Hello World!

Proof of concept protoc-plugin for generating service clients for use with @improbable-eng/grpc-web.

## Why?
See conversation in improbable-eng/ts-protoc-gen#145

## Design Choices
1. This package uses [protoc-plugin](https://github.com/konsumer/node-protoc-plugin) which provides the ability to [extract comments from the source proto](https://github.com/konsumer/node-protoc-plugin#findcommentbypath) and in-line them into the generated code; this was a much requested feature on ts-protoc-gen

2. [ts-morph](https://dsherret.github.io/ts-morph/) is used to build TypeScript source code in-line; this is then compiled into TypeScript definition files (`.d.ts`) and JavaScript source files. This is great as it reduces the number of code-paths required.

## What's left to do?
Loads, off the top of my head:

1. Generate service clients, at present we are only generating classes required to use directly against grpc-web ("Raw!")
2. Add unit/integration test coverage!
3. Add support for in-lined documentation from source protos.

client/protoc-gen-improbable-grpc-web/README.md

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+# @improbable-eng/protoc-gen-improbable-grpc-web
+protoc-plugin for generating @improbable-eng/grpc-web service clients. 
+
+## Usage
+This plugin should be used in conjunction with the [protoc-js plugin](https://developers.google.com/protocol-buffers/docs/reference/javascript-generated) with the following caveats: 
+1. The output directory must be consistent between both plugins (ie: `js_out` and `improbable-grpc-web_out`).
+2. You must use `import_style=commonjs,binary` in your protoc-js plugin configuration.
+
+```bash
+OUT_DIR="generated"
+protoc \
+    --plugin=protoc-gen-improbable-grpc-web=./bin/protoc-gen-improbable-grpc-web \
+    --js_out=import_style=commonjs,binary:${OUT_DIR} \
+    --improbable-grpc-web_out=${OUT_DIR} \
+    ./proto/some.proto
+```

client/protoc-gen-improbable-grpc-web/bin/protoc-gen-improbable-grpc-web

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+#!/usr/bin/env node
+
+require('../lib/index');

client/protoc-gen-improbable-grpc-web/generate-protos.sh

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+#!/bin/bash
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd -P)"
+PROTOBUF_DIR=${PROTOBUF_DIR-${SCRIPT_DIR}/proto}
+PROTOGEN_DIR=generated/_proto
+GENERATION_DIR=${GENERATION_DIR-${SCRIPT_DIR}/${PROTOGEN_DIR}}
+
+mkdir -p ${GENERATION_DIR} 2> /dev/null
+PROTO_SOURCES=$(npx glob-cli2 './proto/**/*.proto')
+
+protoc \
+    --plugin=protoc-gen-improbable-grpc-web=./bin/protoc-gen-improbable-grpc-web \
+    --js_out=import_style=commonjs,binary:${GENERATION_DIR} \
+    --improbable-grpc-web_out=service=true:${GENERATION_DIR} \
+    ${PROTO_SOURCES}