Merge pull request #517 from python/main

sthagen · web-flow · commit d61d997c73f9 · 2021-07-13T07:49:10.000+02:00
Sync Fork from Upstream Repo
diff --git a/.github/workflows/doc.yml b/.github/workflows/doc.yml
@@ -40,7 +40,7 @@ jobs:
     - name: 'Build documentation'
       run: xvfb-run make -C Doc/ PYTHON=../python SPHINXOPTS="-q -W --keep-going -j4" doctest html
     - name: 'Upload'
-      uses: actions/upload-artifact@v2.2.3
+      uses: actions/upload-artifact@v2.2.4
       with:
         name: doc-html
         path: Doc/build/html
diff --git a/Doc/c-api/code.rst b/Doc/c-api/code.rst
@@ -59,3 +59,11 @@ bound into a function.
 
     For efficiently iterating over the line numbers in a code object, use `the API described in PEP 626
     <https://www.python.org/dev/peps/pep-0626/#out-of-process-debuggers-and-profilers>`_.
+
+.. c:function:: int PyCode_Addr2Location(PyObject *co, int byte_offset, int *start_line, int *start_column, int *end_line, int *end_column)
+
+   Sets the passed ``int`` pointers to the source code line and column numbers
+   for the instruction at ``byte_offset``. Sets the value to ``0`` when
+   information is not available for any particular element.
+
+   Returns ``1`` if the function succeeds and 0 otherwise.
diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
@@ -853,6 +853,8 @@ is available in ``argparse`` and adds support for boolean actions such as
     >>> parser.parse_args(['--no-foo'])
     Namespace(foo=False)
 
+.. versionadded:: 3.9
+
 The recommended way to create a custom action is to extend :class:`Action`,
 overriding the ``__call__`` method and optionally the ``__init__`` and
 ``format_usage`` methods.
diff --git a/Doc/library/importlib.metadata.rst b/Doc/library/importlib.metadata.rst
@@ -8,13 +8,11 @@
    :synopsis: The implementation of the importlib metadata.
 
 .. versionadded:: 3.8
+.. versionchanged:: 3.10
+   ``importlib.metadata`` is no longer provisional.
 
 **Source code:** :source:`Lib/importlib/metadata.py`
 
-.. note::
-   This functionality is provisional and may deviate from the usual
-   version semantics of the standard library.
-
 ``importlib.metadata`` is a library that provides for access to installed
 package metadata.  Built in part on Python's import system, this library
 intends to replace similar functionality in the `entry point
diff --git a/Doc/library/os.path.rst b/Doc/library/os.path.rst
@@ -340,6 +340,14 @@ the :mod:`glob` module.)
    that contains symbolic links.  On Windows, it converts forward slashes to
    backward slashes. To normalize case, use :func:`normcase`.
 
+  .. note::
+      On POSIX systems, in accordance with `IEEE Std 1003.1 2013 Edition; 4.13
+      Pathname Resolution <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>`_,
+      if a pathname begins with exactly two slashes, the first component
+      following the leading characters may be interpreted in an implementation-defined
+      manner, although more than two leading characters shall be treated as a
+      single character.
+
    .. versionchanged:: 3.6
       Accepts a :term:`path-like object`.
 
diff --git a/Doc/library/traceback.rst b/Doc/library/traceback.rst
@@ -473,7 +473,7 @@ The output for the example would look similar to this:
    ['Traceback (most recent call last):\n',
     '  File "<doctest default[0]>", line 10, in <module>\n    lumberjack()\n    ^^^^^^^^^^^^\n',
     '  File "<doctest default[0]>", line 4, in lumberjack\n    bright_side_of_death()\n    ^^^^^^^^^^^^^^^^^^^^^^\n',
-    '  File "<doctest default[0]>", line 7, in bright_side_of_death\n    return tuple()[0]\n           ^^^^^^^^^^\n',
+    '  File "<doctest default[0]>", line 7, in bright_side_of_death\n    return tuple()[0]\n           ~~~~~~~^^^\n',
     'IndexError: tuple index out of range\n']
    *** extract_tb:
    [<FrameSummary file <doctest...>, line 10 in <module>>,
@@ -482,7 +482,7 @@ The output for the example would look similar to this:
    *** format_tb:
    ['  File "<doctest default[0]>", line 10, in <module>\n    lumberjack()\n    ^^^^^^^^^^^^\n',
     '  File "<doctest default[0]>", line 4, in lumberjack\n    bright_side_of_death()\n    ^^^^^^^^^^^^^^^^^^^^^^\n',
-    '  File "<doctest default[0]>", line 7, in bright_side_of_death\n    return tuple()[0]\n           ^^^^^^^^^^\n']
+    '  File "<doctest default[0]>", line 7, in bright_side_of_death\n    return tuple()[0]\n           ~~~~~~~^^^\n']
    *** tb_lineno: 10
 
 
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
@@ -1015,6 +1015,39 @@ Internal types
       If a code object represents a function, the first item in :attr:`co_consts` is
       the documentation string of the function, or ``None`` if undefined.
 
