fix: compare prerelease versions against previous stable for size diff (#2324)

Co-authored-by: Willow (GHOST) <git@willow.sh>

Author: joshuaisaact

app/composables/useInstallSizeDiff.ts

@@ -19,17 +19,15 @@ const DEP_INCREASE_THRESHOLD = 5
 function getComparisonVersion(pkg: SlimPackument, resolvedVersion: string): string | null {
   const isCurrentPrerelease = prerelease(resolvedVersion) !== null
 
-  if (isCurrentPrerelease) {
-    const latest = pkg['dist-tags']?.latest
-    if (!latest || latest === resolvedVersion) return null
-    return latest
-  }
-
-  // Find the previous version in time that was stable
   const stableVersions = Object.keys(pkg.time)
     .filter(v => v !== 'modified' && v !== 'created' && valid(v) !== null && prerelease(v) === null)
     .sort((a, b) => compare(a, b))
 
+  if (isCurrentPrerelease) {
+    // Find the highest stable version before this prerelease in semver order
+    return stableVersions.findLast(v => compare(v, resolvedVersion) < 0) ?? null
+  }
+
   const currentIdx = stableVersions.indexOf(resolvedVersion)
   // Don't compare the second version against the first as the first
   // has no baseline so a large size difference is expected

test/nuxt/composables/use-install-size-diff.spec.ts

@@ -84,7 +84,7 @@ describe('useInstallSizeDiff', () => {
       expect(comparisonVersion.value).toBe('1.0.0')
     })
 
-    it('uses the latest dist-tag for a prerelease version', () => {
+    it('compares a prerelease against the previous stable version', () => {
       const pkg = createPackage(
         'test',
         { '1.0.0': '2020-01-01', '2.0.0-beta.1': '2021-01-01' },
@@ -95,20 +95,28 @@ describe('useInstallSizeDiff', () => {
       expect(comparisonVersion.value).toBe('1.0.0')
     })
 
-    it('returns null when the prerelease version is already latest', () => {
+    it('compares an old prerelease against the stable version before it, not latest', () => {
       const pkg = createPackage(
         'test',
-        { '2.0.0-beta.1': '2021-01-01' },
-        { latest: '2.0.0-beta.1' },
+        {
+          '1.16.0': '2024-01-01',
+          '1.17.0-alpha.0': '2024-02-01',
+          '1.18.0': '2024-03-01',
+          '1.50.0': '2025-01-01',
+        },
+        { latest: '1.50.0' },
       )
 
-      const { comparisonVersion } = useInstallSizeDiff('test', '2.0.0-beta.1', pkg, null)
-      expect(comparisonVersion.value).toBeNull()
+      const { comparisonVersion } = useInstallSizeDiff('test', '1.17.0-alpha.0', pkg, null)
+      expect(comparisonVersion.value).toBe('1.16.0')
     })
 
-    it('returns null for a prerelease when there is no latest tag', () => {
-      const pkg = createPackage('test', { '2.0.0-beta.1': '2021-01-01' }, {})
-      pkg['dist-tags'] = {}
+    it('returns null for a prerelease with no prior stable versions', () => {
+      const pkg = createPackage(
+        'test',
+        { '2.0.0-beta.1': '2021-01-01' },
+        { latest: '2.0.0-beta.1' },
+      )
 
       const { comparisonVersion } = useInstallSizeDiff('test', '2.0.0-beta.1', pkg, null)
       expect(comparisonVersion.value).toBeNull()