From 1b1e9a7861b9f6dbddf81676e606f243209147d1 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sun, 28 Dec 2025 05:56:50 +0000
Subject: [PATCH] feat: implement oneof parsing in simplified proto parser

- Implemented `extractBalancedBody` helper to robustly handle nested braces in proto files, replacing fragile regex-based parsing.
- Updated `parseMessages` to use balanced brace extraction, allowing correct parsing of messages containing nested blocks like `oneof`.
- Implemented `parseOneofs` to extract and parse `oneof` definitions within messages.
- Verified changes by adding a test case with `oneof` fields in `packages/test-client/src/service.proto` and running `packages/test-client/test-parser.js`.
---
 packages/test-client/proto-parser.js   | 85 ++++++++++++++++++++++----
 packages/test-client/src/service.proto |  8 +++
 packages/test-client/test-parser.js    | 19 ++++++
 3 files changed, 99 insertions(+), 13 deletions(-)

diff --git a/packages/test-client/proto-parser.js b/packages/test-client/proto-parser.js
index 45c478a..8431723 100644
--- a/packages/test-client/proto-parser.js
+++ b/packages/test-client/proto-parser.js
@@ -110,23 +110,28 @@ function parseMethods(serviceBody) {
  */
 function parseMessages(content) {
   const messages = [];
-  const messageRegex = /message\s+(\w+)\s*\{([^}]+)\}/g;
+  const messageRegex = /message\s+(\w+)\s*\{/g;
   let messageMatch;
 
   while ((messageMatch = messageRegex.exec(content)) !== null) {
     const messageName = messageMatch[1];
-    const messageBody = messageMatch[2];
-
-    const message = {
-      name: messageName,
-      fields: parseFields(messageBody),
-      nestedMessages: [], // TODO: Handle nested messages
-      nestedEnums: [],    // TODO: Handle nested enums
-      oneofs: [],         // TODO: Handle oneofs
-      options: {}
-    };
-
-    messages.push(message);
+    const openBraceIndex = messageMatch.index + messageMatch[0].length - 1;
+
+    const [messageBody, endIndex] = extractBalancedBody(content, openBraceIndex);
+
+    if (messageBody !== null) {
+      const message = {
+        name: messageName,
+        fields: parseFields(messageBody),
+        nestedMessages: [], // TODO: Handle nested messages
+        nestedEnums: [],    // TODO: Handle nested enums
+        oneofs: parseOneofs(messageBody),
+        options: {}
+      };
+
+      messages.push(message);
+      messageRegex.lastIndex = endIndex;
+    }
   }
 
   return messages;
@@ -213,3 +218,57 @@ function parseEnumValues(enumBody) {
 module.exports = {
   parseProtoFile
 };
+
+/**
+ * Parse oneof definitions from message body
+ */
+function parseOneofs(messageBody) {
+  const oneofs = [];
+  const oneofRegex = /oneof\s+(\w+)\s*\{/g;
+  let oneofMatch;
+
+  while ((oneofMatch = oneofRegex.exec(messageBody)) !== null) {
+    const oneofName = oneofMatch[1];
+    const openBraceIndex = oneofMatch.index + oneofMatch[0].length - 1;
+
+    const [oneofBody, endIndex] = extractBalancedBody(messageBody, openBraceIndex);
+
+    if (oneofBody !== null) {
+      const oneof = {
+        name: oneofName,
+        fields: parseFields(oneofBody)
+      };
+
+      oneofs.push(oneof);
+      oneofRegex.lastIndex = endIndex;
+    }
+  }
+
+  return oneofs;
+}
+
+/**
+ * Helper to extract content inside balanced braces
+ * @param {string} content - Full content
+ * @param {number} startIndex - Index of the opening brace
+ * @returns {[string|null, number]} - [extracted content, end index]
+ */
+function extractBalancedBody(content, startIndex) {
+  let depth = 1;
+  let i = startIndex + 1;
+
+  while (i < content.length && depth > 0) {
+    if (content[i] === '{') {
+      depth++;
+    } else if (content[i] === '}') {
+      depth--;
+    }
+    i++;
+  }
+
+  if (depth === 0) {
+    return [content.substring(startIndex + 1, i - 1), i];
+  }
+
+  return [null, i];
+}
diff --git a/packages/test-client/src/service.proto b/packages/test-client/src/service.proto
index 4f25f56..bb4b7d2 100644
--- a/packages/test-client/src/service.proto
+++ b/packages/test-client/src/service.proto
@@ -47,3 +47,11 @@ service UserService {
   // Bidirectional streaming RPC
   rpc Chat(stream StreamMessage) returns (stream StreamMessage);
 }
+
+message OneofMessage {
+  string id = 1;
+  oneof test_oneof {
+    string name = 2;
+    int32 age = 3;
+  }
+}
diff --git a/packages/test-client/test-parser.js b/packages/test-client/test-parser.js
index 01ce259..2b83923 100644
--- a/packages/test-client/test-parser.js
+++ b/packages/test-client/test-parser.js
@@ -46,6 +46,13 @@ protoFile.messages.forEach(message => {
     const typeStr = field.repeated ? `repeated ${field.type}` : field.type;
     console.log(`     • ${field.name}: ${typeStr} = ${field.number}`);
   });
+  console.log(`   - oneofs: ${message.oneofs.length}`);
+  message.oneofs.forEach(oneof => {
+    console.log(`     • Oneof: ${oneof.name}`);
+    oneof.fields.forEach(field => {
+       console.log(`       - ${field.name}: ${field.type} = ${field.number}`);
+    });
+  });
 });
 console.log();
 
@@ -112,6 +119,18 @@ if (protoFile.messages.length > 0) {
       console.log(`   ❌ Field missing fields: ${missingFieldFields.join(', ')}`);
     }
   }
+
+  // Check oneof structure
+  if (message.oneofs.length > 0) {
+     const oneof = message.oneofs[0];
+     const oneofFields = ['name', 'fields'];
+     const missingOneofFields = oneofFields.filter(f => !(f in oneof));
+     if (missingOneofFields.length === 0) {
+        console.log('   ✅ Oneof structure valid');
+     } else {
+        console.log(`   ❌ Oneof missing fields: ${missingOneofFields.join(', ')}`);
+     }
+  }
 }
 
 console.log();