Merge pull request hylang#2595 from Kodiologist/kw-order

Make keyword objects comparable

Author: Kodiologist

NEWS.rst

@@ -1,5 +1,12 @@
 .. default-role:: code
 
+Unreleased
+=============================
+
+Bug Fixes
+------------------------------
+* Keyword objects can now be compared to each other with `<` etc.
+
 0.29.0 (released 2024-05-20)
 =============================
 

docs/syntax.rst

@@ -204,7 +204,7 @@ Thus ``(foo : 3)`` must be rewritten to use runtime unpacking, as in ``(foo #**
 {"" 3})``.
 
 .. autoclass:: hy.models.Keyword
-   :members:  __bool__, __call__
+   :members:  __bool__, __lt__, __call__
 
 .. _dotted-identifiers:
 

hy/models.py

@@ -1,6 +1,6 @@
 import operator
 from contextlib import contextmanager
-from functools import reduce
+from functools import reduce, total_ordering
 from itertools import groupby
 from math import isinf, isnan
 
@@ -206,6 +206,7 @@ def __new__(cls, s, from_parser=False):
 _wrappers[type(None)] = lambda _: Symbol("None")
 
 
+@total_ordering
 class Keyword(Object):
     """
     Represents a keyword, such as ``:foo``.
@@ -251,6 +252,13 @@ def __ne__(self, other):
             return NotImplemented
         return self.name != other.name
 
+    def __lt__(self, other):
+        """Keywords behave like strings under comparison operators, but are incomparable
+        to actual ``str`` objects."""
+        if not isinstance(other, Keyword):
+            return NotImplemented
+        return self.name < other.name
+
     def __bool__(self):
         """The empty keyword ``:`` is false. All others are true."""
         return bool(self.name)

tests/native_tests/keywords.hy

@@ -6,9 +6,11 @@
 
 (defn test-keyword []
   (assert (= :foo :foo))
+  (assert (not (!= :foo :foo)))
+  (assert (!= :foo :bar))
   (assert (= :foo ':foo))
   (setv x :foo)
-  (assert (is (type x) (type ':foo)))
+  (assert (is (type x) (type ':foo) hy.models.Keyword))
   (assert (= (get {:foo "bar"} :foo) "bar"))
   (assert (= (get {:bar "quux"} (get {:foo :bar} :foo)) "quux")))
 
@@ -27,6 +29,16 @@
   (assert (= (. ': name) "")))
 
 
+(defn test-order []
+  ; https://github.com/hylang/hy/issues/2594
+  (assert (< :a :b))
+  (assert (<= :a :b))
+  (assert (> :b :a))
+  (assert (= (sorted [:b :a :c]) [:a :b :c]))
+  (with [(pytest.raises TypeError)]
+    (< :a "b")))
+
+
 (defn test-pickling-keyword []
   ; https://github.com/hylang/hy/issues/1754
   (setv x :test-keyword)