feat: implemented emitImportedFiles flag

Fixes stephenh#294.
This commit puts changes from stephenh#283 behind the flag.

README.markdown

@@ -305,6 +305,9 @@ protoc --plugin=node_modules/ts-proto/protoc-gen-ts_proto ./batching.proto -I.
 
 - With `--ts_proto_opt=outputServices=grpc-js`, ts-proto will output service definitions and server / client stubs in [grpc-js](https://github.com/grpc/grpc-node/tree/master/packages/grpc-js) format.
 
+- With `--ts_proto_opt=emitImportedFiles=false`, ts-proto will not emit `google/protobuf/*` files unless you explicit add files to `protoc` like this
+`protoc --plugin=./node_modules/.bin/protoc-gen-ts_proto my_message.proto google/protobuf/duration.proto`
+
 ### Only Types
 
 If you're looking for `ts-proto` to generate only types for your Protobuf types then passing all three of `outputEncodeMethods`, `outputJsonMethods`, and `outputClientImpl` as `false` is probably what you want, i.e.:

src/options.ts

@@ -48,6 +48,7 @@ export type Options = {
   outputSchema: boolean;
   // An alias of !output
   onlyTypes: boolean;
+  emitImportedFiles: boolean;
 };
 
 export function defaultOptions(): Options {
@@ -77,6 +78,7 @@ export function defaultOptions(): Options {
     exportCommonSymbols: true,
     outputSchema: false,
     onlyTypes: false,
+    emitImportedFiles: true,
   };
 }
 

src/plugin.ts

@@ -24,8 +24,9 @@ async function main() {
   const utils = makeUtils(options);
   const ctx: Context = { typeMap, options, utils };
 
+  const filesToGenerate = options.emitImportedFiles ? request.protoFile : protoFilesToGenerate(request);
   const files = await Promise.all(
-    protoFilesToGenerate(request).map(async (file) => {
+    filesToGenerate.map(async (file) => {
       const [path, code] = generateFile(ctx, file);
       const spec = await code.toStringWithImports({ ...getTsPoetOpts(options), path });
       return { name: path, content: prefixDisableLinter(spec) };

tests/options-test.ts

@@ -8,6 +8,7 @@ describe('options', () => {
         "addNestjsRestParameter": false,
         "constEnums": false,
         "context": false,
+        "emitImportedFiles": true,
         "env": "both",
         "esModuleInterop": false,
         "exportCommonSymbols": true,