rustfmt --skip-children emulation script

rustfmt-skip-children.sh

#!/bin/bash
#
# This script filters rustfmt output for format-on-save workflows in text
# editors.
#
# Usage:
#
#   rustfmt-skip-children /path/to/source
#
# In particular, it:
#
# 1. Removes output for all but the first file in the output. rustfmt prior to
#    v2.0 will not only emit formatted source for the provided file, but also
#    for local modules that it depends on. This is not very useful if you're
#    doing single-file formatting, e.g., for format-on-save.
# 2. Removes some metadata output that precedes the actual formatting output,
#    such as the filename and the following blank line. You can also do this
#    simply by passing --quiet to rustfmt, but the metadata is necessary for
#    achieving item 1 above.
#
# Note that this script is not necessary for rustfmt 2.0 and onward. Read more
# at https://github.com/rust-lang/rustfmt/issues/3893#issuecomment-546747980

set -euo pipefail

~/.cargo/bin/rustfmt --emit stdout "$1" | awk "
  BEGIN {print_ok = 0}
  {
    if (\$0 == \"$(realpath $1):\") {
      print_ok = 1;

      # rustfmt includes a blank line after the filename
      getline;
      next;
    }

    if (/^(\/[^/]+)*\/[^/]+:/) {
      print_ok = 0;
      next;
    }

    if (print_ok == 1) {print}
  }
"