bpo-39220: Do not optimise annotation if 'from __future__ import annotations' is used (GH-17866)

Do not apply AST-based optimizations if 'from __future__ import annotations' is used in order to
prevent information lost in the final version of the annotations.

5 files changed, 67 insertions, 40 deletions

diff --git a/Include/compile.h b/Include/compile.h
index 1cda955..c0c73b2 100644
--- a/Include/compile.h
+++ b/Include/compile.h
@@ -83,7 +83,12 @@ PyAPI_FUNC(PyObject*) _Py_Mangle(PyObject *p, PyObject *name);
 PyAPI_FUNC(int) PyCompile_OpcodeStackEffect(int opcode, int oparg);
 PyAPI_FUNC(int) PyCompile_OpcodeStackEffectWithJump(int opcode, int oparg, int jump);
 
-PyAPI_FUNC(int) _PyAST_Optimize(struct _mod *, PyArena *arena, int optimize);
+typedef struct {
+    int optimize;
+    int ff_features;
+} _PyASTOptimizeState;
+
+PyAPI_FUNC(int) _PyAST_Optimize(struct _mod *, PyArena *arena, _PyASTOptimizeState *state);
 
 #ifdef __cplusplus
 }
diff --git a/Lib/test/test_future.py b/Lib/test/test_future.py
index d83c47e..9b88e3f 100644
--- a/Lib/test/test_future.py
+++ b/Lib/test/test_future.py
@@ -111,6 +111,10 @@ class AnnotationsFutureTestCase(unittest.TestCase):
             ...
         def g(arg: {ann}) -> None:
             ...
+        async def f2() -> {ann}:
+            ...
+        async def g2(arg: {ann}) -> None:
+            ...
         var: {ann}
         var2: {ann} = None
         """
@@ -121,9 +125,13 @@ class AnnotationsFutureTestCase(unittest.TestCase):
         exec(self.template.format(ann=annotation), {}, scope)
         func_ret_ann = scope['f'].__annotations__['return']
         func_arg_ann = scope['g'].__annotations__['arg']
+        async_func_ret_ann = scope['f2'].__annotations__['return']
+        async_func_arg_ann = scope['g2'].__annotations__['arg']
         var_ann1 = scope['__annotations__']['var']
         var_ann2 = scope['__annotations__']['var2']
         self.assertEqual(func_ret_ann, func_arg_ann)
+        self.assertEqual(func_ret_ann, async_func_ret_ann)
+        self.assertEqual(func_ret_ann, async_func_arg_ann)
         self.assertEqual(func_ret_ann, var_ann1)
         self.assertEqual(func_ret_ann, var_ann2)
         return func_ret_ann
@@ -288,6 +296,7 @@ class AnnotationsFutureTestCase(unittest.TestCase):
         eq('(((a, b)))', '(a, b)')
         eq("(x:=10)")
         eq("f'{(x:=10):=10}'")
+        eq("1 + 2 + 3")
 
     def test_fstring_debug_annotations(self):
         # f-strings with '=' don't round trip very well, so set the expected
@@ -299,6 +308,5 @@ class AnnotationsFutureTestCase(unittest.TestCase):
         self.assertAnnotationEqual("f'{x=!a}'", expected="f'x={x!a}'")
         self.assertAnnotationEqual("f'{x=!s:*^20}'", expected="f'x={x!s:*^20}'")
 
-
 if __name__ == "__main__":
     unittest.main()
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-01-06-13-58-37.bpo-39220.KGFovE.rst b/Misc/NEWS.d/next/Core and Builtins/2020-01-06-13-58-37.bpo-39220.KGFovE.rst
new file mode 100644
index 0000000..617d35e
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-01-06-13-58-37.bpo-39220.KGFovE.rst
@@ -0,0 +1,2 @@
+Do not optimize annotations if 'from __future__ import annotations' is used.
+Patch by Pablo Galindo.
diff --git a/Python/ast_opt.c b/Python/ast_opt.c
index 7a2b6e6..1393c34 100644
--- a/Python/ast_opt.c
+++ b/Python/ast_opt.c
@@ -35,7 +35,7 @@ unary_not(PyObject *v)
 }
 
 static int
-fold_unaryop(expr_ty node, PyArena *arena, int optimize)
+fold_unaryop(expr_ty node, PyArena *arena, _PyASTOptimizeState *state)
 {
     expr_ty arg = node->v.UnaryOp.operand;
 
