Merge pull request #1656 from Kodiologist/keyword-call

Make HyKeyword callable

NEWS.rst

@@ -7,6 +7,12 @@ Removals
 ------------------------------
 * Empty expressions (`()`) are no longer legal at the top level.
 
+New Features
+------------------------------
+* Keyword objects (not just literal keywords) can be called, as
+  shorthand for `(get obj :key)`, and they accept a default value
+  as a second argument.
+
 0.15.0
 ==============================
 

docs/language/syntax.rst

@@ -83,6 +83,11 @@ the error ``Keyword argument :foo needs a value``. To avoid this, you can quote
 the keyword, as in ``(f ':foo)``, or use it as the value of another keyword
 argument, as in ``(f :arg :foo)``.
 
+Keywords can be called like functions as shorthand for ``get``. ``(:foo obj)``
+is equivalent to ``(get obj :foo)``. An optional ``default`` argument is also
+allowed: ``(:foo obj 2)`` or ``(:foo obj :default 2)`` returns ``2`` if ``(get
+obj :foo)`` raises a ``KeyError``.
+
 .. _mangling:
 
 symbols

hy/compiler.py

@@ -1552,13 +1552,6 @@ class HyASTCompiler(object):
 
         fn = expression[0]
         func = None
-        if isinstance(fn, HyKeyword):
-            if len(expression) > 2:
-                raise HyTypeError(
-                    expression, "keyword calls take only 1 argument")
-            expression.append(expression.pop(0))
-            expression.insert(0, HySymbol("get"))
-            return self.compile(expression)
 
         if isinstance(fn, HySymbol):
 

hy/models.py

@@ -146,6 +146,16 @@ class HyKeyword(HyObject):
     def __bool__(self):
         return bool(self.name)
 
+    _sentinel = object()
+
+    def __call__(self, data, default=_sentinel):
+        try:
+            return data[self]
+        except KeyError:
+            if default is HyKeyword._sentinel:
+                raise
+            return default
+
 
 def strip_digit_separators(number):
     # Don't strip a _ or , if it's the first character, as _42 and

tests/native_tests/language.hy

@@ -1380,9 +1380,24 @@
   (assert (= (len "ℵℵℵ♥♥♥\t♥♥\r\n") 11)))
 
 
-(defn test-keyword-dict-access []
-  "NATIVE: test keyword dict access"
-  (assert (= "test" (:foo {:foo "test"}))))
+(defn test-keyword-get []
+
+  (assert (= (:foo {:foo "test"}) "test"))
+  (setv f :foo)
+  (assert (= (f {:foo "test"}) "test"))
+
+  (with [(pytest.raises KeyError)] (:foo {:a 1 :b 2}))
+  (assert (= (:foo {:a 1 :b 2} 3) 3))
+  (assert (= (:foo {:a 1 :b 2 :foo 5} 3) 5))
+
+  (with [(pytest.raises TypeError)] (:foo "Hello World"))
+  (with [(pytest.raises TypeError)] (:foo (object)))
+
+  ; The default argument should work regardless of the collection type.
+  (defclass G [object]
+    (defn __getitem__ [self k]
+      (raise KeyError)))
+  (assert (= (:foo (G) 15) 15)))
 
 
 (defn test-break-breaking []