo): unknown {
+    const obj: any = {};
+    if (message.id !== 0) {
+      obj.id = Math.round(message.id);
+    }
+    if (message.bio !== "") {
+      obj.bio = message.bio;
+    }
+    if (message.phone !== "") {
+      obj.phone = message.phone;
+    }
+    return obj;
+  },
+
+  create<I extends Exact<DeepPartial<ProfileInfo>, I>>(base?: I): ProfileInfo {
+    return ProfileInfo.fromPartial(base ?? ({} as any));
+  },
+  fromPartial<I extends Exact<DeepPartial<ProfileInfo>, I>>(object: I): ProfileInfo {
+    const message = createBaseProfileInfo();
+    message.id = object.id ?? 0;
+    message.bio = object.bio ?? "";
+    message.phone = object.phone ?? "";
+    return message;
+  },
+};
+
+function createBaseUser(): User {
+  return { id: 0, username: "", profile: null };
+}
+
+export const User = {
+  encode(message: User, writer: _m0.Writer = _m0.Writer.create()): _m0.Writer {
+    if (message.id !== 0) {
+      writer.uint32(8).int32(message.id);
+    }
+    if (message.username !== "") {
+      writer.uint32(18).string(message.username);
+    }
+    if (message.profile !== undefined && message.profile !== null) {
+      ProfileInfo.encode(message.profile, writer.uint32(26).fork()).ldelim();
+    }
+    return writer;
+  },
+
+  decode(input: _m0.Reader | Uint8Array, length?: number): User {
+    const reader = input instanceof _m0.Reader ? input : _m0.Reader.create(input);
+    let end = length === undefined ? reader.len : reader.pos + length;
+    const message = createBaseUser();
+    while (reader.pos < end) {
+      const tag = reader.uint32();
+      switch (tag >>> 3) {
+        case 1:
+          if (tag !== 8) {
+            break;
+          }
+
+          message.id = reader.int32();
+          continue;
+        case 2:
+          if (tag !== 18) {
+            break;
+          }
+
+          message.username = reader.string();
+          continue;
+        case 3:
+          if (tag !== 26) {
+            break;
+          }
+
+          message.profile = ProfileInfo.decode(reader, reader.uint32());
+          continue;
+      }
+      if ((tag & 7) === 4 || tag === 0) {
+        break;
+      }
+      reader.skipType(tag & 7);
+    }
+    return message;
+  },
+
+  fromJSON(object: any): User {
+    return {
+      id: isSet(object.id) ? globalThis.Number(object.id) : 0,
+      username: isSet(object.username) ? globalThis.String(object.username) : "",
+      profile: isSet(object.profile) ? ProfileInfo.fromJSON(object.profile) : null,
+    };
+  },
+
+  toJSON(message: User): unknown {
+    const obj: any = {};
+    if (message.id !== 0) {
+      obj.id = Math.round(message.id);
+    }
+    if (message.username !== "") {
+      obj.username = message.username;
+    }
+    if (message.profile !== undefined && message.profile !== null) {
+      obj.profile = ProfileInfo.toJSON(message.profile);
+    }
+    return obj;
+  },
+
+  create<I extends Exact<DeepPartial<User>, I>>(base?: I): User {
+    return User.fromPartial(base ?? ({} as any));
+  },
+  fromPartial<I extends Exact<DeepPartial<User>, I>>(object: I): User {
+    const message = createBaseUser();
+    message.id = object.id ?? 0;
+    message.username = object.username ?? "";
+    message.profile = (object.profile !== undefined && object.profile !== null)
+      ? ProfileInfo.fromPartial(object.profile)
+      : undefined;
+    return message;
+  },
+};
+
+function createBaseUserById(): UserById {
+  return { id: 0 };
+}
+
+export const UserById = {
+  encode(message: UserById, writer: _m0.Writer = _m0.Writer.create()): _m0.Writer {
+    if (message.id !== 0) {
+      writer.uint32(8).int32(message.id);
+    }
+    return writer;
+  },
+
+  decode(input: _m0.Reader | Uint8Array, length?: number): UserById {
+    const reader = input instanceof _m0.Reader ? input : _m0.Reader.create(input);
+    let end = length === undefined ? reader.len : reader.pos + length;
+    const message = createBaseUserById();
+    while (reader.pos < end) {
+      const tag = reader.uint32();
+      switch (tag >>> 3) {
+        case 1:
+          if (tag !== 8) {
+            break;
+          }
+
+          message.id = reader.int32();
+          continue;
+      }
+      if ((tag & 7) === 4 || tag === 0) {
+        break;
+      }
+      reader.skipType(tag & 7);
+    }
+    return message;
+  },
+
+  fromJSON(object: any): UserById {
+    return { id: isSet(object.id) ? globalThis.Number(object.id) : 0 };
+  },
+
+  toJSON(message: UserById): unknown {
+    const obj: any = {};
+    if (message.id !== 0) {
+      obj.id = Math.round(message.id);
+    }
+    return obj;
+  },
+
+  create<I extends Exact<DeepPartial<UserById>, I>>(base?: I): UserById {
+    return UserById.fromPartial(base ?? ({} as any));
+  },
+  fromPartial<I extends Exact<DeepPartial<UserById>, I>>(object: I): UserById {
+    const message = createBaseUserById();
+    message.id = object.id ?? 0;
+    return message;
+  },
+};
+
+export interface HeroService {
+  FindOneHero(request: UserById): Promise<User>;
+}
+
+export const HeroServiceServiceName = "useNullAsOptional.HeroService";
+export class HeroServiceClientImpl implements HeroService {
+  private readonly rpc: Rpc;
+  private readonly service: string;
+  constructor(rpc: Rpc, opts?: { service?: string }) {
+    this.service = opts?.service || HeroServiceServiceName;
+    this.rpc = rpc;
+    this.FindOneHero = this.FindOneHero.bind(this);
+  }
+  FindOneHero(request: UserById): Promise<User> {
+    const data = UserById.encode(request).finish();
+    const promise = this.rpc.request(this.service, "FindOneHero", data);
+    return promise.then((data) => User.decode(_m0.Reader.create(data)));
+  }
+}
+
+interface Rpc {
+  request(service: string, method: string, data: Uint8Array): Promise<Uint8Array>;
+}
+
+type Builtin = Date | Function | Uint8Array | string | number | boolean | undefined;
+
+export type DeepPartial<T> = T extends Builtin ? T
+  : T extends globalThis.Array<infer U> ? globalThis.Array<DeepPartial<U>>
+  : T extends ReadonlyArray<infer U> ? ReadonlyArray<DeepPartial<U>>
+  : T extends {} ? { [K in keyof T]?: DeepPartial<T[K]> }
+  : Partial<T>;
+
+type KeysOfUnion<T> = T extends T ? keyof T : never;
+export type Exact<P, I extends P> = P extends Builtin ? P
+  : P & { [K in keyof P]: Exact<P[K], I[K]> } & { [K in Exclude<keyof I, KeysOfUnion<P>>]: never };
+
+function isSet(value: any): boolean {
+  return value !== null && value !== undefined;
+}