Don't insert trailing commas into attribute argument lists#1215
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allevato merged 1 commit intoJun 8, 2026
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Thanks! This seems like a straightforward solution for now vs. trying to hard-code which attributes support this and which don't.
There may be some divergence between what we do here and what tools like SwiftLint might do, to which my answer is still "you shouldn't use multiple linters to check the same rule".
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… don't insert trailing commas into attribute argument lists under multilineTrailingCommaBehavior: alwaysUsed (mirror swiftlang/swift-format#1215); recognize Swift 6.2 'isolated' declaration modifier in SortModifiers' canonical isolation slot alongside 'nonisolated' (mirror realm/SwiftLint#6759); compute NestedCallLayout.columnOffset in grapheme clusters uniformly instead of mixing String.count on tokens with UTF-8 byte length on trivia, fixing column over-count when preceding tokens or trivia contain multi-byte characters (mirror realm/SwiftLint#6747)
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fixes #1178.
alwaysUsed inserted a trailing comma into multiline @attached(...) arguments, which the parser rejects (see swiftlang/swift-syntax#3306). macro role and custom attributes are syntactically indistinguishable, so never insert into any attribute's argument list. an existing comma is still managed as configured.