syntax: heredoc trailing comment duplicated on each format when inside indented block

[mbertheau]

Summary

When a heredoc with a trailing comment (e.g., <<-EOF # comment) is inside an indented block, shfmt duplicates the comment after EOF on each run. This is non-idempotent behavior.

Steps to reproduce

$ cat test.sh
#!/bin/bash
if true; then
  cat <<-EOF # comment
    content
EOF
fi

$ shfmt -w test.sh
$ cat test.sh
#!/bin/bash
if true; then
  cat <<-EOF # comment
    content
EOF
  # comment
fi

$ shfmt -w test.sh
$ cat test.sh
#!/bin/bash
if true; then
  cat <<-EOF # comment
    content
EOF
  # comment
  # comment
fi

Each invocation adds another copy of the comment.

Environment

• shfmt version: v3.12.0
• OS: Linux (Fedora 42)

Related issues

• syntax: inline comment on a heredoc gets misplaced #623 (closed) was about heredoc inline comments being misplaced
• Comments in a subshell are moved every time the formatter runs #1084 (open) is a similar non-idempotent comment formatting bug (spaces added to subshell comments)