Add support for inferring the arguments to namedtuple invocations, to support cases like this:

fields = ['a', 'b', 'c']
A = collections.namedtuple('A', fields)

3 files changed, 44 insertions, 5 deletions

diff --git a/ChangeLog b/ChangeLog
index 3328549..4df1b16 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,8 @@ Change log for the astroid package (used to be astng)
 =====================================================
 
 --
+    * Add support for inferring arguments to namedtuple invocations.
+
     * Make sure that objects returned for namedtuple
       inference have parents.
 
diff --git a/brain/py2stdlib.py b/brain/py2stdlib.py
index 31a2477..27507ec 100644
--- a/brain/py2stdlib.py
+++ b/brain/py2stdlib.py
@@ -5,7 +5,8 @@ Currently help understanding of :
 * hashlib.md5 and hashlib.sha1
 """
 
-from astroid import MANAGER, AsStringRegexpPredicate, UseInferenceDefault, inference_tip
+from astroid import MANAGER, AsStringRegexpPredicate, UseInferenceDefault, inference_tip, YES
+from astroid import exceptions
 from astroid import nodes
 from astroid.builder import AstroidBuilder
 
@@ -183,6 +184,16 @@ MODULE_TRANSFORMS['subprocess'] = subprocess_transform
 
 def infer_named_tuple(node, context=None):
     """Specific inference function for namedtuple CallFunc node"""
+    def infer_first(node):
+        try:
+            value = node.infer().next()
+            if value is YES:
+                raise UseInferenceDefault()
+            else:
+                return value
+        except StopIteration:
+            raise InferenceError()
+
     # node is a CallFunc node, class name as first argument and generated class
     # attributes as second argument
     if len(node.args) != 2:
@@ -191,12 +202,13 @@ def infer_named_tuple(node, context=None):
     # namedtuple list of attributes can be a list of strings or a
     # whitespace-separate string
     try:
-        name = node.args[0].value
+        name = infer_first(node.args[0]).value
+        names = infer_first(node.args[1])
         try:
-            attributes = node.args[1].value.split()
+            attributes = names.value.split()
         except AttributeError:
-            attributes = [const.value for const in node.args[1].elts]
-    except AttributeError:
+            attributes = [infer_first(const).value for const in names.elts]
+    except (AttributeError, exceptions.InferenceError):
         raise UseInferenceDefault()
     # we want to return a Class node instance with proper attributes set
     class_node = nodes.Class(name, 'docstring')
diff --git a/test/unittest_brain.py b/test/unittest_brain.py
index dac25e6..7b750cf 100644
--- a/test/unittest_brain.py
+++ b/test/unittest_brain.py
@@ -19,6 +19,7 @@
 from logilab.common.testlib import TestCase, unittest_main
 
 from astroid import MANAGER
+from astroid import bases
 from astroid import test_utils
 import astroid
 
@@ -52,5 +53,29 @@ class NamedTupleTest(TestCase):
         for anc in klass.ancestors():
             self.assertFalse(anc.parent is None)
 
+    def test_namedtuple_inference(self):
+        klass = test_utils.extract_node("""
+        from collections import namedtuple
+
+        name = "X"
+        fields = ["a", "b", "c"]
+        class X(namedtuple(name, fields)):
+           pass
+        """)
+        for base in klass.ancestors():
+            if base.name == 'X':
+                break
+        self.assertItemsEqual(["a", "b", "c"], base.instance_attrs.keys())
+
+    def test_namedtuple_inference_failure(self):
+        klass = test_utils.extract_node("""
+        from collections import namedtuple
+
+        def foo(fields):
+           return __(namedtuple("foo", fields))
+        """)
+        self.assertIs(bases.YES, klass.infer().next())
+
+
 if __name__ == '__main__':
     unittest_main()