improved type checking for MultiFileReader (enables more file-like objects including codecs.open etc.), more tests to match. also corrected some error messages with appropriate class name.

boltons/ioutils.py

@@ -1,4 +1,4 @@
-# -*- coding: UTF-8 -*-
+# -*- coding: utf-8 -*-
 
 # Coding decl above needed for rendering the emdash properly in the
 # documentation.
@@ -409,11 +409,16 @@ class SpooledStringIO(SpooledIOBase):
 class MultiFileReader(object):
 
     def __init__(self, *fileobjs):
-        if all(isinstance(f, TextIOBase) for f in fileobjs):
-            self._joiner = ''
-        elif any(isinstance(f, TextIOBase) for f in fileobjs):
-            raise ValueError('All arguments to MultiFileReader must be either '
-                             'bytes IO or text IO, not a mix')
+        if not all([callable(getattr(f, 'read', None)) and
+                    callable(getattr(f, 'seek', None)) for f in fileobjs]):
+            raise TypeError('MultiFileReader expected file-like objects'
+                            ' with .read() and .seek()')
+        if all([hasattr(f, 'encoding') for f in fileobjs]):
+            # codecs.open and io.TextIOBase
+            self._joiner = u''
+        elif any([hasattr(f, 'encoding') for f in fileobjs]):
+            raise ValueError('All arguments to MultiFileReader must handle'
+                             ' bytes OR text, not a mix')
         else:
             self._joiner = b''
         self._fileobjs = fileobjs
@@ -434,11 +439,9 @@ class MultiFileReader(object):
     def seek(self, offset, whence=os.SEEK_SET):
         if whence != os.SEEK_SET:
             raise NotImplementedError(
-                'fileprepender does not support anything other'
-                ' than os.SEEK_SET for whence on seek()')
+                'MultiFileReader.seek() only supports os.SEEK_SET')
         if offset != 0:
             raise NotImplementedError(
-                'fileprepender only supports seeking to start, but that '
-                'could be fixed if you need it')
+                'MultiFileReader only supports seeking to start at this time')
         for f in self._fileobjs:
             f.seek(0)

tests/test_ioutils.py

@@ -1,14 +1,18 @@
 import io
 import os
+import sys
+import codecs
 import random
 import string
-import sys
 from tempfile import mkdtemp
 from unittest import TestCase
 from zipfile import ZipFile, ZIP_DEFLATED
 
 from boltons import ioutils
 
+CUR_FILE_PATH = os.path.abspath(__file__)
+
+
 # Python2/3 compat
 if sys.version_info[0] == 3:
     text_type = str
@@ -412,3 +416,29 @@ class TestMultiFileReader(TestCase):
     def test_no_mixed_bytes_and_text(self):
         self.assertRaises(ValueError, ioutils.MultiFileReader,
                           io.BytesIO(b'narf'), io.StringIO(u'troz'))
+
+    def test_open(self):
+        with open(CUR_FILE_PATH, 'r') as f:
+            r_file_str = f.read()
+        with open(CUR_FILE_PATH, 'r') as f1:
+            with open(CUR_FILE_PATH, 'r') as f2:
+                mfr = ioutils.MultiFileReader(f1, f2)
+                r_double_file_str = mfr.read()
+
+        assert r_double_file_str == (r_file_str * 2)
+
+        with open(CUR_FILE_PATH, 'rb') as f:
+            rb_file_str = f.read()
+        with open(CUR_FILE_PATH, 'rb') as f1:
+            with open(CUR_FILE_PATH, 'rb') as f2:
+                mfr = ioutils.MultiFileReader(f1, f2)
+                rb_double_file_str = mfr.read()
+
+        assert rb_double_file_str == (rb_file_str * 2)
+
+        utf8_file_str = codecs.open(CUR_FILE_PATH, encoding='utf8').read()
+        f1, f2 = (codecs.open(CUR_FILE_PATH, encoding='utf8'),
+                  codecs.open(CUR_FILE_PATH, encoding='utf8'))
+        mfr = ioutils.MultiFileReader(f1, f2)
+        utf8_double_file_str = mfr.read()
+        assert utf8_double_file_str == (utf8_file_str * 2)