Merge pull request #226 from datacamp/feature-ext

Feature ext

Author: machow

pythonwhat/check_syntax.py

@@ -47,24 +47,40 @@ def __init__(self, state):
         self._crnt_sct = None
         self._waiting_on_call = False
 
+    def _double_attr_error(self):
+        raise AttributeError("Did you forget to call a statement? "
+                                "e.g. Ex().check_list_comp.check_body()")
+
     def __getattr__(self, attr):
         if attr not in ATTR_SCTS: raise AttributeError("No SCT named %s"%attr)
-        elif self._waiting_on_call: 
-            raise AttributeError("Did you forget to call a statement? "
-                                 "e.g. Ex().check_list_comp.check_body()")
+        elif self._waiting_on_call: self._double_attr_error()
         else:
             # make a copy to return, 
             # in case someone does: a = chain.a; b = chain.b
-            chain = copy.copy(self)
-            chain._crnt_sct = ATTR_SCTS[attr]
-            chain._waiting_on_call = True
-            return chain
+            return self._sct_copy(ATTR_SCTS[attr])
 
     def __call__(self, *args, **kwargs):
         self._state = self._crnt_sct(state=self._state, *args, **kwargs)
         self._waiting_on_call = False
         return self
 
+    def __rshift__(self, f):
+        if self._waiting_on_call:
+            self._double_attr_error()
+        elif type(f) == Chain:
+            raise BaseException("did you use a result of the Ex() function on the right hand side of the >> operator?")
+        elif not callable(f):
+            raise BaseException("right hand side of >> operator should be an SCT, so must be callable!")
+        else:
+            chain = self._sct_copy(f)
+            return chain()
+
+    def _sct_copy(self, f):
+        chain = copy.copy(self)
+        chain._crnt_sct = f
+        chain._waiting_on_call = True
+        return chain
+
 class F(Chain):
     def __init__(self, stack = None):
         self._crnt_sct = None
@@ -85,8 +101,8 @@ def _from_func(cls, f):
         func_chain._stack.append(f)
         return func_chain
 
-def Ex():
-    return Chain(State.root_state)
+def Ex(state = None):
+    return Chain(state or State.root_state)
 
 # Prepare SCTs that may be chained attributes ----------------------
 # decorate functions that may try to run test_* function nodes as subtests

tests/test_spec.py

@@ -299,12 +299,73 @@ def gen_exercise(*args, **kwargs):
         setattr(TestOverride, test_name, pf) 
 
 
-#class TestSetContext(unittest.TestCase):
-#    def setUp(self):
-#        self.data = {
-#                "DC_PEC": "",
-#                "DC_SOLUTION": "[(i,j) for i,j in enumerate(range(10))]"
-#                }
+# Test SCT Ex syntax (copied from sqlwhat)  -----------------------------------
+
+import pytest
+from pythonwhat.check_syntax import Ex, F, state_dec
+
+@pytest.fixture
+def addx():
+    return lambda x, state=None: state + x
+
+@pytest.fixture
+def f():
+    return F._from_func(lambda state=None: state + 'b')
+
+@pytest.fixture
+def f2():
+    return F._from_func(lambda state=None: state + 'c')
+
+def test_f_from_func(f):
+    assert f('a') == 'ab'
+
+def test_f_sct_copy_kw(addx):
+    assert F()._sct_copy(addx)(x = 'x')('state') == 'statex'
+
+def test_f_sct_copy_pos(addx):
+    assert F()._sct_copy(addx)('x')('state') == 'statex'
+
+def test_ex_sct_copy_kw(addx):
+    assert Ex('state')._sct_copy(addx)(x = 'x')._state == 'statex'
+
+def test_ex_sct_copy_pos(addx):
+    assert Ex('state')._sct_copy(addx)('x')._state == 'statex'
+
+def test_f_2_funcs(f, addx):
+    g = f._sct_copy(addx)
+    
+    assert g(x = 'x')('a') == 'abx'
+
+def test_f_add_unary_func(f):
+    g = f >> (lambda state=None: state + 'c')
+    assert g('a') == 'abc'
+
+def test_f_add_f(f, f2):
+    g = f >> f2
+    assert g('a') == 'abc'
+
+def test_f_from_state_dec(addx):
+    dec_addx = state_dec(addx)
+    f = dec_addx(x = 'x')
+    isinstance(f, F)
+    assert f('state') == 'statex'
+
+@pytest.fixture
+def ex():
+    return Ex('state')._sct_copy(lambda x, state=None: state + x)('x')
+
+def test_ex_add_f(ex, f):
+    (ex >> f)._state = 'statexb'
+
+def test_ex_add_unary(ex):
+    (ex >> (lambda state=None: state + 'b'))._state == 'statexb'
+
+def test_ex_add_ex_err(ex):
+    with pytest.raises(BaseException): ex >> ex
+
+def test_f_add_ex_err(f, ex):
+    with pytest.raises(BaseException): f >> ex
+
 
 if __name__ == "__main__":
     unittest.main()