compat: Buffer: allow optional positional arguments to be undefined (#4911)

* fix `Buffer` compat with Node.js: compare

* fix `Buffer` compat with Node.js: copy

1 files changed, 51 insertions, 14 deletions

diff --git a/src/bun.js/bindings/JSBuffer.cpp b/src/bun.js/bindings/JSBuffer.cpp
index 0ff8b76a5..f77cffac3 100644
--- a/src/bun.js/bindings/JSBuffer.cpp
+++ b/src/bun.js/bindings/JSBuffer.cpp
@@ -865,28 +865,49 @@ static inline JSC::EncodedJSValue jsBufferPrototypeFunction_compareBody(JSC::JSG
     size_t sourceEndInit = castedThis->byteLength();
     size_t sourceEnd = sourceEndInit;
 
+    JSValue targetStartValue = jsUndefined();
+    JSValue targetEndValue = jsUndefined();
+    JSValue sourceStartValue = jsUndefined();
+    JSValue sourceEndValue = jsUndefined();
+
     switch (callFrame->argumentCount()) {
     default:
-        sourceEnd = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(4));
-        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+        sourceEndValue = callFrame->uncheckedArgument(4);
         FALLTHROUGH;
     case 4:
-        sourceStart = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(3));
-        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+        sourceStartValue = callFrame->uncheckedArgument(3);
         FALLTHROUGH;
     case 3:
-        targetEnd = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(2));
-        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+        targetEndValue = callFrame->uncheckedArgument(2);
         FALLTHROUGH;
     case 2:
-        targetStart = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(1));
-        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+        targetStartValue = callFrame->uncheckedArgument(1);
         break;
     case 1:
     case 0:
         break;
     }
 
+    if (!targetStartValue.isUndefined()) {
+        targetStart = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(1));
+        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+    }
+
+    if (!targetEndValue.isUndefined()) {
+        targetEnd = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(2));
+        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+    }
+
+    if (!sourceStartValue.isUndefined()) {
+        sourceStart = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(3));
+        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+    }
+
+    if (!sourceEndValue.isUndefined()) {
+        sourceEnd = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(4));
+        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+    }
+
     targetStart = std::min(targetStart, std::min(targetEnd, targetEndInit));
     sourceStart = std::min(sourceStart, std::min(sourceEnd, sourceEndInit));
 
@@ -931,24 +952,40 @@ static inline JSC::EncodedJSValue jsBufferPrototypeFunction_copyBody(JSC::JSGlob
     size_t sourceEndInit = castedThis->byteLength();
     size_t sourceEnd = sourceEndInit;
 
+    JSValue targetStartValue = jsUndefined();
+    JSValue sourceStartValue = jsUndefined();
+    JSValue sourceEndValue = jsUndefined();
+
     switch (callFrame->argumentCount()) {
     default:
-        sourceEnd = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(3));
-        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+        sourceEndValue = callFrame->uncheckedArgument(3);
         FALLTHROUGH;
     case 3:
-        sourceStart = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(2));
-        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+        sourceStartValue = callFrame->uncheckedArgument(2);
         FALLTHROUGH;
     case 2:
-        targetStart = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(1));
-        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+        targetStartValue = callFrame->uncheckedArgument(1);
         break;
     case 1:
     case 0:
         break;
     }
 
+    if (!targetStartValue.isUndefined()) {
+        targetStart = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(1));
+        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+    }
+
+    if (!sourceStartValue.isUndefined()) {
+        sourceStart = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(2));
+        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+    }
+
+    if (!sourceEndValue.isUndefined()) {
+        sourceEnd = parseIndex(lexicalGlobalObject, throwScope, callFrame->uncheckedArgument(3));
+        RETURN_IF_EXCEPTION(throwScope, JSValue::encode(jsUndefined()));
+    }
+
     targetStart = std::min(targetStart, targetEnd);
     sourceEnd = std::min(sourceEnd, sourceEndInit);
     sourceStart = std::min(sourceStart, sourceEnd);