[Observation] Reduce the scope of the observation shouldNotifyObservers to only apply to observation and not side effects of accessors like willSet or didSet (#79518)

phausler · web-flow · commit a3d699241c53 · 2025-02-21T11:32:19.000-08:00
diff --git a/lib/Macros/Sources/ObservationMacros/ObservableMacro.swift b/lib/Macros/Sources/ObservationMacros/ObservableMacro.swift
@@ -361,10 +361,13 @@ public struct ObservationTrackedMacro: AccessorMacro {
       }
       """
 
+    // the guard else case must include the assignment else
+    // cases that would notify then drop the side effects of `didSet` etc
     let setAccessor: AccessorDeclSyntax =
       """
       set {
         guard shouldNotifyObservers(_\(identifier), newValue) else {
+          _\(identifier) = newValue
           return
         }
         withMutation(keyPath: \\.\(identifier)) {

Original file line number	Diff line number	Diff line change
`@@ -361,10 +361,13 @@ public struct ObservationTrackedMacro: AccessorMacro {`
`361`	`361`	`}`
`362`	`362`	`"""`
`363`	`363`
	`364`	`+ // the guard else case must include the assignment else`
	`365`	+ // cases that would notify then drop the side effects of `didSet` etc
`364`	`366`	`let setAccessor: AccessorDeclSyntax =`
`365`	`367`	`"""`
`366`	`368`	`set {`
`367`	`369`	`guard shouldNotifyObservers(_\(identifier), newValue) else {`
	`370`	`+ _\(identifier) = newValue`
`368`	`371`	`return`
`369`	`372`	`}`
`370`	`373`	`withMutation(keyPath: \\.\(identifier)) {`