load protobuf.js JSON descriptor

packages/proto-loader/src/index.ts

@@ -395,6 +395,23 @@ export function loadSync(
   return createPackageDefinition(root, options!);
 }
 
+export function fromJSON(
+  json: Protobuf.INamespace,
+  root?: Protobuf.Root
+): PackageDefinition {
+  const options: Options = json.options || {};
+  const newRoot: Protobuf.Root = root || new Protobuf.Root();
+  if (!!options.includeDirs) {
+    if (!Array.isArray(options.includeDirs)) {
+      throw new Error('The includeDirs option must be an array');
+    }
+    addIncludePathResolver(newRoot, options.includeDirs as string[]);
+  }
+  const loadedRoot = Protobuf.Root.fromJSON(json, newRoot);
+  loadedRoot.resolveAll();
+  return createPackageDefinition(newRoot, options!);
+}
+
 export function loadFileDescriptorSetFromBuffer(
   descriptorSet: Buffer,
   options?: Options

packages/proto-loader/test/descriptor_type_test.ts

@@ -102,6 +102,15 @@ describe('Descriptor types', () => {
     proto_loader.loadSync(`${TEST_PROTO_DIR}/well_known.proto`);
   });
 
+  it('Can load JSON descriptors', () => {
+    // This is protobuf.js JSON descriptor
+    // https://github.com/protobufjs/protobuf.js#using-json-descriptors
+    const buffer = readFileSync(`${TEST_PROTO_DIR}/rpc.proto.json`);
+    const json = JSON.parse(buffer.toString());
+    // This will throw if the rpc descriptor JSON cannot be decoded
+    proto_loader.fromJSON(json);
+  });
+
   it('Can load binary-encoded proto file descriptor sets', () => {
     const buffer = readFileSync(`${TEST_PROTO_DIR}/rpc.desc.bin`);
     // This will throw if the rpc descriptor cannot be decoded

packages/proto-loader/test_protos/rpc.proto.json

@@ -0,0 +1,16 @@
+{
+  "nested": {
+    "awesomepackage": {
+      "nested": {
+        "AwesomeMessage": {
+          "fields": {
+            "awesomeField": {
+              "type": "string",
+              "id": 1
+            }
+          }
+        }
+      }
+    }
+  }
+}