Rake removes trailing whitespaces from parameters when task is being executed from command line.

まず、提供されている rake ws[...] の例を使ってコマンドラインの動作を再現し、コンソールでの Rake::Task の呼び出しと比較します。コマンドラインのタスク引数の解析を追跡します。引用符で囲まれたパラメータの先頭と末尾の空白が保持され、直接の呼び出しおよび ARGV と一致すれば完了です。

Having a simple rake task:

  task :ws, [:str] => :environment do |t, args|
    puts args.str.inspect
  end

I get following results when run this task in command line:

  $ rake ws[' ']
  nil
  
  $ rake ws['    ']
  nil
  
  $ rake ws['    1']
  "    1"
  
  $ rake ws['    1    ']
  "    1"
  
  $ rake 'ws[ ]'
  nil
  
  $ rake 'ws[    ]'
  nil
  
  $ rake 'ws[    1]'
  "    1"
  
  $ rake 'ws[    1    ]'
  "    1"

While when the task is being invoked in rails console everything works as expected:

  2.3.3 :258 > Rake::Task['ws'].invoke(' ')
  " "
  2.3.3 :259 > Rake::Task['ws'].reenable
  2.3.3 :260 > Rake::Task['ws'].invoke('    ')
  "    "
  2.3.3 :261 > Rake::Task['ws'].reenable
  2.3.3 :262 > Rake::Task['ws'].invoke('    1')
  "    1"
  2.3.3 :263 > Rake::Task['ws'].reenable
  2.3.3 :264 > Rake::Task['ws'].invoke('    1    ')
  "    1    "

Again, it is definitely not the OS who is responsible for that trimming, since it shouldn't trim anything between quote marks. And besides it can be easily tested this way:

  task :ws, [:str] => :environment do |t, args|
    puts args.str.inspect
    puts ARGV[1].inspect
  end

then in command line:

  $ rake 'ws[  1  ]' '  2  '
  "  1"
  "  2  "

Rake version 12.0.0

some investigation on the issue https://stackoverflow.com/questions/45622716/rake-removes-trailing-whitespaces-from-parameters-how-to-prevent#answer-45623592