Implemented transit_types.Boolean plus true,false.

Author: benkamphaus

README.md

@@ -95,8 +95,6 @@ writer.write(TaggedValue("ints", [1,2,3]))
 
 ### Python's bool and int
 
-All caveats of the Python language apply to decoding Transit data.
-
 In Python, bools are subclasses of int (that is, `True` is actually `1`).
 
 ```python
@@ -108,7 +106,7 @@ In Python, bools are subclasses of int (that is, `True` is actually `1`).
 True
 ```
 
-This only becomes problematic when decoding a map that contains bool and
+This becomes problematic when decoding a map that contains bool and
 int keys.  The bool keys may be overridden (ie: you'll only see the int key),
 and the value will be one of any possible bool/int keyed value.
 
@@ -117,6 +115,14 @@ and the value will be one of any possible bool/int keyed value.
 {1: 'World'}
 ```
 
+To counter this problem, the latest version of Transit Python introduces a
+Boolean type with singleton (by convention of use) instances of "true" and
+"false." A Boolean can be converted to a native Python bool with bool(x) where
+x is the "true" or "false" instance. Logical evaluation works correctly with
+Booleans (that is, they override the __nonzero__ method and correctly evaluate
+as true and false in simple logical evaluation), but uses of a Boolean as an
+integer will fail.
+
 ### Default type mapping
 
 |Transit type|Write accepts|Read returns|

tests/exemplars_test.py

@@ -17,7 +17,7 @@
 # then import transit stuff
 from transit.reader import Reader, JsonUnmarshaler, MsgPackUnmarshaler
 from transit.writer import Writer
-from transit.transit_types import Keyword, Symbol, URI, frozendict, TaggedValue, Link
+from transit.transit_types import Keyword, Symbol, URI, frozendict, TaggedValue, Link, true, false
 from StringIO import StringIO
 from transit.helpers import mapcat
 from helpers import ints_centered_on, hash_of_size, array_of_symbools
@@ -96,7 +96,7 @@ def assertEqual(self, val, data):
     globals()["test_" + name + "_json"] = ExemplarTest
 
 ARRAY_SIMPLE = (1, 2, 3)
-ARRAY_MIXED = (0, 1, 2.0, True, False, 'five', Keyword("six"), Symbol("seven"), '~eight', None)
+ARRAY_MIXED = (0, 1, 2.0, true, false, 'five', Keyword("six"), Symbol("seven"), '~eight', None)
 ARRAY_NESTED = (ARRAY_SIMPLE, ARRAY_MIXED)
 SMALL_STRINGS = ("", "a", "ab", "abc", "abcd", "abcde", "abcdef")
 POWERS_OF_TWO = tuple(map(lambda x: pow(2, x), range(66)))
@@ -131,14 +131,14 @@ def assertEqual(self, val, data):
 
 MAP_MIXED = frozendict({Keyword("a"): 1,
                         Keyword("b"): u"a string",
-                        Keyword("c"): True})
+                        Keyword("c"): true})
 
 MAP_NESTED = frozendict({Keyword("simple"): MAP_SIMPLE,
                          Keyword("mixed"): MAP_MIXED})
 
 exemplar("nil", None)
-exemplar("true", True)
-exemplar("false", False)
+exemplar("true", true)
+exemplar("false", false)
 exemplar("zero", 0)
 exemplar("one", 1)
 exemplar("one_string", "hello")

tests/regression.py

@@ -17,7 +17,7 @@
 
 from transit.reader import Reader
 from transit.writer import Writer
-from transit.transit_types import Symbol, frozendict
+from transit.transit_types import Symbol, frozendict, true, false
 from StringIO import StringIO
 
 class RegressionBaseTest(unittest.TestCase):
@@ -37,12 +37,44 @@ def test_roundtrip(self):
 
     globals()["test_" + name + "_json"] = RegressionTest
 
-regression("cache_consistency", ({"Problem?":True},
+regression("cache_consistency", ({"Problem?":true},
                                   Symbol("Here"),
                                   Symbol("Here")))
 regression("one_pair_frozendict", frozendict({"a":1}))
 regression("json_int_max", (2**53+100, 2**63+100))
 regression("newline_in_string", "a\nb")
 
+class BooleanTest(unittest.TestCase):
+    """Even though we're roundtripping transit_types.true and
