arrayConnection: return all elements if cursors are on the outside (#348)

Author: IvanGoncharov

src/connection/__tests__/arrayConnection-test.js

@@ -2,6 +2,7 @@ import { describe, it } from 'mocha';
 import { expect } from 'chai';
 
 import {
+  offsetToCursor,
   connectionFromArray,
   connectionFromArraySlice,
   connectionFromPromisedArray,
@@ -289,19 +290,29 @@ describe('connectionFromArray()', () => {
     });
 
     it('returns all elements if cursors are on the outside', () => {
-      const c = connectionFromArray(arrayABCDE, {
-        before: 'YXJyYXljb25uZWN0aW9uOjY=' /* offsetToCursor(6) */,
-        after: 'YXJyYXljb25uZWN0aW9uOi0x' /* offsetToCursor(-1) */,
-      });
-      expect(c).to.deep.equal({
+      const allEdges = {
         edges: [edgeA, edgeB, edgeC, edgeD, edgeE],
         pageInfo: {
           startCursor: cursorA,
           endCursor: cursorE,
           hasPreviousPage: false,
           hasNextPage: false,
         },
-      });
+      };
+
+      expect(
+        connectionFromArray(arrayABCDE, { before: offsetToCursor(6) }),
+      ).to.deep.equal(allEdges);
+      expect(
+        connectionFromArray(arrayABCDE, { before: offsetToCursor(-1) }),
+      ).to.deep.equal(allEdges);
+
+      expect(
+        connectionFromArray(arrayABCDE, { after: offsetToCursor(6) }),
+      ).to.deep.equal(allEdges);
+      expect(
+        connectionFromArray(arrayABCDE, { after: offsetToCursor(-1) }),
+      ).to.deep.equal(allEdges);
     });
 
     it('returns no elements if cursors cross', () => {

src/connection/arrayConnection.js

@@ -54,11 +54,20 @@ export function connectionFromArraySlice<T>(
   const { after, before, first, last } = args;
   const { sliceStart, arrayLength } = meta;
   const sliceEnd = sliceStart + arraySlice.length;
-  const beforeOffset = getOffsetWithDefault(before, arrayLength);
+
+  let startOffset = Math.max(sliceStart, 0);
+  let endOffset = Math.min(sliceEnd, arrayLength);
+
   const afterOffset = getOffsetWithDefault(after, -1);
+  if (0 <= afterOffset && afterOffset < arrayLength) {
+    startOffset = Math.max(startOffset, afterOffset + 1);
+  }
+
+  const beforeOffset = getOffsetWithDefault(before, endOffset);
+  if (0 <= beforeOffset && beforeOffset < arrayLength) {
+    endOffset = Math.min(endOffset, beforeOffset);
+  }
 
-  let startOffset = Math.max(sliceStart - 1, afterOffset, -1) + 1;
-  let endOffset = Math.min(sliceEnd, beforeOffset, arrayLength);
   if (typeof first === 'number') {
     if (first < 0) {
       throw new Error('Argument "first" must be a non-negative integer');
@@ -76,8 +85,8 @@ export function connectionFromArraySlice<T>(
 
   // If supplied slice is too large, trim it down before mapping over it.
   const slice = arraySlice.slice(
-    Math.max(startOffset - sliceStart, 0),
-    arraySlice.length - (sliceEnd - endOffset),
+    startOffset - sliceStart,
+    endOffset - sliceStart,
   );
 
   const edges = slice.map((value, index) => ({