Fix .onPreview/.onTest not working in Xcode previews#351
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bsudekum wants to merge 1 commit intohmlongco:mainfrom
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Fix .onPreview/.onTest not working in Xcode previews#351bsudekum wants to merge 1 commit intohmlongco:mainfrom
bsudekum wants to merge 1 commit intohmlongco:mainfrom
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Two issues prevented context factories from resolving in previews: 1. Registration and resolution of preview/test contexts were gated behind #if DEBUG. Since isPreview and isTest are runtime checks (environment variables), they don't need compile-time guards. Removed #if DEBUG for preview/test; kept it for debug context. 2. Xcode previews dynamically recompile and inject code, causing nominal types (TypedFactory<P,T>) to have different type identity across module boundaries. The as? TypedFactory<P,T> cast silently fails, so context factories are ignored and the default factory runs instead (often fatalError). Fix: Added untypedFactory property to AnyFactory that exposes the closure as Any. When the nominal struct cast fails, resolution falls back to casting the closure using structural function types (@sendable (P) -> T), which are identity-independent in Swift.
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.onPreviewand.onTestcontext factories silently fail in Xcode previews. The mock is registered and found, but never used — the default factory runs instead (oftenfatalError()), crashing the preview.Cause: Xcode previews dynamically recompile and inject code, creating duplicate
TypedFactory<P,T>types across module boundaries. Theas? TypedFactory<P,T>cast returnsnileven when both sides areTypedFactory<(), BillingUI>— same generic parameters, different runtime type identity.Fix
Add a structural function-type cast fallback. When the nominal
TypedFactory<P,T>cast fails, cast the underlying closure directly via@Sendable (P) -> T. Function types use structural typing inSwift, which is immune to the compilation-unit identity mismatch.
Registrations.swift—AnyFactoryexposesuntypedFactory: Any.resolve()falls back to casting the closure when the struct cast fails. Removed#if DEBUGfromisPreview/isTestinfactoryForCurrentContext().Resolver.swift— Same fallback for the global resolver path.Modifiers.swift— Removed#if DEBUGfrom context registrationdefault:case.The normal (non-preview) path is unchanged — the nominal cast succeeds first and the fallback is never reached.
Why remove
#if DEBUGfrom preview/test gatesisPreviewandisTestarefalsein release, so context factories never resolve outside debug builds. User code already wraps.onPreview/.onTestin#if DEBUG. The.onDebugcontext retains its#if DEBUGguard.