fix: use utc dates, handle division by zero, + add tanstack fixture

Author: danielroe

app/composables/useCharts.ts

@@ -162,7 +162,7 @@ export function smoothPath(pts: { x: number; y: number }[]): string {
   for (let i = 0; i < n; i++) {
     dx[i] = pts[i + 1]!.x - pts[i]!.x
     dy[i] = pts[i + 1]!.y - pts[i]!.y
-    m[i] = dy[i]! / dx[i]!
+    m[i] = dx[i] === 0 ? 0 : dy[i]! / dx[i]!
   }
 
   t[0] = m[0]!

modules/runtime/server/cache.ts

@@ -263,13 +263,13 @@ function getMockForUrl(url: string): MockResult | null {
       const downloads: { day: string; downloads: number }[] = []
       const start = new Date(startDate!)
       const end = new Date(endDate!)
-      for (let d = new Date(start); d <= end; d.setDate(d.getDate() + 1)) {
+      for (let d = new Date(start); d <= end; d.setUTCDate(d.getUTCDate() + 1)) {
         const day = d.toISOString().slice(0, 10)
         const i = downloads.length
         const trend = 1 + trendSlope * i
         const wave = Math.sin((i * 2 * Math.PI) / wavePeriod) * waveAmp
         const noise = Math.sin(i * 7 + s) * 0.05
-        const dow = d.getDay()
+        const dow = d.getUTCDay()
         const weekend = dow === 0 || dow === 6 ? 1 - weekendDip : 1
         downloads.push({
           day,

scripts/generate-fixtures.ts

@@ -40,6 +40,7 @@ const REQUIRED_PACKAGES = [
   'next', // create-command test
   '@nuxt/kit', // scoped package tests, version test (3.20.0)
   '@types/node', // scoped package tests
+  '@tanstack/react-query', // OG image test (scoped with long name)
   // Docs page tests
   'ufo', // docs test with version 1.6.3
   'is-odd', // docs test (3.0.1), install copy test, "no create" test, hyphen-in-name test

test/e2e/og-image.spec.ts

@@ -56,7 +56,7 @@ for (const { path, label } of testCases) {
 
       const imageBuffer = await response.body()
       expect(imageBuffer).toMatchSnapshot({
-        name: `og-image-${path.replace(/\//g, '-').replace(/^-/, '')}.png`,
+        name: `og-image-${path.replace(/\//g, '-').replace(/^-/, '') || 'home'}.png`,
         maxDiffPixelRatio: 0.02,
       })
     })

test/fixtures/mock-routes.cjs

@@ -193,7 +193,7 @@ function matchNpmApi(urlString) {
     const downloads = []
     const startDate = new Date(start)
     const endDate = new Date(end)
-    for (let d = new Date(startDate); d <= endDate; d.setDate(d.getDate() + 1)) {
+    for (let d = new Date(startDate); d <= endDate; d.setUTCDate(d.getUTCDate() + 1)) {
       const day = d.toISOString().slice(0, 10)
       // Sine wave + noise for a realistic-looking sparkline
       const dayIndex = downloads.length

test/fixtures/npm-api/downloads/@tanstack/react-query.json

@@ -0,0 +1,6 @@
+{
+  "downloads": 25603146,
+  "start": "2026-02-20",
+  "end": "2026-02-26",
+  "package": "@tanstack/react-query"
+}