Comment placement in argument lists causes ordering issues

[lionel-]

This call:

list(
  # comment0
  foo  # comment1
  =1, bar  # comment2
  =  # comment3
  # comment4
  2 #comment5
  #comment6
  , #comment7
  #comment8
)

Is currently formatted as:

list(
  # comment0
  # comment1
  foo = 1,
  # comment3
  # comment4
  # comment2
  bar = 2, #comment5 #comment7
  #comment8
  #comment6
)

We need to fix these issues:

• comment2 is pulled down because it becomes a leading comment of the whole argument node
• comment6 is pulled down because it becomes a leading comment of the empty argument, I think because it's an own-line and the default placement puts it on the next node.
• comment7 is formatted on the same line as comment5, because they both become trailing comments of the same node, and both have lines_before = 0. This happens here:

  air/crates/air_r_formatter/src/comments.rs

  Line 951 in e3655e9

  return CommentPlacement::trailing(previous, comment);

[lionel-]

Parse tree:

RRoot {
    bom_token: missing (optional),
    expressions: RExpressionList [
        RCall {
            function: RIdentifier {
                name_token: IDENT@0..5 "list" [Newline("\n")] [],
            },
            arguments: RCallArguments {
                l_paren_token: L_PAREN@5..6 "(" [] [],
                items: RArgumentList [
                    RArgument {
                        name_clause: RArgumentNameClause {
                            name: RIdentifier {
                                name_token: IDENT@6..37 "foo" [Newline("\n"), Whitespace("  "), Comments("# comment0"), Newline("\n"), Whitespace("  ")] [Whitespace("  "), Comments("# comment1")],
                            },
                            eq_token: EQUAL@37..41 "=" [Newline("\n"), Whitespace("  ")] [],
                        },
                        value: RDoubleValue {
                            value_token: R_DOUBLE_LITERAL@41..42 "1" [] [],
                        },
                    },
                    COMMA@42..43 "," [] [],
                    RArgument {
                        name_clause: RArgumentNameClause {
                            name: RIdentifier {
                                name_token: IDENT@43..59 "bar" [Whitespace(" ")] [Whitespace("  "), Comments("# comment2")],
                            },
                            eq_token: EQUAL@59..75 "=" [Newline("\n"), Whitespace("  ")] [Whitespace("  "), Comments("# comment3")],
                        },
                        value: RDoubleValue {
                            value_token: R_DOUBLE_LITERAL@75..102 "2" [Newline("\n"), Whitespace("  "), Comments("# comment4"), Newline("\n"), Whitespace("  ")] [Whitespace(" "), Comments("#comment5")],
                        },
                    },
                    COMMA@102..128 "," [Newline("\n"), Whitespace("  "), Comments("#comment6"), Newline("\n"), Whitespace("  ")] [Whitespace(" "), Comments("#comment7")],
                    RArgument {
                        name_clause: missing (optional),
                        value: missing (optional),
                    },
                ],
                r_paren_token: R_PAREN@128..142 ")" [Newline("\n"), Whitespace("  "), Comments("#comment8"), Newline("\n")] [],
            },
        },
    ],
    eof_token: EOF@142..147 "" [Newline("\n"), Whitespace("    ")] [],
}

Comment placement:

