Merge pull request #13326 from Carreau/clean-ast-asyncify

Remove pre-3.8 code path

IPython/core/async_helpers.py

@@ -1,172 +1,92 b''
 """
 Async helper function that are invalid syntax on Python 3.5 and below.
 
 This code is best effort, and may have edge cases not behaving as expected. In
 particular it contain a number of heuristics to detect whether code is
 effectively async and need to run in an event loop or not.
 
 Some constructs (like top-level `return`, or `yield`) are taken care of
 explicitly to actually raise a SyntaxError and stay as close as possible to
 Python semantics.
 """
 
 
 import ast
-import sys
 import inspect
-from textwrap import dedent, indent
 
 
 class _AsyncIORunner:
-
     def __call__(self, coro):
         """
         Handler for asyncio autoawait
         """
         import asyncio
 
         return asyncio.get_event_loop_policy().get_event_loop().run_until_complete(coro)
 
     def __str__(self):
-        return 'asyncio'
+        return "asyncio"
+
 
 _asyncio_runner = _AsyncIORunner()
 
 
 def _curio_runner(coroutine):
     """
     handler for curio autoawait
     """
     import curio
 
     return curio.run(coroutine)
 
 
 def _trio_runner(async_fn):
     import trio
 
     async def loc(coro):
         """
         We need the dummy no-op async def to protect from
         trio's internal. See https://github.com/python-trio/trio/issues/89
         """
         return await coro
 
     return trio.run(loc, async_fn)
 
 
 def _pseudo_sync_runner(coro):
     """
     A runner that does not really allow async execution, and just advance the coroutine.
 
     See discussion in https://github.com/python-trio/trio/issues/608,
 
     Credit to Nathaniel Smith
     """
     try:
         coro.send(None)
     except StopIteration as exc:
         return exc.value
     else:
         # TODO: do not raise but return an execution result with the right info.
         raise RuntimeError(
             "{coro_name!r} needs a real async loop".format(coro_name=coro.__name__)
         )
 
 
-def _asyncify(code: str) -> str:
-    """wrap code in async def definition.
-
-    And setup a bit of context to run it later.
-    """
-    res = dedent(
-        """
-    async def __wrapper__():
-        try:
-    {usercode}
-        finally:
-            locals()
-    """
-    ).format(usercode=indent(code, " " * 8))
-    return res
-
-
-class _AsyncSyntaxErrorVisitor(ast.NodeVisitor):
-    """
-    Find syntax errors that would be an error in an async repl, but because
-    the implementation involves wrapping the repl in an async function, it
-    is erroneously allowed (e.g. yield or return at the top level)
-    """
-    def __init__(self):
-        if sys.version_info >= (3,8):
-            raise ValueError('DEPRECATED in Python 3.8+')
-        self.depth = 0
-        super().__init__()
-
-    def generic_visit(self, node):
-        func_types = (ast.FunctionDef, ast.AsyncFunctionDef)
-        invalid_types_by_depth = {
-            0: (ast.Return, ast.Yield, ast.YieldFrom),
-            1: (ast.Nonlocal,)
-        }
-
-        should_traverse = self.depth < max(invalid_types_by_depth.keys())
-        if isinstance(node, func_types) and should_traverse:
-            self.depth += 1
-            super().generic_visit(node)
-            self.depth -= 1
-        elif isinstance(node, invalid_types_by_depth[self.depth]):
-            raise SyntaxError()
-        else:
-            super().generic_visit(node)
-
-
-def _async_parse_cell(cell: str) -> ast.AST:
-    """
-    This is a compatibility shim for pre-3.7 when async outside of a function
-    is a syntax error at the parse stage.
-
-    It will return an abstract syntax tree parsed as if async and await outside
-    of a function were not a syntax error.
-    """
-    if sys.version_info < (3, 7):
-        # Prior to 3.7 you need to asyncify before parse
-        wrapped_parse_tree = ast.parse(_asyncify(cell))
-        return wrapped_parse_tree.body[0].body[0]
-    else:
-        return ast.parse(cell)
-
-
 def _should_be_async(cell: str) -> bool:
     """Detect if a block of code need to be wrapped in an `async def`
 
     Attempt to parse the block of code, it it compile we're fine.
     Otherwise we  wrap if and try to compile.
 
     If it works, assume it should be async. Otherwise Return False.
 
     Not handled yet: If the block of code has a return statement as the top
     level, it will be seen as async. This is a know limitation.
     """
-    if sys.version_info > (3, 8):
-        try:
-            code = compile(cell, "<>", "exec", flags=getattr(ast,'PyCF_ALLOW_TOP_LEVEL_AWAIT', 0x0))
-            return inspect.CO_COROUTINE & code.co_flags == inspect.CO_COROUTINE
-        except (SyntaxError, MemoryError):
-            return False
     try:
-        # we can't limit ourself to ast.parse, as it __accepts__ to parse on
-        # 3.7+, but just does not _compile_
-        code = compile(cell, "<>", "exec")
+        code = compile(
+            cell, "<>", "exec", flags=getattr(ast, "PyCF_ALLOW_TOP_LEVEL_AWAIT", 0x0)
+        )
+        return inspect.CO_COROUTINE & code.co_flags == inspect.CO_COROUTINE
     except (SyntaxError, MemoryError):
-        try:
-            parse_tree = _async_parse_cell(cell)
-
-            # Raise a SyntaxError if there are top-level return or yields
-            v = _AsyncSyntaxErrorVisitor()
-            v.visit(parse_tree)
-
-        except (SyntaxError, MemoryError):
-            return False
-        return True
-    return False
+        return False