Sort ProvidedTypes iteration for deterministic source output#413
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eiriktsarpalis merged 2 commits intoeiriktsarpalis:mainfrom Apr 15, 2026
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The source generator iterates provider.ProvidedTypes.Values in two places: SourceFormatter.AddAllSourceFiles and SourceFormatter.FormatGetShapeProviderMethod. Since ProvidedTypes is backed by Dictionary<TKey, TValue>, iteration order is non-deterministic, causing the generated source to vary between compilations even when inputs are identical. This breaks incremental build in projects that reference assemblies using PolyType, because the reference assembly content changes on every build, forcing downstream projects to recompile unnecessarily. Fix: sort by SourceIdentifier (a unique, stable, type-name-derived key) before iterating.
…generator Sort iterations over ImmutableEquatableSet and ImmutableEquatableDictionary collections that feed into generated source output: - ShapeableImplementations (ImmutableEquatableSet<TypeId>): sorted by FullyQualifiedName in three iteration sites that emit interface declarations, method implementations, and type checks. - EnumShapeModel.Members (ImmutableEquatableDictionary<string, string>): sorted by key when emitting enum member dictionary initializers. - AssociatedTypes (ImmutableEquatableSet<AssociatedTypeId>): sorted by ClosedTypeReflectionName when emitting associated type switch cases. Updated snapshot baselines to reflect the new deterministic ordering. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Thanks for making this more comprehensive. :) |
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The source generator iterates
provider.ProvidedTypes.Valuesin two places:SourceFormatter.AddAllSourceFiles— emits per-type source filesSourceFormatter.FormatGetShapeProviderMethod— emitsswitchcases inGetTypeShapeSince
ProvidedTypesis anImmutableEquatableDictionarybacked byDictionary<TKey, TValue>, iteration order is non-deterministic. This causes the generated source to vary between compilations even when inputs are identical.Impact
This breaks incremental build for downstream projects. When a project referencing a PolyType-using library is built:
<>Odisplay class)In our case, a single implementation-only change in one project caused
cscto run for a downstream project that should have been skipped entirely.Fix
Sort by
SourceIdentifier(a unique, stable, type-name-derived key) before iterating in both locations. This is a two-line change.