inspect: Support closures/generators/async-funcs in inspect.signature.

This is a follow-up to b4565b41ea (PR #1043),
to support closures, async functions and generators in `inspect.signature`.

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

python-stdlib/inspect/inspect.py

@@ -1,7 +1,10 @@
 import sys
 
+# Generator function.
 _g = lambda: (yield)
 
+# Closure type.
+_ct = type((lambda x: (lambda: x))(None))
 
 def getmembers(obj, pred=None):
     res = []
@@ -111,9 +114,16 @@ def signature(f):
     elif t is type(setattr):
         # A three-parameter built-in.
         num_args = 3
-    elif t is type(signature):
+    elif t is type(signature) or t is type(_g) or t is _ct:
         # A bytecode function, work out the number of arguments by inspecting the bytecode data.
-        fun_obj = uctypes.struct(id(f), (uctypes.ARRAY | 0, uctypes.LONG | 4))
+        fun_ptr = id(f)
+        num_closed_over = 0
+        if t is _ct:
+            # A closure, the function is the second word.
+            clo_ptr = uctypes.struct(fun_ptr, (uctypes.ARRAY | 0, uctypes.LONG | 3))
+            fun_ptr = clo_ptr[1]
+            num_closed_over = clo_ptr[2]
+        fun_obj = uctypes.struct(fun_ptr, (uctypes.ARRAY | 0, uctypes.LONG | 4))
         bytecode = uctypes.bytearray_at(fun_obj[3], 8)
         # See py/bc.h:MP_BC_PRELUDE_SIG_DECODE_INTO macro.
         i = 0
@@ -127,7 +137,7 @@ def signature(f):
             i += 1
             A |= (z & 0x4) << n
             K |= ((z & 0x08) >> 3) << n
-        num_args = A + K
+        num_args = A + K - num_closed_over
     else:
         raise NotImplementedError("unsupported function type")
 

python-stdlib/inspect/manifest.py

@@ -1,3 +1,3 @@
-metadata(version="0.2.0")
+metadata(version="0.2.1")
 
 module("inspect.py")

python-stdlib/inspect/test_inspect.py

@@ -11,6 +11,22 @@ def gen():
     yield 1
 
 
+def make_closure():
+    a = 1
+    b = 2
+    def closure(x):
+        return a + b + x
+    return closure
+
+
+def make_gen_closure():
+    a = 1
+    b = 2
+    def gen_closure(x):
+        yield a + b + x
+    return gen_closure
+
+
 class Class:
     def meth(self):
         pass
@@ -71,3 +87,6 @@ class TestInspect(unittest.TestCase):
         self.assertEqual(len(inspect.signature(lambda x, y: 0).parameters), 2)
         self.assertEqual(len(inspect.signature(lambda x, y, z: 0).parameters), 3)
         self.assertEqual(len(inspect.signature(lambda x, y, *, z: 0).parameters), 3)
+        self.assertEqual(len(inspect.signature(gen).parameters), 0)
+        self.assertEqual(len(inspect.signature(make_closure()).parameters), 1)
+        self.assertEqual(len(inspect.signature(make_gen_closure()).parameters), 1)