Support nested fields, path segments

Closes grpc-ecosystem#28

Adds support for 2 related cases in URLs:
* Support path segments like in https://google.aip.dev/127, where the
  URL contains a pattern like `post: "/v1/{parent=publishers/*}/books"`
* Support nested field names in the URL, where the URL is structured
  like:
  ```
    option (google.api.http) = {
      patch: "/v3/{intent.name=projects/*/locations/*/agents/*/intents/*}"
      body: "intent"
    };
  ```
  This gets translated to `/v3/${req["intent"]["name"]}`

While here, use the newer protoc-gen-go-grpc plugin for generating
server test code, due to deprecated usage of plugin=grpc (see
https://github.com/protocolbuffers/protobuf-go/releases/tag/v1.20.0#v1.20-grpc-support)

generator/template.go

@@ -468,15 +468,24 @@ func renderURL(r *registry.Registry) func(method data.Method) string {
 	fieldNameFn := fieldName(r)
 	return func(method data.Method) string {
 		methodURL := method.URL
-		reg := regexp.MustCompile("{([^}]+)}")
+		// capture fields like {abc} or {abc=def/ghi/*}. Discard the pattern after the equal sign.
+		reg := regexp.MustCompile("{([^=}]+)=?([^}]+)?}")
 		matches := reg.FindAllStringSubmatch(methodURL, -1)
 		fieldsInPath := make([]string, 0, len(matches))
 		if len(matches) > 0 {
 			log.Debugf("url matches %v", matches)
 			for _, m := range matches {
 				expToReplace := m[0]
-				fieldName := fieldNameFn(m[1])
-				part := fmt.Sprintf(`${req["%s"]}`, fieldName)
+				// convert foo_bar.baz_qux to fieldName `fooBar.bazQux`, part `${req["fooBar"]["bazQux"]}`
+				subFields := strings.Split(m[1], ".")
+				var subFieldNames, partNames []string
+				for _, subField := range subFields {
+					subFieldName := fieldNameFn(subField)
+					subFieldNames = append(subFieldNames, subFieldName)
+					partNames = append(partNames, fmt.Sprintf(`["%s"]`, subFieldName))
+				}
+				fieldName := strings.Join(subFieldNames, ".")
+				part := fmt.Sprintf(`${req%s}`, strings.Join(partNames, ""))
 				methodURL = strings.ReplaceAll(methodURL, expToReplace, part)
 				fieldsInPath = append(fieldsInPath, fmt.Sprintf(`"%s"`, fieldName))
 			}

integration_tests/integration_test.ts

@@ -87,4 +87,19 @@ describe("test grpc-gateway-ts communication", () => {
     const result = await CounterService.HTTPGetWithZeroValueURLSearchParams({ a: "A", b: "", [getFieldName('zero_value_msg')]: { c: 1, d: [1, 0, 2], e: false } }, { pathPrefix: "http://localhost:8081" })
     expect(result).to.deep.equal({ a: "A", b: "hello", [getFieldName('zero_value_msg')]: { c: 2, d: [2, 1, 3], e: true } })
   })
+
+  it('http get request with path segments', async () => {
+    const result = await CounterService.HTTPGetWithPathSegments({ a: "segmented/foo" }, { pathPrefix: "http://localhost:8081" })
+    expect(result.a).to.equal("segmented/foo/hello")
+  })
+
+  it('http post with field paths', async () => {
+    const result = await CounterService.HTTPPostWithFieldPath({ y: { x: 5, [getFieldName("nested_value")]: "foo" } }, { pathPrefix: "http://localhost:8081" })
+    expect(result).to.deep.equal({ xout: 5, yout: "hello/foo" })
+  })
+
+  it('http post with field paths and path segments', async () => {
+    const result = await CounterService.HTTPPostWithFieldPathAndSegments({ y: { x: 10, [getFieldName("nested_value")]: "segmented/foo" } }, { pathPrefix: "http://localhost:8081" })
+    expect(result).to.deep.equal({ xout: 10, yout: "hello/segmented/foo" })
+  })
 })

integration_tests/scripts/gen-server-proto.sh

@@ -1,14 +1,15 @@
 #!/bin/bash
 
 # remove binaries to ensure that binaries present in tools.go are installed
-rm -f $GOBIN/protoc-gen-go $GOBIN/protoc-gen-grpc-gateway $GOBIN/protoc-gen-swagger
+rm -f $GOBIN/protoc-gen-go $GOBIN/protoc-gen-go-grpc $GOBIN/protoc-gen-grpc-gateway $GOBIN/protoc-gen-swagger
 
 go install \
-	github.com/golang/protobuf/protoc-gen-go \
+	google.golang.org/protobuf/cmd/protoc-gen-go \
+	google.golang.org/grpc/cmd/protoc-gen-go-grpc \
 	github.com/grpc-ecosystem/grpc-gateway/protoc-gen-grpc-gateway \
 	github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger
 
-protoc -I . -I ../.. --go_out ./ --go_opt plugins=grpc --go_opt paths=source_relative \
+protoc -I . -I ../.. --go_out ./ --go-grpc_out ./ --go-grpc_opt paths=source_relative \
 	--grpc-gateway_out ./ --grpc-gateway_opt logtostderr=true \
 	--grpc-gateway_opt paths=source_relative \
 	--grpc-gateway_opt generate_unbound_methods=true \

integration_tests/service.go

@@ -107,3 +107,23 @@ func (r *RealCounterService) HTTPGetWithZeroValueURLSearchParams(ctx context.Con
 		},
 	}, nil
 }
+
+func (r *RealCounterService) HTTPGetWithPathSegments(ctx context.Context, in *HTTPGetWithPathSegmentsRequest) (*HTTPGetWithPathSegmentsResponse, error) {
+	return &HTTPGetWithPathSegmentsResponse{
+		A: in.GetA() + "/hello",
+	}, nil
+}
+
+func (r *RealCounterService) HTTPPostWithFieldPath(ctx context.Context, in *HTTPPostWithFieldPathRequest) (*HTTPPostWithFieldPathResponse, error) {
+	return &HTTPPostWithFieldPathResponse{
+		Xout: in.GetY().GetX(),
+		Yout: "hello/" + in.GetY().GetNestedValue(),
+	}, nil
+}
+
+func (r *RealCounterService) HTTPPostWithFieldPathAndSegments(ctx context.Context, in *HTTPPostWithFieldPathRequest) (*HTTPPostWithFieldPathResponse, error) {
+	return &HTTPPostWithFieldPathResponse{
+		Xout: in.GetY().GetX(),
+		Yout: "hello/" + in.GetY().GetNestedValue(),
+	}, nil
+}