Fix issue with slice negative of filtered sequence (#2006)

jdeniau · web-flow · commit 23daf26b51ec · 2024-07-22T14:03:29.000+02:00
diff --git a/__tests__/Range.ts b/__tests__/Range.ts
@@ -190,4 +190,15 @@ describe('Range', () => {
 
     expect(r).toEqual(200);
   });
+
+  it('sliced sequence works even on filtered sequence', () => {
+    expect(Range(0, 3).slice(-2).toArray()).toEqual([1, 2]);
+
+    expect(
+      Range(0, 3)
+        .filter($ => true)
+        .slice(-2)
+        .toArray()
+    ).toEqual([1, 2]);
+  });
 });
diff --git a/src/Operations.js b/src/Operations.js
@@ -408,16 +408,16 @@ export function sliceFactory(collection, begin, end, useKeys) {
     return collection;
   }
 
-  const resolvedBegin = resolveBegin(begin, originalSize);
-  const resolvedEnd = resolveEnd(end, originalSize);
-
-  // begin or end will be NaN if they were provided as negative numbers and
+  // begin or end can not be resolved if they were provided as negative numbers and
   // this collection's size is unknown. In that case, cache first so there is
   // a known size and these do not resolve to NaN.
-  if (resolvedBegin !== resolvedBegin || resolvedEnd !== resolvedEnd) {
+  if (typeof originalSize === 'undefined' && (begin < 0 || end < 0)) {
     return sliceFactory(collection.toSeq().cacheResult(), begin, end, useKeys);
   }
 
+  const resolvedBegin = resolveBegin(begin, originalSize);
+  const resolvedEnd = resolveEnd(end, originalSize);
+
   // Note: resolvedEnd is undefined when the original sequence's length is
   // unknown and this slice did not supply an end and should contain all
   // elements after resolvedBegin.
