enh: make env a MutableMapping

Technologicat · Technologicat · commit 8115a2c7d697 · 2019-03-08T07:11:48.000+02:00
diff --git a/README.md b/README.md
@@ -247,6 +247,8 @@ When the `with` block exits, the environment clears itself. The environment inst
 
 *Changed in v0.13.1.* ``env`` now provides the ``collections.abc.Mapping`` API.
 
+*Changed in v0.14.0.* ``env`` now provides also the ``collections.abc.MutableMapping`` API.
+
 
 ### ``assignonce``
 
diff --git a/unpythonic/collections.py b/unpythonic/collections.py
@@ -91,7 +91,9 @@ def doit(x):
                 for elt in y:
                     x.add(elt)
             return x
-        elif isinstance(x, MutableMapping):
+        # env provides the MutableMapping API, but shouldn't get the general treatment here.
+        # (This is important for the lazify macro.)
+        elif isinstance(x, MutableMapping) and not isinstance(x, env):
             y = {k: doit(v) for k, v in x.items()}
             x.clear()
             x.update(y)
diff --git a/unpythonic/env.py b/unpythonic/env.py
@@ -3,7 +3,7 @@
 
 __all__ = ["env"]
 
-from collections.abc import Container, Sized, Iterable, Mapping
+from collections.abc import Container, Sized, Iterable, Mapping, MutableMapping
 
 class env:
     """Environment for let-like constructs.
@@ -116,6 +116,18 @@ def __eq__(self, other):
     def __len__(self):
         return len(self._env)
 
+    # MutableMapping
+    def pop(self, k, *default):
+        return self._env.pop(k, *default)
+    def popitem(self):
+        return self._env.popitem()
+    def clear(self):
+        return self._env.clear()
+    def update(self, mapping, **bindings):
+        return self._env.update(mapping, **bindings)
+    def setdefault(self, k, *default):
+        return self._env.setdefault(k, *default)
+
     # subscripting
     def __getitem__(self, k):
         return getattr(self, k)
@@ -167,10 +179,6 @@ def __lshift__(self, arg):
         self.set(name, value)
         return self
 
-    def clear(self):
-        """Clear the environment, i.e. forget all bindings."""
-        self._env = {}
-
     def finalize(self):
         """Finalize environment.
 
@@ -217,6 +225,6 @@ def finalize(self):
 #        return _assignonce_wrapper(obj)  # copy-construct obj with wrapper
 
 # register virtual base classes
-for abscls in (Container, Sized, Iterable, Mapping):
+for abscls in (Container, Sized, Iterable, Mapping, MutableMapping):
     abscls.register(env)
 del abscls
