py/modbuiltins: Make built-in dir support the __dir__ special method.

If MICROPY_PY_ALL_SPECIAL_METHODS is enabled then dir() will now delegate
to the special method __dir__ if the object it is listing has this method.

1 files changed, 9 insertions, 0 deletions

diff --git a/tests/basics/special_methods2.py b/tests/basics/special_methods2.py
index ba7cf27cd..1a38a250c 100644
--- a/tests/basics/special_methods2.py
+++ b/tests/basics/special_methods2.py
@@ -94,6 +94,9 @@ class Cud():
         print("__isub__ called")
         return self
 
+    def __dir__(self):
+        return ['a', 'b', 'c']
+
 cud1 = Cud()
 cud2 = Cud()
 
@@ -113,6 +116,12 @@ cud2 // cud1
 cud1 += cud2
 cud1 -= cud2
 
+# test that dir() delegates to __dir__ special method
+print(dir(cud1))
+
+# test that dir() does not delegate to __dir__ for the type
+print('a' in dir(Cud))
+
 # TODO: the following operations are not supported on every ports
 #
 # ne is not supported, !(eq) is called instead