Generate Typescript definition for top level Enums

[rogchap]

Fixes #403

[stanley-cheung]

Thanks for the great contributions! Yea looks like this is a gap that we need to address.

On the other hand, I'd like to start requesting contributors to also add tests for features they added. We already have some tests - running npm test from the packages/grpc-web directory will trigger those.

This PR will fit in to something like https://github.com/grpc/grpc-web/blob/master/packages/grpc-web/test/plugin_test.js. In that test, we assume the protoc-gen-grpc-web is already installed somewhere in the system (in reality, before npm test is run, we will re-compile the plugin every time a PR is updated), then we run the protoc ... --grpc-web_out=... command to actually generate the client stub (you can make up a new .proto file highlighting the Enum change), load the generated stub file via a require() statement and do some test on the client stub class.

Let's do something similar and add a test for this Enum feature.

Thanks!

[rogchap]

@stanley-cheung Totally agree that we should have tests for this.
Hard to load the file via require() as the JS is untouched and it's the TypeScript generation that we need to test.
Do you have any advise on how to test the TypeScript generation; my best thought is doing a string comparison/regex on the file, but that seems ugly.

[stanley-cheung]

I am also hoping someone from the community can give us some advice on how's best to test TS code generation.

Quick thought: perhaps we can exec('tsc')? At least that should weed out some TS compilation errors. I am actually not sure what's the "standard" way of testing TS code in a npm package these days. Also kinda new to this :)

[johanbrandhorst]

Looking at the TS protoc generator Improbable has written, it seems they generate the files and just check properties on the generated types: https://github.com/improbable-eng/ts-protoc-gen/blob/master/test/integration/service/grpcweb.ts.

[rogchap]

From what I understand this would still just test the properties on the compiled JavaScript and not the actual TypeScript file itself; it just looks that way because the test itself is in TypeScript and can import the definition.

[johanbrandhorst]

I plead ignorance, I just wanted to point to the Improbable repo as a possible source for inspiration for writing tests for this repo :).

[rogchap]

So... I've added a basic test to make sure the TypeScript can compile. I manually tested tsc to see if it would fails on a malformed typescript definition file, which it does; so at least we know the TypeScript is right as far as it can compile.

The thing is, we can't test any output from the TypeScript to validate as this is only a definition file and the actual JS is already generated 💁‍♂️.

[stanley-cheung]

LGTM. Thanks for adding the tests!

[pacurtin]

Awesome work you guys are doing. I'm currently using JS web-grpc but I'm looking forward to switching to TS. I'm waiting for this fix to be released so I can do so.

Sorry if this is the wrong place to ask but do you know when the next release is scheduled for?