dns: reading /etc/hosts raised DeprecationWarning for universal lines on Python 3.4+

Solved by always reading in binary mode with explicit decoding.
Plus: new hosts parser in regex, better comment handling.

2 files changed, 30 insertions, 11 deletions

diff --git a/eventlet/support/greendns.py b/eventlet/support/greendns.py
index ee9bc3d..ebdea2d 100644
--- a/eventlet/support/greendns.py
+++ b/eventlet/support/greendns.py
@@ -32,6 +32,7 @@
 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+import re
 import struct
 import sys
 
@@ -154,10 +155,18 @@ class HostsResolver(object):
     :interval: The time between checking for hosts file modification
     """
 
+    LINES_RE = re.compile(r"""
+        \s*  # Leading space
+        ([^\r\n#]+?)  # The actual match, non-greedy so as not to include trailing space
+        \s*  # Trailing space
+        (?:[#][^\r\n]+)?  # Comments
+        (?:$|[\r\n]+)  # EOF or newline
+    """, re.VERBOSE)
+
     def __init__(self, fname=None, interval=HOSTS_TTL):
         self._v4 = {}           # name -> ipv4
         self._v6 = {}           # name -> ipv6
-        self._aliases = {}      # name -> cannonical_name
+        self._aliases = {}      # name -> canonical_name
         self.interval = interval
         self.fname = fname
         if fname is None:
@@ -178,16 +187,15 @@ class HostsResolver(object):
 
         Note that this performs disk I/O so can be blocking.
         """
-        lines = []
         try:
-            with open(self.fname, 'rU') as fp:
-                for line in fp:
-                    line = line.strip()
-                    if line and line[0] != '#':
-                        lines.append(line)
+            with open(self.fname, 'rb') as fp:
+                fdata = fp.read()
         except (IOError, OSError):
-            pass
-        return lines
+            return []
+
+        udata = fdata.decode(errors='ignore')
+
+        return self.LINES_RE.findall(udata)
 
     def _load(self):
         """Load hosts file
diff --git a/tests/greendns_test.py b/tests/greendns_test.py
index efdd628..4a47c5e 100644
--- a/tests/greendns_test.py
+++ b/tests/greendns_test.py
@@ -40,9 +40,20 @@ class TestHostsResolver(tests.LimitedTestCase):
         hr.hosts.write(b'line1\n')
         hr.hosts.flush()
         assert hr._readlines() == ['line0', 'line1']
+        # Test reading of varied newline styles
         hr._last_stat = 0
-        hr.hosts.write(b'#comment0\nline0\n #comment1\nline1')
-        assert hr._readlines() == ['line0', 'line1']
+        hr.hosts.seek(0)
+        hr.hosts.truncate()
+        hr.hosts.write(b'\naa\r\nbb\r  cc  \n\n\tdd ee')
+        hr.hosts.flush()
+        assert hr._readlines() == ['aa', 'bb', 'cc', 'dd ee']
+        # Test comments, including inline comments
+        hr._last_stat = 0
+        hr.hosts.seek(0)
+        hr.hosts.truncate()
+        hr.hosts.write(b' line1\n#comment\nline2 # inline comment\n')
+        hr.hosts.flush()
+        assert hr._readlines() == ['line1', 'line2']
 
     def test_readlines_missing_file(self):
         hr = _make_host_resolver()