[clang-format] AlignTrailingComments has no penalty for not-aligning comments

[rxlecky]

clang-format Version: 13.0.
Description: AlignTrailingComments doesn't always align the block of comments.
Reproduction Steps: Format the following block of code with AlignTrailingComments option on. Notice resulting three different levels of indentation.

#define NODEFERWINDOWPOS // DeferWindowPos routines
#define NOSERVICE // All Service Controller routines, SERVICE_ equates, etc.
#define NOSYSCOMMANDS // SC_*
#define NOVIRTUALKEYCODES // VK_*

Expected Result:

#define NODEFERWINDOWPOS  // DeferWindowPos routines
#define NOSERVICE         // All Service Controller routines, SERVICE_ equates, etc.
#define NOSYSCOMMANDS     // SC_*
#define NOVIRTUALKEYCODES // VK_*

Actual Result:

#define NODEFERWINDOWPOS // DeferWindowPos routines
#define NOSERVICE     // All Service Controller routines, SERVICE_ equates, etc.
#define NOSYSCOMMANDS // SC_*
#define NOVIRTUALKEYCODES // VK_*

[llvmbot]

@llvm/issue-subscribers-bug

[llvmbot]

@llvm/issue-subscribers-clang-format

[mkurdej]

Not sure it's a bug per se, it's just that the penalty for not aligning comments is smaller than the penalty for breaking the comment and putting a part of it on a different line.

Example (with -style=LLVM, implying ColumnLimit: 80 and AlignTrailingComments: true:

#define NODEFERWINDOWPOS //
#define NOSERVICE // Comment that does not exceed 80 chars when unaligned......

#define NODEFERWINDOWPOS //
#define NOSERVICE // Long comment that exceeds 80 chars even when unaligned......

will get formatted to:

#define NODEFERWINDOWPOS //
#define NOSERVICE // Comment that does not exceed 80 chars when unaligned......

#define NODEFERWINDOWPOS //
#define NOSERVICE        // Long comment that exceeds 80 chars even when
                         // unaligned......

However, you there's only PenaltyBreakComment (unsigned) but there's no penalty for not aligning comments. That's an enhancement one could add though.

PRs welcome!

[mkurdej]

BTW, as a workaround, you can manually break the comment and it will get aligned (but there must be some whitespace in front of the comment so that it doesn't get treated as a top-level one).

[rxlecky]

Ahh, that explains the behaviour, thanks Marek! I was able to work around this now that I understand the cause.

Should I close the issue, since this is not really a bug or keep it open to track your suggested enhancement?

[mkurdej]

Let's keep it.
I changed the issue to enhancement.
Maybe somebody will be voluntary to add something like PenaltyUnalignedComment.

[lygstate]

style:

BasedOnStyle: LLVM
IndentWidth: 4
ColumnLimit: 120
BreakBeforeBraces: Linux
IndentCaseLabels: false
AlignArrayOfStructures: Left
AlignTrailingComments:
  Kind: Always
  OverEmptyLines: 2

code:

struct_type array_list[] = {
    {
     "aaa", /* aaa;*/
        aaaaa, /* bbb */
        8192,  /* ccc */
        2,   /* ddd */
        0,            /* eee */
        -1,                    /* fff */
        SOFT   /* ggg */
    },

    {
     "bbb", /* aaa;*/
        bbbbb, /* bbb */
        65536, /* ccc */
        15, /* ddd */
        1000000000, /* eee */
        1000000000, /* fff */
        SOFT        /* ggg */
    },
    {
     "ccc", /* aaa;*/
        ccccc, /* bbb */
        65536, /* ccc */
        15, /* ddd */
        0,          /* eee */
        -1,                  /* fff */
        SOFT        /* ggg */
    }
};

The alignment looks weird