+      .. method:: codeobject.co_positions()
+
+         Returns an iterable over the source code positions of each bytecode
+         instruction in the code object.
+
+         The iterator returns tuples containing the ``(start_line, end_line,
+         start_column, end_column)``. The *i-th* tuple corresponds to the
+         position of the source code that compiled to the *i-th* instruction.
+         Column information is 0-indexed utf-8 byte offsets on the given source
+         line.
+
+         This positional information can be missing. A non-exhaustive lists of
+         cases where this may happen:
+
+         - Running the interpreter with :option:`-X` ``no_debug_ranges``.
+         - Loading a pyc file compiled while using :option:`-X` ``no_debug_ranges``.
+         - Position tuples corresponding to artificial instructions.
+         - Line and column numbers that can't be represented due to
+           implementation specific limitations.
+
+         When this occurs, some or all of the tuple elements can be
+         :const:`None`.
+
+         .. versionadded:: 3.11
+
+         .. note::
+            This feature requires storing column positions in code objects which may
+            result in a small increase of disk usage of compiled Python files or
+            interpreter memory usage. To avoid storing the extra information and/or
+            deactivate printing the extra traceback information, the
+            :option:`-X` ``no_debug_ranges`` command line flag or the :envvar:`PYTHONNODEBUGRANGES`
+            environment variable can be used.
+
    .. _frame-objects:
 
    Frame objects
diff --git a/Doc/whatsnew/3.11.rst b/Doc/whatsnew/3.11.rst
@@ -70,6 +70,83 @@ Summary -- Release highlights
 New Features
 ============
 
+.. _whatsnew311-pep657:
+
+Enhanced error locations in tracebacks
+--------------------------------------
+
+When printing tracebacks, the interpreter will now point to the exact expression
+that caused the error instead of just the line. For example:
+
+.. code-block:: python
+
+    Traceback (most recent call last):
+      File "distance.py", line 11, in <module>
+        print(manhattan_distance(p1, p2))
+              ^^^^^^^^^^^^^^^^^^^^^^^^^^
+      File "distance.py", line 6, in manhattan_distance
+        return abs(point_1.x - point_2.x) + abs(point_1.y - point_2.y)
+                               ^^^^^^^^^
+    AttributeError: 'NoneType' object has no attribute 'x'
+
+Previous versions of the interpreter would point to just the line making it
+ambiguous which object was ``None``. These enhanced errors can also be helpful
+when dealing with deeply nested dictionary objects and multiple function calls,
+
+.. code-block:: python
+
+    Traceback (most recent call last):
+      File "query.py", line 37, in <module>
+        magic_arithmetic('foo')
+        ^^^^^^^^^^^^^^^^^^^^^^^
+      File "query.py", line 18, in magic_arithmetic
+        return add_counts(x) / 25
+               ^^^^^^^^^^^^^
+      File "query.py", line 24, in add_counts
+        return 25 + query_user(user1) + query_user(user2)
+                    ^^^^^^^^^^^^^^^^^
+      File "query.py", line 32, in query_user
+        return 1 + query_count(db, response['a']['b']['c']['user'], retry=True)
+                                   ~~~~~~~~~~~~~~~~~~^^^^^
+    TypeError: 'NoneType' object is not subscriptable
+
+as well as complex arithmetic expressions:
+
+.. code-block:: python
+
+    Traceback (most recent call last):
+      File "calculation.py", line 54, in <module>
+        result = (x / y / z) * (a / b / c)
+                  ~~~~~~^~~
+    ZeroDivisionError: division by zero
+
+See :pep:`657` for more details. (Contributed by Pablo Galindo, Batuhan Taskaya
+and Ammar Askar in :issue:`43950`.)
+
+.. note::
+   This feature requires storing column positions in code objects which may
+   result in a small increase of disk usage of compiled Python files or
+   interpreter memory usage. To avoid storing the extra information and/or
+   deactivate printing the extra traceback information, the
+   :option:`-X` ``no_debug_ranges`` command line flag or the :envvar:`PYTHONNODEBUGRANGES`
+   environment variable can be used.
+
+Column information for code objects
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The information used by the enhanced traceback feature is made available as a
+general API that can be used to correlate bytecode instructions with source
+code. This information can be retrieved using:
+
+- The :meth:`codeobject.co_positions` method in Python.
+- The :c:func:`PyCode_Addr2Location` function in the C-API.
+
+The :option:`-X` ``no_debug_ranges`` option and the environment variable
+:envvar:`PYTHONNODEBUGRANGES` can be used to disable this feature.
+
+See :pep:`657` for more details. (Contributed by Pablo Galindo, Batuhan Taskaya
+and Ammar Askar in :issue:`43950`.)
+
 