[crates/air_r_formatter/tests/quick_test.rs:36:5] Comments::from_node(&parse.syntax(), &RCommentStyle, None) = Comments {
    data: [
        Leading {
            node: 0: R_ARGUMENT@6..42
              0: R_ARGUMENT_NAME_CLAUSE@6..41
                0: R_IDENTIFIER@6..37
                  0: IDENT@6..37 "foo" [Newline("\n"), Whitespace("  "), Comments("# comment0"), Newline("\n"), Whitespace("  ")] [Whitespace("  "), Comments("# comment1")]
                1: EQUAL@37..41 "=" [Newline("\n"), Whitespace("  ")] []
              1: R_DOUBLE_VALUE@41..42
                0: R_DOUBLE_LITERAL@41..42 "1" [] []
            ,
            comment: SourceComment {
                lines_before: 1,
                lines_after: 1,
                piece: SyntaxTriviaPieceComments(
                    Comments("# comment0"),
                ),
                kind: Line,
                formatted: Cell {
                    value: false,
                },
            },
        },
        Leading {
            node: 0: R_IDENTIFIER@6..37
              0: IDENT@6..37 "foo" [Newline("\n"), Whitespace("  "), Comments("# comment0"), Newline("\n"), Whitespace("  ")] [Whitespace("  "), Comments("# comment1")]
            ,
            comment: SourceComment {
                lines_before: 0,
                lines_after: 1,
                piece: SyntaxTriviaPieceComments(
                    Comments("# comment1"),
                ),
                kind: Line,
                formatted: Cell {
                    value: false,
                },
            },
        },
        Leading {
            node: 0: R_IDENTIFIER@43..59
              0: IDENT@43..59 "bar" [Whitespace(" ")] [Whitespace("  "), Comments("# comment2")]
            ,
            comment: SourceComment {
                lines_before: 0,
                lines_after: 1,
                piece: SyntaxTriviaPieceComments(
                    Comments("# comment2"),
                ),
                kind: Line,
                formatted: Cell {
                    value: false,
                },
            },
        },
        Leading {
            node: 0: R_ARGUMENT_NAME_CLAUSE@43..75
              0: R_IDENTIFIER@43..59
                0: IDENT@43..59 "bar" [Whitespace(" ")] [Whitespace("  "), Comments("# comment2")]
              1: EQUAL@59..75 "=" [Newline("\n"), Whitespace("  ")] [Whitespace("  "), Comments("# comment3")]
            ,
            comment: SourceComment {
                lines_before: 0,
                lines_after: 1,
                piece: SyntaxTriviaPieceComments(
                    Comments("# comment3"),
                ),
                kind: Line,
                formatted: Cell {
                    value: false,
                },
            },
        },
        Leading {
            node: 0: R_ARGUMENT_NAME_CLAUSE@43..75
              0: R_IDENTIFIER@43..59
                0: IDENT@43..59 "bar" [Whitespace(" ")] [Whitespace("  "), Comments("# comment2")]
              1: EQUAL@59..75 "=" [Newline("\n"), Whitespace("  ")] [Whitespace("  "), Comments("# comment3")]
            ,
            comment: SourceComment {
                lines_before: 1,
                lines_after: 1,
                piece: SyntaxTriviaPieceComments(
                    Comments("# comment4"),
                ),
                kind: Line,
                formatted: Cell {
                    value: false,
                },
            },
        },
        Trailing {
            node: 2: R_ARGUMENT@43..102
              0: R_ARGUMENT_NAME_CLAUSE@43..75
                0: R_IDENTIFIER@43..59
                  0: IDENT@43..59 "bar" [Whitespace(" ")] [Whitespace("  "), Comments("# comment2")]
                1: EQUAL@59..75 "=" [Newline("\n"), Whitespace("  ")] [Whitespace("  "), Comments("# comment3")]
              1: R_DOUBLE_VALUE@75..102
                0: R_DOUBLE_LITERAL@75..102 "2" [Newline("\n"), Whitespace("  "), Comments("# comment4"), Newline("\n"), Whitespace("  ")] [Whitespace(" "), Comments("#comment5")]
            ,
            comment: SourceComment {
                lines_before: 0,
                lines_after: 1,
                piece: SyntaxTriviaPieceComments(
                    Comments("#comment5"),
                ),
                kind: Line,
                formatted: Cell {
                    value: false,
                },
            },
        },
        Leading {
            node: 4: R_ARGUMENT@128..128
              0: (empty)
              1: (empty)
            ,
            comment: SourceComment {
                lines_before: 1,
                lines_after: 1,
                piece: SyntaxTriviaPieceComments(
                    Comments("#comment6"),
                ),
                kind: Line,
                formatted: Cell {
                    value: false,
                },
            },
        },
        Trailing {
            node: 2: R_ARGUMENT@43..102
              0: R_ARGUMENT_NAME_CLAUSE@43..75
                0: R_IDENTIFIER@43..59
                  0: IDENT@43..59 "bar" [Whitespace(" ")] [Whitespace("  "), Comments("# comment2")]
                1: EQUAL@59..75 "=" [Newline("\n"), Whitespace("  ")] [Whitespace("  "), Comments("# comment3")]
              1: R_DOUBLE_VALUE@75..102
                0: R_DOUBLE_LITERAL@75..102 "2" [Newline("\n"), Whitespace("  "), Comments("# comment4"), Newline("\n"), Whitespace("  ")] [Whitespace(" "), Comments("#comment5")]
            ,
            comment: SourceComment {
                lines_before: 0,
                lines_after: 1,
                piece: SyntaxTriviaPieceComments(
                    Comments("#comment7"),
                ),
                kind: Line,
                formatted: Cell {
                    value: false,
                },
            },
        },
        Trailing {
            node: 2: R_ARGUMENT@43..102
              0: R_ARGUMENT_NAME_CLAUSE@43..75
                0: R_IDENTIFIER@43..59
                  0: IDENT@43..59 "bar" [Whitespace(" ")] [Whitespace("  "), Comments("# comment2")]
                1: EQUAL@59..75 "=" [Newline("\n"), Whitespace("  ")] [Whitespace("  "), Comments("# comment3")]
              1: R_DOUBLE_VALUE@75..102
                0: R_DOUBLE_LITERAL@75..102 "2" [Newline("\n"), Whitespace("  "), Comments("# comment4"), Newline("\n"), Whitespace("  ")] [Whitespace(" "), Comments("#comment5")]
            ,
            comment: SourceComment {
                lines_before: 1,
                lines_after: 1,
                piece: SyntaxTriviaPieceComments(
                    Comments("#comment8"),
                ),
                kind: Line,
                formatted: Cell {
                    value: false,
                },
            },
        },
    ],
}

[lionel-]

Changing lines_before will likely require depending on this PR which makes the SourceComment fields public: biomejs/biome#7052