@@ -212,7 +212,7 @@ safe_mod(PyObject *v, PyObject *w)
 }
 
 static int
-fold_binop(expr_ty node, PyArena *arena, int optimize)
+fold_binop(expr_ty node, PyArena *arena, _PyASTOptimizeState *state)
 {
     expr_ty lhs, rhs;
     lhs = node->v.BinOp.left;
@@ -294,7 +294,7 @@ make_const_tuple(asdl_seq *elts)
 }
 
 static int
-fold_tuple(expr_ty node, PyArena *arena, int optimize)
+fold_tuple(expr_ty node, PyArena *arena, _PyASTOptimizeState *state)
 {
     PyObject *newval;
 
@@ -306,7 +306,7 @@ fold_tuple(expr_ty node, PyArena *arena, int optimize)
 }
 
 static int
-fold_subscr(expr_ty node, PyArena *arena, int optimize)
+fold_subscr(expr_ty node, PyArena *arena, _PyASTOptimizeState *state)
 {
     PyObject *newval;
     expr_ty arg, idx;
@@ -331,7 +331,7 @@ fold_subscr(expr_ty node, PyArena *arena, int optimize)
    in "for" loop and comprehensions.
 */
 static int
-fold_iter(expr_ty arg, PyArena *arena, int optimize)
+fold_iter(expr_ty arg, PyArena *arena, _PyASTOptimizeState *state)
 {
     PyObject *newval;
     if (arg->kind == List_kind) {
@@ -364,7 +364,7 @@ fold_iter(expr_ty arg, PyArena *arena, int optimize)
 }
 
 static int
-fold_compare(expr_ty node, PyArena *arena, int optimize)
+fold_compare(expr_ty node, PyArena *arena, _PyASTOptimizeState *state)
 {
     asdl_int_seq *ops;
     asdl_seq *args;
@@ -378,28 +378,28 @@ fold_compare(expr_ty node, PyArena *arena, int optimize)
     i = asdl_seq_LEN(ops) - 1;
     int op = asdl_seq_GET(ops, i);
     if (op == In || op == NotIn) {
-        if (!fold_iter((expr_ty)asdl_seq_GET(args, i), arena, optimize)) {
+        if (!fold_iter((expr_ty)asdl_seq_GET(args, i), arena, state)) {
             return 0;
         }
     }
     return 1;
 }
 
-static int astfold_mod(mod_ty node_, PyArena *ctx_, int optimize_);
-static int astfold_stmt(stmt_ty node_, PyArena *ctx_, int optimize_);
-static int astfold_expr(expr_ty node_, PyArena *ctx_, int optimize_);
-static int astfold_arguments(arguments_ty node_, PyArena *ctx_, int optimize_);
-static int astfold_comprehension(comprehension_ty node_, PyArena *ctx_, int optimize_);
-static int astfold_keyword(keyword_ty node_, PyArena *ctx_, int optimize_);
-static int astfold_arg(arg_ty node_, PyArena *ctx_, int optimize_);
-static int astfold_withitem(withitem_ty node_, PyArena *ctx_, int optimize_);
-static int astfold_excepthandler(excepthandler_ty node_, PyArena *ctx_, int optimize_);
+static int astfold_mod(mod_ty node_, PyArena *ctx_, _PyASTOptimizeState *state);
+static int astfold_stmt(stmt_ty node_, PyArena *ctx_, _PyASTOptimizeState *state);
+static int astfold_expr(expr_ty node_, PyArena *ctx_, _PyASTOptimizeState *state);
+static int astfold_arguments(arguments_ty node_, PyArena *ctx_, _PyASTOptimizeState *state);
+static int astfold_comprehension(comprehension_ty node_, PyArena *ctx_, _PyASTOptimizeState *state);
+static int astfold_keyword(keyword_ty node_, PyArena *ctx_, _PyASTOptimizeState *state);
+static int astfold_arg(arg_ty node_, PyArena *ctx_, _PyASTOptimizeState *state);
+static int astfold_withitem(withitem_ty node_, PyArena *ctx_, _PyASTOptimizeState *state);
+static int astfold_excepthandler(excepthandler_ty node_, PyArena *ctx_, _PyASTOptimizeState *state);
 #define CALL(FUNC, TYPE, ARG) \
-    if (!FUNC((ARG), ctx_, optimize_)) \
+    if (!FUNC((ARG), ctx_, state)) \
         return 0;
 
 #define CALL_OPT(FUNC, TYPE, ARG) \
-    if ((ARG) != NULL && !FUNC((ARG), ctx_, optimize_)) \
+    if ((ARG) != NULL && !FUNC((ARG), ctx_, state)) \
         return 0;
 
