Allow forecast if no data is flagged as incomplete

Author: mneudert

plugins/CoreVisualizations/JqplotDataGenerator/ForecastBuilder.php

@@ -153,7 +153,10 @@ public function build(
     /**
      * Forecast for monotonic count series: linear elapsed-ratio extrapolation blended with the
      * historical same-period prior. Carries the previous forecast forward when the current tick
-     * has no positive value so a synthetic 0 does not collapse the linear seed to zero.
+     * has no positive value so a synthetic 0 does not collapse the linear seed to zero. When the
+     * current tick is the first incomplete tick (no previous forecast) and historical priors
+     * exist, the blend would otherwise dilute the prior with a meaningless zero, so it falls back
+     * to the prior mean directly.
      *
      * @param array<int, float> $pastValues
      */
@@ -179,6 +182,8 @@ private function buildMonotonicForecastValue(
 
         if ($currentValue <= 0 && $previousForecastValue !== null) {
             $baseForecast = $previousForecastValue;
+        } elseif ($currentValue <= 0 && [] !== $pastValues) {
+            $baseForecast = $priorForecast;
         }
 
         $forecastValue = $this->blendForecastValue($baseForecast, $priorForecast, $weight);

plugins/CoreVisualizations/tests/Unit/JqplotDataGenerator/ForecastBuilderTest.php

@@ -289,6 +289,37 @@ public function testBuildReusesForecastAsSyntheticDataForLaterNoDataDaysAndRecal
         self::assertSame([[null, null, null, null, 47.9996, 58.3997, 74.7198, 59.9994]], $forecastData);
     }
 
+    public function testBuildMonotonicReturnsFullPriorWhenIncompleteTickHasNoData(): void
+    {
+        $site = $this->createSiteMock();
+
+        // The "today" tick exists in the date range but has no archived data yet — currentValue
+        // is 0 and there is no earlier incomplete tick to carry a forecast forward from. The
+        // blend would otherwise dilute the historical prior with a meaningless zero; the builder
+        // must return the full prior mean instead. Apr 3/10/17/24 are all Fridays so the daily
+        // weekday filter keeps every prior tick in the sample.
+        $dataTables = [
+            $this->createDataTableForDay('2026-04-03', $site),
+            $this->createDataTableForDay('2026-04-10', $site),
+            $this->createDataTableForDay('2026-04-17', $site),
+            $this->createDataTableForDay('2026-04-24', $site, '2026-04-24 00:00:00'),
+        ];
+
+        $forecastData = (new ForecastBuilder())->build(
+            ['Visits' => [80.0, 100.0, 60.0, 0.0]],
+            $dataTables,
+            [
+                ArchiveState::COMPLETE,
+                ArchiveState::COMPLETE,
+                ArchiveState::COMPLETE,
+                ArchiveState::INCOMPLETE,
+            ],
+            ['Visits' => false]
+        );
+
+        self::assertSame([[null, null, null, 80.0]], $forecastData);
+    }
+
     public function testBuildDoesNotCarryForwardAcrossSuppressedForecastGap(): void
     {
         $site = $this->createSiteMock();