Checks for the presence of the dart2js issue https://github.com/dart-lang/sdk/issues/28727 in a given compiled JS file, and sets the exit code if it is found.

dart-lang_issue_28727_checker.sh

#!/usr/bin/env bash

# Checks for the presence of the dart2js issue https://github.com/dart-lang/sdk/issues/28727
# in a given compiled JS file, and sets the exit code if it is found.
#
# For use on `pub build` output, or other output where the dart2js `minify` is enabled.
#
# Usage:
#     ./dart-lang_issue_28727_checker.sh <pub_build_output.dart.js>

echo ''
echo 'Checking whether is affected by dart2js issue https://github.com/dart-lang/sdk/issues/28727'
echo ''
echo "Searching for duplicate argument names in JS functions in $1..."
echo ''

grep -E 'function( [a-zA-Z0-9\$_]+)?\(([a-zA-Z0-9\$_]+,)*([a-zA-Z0-9\$_]+),([a-zA-Z0-9\$_]+,)*\3(,[a-zA-Z0-9\$_]+)*\)' "$1"
grep_exit_code=$?

if [ $grep_exit_code -eq 0 ]; then
    red=$(tput setaf 1)
    bold=$(tput bold)
    normal=$(tput sgr0)

    echo -n "${red}"
    echo ''
    echo 'Duplicate argument found. There may be issues present only in minified dart2js code.'
    echo 'Please reach out in Support: H5 / Dart for instructions on how to proceed.'
    echo -n "${normal}"
    echo ''
elif [ $grep_exit_code -eq 1 ]; then
    echo 'Everything looks good!'
    echo ''
    echo 'Your minified dart2js should be safe'
    echo ''

    exit 0
else
    echo ''
    echo 'Something went wrong while grepping'
    echo ''
fi

exit 1