 #define CALL_SEQ(FUNC, TYPE, ARG) { \
@@ -407,7 +407,7 @@ static int astfold_excepthandler(excepthandler_ty node_, PyArena *ctx_, int opti
     asdl_seq *seq = (ARG); /* avoid variable capture */ \
     for (i = 0; i < asdl_seq_LEN(seq); i++) { \
         TYPE elt = (TYPE)asdl_seq_GET(seq, i); \
-        if (elt != NULL && !FUNC(elt, ctx_, optimize_)) \
+        if (elt != NULL && !FUNC(elt, ctx_, state)) \
             return 0; \
     } \
 }
@@ -417,13 +417,13 @@ static int astfold_excepthandler(excepthandler_ty node_, PyArena *ctx_, int opti
     asdl_int_seq *seq = (ARG); /* avoid variable capture */ \
     for (i = 0; i < asdl_seq_LEN(seq); i++) { \
         TYPE elt = (TYPE)asdl_seq_GET(seq, i); \
-        if (!FUNC(elt, ctx_, optimize_)) \
+        if (!FUNC(elt, ctx_, state)) \
             return 0; \
     } \
 }
 
 static int
-astfold_body(asdl_seq *stmts, PyArena *ctx_, int optimize_)
+astfold_body(asdl_seq *stmts, PyArena *ctx_, _PyASTOptimizeState *state)
 {
     int docstring = _PyAST_GetDocString(stmts) != NULL;
     CALL_SEQ(astfold_stmt, stmt_ty, stmts);
@@ -445,7 +445,7 @@ astfold_body(asdl_seq *stmts, PyArena *ctx_, int optimize_)
 }
 
 static int
-astfold_mod(mod_ty node_, PyArena *ctx_, int optimize_)
+astfold_mod(mod_ty node_, PyArena *ctx_, _PyASTOptimizeState *state)
 {
     switch (node_->kind) {
     case Module_kind:
@@ -464,7 +464,7 @@ astfold_mod(mod_ty node_, PyArena *ctx_, int optimize_)
 }
 
 static int
-astfold_expr(expr_ty node_, PyArena *ctx_, int optimize_)
+astfold_expr(expr_ty node_, PyArena *ctx_, _PyASTOptimizeState *state)
 {
     switch (node_->kind) {
     case BoolOp_kind:
@@ -563,7 +563,7 @@ astfold_expr(expr_ty node_, PyArena *ctx_, int optimize_)
         break;
     case Name_kind:
         if (_PyUnicode_EqualToASCIIString(node_->v.Name.id, "__debug__")) {
-            return make_const(node_, PyBool_FromLong(!optimize_), ctx_);
+            return make_const(node_, PyBool_FromLong(!state->optimize), ctx_);
         }
         break;
     default:
@@ -573,14 +573,14 @@ astfold_expr(expr_ty node_, PyArena *ctx_, int optimize_)
 }
 
 static int
-astfold_keyword(keyword_ty node_, PyArena *ctx_, int optimize_)
+astfold_keyword(keyword_ty node_, PyArena *ctx_, _PyASTOptimizeState *state)
 {
     CALL(astfold_expr, expr_ty, node_->value);
     return 1;
 }
 
 static int
-astfold_comprehension(comprehension_ty node_, PyArena *ctx_, int optimize_)
+astfold_comprehension(comprehension_ty node_, PyArena *ctx_, _PyASTOptimizeState *state)
 {
     CALL(astfold_expr, expr_ty, node_->target);
     CALL(astfold_expr, expr_ty, node_->iter);
@@ -591,7 +591,7 @@ astfold_comprehension(comprehension_ty node_, PyArena *ctx_, int optimize_)
 }
 
 static int
-astfold_arguments(arguments_ty node_, PyArena *ctx_, int optimize_)
+astfold_arguments(arguments_ty node_, PyArena *ctx_, _PyASTOptimizeState *state)
 {
     CALL_SEQ(astfold_arg, arg_ty, node_->posonlyargs);
     CALL_SEQ(astfold_arg, arg_ty, node_->args);
@@ -604,27 +604,33 @@ astfold_arguments(arguments_ty node_, PyArena *ctx_, int optimize_)
 }
 
 static int
-astfold_arg(arg_ty node_, PyArena *ctx_, int optimize_)
+astfold_arg(arg_ty node_, PyArena *ctx_, _PyASTOptimizeState *state)
 {
-    CALL_OPT(astfold_expr, expr_ty, node_->annotation);
+    if (!(state->ff_features & CO_FUTURE_ANNOTATIONS)) {
+        CALL_OPT(astfold_expr, expr_ty, node_->annotation);
+    }
     return 1;
 }
 
