feat: support mapping ObjectId message as mongodb.ObjectId

README.markdown

@@ -161,6 +161,10 @@ creating a class and calling the right getters/setters.
 
 - `fromJSON`/`toJSON` use the [proto3 canonical JSON encoding format](https://developers.google.com/protocol-buffers/docs/proto3#json) (e.g. timestamps are ISO strings), unlike [`protobufjs`](https://github.com/protobufjs/protobuf.js/issues/1304). 
 
+- ObjectIds can be mapped as `mongodb.ObjectId`
+
+  (Configurable with the `useObjectId` parameter.)
+
 # Auto-Batching / N+1 Prevention
 
 (Note: this is currently only supported by the Twirp clients.)
@@ -333,6 +337,8 @@ Generated code will be placed in the Gradle build directory.
 
 - With `--ts_proto_opt=useDate=false`, fields of type `google.protobuf.Timestamp` will not be mapped to type `Date` in the generated types. See [Timestamp](#timestamp) for more details.
 
+- With `--ts_proto_opt=useObjectId=true`, fields of a type called ObjectId where the message is constructed to have on field called value that is a string will be mapped to type `mongodb.ObjectId` in the generated types. This will require your project to install the mongodb npm package. See [ObjectId](#objectid) for more details.
+
 - With `--ts_proto_opt=outputSchema=true`, meta typings will be generated that can later be used in other code generators.
 
 - With `--ts_proto_opt=outputTypeRegistry=true`, the type registry will be generated that can be used to resolve message types by fully-qualified name. Also, each message will get extra `$type` field containing fully-qualified name.
@@ -671,7 +677,6 @@ The representation of `google.protobuf.Timestamp` is configurable by the `useDat
 | --------------------------- | ---------------------- | ------------------------------------ | ---------------- |
 | `google.protobuf.Timestamp` | `Date`                 | `{ seconds: number, nanos: number }` | `string`         |
 
-
 # Number Types
 
 Numbers are by default assumed to be plain JavaScript `number`s.

integration/use-objectid-true-external-import/objectid/objectid.proto

@@ -0,0 +1,7 @@
+syntax = "proto3";
+
+package foo.objectid;
+
+message ObjectId {
+  string value = 1;
+}

integration/use-objectid-true-external-import/objectid/objectid.ts

@@ -0,0 +1,86 @@
+/* eslint-disable */
+import { util, configure, Writer, Reader } from 'protobufjs/minimal';
+import * as Long from 'long';
+
+export const protobufPackage = 'foo.objectid';
+
+export interface ObjectId {
+  value: string;
+}
+
+function createBaseObjectId(): ObjectId {
+  return { value: '' };
+}
+
+export const ObjectId = {
+  encode(message: ObjectId, writer: Writer = Writer.create()): Writer {
+    if (message.value !== '') {
+      writer.uint32(10).string(message.value);
+    }
+    return writer;
+  },
+
+  decode(input: Reader | Uint8Array, length?: number): ObjectId {
+    const reader = input instanceof Reader ? input : new Reader(input);
+    let end = length === undefined ? reader.len : reader.pos + length;
+    const message = createBaseObjectId();
+    while (reader.pos < end) {
+      const tag = reader.uint32();
+      switch (tag >>> 3) {
+        case 1:
+          message.value = reader.string();
+          break;
+        default:
+          reader.skipType(tag & 7);
+          break;
+      }
+    }
+    return message;
+  },
+
+  fromJSON(object: any): ObjectId {
+    return {
+      value: isSet(object.value) ? String(object.value) : '',
+    };
+  },
+
+  toJSON(message: ObjectId): unknown {
+    const obj: any = {};
+    message.value !== undefined && (obj.value = message.value);
+    return obj;
+  },
+
+  fromPartial<I extends Exact<DeepPartial<ObjectId>, I>>(object: I): ObjectId {
+    const message = createBaseObjectId();
+    message.value = object.value ?? '';
+    return message;
+  },
+};
+
+type Builtin = Date | Function | Uint8Array | string | number | boolean | undefined;
+
+export type DeepPartial<T> = T extends Builtin
+  ? T
+  : T extends Array<infer U>
+  ? 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]> } & Record<Exclude<keyof I, KeysOfUnion<P>>, never>;
+
+// If you get a compile-error about 'Constructor<Long> and ... have no overlap',
+// add '--ts_proto_opt=esModuleInterop=true' as a flag when calling 'protoc'.
+if (util.Long !== Long) {
+  util.Long = Long as any;
+  configure();
+}
+
+function isSet(value: any): boolean {
+  return value !== null && value !== undefined;
+}

integration/use-objectid-true-external-import/parameters.txt

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

integration/use-objectid-true-external-import/use-objectid-true-external-import-test.ts

@@ -0,0 +1,51 @@
+import { Todo } from './use-objectid-true';
+
+import * as mongodb from 'mongodb';
+
+const id1 = new mongodb.ObjectId();
+const id2 = new mongodb.ObjectId();
+
+describe('useMongoObjectId=true External Import', () => {
+  it('generates types that compile and encode', () => {
+    const output = Todo.encode({
+      id: '6883ed6e-bd0d-4817-ba58-c2a53c73edc2',
+      oid: id1,
+      repeatedOid: [id1, id2],
+      mapOfOids: {
+        id1,
+        id2,
+      },
+    }).finish();
+
+    expect(Todo.decode(output)).toMatchInlineSnapshot(`
+      Object {
+        "id": "6883ed6e-bd0d-4817-ba58-c2a53c73edc2",
+        "mapOfOids": Object {
+          "id1": "${id1.toString()}",
+          "id2": "${id2.toString()}",
+        },
+        "oid": "${id1.toString()}",
+        "optionalOid": undefined,
+        "repeatedOid": Array [
+          "${id1.toString()}",
+          "${id2.toString()}",
+        ],
+      }
+    `);
+
+    expect(Todo.toJSON(Todo.decode(output))).toMatchInlineSnapshot(`
+      Object {
+        "id": "6883ed6e-bd0d-4817-ba58-c2a53c73edc2",
+        "mapOfOids": Object {
+          "id1": "${id1.toString()}",
+          "id2": "${id2.toString()}",
+        },
+        "oid": "${id1.toString()}",
+        "repeatedOid": Array [
+          "${id1.toString()}",
+          "${id2.toString()}",
+        ],
+      }
+    `);
+  });
+});

integration/use-objectid-true-external-import/use-objectid-true.proto

@@ -0,0 +1,13 @@
+syntax = "proto3";
+
+package foo;
+
+import "objectid/objectid.proto";
+
+message Todo {
+  string id = 1;
+  foo.objectid.ObjectId oid = 2;
+  repeated foo.objectid.ObjectId repeated_oid = 3;
+  optional foo.objectid.ObjectId optional_oid = 4;
+  map<string, foo.objectid.ObjectId> map_of_oids = 5;
+}