From f5aa2e36e1d792a5c73fb69a028ad5e71e9a0d68 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Wiedemann?= <jerome@wnetworks.org>
Date: Mon, 1 Mar 2021 10:10:21 +0000
Subject: [PATCH] fix(start_with_last): `start_with_last` would sometimes throw

---
 .devcontainer/ui-lovelace.yaml | 21 +++++++++++++++++++++
 src/graphEntry.ts              |  2 +-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/.devcontainer/ui-lovelace.yaml b/.devcontainer/ui-lovelace.yaml
index e062dd5..3eb21c2 100644
--- a/.devcontainer/ui-lovelace.yaml
+++ b/.devcontainer/ui-lovelace.yaml
@@ -882,3 +882,24 @@ views:
                   func: first
                   duration: 10min
                   start_with_last: true
+          - type: custom:apexcharts-card
+            graph_span: 1 week
+            span:
+              end: week
+            all_series_config:
+              type: column
+              extend_to_end: false
+              group_by:
+                fill: 'null'
+            series:
+              - entity: sensor.random0_100
+                name: last
+                group_by:
+                  func: last
+                  duration: 10min
+              - entity: sensor.random0_100
+                name: first
+                group_by:
+                  func: first
+                  duration: 10min
+                  start_with_last: true
diff --git a/src/graphEntry.ts b/src/graphEntry.ts
index 6fe9e1f..f0d6f59 100644
--- a/src/graphEntry.ts
+++ b/src/graphEntry.ts
@@ -394,7 +394,7 @@ export default class GraphEntry {
       }
       if (this._config.group_by.start_with_last) {
         if (index > 0) {
-          if (bucket.data[0][0] !== bucket.timestamp) {
+          if (bucket.data.length === 0 || bucket.data[0][0] !== bucket.timestamp) {
             const prevBucketData = buckets[index - 1].data;
             bucket.data.unshift([bucket.timestamp, prevBucketData[prevBucketData.length - 1][1]]);
           }