From d10a241f05ee1ecb783ce84e8f0113e34ac0cf95 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Tue, 18 Aug 2026 17:09:03 +0000
Subject: [PATCH] =?UTF-8?q?Fix=20dashboard=20showing=20"n/a"=20for=20a=20l?=
 =?UTF-8?q?egitimate=200.0=20=C2=B0C=20reading?=
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app.js gated the temperature display on `snap.temperature?.celsius`
truthiness, so an exact 0 °C reading (plausible for a Pi in an
unheated/outdoor enclosure) rendered as "n/a" indistinguishably from a
failed sensor read. A successful reading always carries a non-empty
zone, while a failed collection yields zone: "", so key off
`snap.temperature?.zone` instead.

Closes #64
---
 internal/web/assets/app.js       |  2 +-
 internal/web/temperature_test.go | 27 +++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 internal/web/temperature_test.go

diff --git a/internal/web/assets/app.js b/internal/web/assets/app.js
index e0b686e..3a92f2d 100644
--- a/internal/web/assets/app.js
+++ b/internal/web/assets/app.js
@@ -218,7 +218,7 @@
 
     // Temperature
     const tempEl = document.getElementById('temp-value');
-    if (snap.temperature?.celsius) {
+    if (snap.temperature?.zone) {
       setText('temp-value', snap.temperature.celsius.toFixed(1) + ' °C');
       tempEl.className = 'metric-value ' + levelClass(snap.temperature.celsius, t.temperature_warn_c, t.temperature_crit_c);
     } else {
diff --git a/internal/web/temperature_test.go b/internal/web/temperature_test.go
new file mode 100644
index 0000000..a6529cf
--- /dev/null
+++ b/internal/web/temperature_test.go
@@ -0,0 +1,27 @@
+package web
+
+import (
+	"strings"
+	"testing"
+)
+
+// TestAppJS_TemperatureNAUsesZoneNotCelsius guards against regressing issue
+// #64: a legitimate 0.0 °C reading must not render as "n/a". A failed
+// collection is distinguished by an empty zone (Temperature.Zone is always
+// set on a successful reading), not by the celsius value's truthiness —
+// 0 is a valid, falsy reading that a `snap.temperature?.celsius` check would
+// wrongly treat as missing.
+func TestAppJS_TemperatureNAUsesZoneNotCelsius(t *testing.T) {
+	data, err := assetsFS.ReadFile("assets/app.js")
+	if err != nil {
+		t.Fatalf("read app.js: %v", err)
+	}
+	src := string(data)
+
+	if strings.Contains(src, "snap.temperature?.celsius)") || strings.Contains(src, "snap.temperature && snap.temperature.celsius)") {
+		t.Errorf("app.js must not gate the temperature display on celsius truthiness (0 °C is a valid reading)")
+	}
+	if !strings.Contains(src, "snap.temperature?.zone") {
+		t.Errorf("expected app.js to key the temperature \"n/a\" fallback off snap.temperature?.zone")
+	}
+}