bpo-32110: codecs.StreamReader.read(n) now returns not more than n (#4499)

characters/bytes for non-negative n.  This makes it compatible with
read() methods of other file-like objects.

1 files changed, 16 insertions, 2 deletions

diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index de6868a..eb21a39 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -196,19 +196,33 @@ class ReadTest(MixInCheckStateHandling):
         self.assertEqual(f.read(), ''.join(lines[1:]))
         self.assertEqual(f.read(), '')
 
+        # Issue #32110: Test readline() followed by read(n)
+        f = getreader()
+        self.assertEqual(f.readline(), lines[0])
+        self.assertEqual(f.read(1), lines[1][0])
+        self.assertEqual(f.read(0), '')
+        self.assertEqual(f.read(100), data[len(lines[0]) + 1:][:100])
+
         # Issue #16636: Test readline() followed by readlines()
         f = getreader()
         self.assertEqual(f.readline(), lines[0])
         self.assertEqual(f.readlines(), lines[1:])
         self.assertEqual(f.read(), '')
 
-        # Test read() followed by read()
+        # Test read(n) followed by read()
         f = getreader()
         self.assertEqual(f.read(size=40, chars=5), data[:5])
         self.assertEqual(f.read(), data[5:])
         self.assertEqual(f.read(), '')
 
-        # Issue #12446: Test read() followed by readlines()
+        # Issue #32110: Test read(n) followed by read(n)
+        f = getreader()
+        self.assertEqual(f.read(size=40, chars=5), data[:5])
+        self.assertEqual(f.read(1), data[5])
+        self.assertEqual(f.read(0), '')
+        self.assertEqual(f.read(100), data[6:106])
+
+        # Issue #12446: Test read(n) followed by readlines()
         f = getreader()
         self.assertEqual(f.read(size=40, chars=5), data[:5])
         self.assertEqual(f.readlines(), [lines[0][5:]] + lines[1:])