fix(NODE-6165): useBigInt64 causes compareTopologyVersion to throw (#4109)

Co-authored-by: Bailey Pearson <[email protected]>

Author: nbbeeken

Diff for: src/sdam/server_description.ts

@@ -258,10 +258,19 @@ export function compareTopologyVersion(
   }
 
   // TODO(NODE-2674): Preserve int64 sent from MongoDB
-  const currentCounter = Long.isLong(currentTv.counter)
-    ? currentTv.counter
-    : Long.fromNumber(currentTv.counter);
-  const newCounter = Long.isLong(newTv.counter) ? newTv.counter : Long.fromNumber(newTv.counter);
+  const currentCounter =
+    typeof currentTv.counter === 'bigint'
+      ? Long.fromBigInt(currentTv.counter)
+      : Long.isLong(currentTv.counter)
+      ? currentTv.counter
+      : Long.fromNumber(currentTv.counter);
+
+  const newCounter =
+    typeof newTv.counter === 'bigint'
+      ? Long.fromBigInt(newTv.counter)
+      : Long.isLong(newTv.counter)
+      ? newTv.counter
+      : Long.fromNumber(newTv.counter);
 
   return currentCounter.compare(newCounter);
 }

Diff for: test/unit/sdam/server_description.test.ts

@@ -130,6 +130,22 @@ describe('ServerDescription', function () {
         currentTv: { processId: processIdZero, counter: Long.fromNumber(2) },
         newTv: { processId: processIdZero, counter: Long.fromNumber(2) },
         out: 0
+      },
+      {
+        title: 'when process ids are equal and both counter values are zero bigints',
+        // @ts-expect-error: Testing that the function handles bigints
+        currentTv: { processId: processIdZero, counter: 0n },
+        // @ts-expect-error: Testing that the function handles bigints
+        newTv: { processId: processIdZero, counter: 0n },
+        out: 0
+      },
+      {
+        title: 'when process ids are equal and both counter values are non-zero bigints',
+        // @ts-expect-error: Testing that the function handles bigints
+        currentTv: { processId: processIdZero, counter: 2n },
+        // @ts-expect-error: Testing that the function handles bigints
+        newTv: { processId: processIdZero, counter: 2n },
+        out: 0
       }
     ];
     const compareTopologyVersionLessThanTests: CompareTopologyVersionTest[] = [
@@ -178,6 +194,12 @@ describe('ServerDescription', function () {
         currentTv: { processId: processIdZero, counter: Long.fromNumber(3) },
         newTv: { processId: processIdZero, counter: Long.fromNumber(2) },
         out: 1
+      },
+      {
+        title: 'when processIds are equal but new counter is less than current (bigint)',
+        currentTv: { processId: processIdZero, counter: 3n },
+        newTv: { processId: processIdZero, counter: 2n },
+        out: 1
       }
     ];