11import type { TurbopackMessageAction } from '../../../../server/dev/hot-reloader-types'
22import type { Update as TurbopackUpdate } from '../../../../build/swc/types'
33
4+ declare global {
5+ interface Window {
6+ __NEXT_HMR_TURBOPACK_REPORT_NOISY_NOOP_EVENTS : boolean | undefined
7+ }
8+ }
9+
10+ // How long to wait before reporting the HMR start, used to suppress irrelevant
11+ // `BUILDING` events. Does not impact reported latency.
12+ const TURBOPACK_HMR_START_DELAY_MS = 100
13+
414interface Built {
15+ hasUpdates : boolean
516 updatedModules : Set < string >
617 startMsSinceEpoch : number
718 endMsSinceEpoch : number
@@ -11,39 +22,89 @@ export class TurbopackHmr {
1122 #updatedModules: Set < string >
1223 #startMsSinceEpoch: number | undefined
1324 #lastUpdateMsSinceEpoch: number | undefined
25+ #deferredReportHmrStartId: ReturnType < typeof setTimeout > | undefined
1426
1527 constructor ( ) {
1628 this . #updatedModules = new Set ( )
1729 }
1830
31+ // HACK: Turbopack tends to generate a lot of irrelevant "BUILDING" actions,
32+ // as it reports *any* compilation, including fully no-op/cached compilations
33+ // and those unrelated to HMR. Fixing this would require significant
34+ // architectural changes.
35+ //
36+ // Work around this by deferring any "rebuilding" message by 100ms. If we get
37+ // a BUILT event within that threshold and nothing has changed, just suppress
38+ // the message entirely.
39+ #runDeferredReportHmrStart( ) {
40+ if ( this . #deferredReportHmrStartId != null ) {
41+ console . log ( '[Fast Refresh] rebuilding' )
42+ this . #cancelDeferredReportHmrStart( )
43+ }
44+ }
45+
46+ #cancelDeferredReportHmrStart( ) {
47+ clearTimeout ( this . #deferredReportHmrStartId)
48+ this . #deferredReportHmrStartId = undefined
49+ }
50+
1951 onBuilding ( ) {
2052 this . #lastUpdateMsSinceEpoch = undefined
53+ this . #cancelDeferredReportHmrStart( )
2154 this . #startMsSinceEpoch = Date . now ( )
55+
56+ if ( self . __NEXT_HMR_TURBOPACK_REPORT_NOISY_NOOP_EVENTS ) {
57+ // debugging feature: don't defer/suppress noisy no-op HMR update messages
58+ this . #runDeferredReportHmrStart( )
59+ } else {
60+ // report the HMR start after a short delay
61+ this . #deferredReportHmrStartId = setTimeout (
62+ ( ) => this . #runDeferredReportHmrStart( ) ,
63+ TURBOPACK_HMR_START_DELAY_MS
64+ )
65+ }
2266 }
2367
2468 onTurbopackMessage ( msg : TurbopackMessageAction ) {
69+ this . #runDeferredReportHmrStart( )
2570 this . #lastUpdateMsSinceEpoch = Date . now ( )
2671 const updatedModules = extractModulesFromTurbopackMessage ( msg . data )
2772 for ( const module of updatedModules ) {
2873 this . #updatedModules. add ( module )
2974 }
3075 }
3176
32- onBuilt ( ) : Built {
77+ onBuilt ( ) : Built | null {
78+ // check that we got *any* `TurbopackMessageAction`, even if
79+ // `updatedModules` is empty (not everything gets recorded there).
80+ const hasUpdates = this . #lastUpdateMsSinceEpoch != null
81+ if ( ! hasUpdates && this . #deferredReportHmrStartId != null ) {
82+ // suppress the update entirely
83+ this . #cancelDeferredReportHmrStart( )
84+ return null
85+ }
86+
87+ this . #runDeferredReportHmrStart( )
88+
89+ // Turbopack has a debounce which causes every BUILT message to appear
90+ // 30ms late. We don't want to include this latency in our reporting, so
91+ // prefer to use the last TURBOPACK_MESSAGE time.
92+ const endMsSinceEpoch = this . #lastUpdateMsSinceEpoch ?? Date . now ( )
93+ const latencyMs = endMsSinceEpoch - this . #startMsSinceEpoch!
94+ console . log ( `[Fast Refresh] done in ${ latencyMs } )
95+
3396 const result = {
97+ hasUpdates,
3498 updatedModules : this . #updatedModules,
3599 startMsSinceEpoch : this . #startMsSinceEpoch! ,
36- // Turbopack has a debounce which causes every BUILT message to appear
37- // 30ms late. We don't want to include this latency in our reporting, so
38- // prefer to use the last TURBOPACK_MESSAGE time.
39100 endMsSinceEpoch : this . #lastUpdateMsSinceEpoch ?? Date . now ( ) ,
40101 }
41102 this . #updatedModules = new Set ( )
42103 return result
43104 }
44105}
45106
46- export function extractModulesFromTurbopackMessage (
107+ function extractModulesFromTurbopackMessage (
47108 data : TurbopackUpdate | TurbopackUpdate [ ]
48109) : Set < string > {
49110 const updatedModules : Set < string > = new Set ( )
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