Experimental Typescript support

[stanley-cheung]

For #255

I am going to try to expand on this. For my very initial understanding, this seems to work.

Feedback highly appreciated!

cc: @jonahbron

[stanley-cheung]

So far, this PR demos how a typescript project can make use of the index.d.ts typings for the grpc-web module. I hand-wrote an echo_grpc_web_pb.ts file that could be generated from a future grpc-web x TS protoc plugin. To test whether the index.d.ts typings do matter, I flip, let's say, a method parameter from a string to a number. Now the tsc command will fail because a string is being passed.

To run:

$ docker-compose build ts-client
$ docker run -it --rm grpc-web:ts-client /bin/bash
$ cd /github/grpc-web/net/grpc/gateway/examples/echo/ts-example
$ node dist/client.js

[jonahbron]

That looks right to me. One alternative to the echo_grpc_web_pb.ts file I've seen in ts-protoc-gen is producing .d.ts for the generated files too. That way the JS generator can still be used as-is.

[aberasarte]

I think that we could add the suppressCorsPreflight option to the GrpcWebClientBaseOptions interface as well:

suppressCorsPreflight?: boolean

[stanley-cheung]

Will do.

[stanley-cheung]

That looks right to me. One alternative to the echo_grpc_web_pb.ts file I've seen in ts-protoc-gen is producing .d.ts for the generated files too. That way the JS generator can still be used as-is.

Will try that. Thanks.

[stanley-cheung]

Added a full Typescript example up to this point.

ts-example/EchoServiceClient.ts: a hand-written would-be full-TS codegen output

ts-example/echo_grpc_web_pb.d.ts: .d.ts typings that are meant to work alongside existing echo_grpc_web_pb.js CommonJS codegen output
ts-example/echo_pb.d.ts: .d.ts typings for protobuf message types, meant to work alongside echo_pb.js like above

ts-example/client.ts: TS client app code

Uncomment either Line 25 or Line 26 to try between the two modes above:

import {EchoServiceClient} from './echo_grpc_web_pb';   // .d.ts typings for existing JS codegen output
// import {EchoServiceClient} from './EchoServiceClient';  // full-TS codegen output

[stanley-cheung]

Added 2 modes to the protoc-gen-grpc-web protoc plugin

• import_style=commonjs+dts: this will generate .d.ts typings for both the <proto>_grpc_web_pb.js service stub and the <proto>_pb.js proto message classes
• import_style=typescript: this will generate <proto>ServiceClientPb.ts typescript service stub

[stanley-cheung]

Squashing commits. Got internal reviewed. Will merge this soon.