added commands cache tests is_only_functional_alias()

tests/test_commands_cache.py

@@ -1,6 +1,8 @@
+import os
+import builtins
+
 import pytest
 
-import os
 from xonsh.commands_cache import (CommandsCache, predict_shell,
                                   SHELL_PREDICTOR_PARSER, predict_true, predict_false)
 from tools import skip_if_on_windows
@@ -82,3 +84,29 @@ def test_commands_cache_predictor_default(args):
                                           timeout=1, failure=None)
     expected = predict_false if use_tty else predict_true
     assert result == expected
+
+
+def test_cd_is_only_functional_alias(xonsh_builtins):
+    cc = CommandsCache()
+    builtins.aliases['cd'] = lambda args: os.chdir(args[0])
+    assert cc.is_only_functional_alias('cd')
+
+
+def test_non_exist_is_only_functional_alias(xonsh_builtins):
+    cc = CommandsCache()
+    assert not cc.is_only_functional_alias('<not really a command name>')
+
+
+@skip_if_on_windows
+def test_bash_is_only_functional_alias(xonsh_builtins):
+    builtins.__xonsh_env__['PATH'] = os.environ['PATH'].split(os.pathsep)
+    cc = CommandsCache()
+    assert not cc.is_only_functional_alias('bash')
+
+
+@skip_if_on_windows
+def test_bash_and_is_alias_is_only_functional_alias(xonsh_builtins):
+    builtins.__xonsh_env__['PATH'] = os.environ['PATH'].split(os.pathsep)
+    cc = CommandsCache()
+    builtins.aliases['bash'] = lambda args: os.chdir(args[0])
+    assert not cc.is_only_functional_alias('bash')

xonsh/commands_cache.py

@@ -189,10 +189,12 @@ class CommandsCache(cabc.Mapping):
                       None)
         if cached:
             (path, alias) = self._cmds_cache[cached]
-            if not alias or ignore_alias:
-                return path
-            else:
+            ispure = path == pathbasename(path)
+            if alias and ignore_alias and ispure:
+                # pure alias, which we are ignoring
                 return None
+            else:
+                return path
         elif os.path.isfile(name) and name != pathbasename(name):
             return name
 
@@ -212,7 +214,8 @@ class CommandsCache(cabc.Mapping):
         val = self._cmds_cache.get(name, None)
         if val is None:
             return False
-        return val == (name, True)
+        return val == (name, True) and \
+               self.locate_binary(name, ignore_alias=True) is None
 
     def predict_threadable(self, cmd):
         """Predicts whether a command list is able to be run on a background