Merge pull request #458 from nucleic/py310-fixes

core: prune return None from inserted Python blocks

.github/workflows/ci.yml

@@ -22,8 +22,18 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        python-version: ['3.7', '3.8', '3.9', '3.10.0-rc.2']
+        python-version: ['3.7', '3.8', '3.9', '3.10.0']
         qt-binding: [pyqt5, pyside2]
+        exclude:
+          - os: ubuntu-latest
+            python-version: '3.10.0'
+            qt-binding: pyside2
+          - os: windows-latest
+            python-version: '3.10.0'
+            qt-binding: pyside2
+          - os: macos-latest
+            python-version: '3.10.0'
+            qt-binding: pyside2
       fail-fast: false
     steps:
       - name: Install linux only test dependency
@@ -50,7 +60,6 @@ jobs:
           pip install https://github.com/nucleic/atom/tarball/main
           pip install https://github.com/nucleic/kiwi/tarball/main
       - name: Install Qt bindings
-        if: matrix.python-version != '3.10.0-rc.1'
         run: |
           pip install numpy qtpy '${{matrix.qt-binding}}'
       - name: Install extra dependencies
@@ -68,11 +77,7 @@ jobs:
           python setup.py develop
       - name: Install pytest
         run: |
-          pip install pytest pytest-cov
-      - name: Install pytest-qt
-        if: matrix.python-version != '3.10.0-rc.2'
-        run: |
-          pip install  pytest-qt
+          pip install pytest pytest-cov pytest-qt
       - name: Run tests (Windows, Mac)
         if: matrix.os != 'ubuntu-latest'
         run: python -X dev -m pytest tests --cov enaml --cov-report xml

enaml/compat.py

@@ -16,6 +16,8 @@
 
 PY39 = sys.version_info >= (3, 9)
 
+PY310 = sys.version_info >= (3, 10)
+
 
 STRING_ESCAPE_SEQUENCE_RE = re.compile(r'''
     ( \\U........      # 8-digit hex escapes

enaml/core/code_generator.py

@@ -1,16 +1,42 @@
 #------------------------------------------------------------------------------
-# Copyright (c) 2013-2020, Nucleic Development Team.
+# Copyright (c) 2013-2021, Nucleic Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file LICENSE, distributed with this software.
 #------------------------------------------------------------------------------
+import ast
 from contextlib import contextmanager
 
 import bytecode as bc
 from atom.api import Atom, Bool, Int, List, Str
 
-from ..compat import POS_ONLY_ARGS, PY38, PY39
+from ..compat import POS_ONLY_ARGS, PY38, PY39, PY310
+
+
+class _ReturnNoneIdentifier(ast.NodeVisitor):
+    """Visit top level nodes looking for return None."""
+
+    def __init__(self) -> None:
+        super().__init__()
+        # Lines on which an explicit return None or return exist
+        self.lines = set()
+
+    def visit_Return(self, node: ast.Return) -> None:
+        if not node.value or (
+            isinstance(node.value, ast.Constant) and node.value.value is None
+        ):
+            self.lines.add(node.lineno)
+
+    # Do not inspect nodes in which a return None won't be relevant.
+    def visit_AsyncFunctionDef(self, node):
+        pass
+
+    def visit_FunctionDef(self, node):
+        pass
+
+    def visit_ClassDef(self, node):
+        pass
 
 
 class CodeGenerator(Atom):
@@ -433,12 +459,41 @@ def insert_python_block(self, pydata, trim=True):
         """ Insert the compiled code for a Python Module ast or string.
 
