py/objfun: Implement function.__code__ and function constructor.

This allows retrieving the code object of a function using
`function.__code__`, and then reconstructing a function from a code object
using `FunctionType(code_object)`.

This feature is controlled by `MICROPY_PY_FUNCTION_ATTRS_CODE` and is
enabled at the full-features level.

Signed-off-by: Damien George <damien@micropython.org>

6 files changed, 80 insertions, 4 deletions

diff --git a/tests/basics/fun_code.py b/tests/basics/fun_code.py
new file mode 100644
index 000000000..59e1f7ec0
--- /dev/null
+++ b/tests/basics/fun_code.py
@@ -0,0 +1,36 @@
+# Test function.__code__ attribute.
+
+try:
+    (lambda: 0).__code__
+except AttributeError:
+    print("SKIP")
+    raise SystemExit
+
+
+def f():
+    return a
+
+
+ftype = type(f)
+
+# Test __code__ access and function constructor.
+code = f.__code__
+print(type(ftype(code, {})) is ftype)
+
+# Test instantiating multiple code's with different globals dicts.
+code = f.__code__
+f1 = ftype(code, {"a": 1})
+f2 = ftype(code, {"a": 2})
+print(f1(), f2())
+
+# Test bad first argument type.
+try:
+    ftype(None, {})
+except TypeError:
+    print("TypeError")
+
+# Test bad second argument type.
+try:
+    ftype(f.__code__, None)
+except TypeError:
+    print("TypeError")
diff --git a/tests/basics/fun_code_micropython.py b/tests/basics/fun_code_micropython.py
new file mode 100644
index 000000000..2c319a2db
--- /dev/null
+++ b/tests/basics/fun_code_micropython.py
@@ -0,0 +1,19 @@
+# Test MicroPython-specific restrictions of function.__code__ attribute.
+
+try:
+    (lambda: 0).__code__
+except AttributeError:
+    print("SKIP")
+    raise SystemExit
+
+
+def f_with_children():
+    def g():
+        pass
+
+
+# Can't access __code__ when function has children.
+try:
+    f_with_children.__code__
+except AttributeError:
+    print("AttributeError")
diff --git a/tests/basics/fun_code_micropython.py.exp b/tests/basics/fun_code_micropython.py.exp
new file mode 100644
index 000000000..d169edffb
--- /dev/null
+++ b/tests/basics/fun_code_micropython.py.exp
@@ -0,0 +1 @@
+AttributeError
diff --git a/tests/basics/subclass_native1.py b/tests/basics/subclass_native1.py
index 288a686d1..74b377eac 100644
--- a/tests/basics/subclass_native1.py
+++ b/tests/basics/subclass_native1.py
@@ -21,11 +21,9 @@ print(a + [20, 30, 40])
 # TODO: Faults
 #print(a + a)
 
-def foo():
-    print("hello from foo")
-
+# subclassing a type that doesn't have make_new at the C level (not allowed)
 try:
-    class myfunc(type(foo)):
+    class myfunc(type([].append)):
         pass
 except TypeError:
     print("TypeError")
diff --git a/tests/micropython/native_fun_attrs_code.py b/tests/micropython/native_fun_attrs_code.py
new file mode 100644
index 000000000..d277a7b9b
--- /dev/null
+++ b/tests/micropython/native_fun_attrs_code.py
@@ -0,0 +1,21 @@
+# Test MicroPython-specific restrictions of function.__code__ attribute.
+
+try:
+    (lambda: 0).__code__
+except AttributeError:
+    print("SKIP")
+    raise SystemExit
+
+import micropython
+
+
+@micropython.native
+def f_native():
+    pass
+
+
+# Can't access __code__ when function is native code.
+try:
+    f_native.__code__
+except AttributeError:
+    print("AttributeError")
diff --git a/tests/micropython/native_fun_attrs_code.py.exp b/tests/micropython/native_fun_attrs_code.py.exp
new file mode 100644
index 000000000..d169edffb
--- /dev/null
+++ b/tests/micropython/native_fun_attrs_code.py.exp
@@ -0,0 +1 @@
+AttributeError