 
 Other Language Changes
diff --git a/Lib/posixpath.py b/Lib/posixpath.py
@@ -352,6 +352,7 @@ def normpath(path):
     initial_slashes = path.startswith(sep)
     # POSIX allows one or two initial slashes, but treats three or more
     # as single slash.
+    # (see http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13)
     if (initial_slashes and
         path.startswith(sep*2) and not path.startswith(sep*3)):
         initial_slashes = 2
diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
@@ -12,9 +12,11 @@
                           requires_debug_ranges, has_no_debug_ranges)
 from test.support.os_helper import TESTFN, unlink
 from test.support.script_helper import assert_python_ok, assert_python_failure
-import textwrap
 
+import os
+import textwrap
 import traceback
+from functools import partial
 
 
 test_code = namedtuple('code', ['co_filename', 'co_name'])
@@ -406,6 +408,82 @@ def f_with_multiline():
         result_lines = self.get_exception(f_with_multiline)
         self.assertEqual(result_lines, expected_f.splitlines())
 
+    def test_caret_for_binary_operators(self):
+        def f_with_binary_operator():
+            divisor = 20
+            return 10 + divisor / 0 + 30
+
+        lineno_f = f_with_binary_operator.__code__.co_firstlineno
+        expected_error = (
+            'Traceback (most recent call last):\n'
+            f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
+            '    callable()\n'
+            '    ^^^^^^^^^^\n'
+            f'  File "{__file__}", line {lineno_f+2}, in f_with_binary_operator\n'
+            '    return 10 + divisor / 0 + 30\n'
+            '                ~~~~~~~~^~~\n'
+        )
+        result_lines = self.get_exception(f_with_binary_operator)
+        self.assertEqual(result_lines, expected_error.splitlines())
+
+    def test_caret_for_binary_operators_two_char(self):
+        def f_with_binary_operator():
+            divisor = 20
+            return 10 + divisor // 0 + 30
+
+        lineno_f = f_with_binary_operator.__code__.co_firstlineno
+        expected_error = (
+            'Traceback (most recent call last):\n'
+            f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
+            '    callable()\n'
+            '    ^^^^^^^^^^\n'
+            f'  File "{__file__}", line {lineno_f+2}, in f_with_binary_operator\n'
+            '    return 10 + divisor // 0 + 30\n'
+            '                ~~~~~~~~^^~~\n'
+        )
+        result_lines = self.get_exception(f_with_binary_operator)
+        self.assertEqual(result_lines, expected_error.splitlines())
+
+    def test_caret_for_subscript(self):
+        def f_with_subscript():
+            some_dict = {'x': {'y': None}}
+            return some_dict['x']['y']['z']
+
+        lineno_f = f_with_subscript.__code__.co_firstlineno
+        expected_error = (
+            'Traceback (most recent call last):\n'
+            f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
+            '    callable()\n'
+            '    ^^^^^^^^^^\n'
+            f'  File "{__file__}", line {lineno_f+2}, in f_with_subscript\n'
+            "    return some_dict['x']['y']['z']\n"
+            '           ~~~~~~~~~~~~~~~~~~~^^^^^\n'
+        )
+        result_lines = self.get_exception(f_with_subscript)
+        self.assertEqual(result_lines, expected_error.splitlines())
+
+    def test_traceback_specialization_with_syntax_error(self):
+        bytecode = compile("1 / 0 / 1 / 2\n", TESTFN, "exec")
+
+        with open(TESTFN, "w") as file:
+            # make the file's contents invalid
+            file.write("1 $ 0 / 1 / 2\n")
+        self.addCleanup(unlink, TESTFN)
+
+        func = partial(exec, bytecode)
+        result_lines = self.get_exception(func)
+
+        lineno_f = bytecode.co_firstlineno
+        expected_error = (
+            'Traceback (most recent call last):\n'
+            f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
+            '    callable()\n'
+            '    ^^^^^^^^^^\n'
+            f'  File "{TESTFN}", line {lineno_f}, in <module>\n'
+            "    1 $ 0 / 1 / 2\n"
+            '    ^^^^^\n'
+        )
+        self.assertEqual(result_lines, expected_error.splitlines())
 
