Fix proto3 extension presence for singular, non-optional scalar (#689)

bufbuild · Jan 31, 2024 · eeb911a · eeb911a
1 parent 8a021d7
commit eeb911a
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Showing 3 changed files with 12 additions and 4 deletions.
diff --git a/packages/protobuf-bench/README.md b/packages/protobuf-bench/README.md
@@ -10,5 +10,5 @@ server would usually do.
 
 | code generator      | bundle size             | minified               | compressed         |
 |---------------------|------------------------:|-----------------------:|-------------------:|
-| protobuf-es         | 96,275 b      | 41,035 b | 10,663 b |
+| protobuf-es         | 96,441 b      | 41,150 b | 10,720 b |
 | protobuf-javascript | 394,384 b  | 288,654 b | 45,122 b |
diff --git a/packages/protobuf-test/src/extensions-proto3.test.ts b/packages/protobuf-test/src/extensions-proto3.test.ts
@@ -55,10 +55,11 @@ describe("setExtension() proto3", () => {
       expect(hasExtension(msg, ext)).toBeTruthy();
       expect(getExtension(msg, ext)).toStrictEqual(123);
     });
-    it("should not set zero value", () => {
+    it("should set zero value, even without optional keyword", () => {
+      // Implicit presence does not apply to extensions, see https://github.com/protocolbuffers/protobuf/issues/8234
       const msg = new FileOptions();
       setExtension(msg, ext, 0);
-      expect(hasExtension(msg, ext)).toBeFalsy();
+      expect(hasExtension(msg, ext)).toBeTruthy();
       expect(getExtension(msg, ext)).toStrictEqual(0);
     });
   });

diff --git a/packages/protobuf/src/extension-accessor.ts b/packages/protobuf/src/extension-accessor.ts
@@ -20,6 +20,7 @@ import {
   filterUnknownFields,
 } from "./private/extensions.js";
 import type { Extension } from "./extension.js";
+import type { FieldInfo } from "./field.js";
 
 /**
  * Retrieve an extension value from a message.
@@ -87,7 +88,13 @@ export function setExtension<E extends Message<E>, V>(
     }
   }
   const writer = writeOpt.writerFactory();
-  extension.runtime.bin.writeField(extension.field, value, writer, writeOpt);
+  let f: FieldInfo = extension.field;
+  // Implicit presence does not apply to extensions, see https://github.com/protocolbuffers/protobuf/issues/8234
+  // We patch the field info to use explicit presence:
+  if (!f.opt && !f.repeated && (f.kind == "enum" || f.kind == "scalar")) {
+    f = { ...extension.field, opt: true } as FieldInfo;
+  }
+  extension.runtime.bin.writeField(f, value, writer, writeOpt);
   const reader = readOpt.readerFactory(writer.finish());
   while (reader.pos < reader.len) {
     const [no, wireType] = reader.tag();