C#: Preserve NullSafe marker through CSharpTemplate.Rewrite()#7140
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knutwannheden merged 2 commits intomainfrom Mar 26, 2026
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C#: Preserve NullSafe marker through CSharpTemplate.Rewrite()#7140knutwannheden merged 2 commits intomainfrom
NullSafe marker through CSharpTemplate.Rewrite()#7140knutwannheden merged 2 commits intomainfrom
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Move the NullSafe marker from the Name Identifier to the MethodInvocation/FieldAccess node where it semantically belongs, and teach the pattern matcher and template engine to preserve it through rewrites. - Parser: place NullSafe on MI/FA Markers instead of Name Markers - Printer: check mi.Markers instead of mi.Name.Markers - Pattern matching: asymmetric NullSafe check — pattern without ?. matches both . and ?. access, but pattern with ?. only matches ?. - Template substitution: when a capture was the select of a NullSafe MI/FA, transfer the marker to the template output MI/FA
knutwannheden
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NullSafe marker through CSharpTemplate.Rewrite()
… preservation Move the NullSafe marker for ?[ from ArrayDimension.Markers to ArrayAccess.Markers for consistency with MethodInvocation and FieldAccess. Split the combined space into Dimension prefix (space before ?) and NullSafe.DotPrefix (space between ? and [). Add NullSafe recording and transfer for ArrayAccess in the pattern matcher and template engine.
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Motivation
When
CSharpTemplate.Rewrite()transforms a chained method call that has a?.(NullSafe marker) on an intermediate call, the marker was lost in the output because the template builds a fresh tree. For example,dict["key"]?.Where(x => x > 0).First()rewritten todict["key"]?.First(x => x > 0)would lose the?., producingdict["key"].First(x => x > 0)instead.Two root causes: (1) the NullSafe marker lived on the Name Identifier rather than the MethodInvocation/FieldAccess node, making it invisible to structural comparison and unintuitive for recipe authors; (2) the pattern matcher and template engine had no mechanism to preserve it.
Summary
mi.Name.Markerstomi.Markers(andfa.Markersfor FieldAccess) across parser and printer — this is the semantically correct location since?.describes the access operation, not the name?.matches both.and?.access (lenient), but a pattern with?.only matches?.(strict). This avoids forcing recipe authors to duplicate patternsTest plan
PreservesNullConditionalInRewrite—{x}.Where({pred}).First()→{x}.First({pred})preserves?.PreservesNullConditionalOnFieldAccess—{x}.Length→{x}.Countpreserves?.NullConditionalNotAddedWhenOriginalHasNone— no spurious?.addedRegularDotPatternMatchesNullConditionalAccess— pattern without?.now matches?.NullConditionalPatternDoesNotMatchRegularDotAccess— pattern with?.still rejects.