 static int
-astfold_stmt(stmt_ty node_, PyArena *ctx_, int optimize_)
+astfold_stmt(stmt_ty node_, PyArena *ctx_, _PyASTOptimizeState *state)
 {
     switch (node_->kind) {
     case FunctionDef_kind:
         CALL(astfold_arguments, arguments_ty, node_->v.FunctionDef.args);
         CALL(astfold_body, asdl_seq, node_->v.FunctionDef.body);
         CALL_SEQ(astfold_expr, expr_ty, node_->v.FunctionDef.decorator_list);
-        CALL_OPT(astfold_expr, expr_ty, node_->v.FunctionDef.returns);
+        if (!(state->ff_features & CO_FUTURE_ANNOTATIONS)) {
+            CALL_OPT(astfold_expr, expr_ty, node_->v.FunctionDef.returns);
+        }
         break;
     case AsyncFunctionDef_kind:
         CALL(astfold_arguments, arguments_ty, node_->v.AsyncFunctionDef.args);
         CALL(astfold_body, asdl_seq, node_->v.AsyncFunctionDef.body);
         CALL_SEQ(astfold_expr, expr_ty, node_->v.AsyncFunctionDef.decorator_list);
-        CALL_OPT(astfold_expr, expr_ty, node_->v.AsyncFunctionDef.returns);
+        if (!(state->ff_features & CO_FUTURE_ANNOTATIONS)) {
+            CALL_OPT(astfold_expr, expr_ty, node_->v.AsyncFunctionDef.returns);
+        }
         break;
     case ClassDef_kind:
         CALL_SEQ(astfold_expr, expr_ty, node_->v.ClassDef.bases);
@@ -648,7 +654,9 @@ astfold_stmt(stmt_ty node_, PyArena *ctx_, int optimize_)
         break;
     case AnnAssign_kind:
         CALL(astfold_expr, expr_ty, node_->v.AnnAssign.target);
-        CALL(astfold_expr, expr_ty, node_->v.AnnAssign.annotation);
+        if (!(state->ff_features & CO_FUTURE_ANNOTATIONS)) {
+            CALL(astfold_expr, expr_ty, node_->v.AnnAssign.annotation);
+        }
         CALL_OPT(astfold_expr, expr_ty, node_->v.AnnAssign.value);
         break;
     case For_kind:
@@ -707,7 +715,7 @@ astfold_stmt(stmt_ty node_, PyArena *ctx_, int optimize_)
 }
 
 static int
-astfold_excepthandler(excepthandler_ty node_, PyArena *ctx_, int optimize_)
+astfold_excepthandler(excepthandler_ty node_, PyArena *ctx_, _PyASTOptimizeState *state)
 {
     switch (node_->kind) {
     case ExceptHandler_kind:
@@ -721,7 +729,7 @@ astfold_excepthandler(excepthandler_ty node_, PyArena *ctx_, int optimize_)
 }
 
 static int
-astfold_withitem(withitem_ty node_, PyArena *ctx_, int optimize_)
+astfold_withitem(withitem_ty node_, PyArena *ctx_, _PyASTOptimizeState *state)
 {
     CALL(astfold_expr, expr_ty, node_->context_expr);
     CALL_OPT(astfold_expr, expr_ty, node_->optional_vars);
@@ -734,9 +742,9 @@ astfold_withitem(withitem_ty node_, PyArena *ctx_, int optimize_)
 #undef CALL_INT_SEQ
 
 int
-_PyAST_Optimize(mod_ty mod, PyArena *arena, int optimize)
+_PyAST_Optimize(mod_ty mod, PyArena *arena, _PyASTOptimizeState *state)
 {
-    int ret = astfold_mod(mod, arena, optimize);
+    int ret = astfold_mod(mod, arena, state);
     assert(ret || PyErr_Occurred());
     return ret;
 }
diff --git a/Python/compile.c b/Python/compile.c
index 486b7bb..a8ab873 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -354,7 +354,11 @@ PyAST_CompileObject(mod_ty mod, PyObject *filename, PyCompilerFlags *flags,
     c.c_nestlevel = 0;
     c.c_do_not_emit_bytecode = 0;
 
-    if (!_PyAST_Optimize(mod, arena, c.c_optimize)) {
+    _PyASTOptimizeState state;
+    state.optimize = c.c_optimize;
+    state.ff_features = merged;
+
+    if (!_PyAST_Optimize(mod, arena, &state)) {
         goto finally;
     }