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[Performance] Replace O(n²) array scans in appDiff with Map/Set lookups #8599

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[Performance] Replace O(n²) array scans in appDiff with Map/Set lookups #8599

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13 changes: 8 additions & 5 deletions packages/app/src/cli/services/dev/app-events/app-diffing.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -20,17 +20,20 @@ interface AppExtensionsDiff {
*/
export function appDiff(app: AppInterface, newApp: AppInterface, includeUpdated = true): AppExtensionsDiff {
const oldExtensions = app.realExtensions
const oldExtensionsUids = oldExtensions.map((ext) => ext.uid)
const newExtensions = newApp.realExtensions
const newExtensionsUids = newExtensions.map((ext) => ext.uid)

const createdExtensions = newExtensions.filter((ext) => !oldExtensionsUids.includes(ext.uid))
const deletedExtensions = oldExtensions.filter((ext) => !newExtensionsUids.includes(ext.uid))
// Indexing by uid keeps every lookup below O(1). The previous implementation scanned the opposite
// array for each extension, which is O(n²) on a path that runs on every file change during `app dev`.
const oldExtensionsByUid = new Map(oldExtensions.map((ext) => [ext.uid, ext]))
const newExtensionsUids = new Set(newExtensions.map((ext) => ext.uid))

const createdExtensions = newExtensions.filter((ext) => !oldExtensionsByUid.has(ext.uid))
const deletedExtensions = oldExtensions.filter((ext) => !newExtensionsUids.has(ext.uid))

let updatedExtensions
if (includeUpdated) {
updatedExtensions = newExtensions.filter((ext) => {
const oldExtension = oldExtensions.find((oldExt) => oldExt.uid === ext.uid)
const oldExtension = oldExtensionsByUid.get(ext.uid)
if (!oldExtension) return false
const configChanged = JSON.stringify(oldExtension.configuration) !== JSON.stringify(ext.configuration)
const extensionPathChanged = oldExtension.configurationPath !== ext.configurationPath
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