+    transit_types.false now, make sure we can still write Python bools.
+
+    Additionally, make sure we can still do basic logical evaluation on transit
+    Boolean values.
+    """
+    def test_write_bool(self):
+        for protocol in ("json", "json-verbose", "msgpack"):
+            io = StringIO()
+            w = Writer(io, protocol)
+            w.write((True, False))
+            r = Reader(protocol)
+            io.seek(0)
+            out_data = r.read(io)
+            assert out_data[0] == true
+            assert out_data[1] == false
+
+    def test_basic_eval(self):
+        assert true
+        assert not false
+
+    def test_or(self):
+        assert true or false
+        assert not (false or false)
+        assert true or true
+
+    def test_and(self):
+        assert not (true and false)
+        assert true and true
+        assert not (false and false)
+
 if __name__ == '__main__':
     unittest.main()

transit/decoder.py

@@ -18,6 +18,7 @@
 from helpers import pairs
 import read_handlers as rh
 from rolling_cache import RollingCache, is_cacheable, is_cache_key
+from transit_types import true, false
 
 class Tag(object):
     def __init__(self, tag):
@@ -88,8 +89,9 @@ def _decode(self, node, cache, as_map_key):
             return self.decode_list(node, cache, as_map_key)
         elif tp is str:
             return self.decode_string(unicode(node, "utf-8"), cache, as_map_key)
-        else:
-            return node
+        elif tp is bool:
+            return true if node else false
+        return node
 
     def decode_list(self, node, cache, as_map_key):
         """Special case decodes map-as-array.

transit/read_handlers.py

@@ -47,7 +47,7 @@ def from_rep(v):
 class BooleanHandler(object):
     @staticmethod
     def from_rep(x):
-        return x == "t"
+        return transit_types.true if x == "t" else transit_types.false
 
 class IntHandler(object):
     @staticmethod

transit/transit_types.py

@@ -188,3 +188,29 @@ def as_map(self):
     @property
     def as_array(self):
         return [self.href, self.rel, self.name, self.render, self.prompt]
+
+class Boolean(object):
+    """To allow a separate t/f that won't hash as 1/0. Don't call directly,
+    instead use true and false as singleton objects. Can use with type check.
+
+    Note that the Booleans are for preserving hash/set bools that duplicate 1/0
+    and not designed for use in Python outside of logical evaluation (don't treat
+    as an int, they're not). You can get a Python bool using bool(x)
+    where x is a true or false Boolean.
+    """
+    def __init__(self, name):
+        self.v = True if name == "true" else False
+        self.name = name
+
+    def __nonzero__(self):
+        return self.v
+
+    def __repr__(self):
+        return self.name
+
+    def __str__(self):
+        return self.name
+
+# lowercase rep matches java/clojure
+false = Boolean("false")
+true = Boolean("true")

transit/write_handlers.py

@@ -14,7 +14,7 @@
 
 from constants import *
 from class_hash import ClassDict
-from transit_types import Keyword, Symbol, URI, frozendict, TaggedValue, Link
+from transit_types import Keyword, Symbol, URI, frozendict, TaggedValue, Link, Boolean
 import uuid
 import datetime, time
 from dateutil import tz
@@ -103,7 +103,7 @@ def tag(_):
         return '?'
     @staticmethod
     def rep(b):
-        return b
+        return bool(b)
     @staticmethod
     def string_rep(b):
         return 't' if b else 'f'
@@ -258,6 +258,7 @@ def __init__(self):
         super(WriteHandler, self).__init__()
         self[type(None)] = NoneHandler
         self[bool] = BooleanHandler
+        self[Boolean] = BooleanHandler
         self[str] = StringHandler
         self[unicode] = StringHandler
         self[list] = ArrayHandler