From 3d66c4eab5bb9dcbbb4f2ce260ed6ee55f4e52d3 Mon Sep 17 00:00:00 2001
From: Max Metral <max.metral@sesamecare.com>
Date: Sun, 31 Mar 2024 23:28:50 -0400
Subject: [PATCH] fix(cursor): optimization was wrong, can't use empty cursor
 for completion

---
 src/asDataGenerator.ts  |  5 -----
 src/multiSourcePager.ts |  6 +-----
 src/queuePager.spec.ts  | 12 ++++++------
 3 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/src/asDataGenerator.ts b/src/asDataGenerator.ts
index b886be8..491c850 100644
--- a/src/asDataGenerator.ts
+++ b/src/asDataGenerator.ts
@@ -8,11 +8,6 @@ export function asDataGenerator<T extends ResultWithCursor>(
 
   return {
     async *getGenerator(cursor: string | undefined) {
-      if (cursor === '') {
-        // The special empty string cursor indicates we should not fetch any more.
-        return;
-      }
-
       let currentCursor = cursor;
       let continueFetching = true;
 
diff --git a/src/multiSourcePager.ts b/src/multiSourcePager.ts
index 6b1acc4..2d83032 100644
--- a/src/multiSourcePager.ts
+++ b/src/multiSourcePager.ts
@@ -47,8 +47,6 @@ export async function multiSourcePager<Types extends Array<Source>>(
         index,
         key: dataSources[index].sortKey(item.value),
       });
-    } else {
-      cursors[index] = '';
     }
   }));
 
@@ -65,9 +63,7 @@ export async function multiSourcePager<Types extends Array<Source>>(
 
         // Fetch next item from the generator of the data source that the last item came from
         const nextResult = await generators[index].next();
-        if (nextResult.done) {
-          cursors[index] = '';
-        } else {
+        if (!nextResult.done) {
           queue.push({
             result: nextResult.value,
             index,
diff --git a/src/queuePager.spec.ts b/src/queuePager.spec.ts
index 34846a5..54c7890 100644
--- a/src/queuePager.spec.ts
+++ b/src/queuePager.spec.ts
@@ -82,12 +82,12 @@ describe('multi source pager', () => {
             "type": "letter",
           },
           {
-            "cursor": "WyIiLCIyMDIzLTAxLTA2VDAwOjAwOjAwLjAwMFojRkYiXQ==",
+            "cursor": "WyIyMDIzLTAxLTA1VDAwOjAwOjAwLjAwMFojRSIsIjIwMjMtMDEtMDZUMDA6MDA6MDAuMDAwWiNGRiJd",
             "data": "FF",
             "type": "letter",
           },
           {
-            "cursor": "WyIiLCIyMDIzLTAxLTA3VDAwOjAwOjAwLjAwMFojR0ciXQ==",
+            "cursor": "WyIyMDIzLTAxLTA1VDAwOjAwOjAwLjAwMFojRSIsIjIwMjMtMDEtMDdUMDA6MDA6MDAuMDAwWiNHRyJd",
             "data": "GG",
             "type": "letter",
           },
@@ -98,7 +98,7 @@ describe('multi source pager', () => {
       expect(p4.results).toMatchInlineSnapshot(`
         [
           {
-            "cursor": "WyIiLCIyMDIzLTAxLTA4VDAwOjAwOjAwLjAwMFojSEgiXQ==",
+            "cursor": "WyIyMDIzLTAxLTA1VDAwOjAwOjAwLjAwMFojRSIsIjIwMjMtMDEtMDhUMDA6MDA6MDAuMDAwWiNISCJd",
             "data": "HH",
             "type": "letter",
           },
@@ -137,17 +137,17 @@ describe('multi source pager', () => {
           "type": "letter",
         },
         {
-          "cursor": "WyIyMDIzLTAxLTAzVDAwOjAwOjAwLjAwMFojQyIsIiJd",
+          "cursor": "WyIyMDIzLTAxLTAzVDAwOjAwOjAwLjAwMFojQyIsIjIwMjMtMDEtMDJUMDA6MDA6MDAuMDAwWiNCQkIiXQ==",
           "data": "C",
           "type": "letter",
         },
         {
-          "cursor": "WyIyMDIzLTAxLTA0VDAwOjAwOjAwLjAwMFojRCIsIiJd",
+          "cursor": "WyIyMDIzLTAxLTA0VDAwOjAwOjAwLjAwMFojRCIsIjIwMjMtMDEtMDJUMDA6MDA6MDAuMDAwWiNCQkIiXQ==",
           "data": "D",
           "type": "letter",
         },
         {
-          "cursor": "WyIyMDIzLTAxLTA1VDAwOjAwOjAwLjAwMFojRSIsIiJd",
+          "cursor": "WyIyMDIzLTAxLTA1VDAwOjAwOjAwLjAwMFojRSIsIjIwMjMtMDEtMDJUMDA6MDA6MDAuMDAwWiNCQkIiXQ==",
           "data": "E",
           "type": "letter",
         },