Fix failing test for Zone.to_file

A fix for https://github.com/rthalley/dnspython/issues/94

Make the to_file method work on string files, unless explicitly told
to do binary encoding.
Take the line terminator from os, rather than relying on the print
function.

Change the test to use a text file rather than binary, and add a new
test for to_file with a binary file.

2 files changed, 30 insertions, 9 deletions

diff --git a/dns/zone.py b/dns/zone.py
index 9193a7d..b162ad3 100644
--- a/dns/zone.py
+++ b/dns/zone.py
@@ -21,6 +21,7 @@ import builtins
 import io
 import re
 import sys
+import os
 
 import dns.exception
 import dns.name
@@ -444,7 +445,7 @@ class Zone(object):
                     for rdata in rds:
                         yield (name, rds.ttl, rdata)
 
-    def to_file(self, f, sorted=True, relativize=True, nl=None):
+    def to_file(self, f, sorted=True, relativize=True, nl=None, binary=False):
         """Write a zone to a file.
 
         @param f: file or string.  If I{f} is a string, it is treated
@@ -460,17 +461,23 @@ class Zone(object):
         output will use the platform's native end-of-line marker (i.e.
         LF on POSIX, CRLF on Windows, CR on Macintosh).
         @type nl: string or None
+        @param binary: True if the file is open in binary mode
+        @type binary: bool
         """
 
         if nl is None:
-            opts = 'w'
-        else:
-            opts = 'wb'
+            nl = os.linesep
+
         if isinstance(f, str):
-            f = open(f, opts)
+            if binary:
+                mode = 'wb'
+            else:
+                mode = 'w'
+            f = open(f, mode)
             want_close = True
         else:
             want_close = False
+
         try:
             if sorted:
                 names = builtins.sorted(self.keys())
@@ -479,11 +486,12 @@ class Zone(object):
             for n in names:
                 l = self[n].to_text(n, origin=self.origin,
                                     relativize=relativize)
-                if nl is None:
-                    print(l, file=f)
-                else:
+                if binary:
                     f.write(l.encode('ascii'))
                     f.write(nl.encode('ascii'))
+                else:
+                    f.write(l)
+                    f.write(nl)
         finally:
             if want_close:
                 f.close()
diff --git a/tests/test_zone.py b/tests/test_zone.py
index 67fc2ae..08557ad 100644
--- a/tests/test_zone.py
+++ b/tests/test_zone.py
@@ -121,12 +121,25 @@ class ZoneTestCase(unittest.TestCase):
                 os.unlink('example2.out')
         self.assertTrue(ok)
 
+    def testFromFile2b(self):
+        """Test to_file with a binary file"""
+        z = dns.zone.from_file('example', 'example', relativize=False)
+        ok = False
+        try:
+            with open('example2b.out', 'wb') as f:
+                z.to_file(f, relativize=False, nl='\x0a', binary=True)
+            ok = filecmp.cmp('example2b.out', 'example2.good')
+        finally:
+            if not _keep_output:
+                os.unlink('example2b.out')
+        self.assertTrue(ok)
+
     def testToText(self):
         z = dns.zone.from_file('example', 'example')
         ok = False
         try:
             text_zone = z.to_text(nl='\x0a')
-            f = open('example3.out', 'wb')
+            f = open('example3.out', 'w')
             f.write(text_zone)
             f.close()
             ok = filecmp.cmp('example3.out', 'example3.good')