I discovered that adding a trailing comment to the left brace of the accessor block will mess up the indentation levels of the generated getter.

I mildly prefer just keeping node.bindings[node.bindings.startIndex] TBH. Maybe we should have a mutate method or something similar to make this a little nicer, or just wait until we can use variadic generics and then update with...

I agree that the bindings key path is a little confusing, it just seems a little over-complicated

What do you think about having var binding = node.bindings.first in the guard, then using binding.accessorBlock = … etc below and finalizing the new node by setting node.bindings = [binding]. That seems like the cleanest solution to me.

I agree that the bindings key path is a little confusing, it just seems a little over-complicated

What do you think about having var binding = node.bindings.first in the guard, then using binding.accessorBlock = … etc below and finalizing the new node by setting node.bindings = [binding]. That seems like the cleanest solution to me.

This would still be an issue if the macro expands to an accessor that doesn’t have a newline after the {, right? Ie. you have a macro that expands to { 1 } and has formatting disabled, so no newline gets added by BasicFormat.

If that’s the case, I would just move the trailing trivia after the closing brace. That way you can conceptually think of the accessor as being inserted before the binding’s trailing trivia.

How could I disable formatting for a test case?

You'll need to add a new macro and then set static let formatMode: FormatMode = .disabled in its definition. Also, nice catch @ahoppen! I forgot about that case :)

I couldn't figure out how to make an AccessorMacro expand into something like { 1 }, how could I do this?

The following should test it

func testNew() {
  struct ConstantOneSingleLineGetter: AccessorMacro {
    static var formatMode: FormatMode { .disabled }

    static func expansion(
      of node: AttributeSyntax,
      providingAccessorsOf declaration: some DeclSyntaxProtocol,
      in context: some MacroExpansionContext
    ) throws -> [AccessorDeclSyntax] {
      return [
        """
        get { 1 }
        """
      ]
    }
  }

  assertMacroExpansion(
    """
    @constantOne
    var x: Int // hello
    """,
    expandedSource: """
      var x: Int { // hello
        get { 1 }
      }
      """,
    macros: ["constantOne": ConstantOneSingleLineGetter.self],
    indentationWidth: indentationWidth
  )
}