Fix buffering bug in the 'read' builtin.

The last test case in builtin-io.test.sh now passes.

core/builtin.py

@@ -485,6 +485,23 @@ def _AppendParts(s, spans, max_results, join_next, parts):
READ_SPEC.ShortFlag('-n', args.Int)


# sys.stdin.readline() in Python has buffering!  TODO: Rewrite this tight loop
# in C?  Less garbage probably.
# NOTE that dash, mksh, and zsh all read a single byte at a time.  It appears
# to be required by POSIX?  Could try libc getline and make this an option.
def ReadLineFromStdin():
  chars = []
  while True:
    c = os.read(0, 1)
    if not c:
      break
    chars.append(c)

    if c == '\n':
      break
  return ''.join(chars)


def Read(argv, splitter, mem):
  arg, i = READ_SPEC.Parse(argv)

@@ -513,7 +530,7 @@ def Read(argv, splitter, mem):
  parts = []
  join_next = False
  while True:
    line = sys.stdin.readline()
    line = ReadLineFromStdin()
    #log('LINE %r', line)
    if not line:  # EOF
      status = 1

core/process_test.py

@@ -8,9 +8,11 @@
import unittest

from core.id_kind import Id
from core import builtin
from osh import ast_ as ast

from core import process  # module under test
from core import runtime
from core import util
from core.cmd_exec_test import InitExecutor  # helper

@@ -34,6 +36,32 @@ def _ExtProc(argv):

class ProcessTest(unittest.TestCase):

  def testStdinRedirect(self):
    waiter = process.Waiter()
    fd_state = process.FdState()

    PATH = '_tmp/one-two.txt'
    # Write two lines
    with open(PATH, 'w') as f:
      f.write('one\ntwo\n')

    # Should get the first line twice, because Pop() closes it!

    r = runtime.PathRedirect(Id.Redir_Less, 0, PATH)
    fd_state.Push([r], waiter)
    #line1 = sys.stdin.readline()
    line1 = builtin.ReadLineFromStdin()
    fd_state.Pop()

    fd_state.Push([r], waiter)
    #line2 = sys.stdin.readline()
    line2 = builtin.ReadLineFromStdin()
    fd_state.Pop()

    # sys.stdin.readline() would erroneously return 'two' because of buffering.
    self.assertEqual('one\n', line1)
    self.assertEqual('one\n', line2)

  def testProcess(self):

    # 3 fds.  Does Python open it?  Shell seems to have it too.  Maybe it

test/spec.sh

@@ -261,7 +261,7 @@ builtins() {
}

builtin-io() {
  sh-spec spec/builtin-io.test.sh --osh-failures-allowed 1 \
  sh-spec spec/builtin-io.test.sh \
    ${REF_SHELLS[@]} $ZSH $BUSYBOX_ASH $OSH "$@"
}