Add support for jstype annotation

Required an upgrade to google-protobuf 3.6.1, otherwise very straight forward.

Fixes #17

README.md

@@ -172,3 +172,12 @@ client.getUser(req, (err, user) => { /* ... */ });
 For a sample of the generated protos and service definitions, see [examples](https://github.com/improbable-eng/ts-protoc-gen/tree/master/examples).
 
 To generate the examples from protos, please run `./generate.sh`
+
+## Gotchas
+By default the google-protobuf library will use the JavaScript number type to store 64bit float and integer values; this can lead to overflow problems as you exceed JavaScript's `Number.MAX_VALUE`. To work around this, you should consider using the `jstype` annotation on any 64bit fields, ie:
+
+```proto
+message Example {
+  uint64 bigInt = 1 [jstype = JS_STRING];
+}
+```

package.json

@@ -29,7 +29,7 @@
   "author": "Improbable",
   "license": "Apache-2.0",
   "dependencies": {
-    "google-protobuf": "^3.5.0"
+    "google-protobuf": "^3.6.1"
   },
   "devDependencies": {
     "@types/chai": "^3.5.2",

proto/examplecom/annotations.proto

@@ -0,0 +1,7 @@
+syntax = "proto3";
+
+package examplecom;
+
+message AnnotatedMessage {
+  uint64 bigInt = 1 [jstype = JS_STRING];
+}

src/ts/message.ts

@@ -3,12 +3,16 @@ import {
   withinNamespaceFromExportEntry, normaliseFieldObjectName
 } from "../util";
 import {ExportMap} from "../ExportMap";
-import {FieldDescriptorProto, FileDescriptorProto, DescriptorProto} from "google-protobuf/google/protobuf/descriptor_pb";
+import {
+  FieldDescriptorProto, FileDescriptorProto, DescriptorProto,
+  FieldOptions
+} from "google-protobuf/google/protobuf/descriptor_pb";
 import {MESSAGE_TYPE, BYTES_TYPE, ENUM_TYPE, getFieldType, getTypeName} from "./FieldTypes";
 import {Printer} from "../Printer";
 import {printEnum} from "./enum";
 import {printOneOfDecl} from "./oneof";
 import {printExtension} from "./extensions";
+import JSType = FieldOptions.JSType;
 
 function hasFieldPresence(field: FieldDescriptorProto, fileDescriptor: FileDescriptorProto): boolean {
   if (field.getLabel() === FieldDescriptorProto.Label.LABEL_REPEATED) {
@@ -104,7 +108,20 @@ export function printMessage(fileName: string, exportMap: ExportMap, messageDesc
         exportType = filePathToPseudoNamespace(fieldEnumType.fileName) + "." + withinNamespace;
       }
     } else {
-      exportType = getTypeName(type);
+      if (field.getOptions() && field.getOptions().hasJstype()) {
+        switch (field.getOptions().getJstype()) {
+          case JSType.JS_NUMBER:
+            exportType = "number";
+            break;
+          case JSType.JS_STRING:
+            exportType = "string";
+            break;
+          default:
+            exportType = getTypeName(type);
+        }
+      } else {
+        exportType = getTypeName(type);
+      }
     }
 
     let hasClearMethod = false;

test/integration/annotations.ts

@@ -0,0 +1,10 @@
+import { assert } from "chai";
+import { AnnotatedMessage } from "../../examples/generated/proto/examplecom/annotations_pb";
+
+describe("annotations", () => {
+  it("should detect and honor the `jstype` annotation", () => {
+    const msg = new AnnotatedMessage();
+    msg.setBigint("123456789123456789");
+    assert.strictEqual(msg.getBigint(), "123456789123456789");
+  });
+});