         """
+        if PY310:
+            _inspector = _ReturnNoneIdentifier()
+            _inspector.visit(pydata)
         code = compile(pydata, self.filename, mode='exec')
         bc_code = bc.Bytecode.from_code(code)
-        # Skip the LOAD_CONST RETURN_VALUE pair if it exists (on Python 3.10+
-        # if the module ends on a raise, that pair which is unreachable is ommitted)
-        if trim and bc_code[-1].name == "RETURN_VALUE":
+        # On python 3.10 with a with or try statement the implicit return None
+        # can be duplicated. We remove return None from all basic blocks when
+        # it was not present in the AST
+        if PY310:
+            cfg = bc.ControlFlowGraph.from_bytecode(bc_code)
+            new_end = None
+            last_block = cfg[-1]
+            for block in list(cfg):
+                if (
+                    block[-1].name == "RETURN_VALUE"
+                    and block[-2].name == "LOAD_CONST"
+                    and block[-2].arg is None
+                    and block[-1].lineno not in _inspector.lines
+                ):
+                    del block[-2:]
+                    # If we have multiple block jump to the end of the last block
+                    # to execute the code that may be appended to this block
+                    if block is not last_block:
+                        # We use a NOP to be sure to always have a valid jump target
+                        new_end = new_end or cfg.add_block([bc.Instr("NOP")])
+                        block.append(bc.Instr("JUMP_FORWARD", new_end))
+
+            if new_end is not None:
+                last_block.next_block = new_end
+
+            bc_code = cfg.to_bytecode()
+        # Skip the LOAD_CONST RETURN_VALUE pair if it exists
+        elif trim and bc_code[-1].name == "RETURN_VALUE":
             bc_code = bc_code[:-2]
+
         self.code_ops.extend(bc_code)
 
     def insert_python_expr(self, pydata, trim=True):

enaml/core/enaml_compiler.py

@@ -1,11 +1,11 @@
 #------------------------------------------------------------------------------
-# Copyright (c) 2013, Nucleic Development Team.
+# Copyright (c) 2013-2021, Nucleic Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file LICENSE, distributed with this software.
 #------------------------------------------------------------------------------
-import sys
+import ast
 
 from . import compiler_common as cmn
 from .enaml_ast import Module
@@ -183,7 +183,7 @@ def visit_Module(self, node):
         # Generate the startup code for the module.
         cg.set_lineno(1)
         for start in STARTUP:
-            cg.insert_python_block(start)
+            cg.insert_python_block(ast.parse(start))
 
         # Create the template map.
         cg.build_map()
@@ -198,7 +198,7 @@ def visit_Module(self, node):
 
         # Generate the cleanup code for the module.
         for end in CLEANUP:
-            cg.insert_python_block(end)
+            cg.insert_python_block(ast.parse(end))
 
         # Finalize the ops and return the code object.
         cg.load_const(None)

releasenotes.rst

@@ -9,7 +9,9 @@ Dates are written as DD/MM/YYYY
 - fix operator bindings in template instances PR #445
 - fix FlowLayout error with FlowItems that have non-zero stretch or ortho_stretch PR #448
 - add support for styling notebook tabs PR #452
-- drop official support for Python 3.6
+- drop official support for Python 3.6 and add minimal support for Python 3.10
+  As with earlier Python version, support for 3.10 is currently limited to running on
+  Python 3.10 excluding any features that were added on Python 3.10
 
 0.13.0 - 19/04/2021
 -------------------

tests/core/test_code_generator.py

@@ -0,0 +1,27 @@
+#------------------------------------------------------------------------------
+# Copyright (c) 2021, Nucleic Development Team.
+#
+# Distributed under the terms of the Modified BSD License.
+#
+# The full license is in the file COPYING.txt, distributed with this software.
+#------------------------------------------------------------------------------
+"""Test for the code generator."""
+import ast
+import pytest
+
+from enaml.core.code_generator import CodeGenerator
+
+
+# Since we cannot have a return outside a function I am not sure we can ever
+# encounter a non-implicit return opcode.
+@pytest.mark.parametrize("source, return_on_lines", [
+    ("pass", []),
+    ("for i in range(10):\n    i", []),
+    ("with open(f) as f:\n   print(f.readlines())", []),
+])
+def test_python_block_insertion(source, return_on_lines):
+    cg = CodeGenerator()
+    cg.insert_python_block(ast.parse(source))
+    for i in cg.code_ops:
+        if getattr(i, "name", "") == "RETURN_VALUE":
+            assert i.lineno in return_on_lines