Merge pull request #3540 from WarriorOfWire/async_syntax

__await__ magic method and async/await

4 files changed, 36 insertions, 3 deletions

diff --git a/py/circuitpy_mpconfig.h b/py/circuitpy_mpconfig.h
index 0583ae1c9..5ffdd4c8f 100644
--- a/py/circuitpy_mpconfig.h
+++ b/py/circuitpy_mpconfig.h
@@ -79,7 +79,6 @@
 
 #define MICROPY_PY_ARRAY                 (1)
 #define MICROPY_PY_ARRAY_SLICE_ASSIGN    (1)
-#define MICROPY_PY_ASYNC_AWAIT           (0)
 #define MICROPY_PY_ATTRTUPLE             (1)
 
 #define MICROPY_PY_BUILTINS_BYTEARRAY    (1)
diff --git a/py/circuitpy_mpconfig.mk b/py/circuitpy_mpconfig.mk
index 9b9bd83b4..91850448d 100644
--- a/py/circuitpy_mpconfig.mk
+++ b/py/circuitpy_mpconfig.mk
@@ -32,6 +32,9 @@
 CIRCUITPY_FULL_BUILD ?= 1
 CFLAGS += -DCIRCUITPY_FULL_BUILD=$(CIRCUITPY_FULL_BUILD)
 
+# async/await language keyword support
+MICROPY_PY_ASYNC_AWAIT ?= $(CIRCUITPY_FULL_BUILD)
+CFLAGS += -DMICROPY_PY_ASYNC_AWAIT=$(MICROPY_PY_ASYNC_AWAIT)
 
 CIRCUITPY_AESIO ?= 0
 CFLAGS += -DCIRCUITPY_AESIO=$(CIRCUITPY_AESIO)
diff --git a/py/compile.c b/py/compile.c
index 653aae004..04bcf5bc1 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -853,7 +853,7 @@ STATIC void compile_decorated(compiler_t *comp, mp_parse_node_struct_t *pns) {
         mp_parse_node_struct_t *pns0 = (mp_parse_node_struct_t*)pns_body->nodes[0];
         body_name = compile_funcdef_helper(comp, pns0, emit_options);
         scope_t *fscope = (scope_t*)pns0->nodes[4];
-        fscope->scope_flags |= MP_SCOPE_FLAG_GENERATOR;
+        fscope->scope_flags |= MP_SCOPE_FLAG_GENERATOR | MP_SCOPE_FLAG_ASYNC;
     #endif
     } else {
         assert(MP_PARSE_NODE_STRUCT_KIND(pns_body) == PN_classdef); // should be
@@ -2632,6 +2632,12 @@ STATIC void compile_yield_expr(compiler_t *comp, mp_parse_node_struct_t *pns) {
         EMIT_ARG(yield, MP_EMIT_YIELD_VALUE);
     } else if (MP_PARSE_NODE_IS_STRUCT_KIND(pns->nodes[0], PN_yield_arg_from)) {
         pns = (mp_parse_node_struct_t*)pns->nodes[0];
+#if MICROPY_PY_ASYNC_AWAIT
+        if(comp->scope_cur->scope_flags & MP_SCOPE_FLAG_ASYNC) {
+            compile_syntax_error(comp, (mp_parse_node_t)pns, translate("'yield from' inside async function"));
+            return;
+        }
+#endif
         compile_node(comp, pns->nodes[0]);
         compile_yield_from(comp);
     } else {
@@ -2648,7 +2654,14 @@ STATIC void compile_atom_expr_await(compiler_t *comp, mp_parse_node_struct_t *pn
     }
     compile_require_async_context(comp, pns);
     compile_atom_expr_normal(comp, pns);
-    compile_yield_from(comp);
+
+    // If it's an awaitable thing, need to reach for the __await__ method for the coroutine.
+    // async def functions' __await__ return themselves, which are able to receive a send(),
+    // while other types with custom __await__ implementations return async generators.
+    EMIT_ARG(load_method, MP_QSTR___await__, false);
+    EMIT_ARG(call_method, 0, 0, 0);
+    EMIT_ARG(load_const_tok, MP_TOKEN_KW_NONE);
+    EMIT_ARG(yield, MP_EMIT_YIELD_FROM);
 }
 #endif
 
diff --git a/py/objgenerator.c b/py/objgenerator.c
index df421b60c..5e651ac26 100644
--- a/py/objgenerator.c
+++ b/py/objgenerator.c
@@ -225,6 +225,21 @@ STATIC mp_obj_t gen_instance_send(mp_obj_t self_in, mp_obj_t send_value) {
 
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(gen_instance_send_obj, gen_instance_send);
 
+#if MICROPY_PY_ASYNC_AWAIT
+STATIC mp_obj_t gen_instance_await(mp_obj_t self_in) {
+    mp_obj_gen_instance_t *self = MP_OBJ_TO_PTR(self_in);
+    if ( !self->coroutine_generator ) {
+        // Pretend like a generator does not have this coroutine behavior.
+        // Pay no attention to the dir() behind the curtain
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_AttributeError,
+            translate("type object 'generator' has no attribute '__await__'")));
+    }
+    // You can directly call send on a coroutine generator or you can __await__ then send on the return of that.
+    return self;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(gen_instance_await_obj, gen_instance_await);
+#endif
+
 STATIC mp_obj_t gen_instance_close(mp_obj_t self_in);
 STATIC mp_obj_t gen_instance_throw(size_t n_args, const mp_obj_t *args) {
     mp_obj_t exc = (n_args == 2) ? args[1] : args[2];
@@ -280,6 +295,9 @@ STATIC const mp_rom_map_elem_t gen_instance_locals_dict_table[] = {
     #if MICROPY_PY_GENERATOR_PEND_THROW
     { MP_ROM_QSTR(MP_QSTR_pend_throw), MP_ROM_PTR(&gen_instance_pend_throw_obj) },
     #endif
+    #if MICROPY_PY_ASYNC_AWAIT
+    { MP_ROM_QSTR(MP_QSTR___await__), MP_ROM_PTR(&gen_instance_await_obj) },
+    #endif
 };
 
 STATIC MP_DEFINE_CONST_DICT(gen_instance_locals_dict, gen_instance_locals_dict_table);