 @cpython_only
 @requires_debug_ranges()
@@ -1615,7 +1693,7 @@ def f():
         self.assertEqual(
             output.getvalue().split('\n')[-5:],
             ['    x/0',
-             '    ^^^',
+             '    ~^~',
              '    x = 12',
              'ZeroDivisionError: division by zero',
              ''])
diff --git a/Lib/traceback.py b/Lib/traceback.py
@@ -494,9 +494,23 @@ def format(self):
                     colno = _byte_offset_to_character_offset(frame._original_line, frame.colno)
                     end_colno = _byte_offset_to_character_offset(frame._original_line, frame.end_colno)
 
+                    try:
+                        anchors = _extract_caret_anchors_from_line_segment(
+                            frame._original_line[colno - 1:end_colno]
+                        )
+                    except Exception:
+                        anchors = None
+
                     row.append('    ')
                     row.append(' ' * (colno - stripped_characters))
-                    row.append('^' * (end_colno - colno))
+
+                    if anchors:
+                        row.append(anchors.primary_char * (anchors.left_end_offset))
+                        row.append(anchors.secondary_char * (anchors.right_start_offset - anchors.left_end_offset))
+                        row.append(anchors.primary_char * (end_colno - colno - anchors.right_start_offset))
+                    else:
+                        row.append('^' * (end_colno - colno))
+
                     row.append('\n')
 
             if frame.locals:
@@ -520,6 +534,50 @@ def _byte_offset_to_character_offset(str, offset):
     return len(as_utf8[:offset + 1].decode("utf-8"))
 
 
+_Anchors = collections.namedtuple(
+    "_Anchors",
+    [
+        "left_end_offset",
+        "right_start_offset",
+        "primary_char",
+        "secondary_char",
+    ],
+    defaults=["~", "^"]
+)
+
+def _extract_caret_anchors_from_line_segment(segment):
+    import ast
+
+    try:
+        tree = ast.parse(segment)
+    except SyntaxError:
+        return None
+
+    if len(tree.body) != 1:
+        return None
+
+    statement = tree.body[0]
+    match statement:
+        case ast.Expr(expr):
+            match expr:
+                case ast.BinOp():
+                    operator_str = segment[expr.left.end_col_offset:expr.right.col_offset]
+                    operator_offset = len(operator_str) - len(operator_str.lstrip())
+
+                    left_anchor = expr.left.end_col_offset + operator_offset
+                    right_anchor = left_anchor + 1
+                    if (
+                        operator_offset + 1 < len(operator_str)
+                        and not operator_str[operator_offset + 1].isspace()
+                    ):
+                        right_anchor += 1
+                    return _Anchors(left_anchor, right_anchor)
+                case ast.Subscript():
+                    return _Anchors(expr.value.end_col_offset, expr.slice.end_col_offset + 1)
+
+    return None
+
+
 class TracebackException:
     """An exception ready for rendering.
 
diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-07-06-15-27-11.bpo-43950.LhL2-q.rst b/Misc/NEWS.d/next/Core and Builtins/2021-07-06-15-27-11.bpo-43950.LhL2-q.rst
@@ -0,0 +1,6 @@
+Code objects can now provide the column information for instructions when
+available. This is levaraged during traceback printing to show the
+expressions responsible for errors.
+
+Contributed by Pablo Galindo, Batuhan Taskaya and Ammar Askar as part of
+:pep:`657`.
diff --git a/Misc/NEWS.d/next/Documentation/2021-07-12-11-39-20.bpo-44613.DIXNzc.rst b/Misc/NEWS.d/next/Documentation/2021-07-12-11-39-20.bpo-44613.DIXNzc.rst
diff --git a/Python/traceback.c b/Python/traceback.c
