Walk type

.bumpversion.cfg

@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 0.1.23
+current_version = 0.1.24
 commit = True
 tag = True
 

CHANGELOG.rst

@@ -1,3 +1,13 @@
+0.1.24 (2019-07-28)
+-------------------
+
+
+No significant changes.
+
+
+----
+
+
 0.1.23 (2019-07-28)
 -------------------
 

changelog.d/47.breaking

@@ -0,0 +1 @@
+``walk -t`` no longer uses ``eval`` on the left-hand side of the equal sign. That value can only refer to a type by name.

docs/conf.py

@@ -29,7 +29,7 @@
 year = "2019"
 author = "Mario contributors"
 copyright = "{0}, {1}".format(year, author)
-version = release = "0.1.23"
+version = release = "0.1.24"
 
 pygments_style = "trac"
 templates_path = ["."]

setup.py

@@ -34,7 +34,7 @@ def read(*names, **kwargs):
 # Enable code coverage for C code: we can't use CFLAGS=-coverage in tox.ini, since that may mess with compiling
 setup(
     name="mario-addons",
-    version="0.1.23",
+    version="0.1.24",
     description="More commands for Mario.",
     long_description="%s\n%s"
     % (

src/mario_addons/__init__.py

@@ -1,3 +1,3 @@
 """Addons for mario."""
 
-__version__ = "0.1.23"
+__version__ = "0.1.24"

src/mario_addons/plugins/addons.toml

@@ -61,7 +61,7 @@ section = 'Traversals'
 inject_values=['t']
 short_help = "[EXPERIMENTAL] Walk a tree from the bottom up."
 help = """
-[EXPERIMENTAL] Walk a tree from the bottom up, transforming objects as you go. Note this command uses ``eval`` on the transformer arguments.
+[EXPERIMENTAL] Walk a tree from the bottom up, transforming objects as you go.
 
 For example,
 
@@ -90,7 +90,7 @@ For example,
 [[command.options]]
 name = "-t"
 multiple=true
-help="Transformers for types. Pass a type-function pair. Each instance of the type will be converted with the function. For example, use ``-tdict=collections.OrderedDict`` to convert all ``dict`` objects to ``OrderedDict``. ``eval`` is used on both sides of the ``=``."
+help="Transformers for types. Pass a type-function pair. Each instance of the type will be converted with the function. For example, use ``-tdict=collections.OrderedDict`` to convert all ``dict`` objects to ``OrderedDict``. The right-hand side of the ``=`` is Python code which will be executed. It may use ``x`` as a reference to the input value."
 
 [[command.stages]]
 command = 'map'

src/mario_addons/plugins/walking.py

@@ -1,5 +1,6 @@
 """Functions for walking a tree."""
 
+import builtins
 import collections.abc
 import typing as t
 
@@ -48,17 +49,53 @@ def make_func(code: str, namespace: t.Dict[str, object]) -> t.Callable:
     return lambda x: eval(code, {**namespace, "x": x})
 
 
+def prefixes(multi_attribute_access: str) -> t.List[str]:
+    """Get prefixes of a namepsaced name.
+
+    >>> prefixes('a.b.c')
+    ['a.b.c', 'a.b', 'a']
+    """
+    split = multi_attribute_access.split(".")
+    out = []
+    while split:
+        out.append(".".join(split))
+        split.pop(-1)
+    return out
+
+
+def get_type_object(namespaced_type_name: str) -> t.Type:
+    """Turns a qualname into the corresponding object."""
+
+    if "." not in namespaced_type_name:
+        return getattr(builtins, namespaced_type_name)
+
+    name_to_module = mario.interpret.build_name_to_module(namespaced_type_name)
+    for module_name in prefixes(namespaced_type_name):
+        module = name_to_module.get(module_name)
+        if module is not None:
+            break
+    else:
+        raise ImportError(module_name)
+
+    obj = module
+    # pylint: disable=undefined-loop-variable
+    remainder = namespaced_type_name[len(module_name) :]
+    names = [name for name in remainder.split(".") if name]
+
+    while names:
+        obj = getattr(obj, names[0])
+        names.pop()
+
+    return obj
+
+
 def build_mapping(pairs: t.Iterable[t.Tuple[str, str]]):
     """Build a type-to-transformer mapping."""
     mapping = {}
 
     for input_type, converter in pairs:
-        input_type_namespace = mario.interpret.build_name_to_module(input_type)
         converter_namespace = mario.interpret.build_name_to_module(converter)
-        # pylint: disable=eval-used
-        mapping[eval(input_type, input_type_namespace)] = make_func(
-            converter, converter_namespace
-        )
+        mapping[get_type_object(input_type)] = make_func(converter, converter_namespace)
     return mapping
 
 

tests/test_walking.py

@@ -0,0 +1,17 @@
+"""Test the walking module."""
+
+import pytest
+
+from mario_addons.plugins import walking
+
+
+@pytest.mark.parametrize("name", ["collections.OrderedDict", "int"])
+def test_get_type_object(name):
+    """The type object has the right the module name and qualname."""
+    result = walking.get_type_object(name)
+    assert isinstance(result, type)
+
+    expected_name = result.__module__ + "." + result.__qualname__
+    if expected_name.startswith("builtins."):
+        expected_name = expected_name[len("builtins.") :]
+    assert expected_name == name