in generators/coroutines, save away the current exception in the 'return' case...

in generators/coroutines, save away the current exception in the 'return' case of finally clauses as 'return' actually raises an (Async)StopIteration exception

Cython/Compiler/Nodes.py

@@ -6994,6 +6994,7 @@ class TryFinallyStatNode(StatNode):
     #  body             StatNode
     #  finally_clause   StatNode
     #  finally_except_clause  deep-copy of finally_clause for exception case
+    #  in_generator     inside of generator => must store away current exception also in return case
     #
     #  Each of the continue, break, return and error gotos runs
     #  into its own deep-copy of the finally block code.
@@ -7011,6 +7012,7 @@ class TryFinallyStatNode(StatNode):
     finally_except_clause = None
 
     is_try_finally_in_nogil = False
+    in_generator = False
 
     @staticmethod
     def create_analysed(pos, env, body, finally_clause):
@@ -7129,16 +7131,25 @@ class TryFinallyStatNode(StatNode):
 
         code.set_all_labels(old_labels)
         return_label = code.return_label
+        exc_vars = ()
+
         for i, (new_label, old_label) in enumerate(zip(new_labels, old_labels)):
             if not code.label_used(new_label):
                 continue
             if new_label == new_error_label and preserve_error:
                 continue  # handled above
 
-            code.put('%s: ' % new_label)
-            code.putln('{')
+            code.putln('%s: {' % new_label)
             ret_temp = None
-            if old_label == return_label and not self.finally_clause.is_terminator:
+            if old_label == return_label:
+                # return actually raises an (uncatchable) exception in generators that we must preserve
+                if self.in_generator:
+                    code.putln("__Pyx_PyThreadState_declare")
+                    exc_vars = tuple([
+                        code.funcstate.allocate_temp(py_object_type, manage_ref=False)
+                        for _ in range(6)])
+                    self.put_error_catcher(code, [], exc_vars)
+                if not self.finally_clause.is_terminator:
                     # store away return value for later reuse
                     if (self.func_return_type and
                             not self.is_try_finally_in_nogil and
@@ -7148,13 +7159,19 @@ class TryFinallyStatNode(StatNode):
                         code.putln("%s = %s;" % (ret_temp, Naming.retval_cname))
                         if self.func_return_type.is_pyobject:
                             code.putln("%s = 0;" % Naming.retval_cname)
+
             fresh_finally_clause().generate_execution_code(code)
+
+            if old_label == return_label:
                 if ret_temp:
                     code.putln("%s = %s;" % (Naming.retval_cname, ret_temp))
                     if self.func_return_type.is_pyobject:
                         code.putln("%s = 0;" % ret_temp)
                     code.funcstate.release_temp(ret_temp)
                     ret_temp = None
+                if self.in_generator:
+                    self.put_error_uncatcher(code, exc_vars)
+
             if not self.finally_clause.is_terminator:
                 code.put_goto(old_label)
             code.putln('}')
@@ -7169,7 +7186,7 @@ class TryFinallyStatNode(StatNode):
         self.finally_clause.generate_function_definitions(env, code)
 
     def put_error_catcher(self, code, temps_to_clean_up, exc_vars,
-                          exc_lineno_cnames, exc_filename_cname):
+                          exc_lineno_cnames=None, exc_filename_cname=None):
         code.globalstate.use_utility_code(restore_exception_utility_code)
         code.globalstate.use_utility_code(get_exception_utility_code)
         code.globalstate.use_utility_code(swap_exception_utility_code)
@@ -7202,12 +7219,13 @@ class TryFinallyStatNode(StatNode):
         if self.is_try_finally_in_nogil:
             code.put_release_ensured_gil()
 
-    def put_error_uncatcher(self, code, exc_vars, exc_lineno_cnames, exc_filename_cname):
+    def put_error_uncatcher(self, code, exc_vars, exc_lineno_cnames=None, exc_filename_cname=None):
         code.globalstate.use_utility_code(restore_exception_utility_code)
         code.globalstate.use_utility_code(reset_exception_utility_code)
 
         if self.is_try_finally_in_nogil:
             code.put_ensure_gil(declare_gilstate=False)
+        if self.in_generator:
             code.putln("__Pyx_PyThreadState_assign")  # re-assign in case a generator yielded
 
         # not using preprocessor here to avoid warnings about
@@ -7235,6 +7253,7 @@ class TryFinallyStatNode(StatNode):
         code.globalstate.use_utility_code(reset_exception_utility_code)
         if self.is_try_finally_in_nogil:
             code.put_ensure_gil(declare_gilstate=False)
+        if self.in_generator:
             code.putln("__Pyx_PyThreadState_assign")  # re-assign in case a generator yielded
 
         # not using preprocessor here to avoid warnings about

Cython/Compiler/ParseTreeTransforms.pxd

@@ -51,6 +51,7 @@ cdef class AlignFunctionDefinitions(CythonTransform):
 cdef class YieldNodeCollector(TreeVisitor):
     cdef public list yields
     cdef public list returns
+    cdef public list finallys
     cdef public bint has_return_value
     cdef public bint has_yield
     cdef public bint has_await

Cython/Compiler/ParseTreeTransforms.py

@@ -2458,6 +2458,7 @@ class YieldNodeCollector(TreeVisitor):
         super(YieldNodeCollector, self).__init__()
         self.yields = []
         self.returns = []
+        self.finallys = []
         self.has_return_value = False
         self.has_yield = False
         self.has_await = False
@@ -2481,6 +2482,10 @@ class YieldNodeCollector(TreeVisitor):
             self.has_return_value = True
         self.returns.append(node)
 
+    def visit_TryFinallyStatNode(self, node):
+        self.visitchildren(node)
+        self.finallys.append(node)
+
     def visit_ClassDefNode(self, node):
         pass
 
@@ -2531,7 +2536,7 @@ class MarkClosureVisitor(CythonTransform):
 
         for i, yield_expr in enumerate(collector.yields, 1):
             yield_expr.label_num = i
-        for retnode in collector.returns:
+        for retnode in collector.returns + collector.finallys:
             retnode.in_generator = True
 
         gbody = Nodes.GeneratorBodyDefNode(