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# Copyright 2022 DeepMind Technologies Limited
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Utility for formatting AST node as Python code."""
import contextlib
import dataclasses
from typing import Any, Iterable, Mapping, Sequence
INDENT_WIDTH = 4
MAX_LINE_WIDTH = 80
SIMPLE_TYPES = frozenset([int, float, str, bool, bytes, type(None)])
def format_as_python_code(obj: Any) -> str:
"""Formats an AST node object as well-indented Python code."""
formatter = _Formatter()
formatter.add(obj)
return str(formatter)
def _is_all_simple(seq: Iterable[Any]) -> bool:
return all(type(obj) in SIMPLE_TYPES for obj in seq)
class _Formatter:
"""A helper for pretty-printing AST nodes as Python code."""
def __init__(self):
self._line_prefix = ''
self._lines = []
self._add_to_last_line = False
@contextlib.contextmanager
def _indent(self, width: int = INDENT_WIDTH):
self._line_prefix += ' ' * width
yield
self._line_prefix = self._line_prefix[:-width]
@contextlib.contextmanager
def _append_at_end(self, s):
yield
self._lines[-1] += s
def _add_line(self, line: str, no_break: bool = False):
if self._add_to_last_line:
self._lines[-1] += line
else:
self._lines.append(self._line_prefix + line)
self._add_to_last_line = no_break
def _add_dict(self, obj: Mapping[Any, Any]):
"""Adds a dict to the formatted output."""
self._add_line('dict([')
with self._indent():
for k, v in obj.items():
# Try to fit everything into a single line first.
if _is_all_simple((k, v)):
single_line = f'({k!r}, {v!r}),'
if len(self._line_prefix) + len(single_line) <= MAX_LINE_WIDTH:
self._add_line(single_line)
continue
self._add_line(f"('{k}',")
with self._append_at_end('),'):
with self._indent(1):
self.add(v)
self._add_line('])')
def _add_dataclass(self, obj: Any):
"""Adds a dataclass object to the formatted output."""
# Filter out default values.
kv_pairs = []
for k in dataclasses.fields(obj):
v = getattr(obj, k.name)
if v != k.default:
kv_pairs.append((k, v))
# Try to fit everything into a single line first.
if _is_all_simple(v for _, v in kv_pairs):
single_line = ', '.join(f'{k.name}={v!r}' for k, v in kv_pairs)
single_line = f'{obj.__class__.__name__}({single_line})'
if len(self._line_prefix) + len(single_line) <= MAX_LINE_WIDTH:
self._add_line(single_line)
return
self._add_line(obj.__class__.__name__ + '(')
with self._indent():
for k, v in kv_pairs:
self._add_line(k.name + '=', no_break=True)
with self._append_at_end(','):
self.add(v)
self._add_line(')')
def _add_sequence(self, obj: Sequence[Any]) -> None:
"""Adds a sequence to the formatted output."""
default_str = repr(obj)
open_token, close_token = default_str[0], default_str[-1]
# Try to fit everything into a single line first.
if _is_all_simple(obj):
single_line = (
f"{open_token}{', '.join(repr(o) for o in obj)}{close_token}")
if close_token == ')' and len(obj) == 1:
single_line = f'{single_line[:-1]},)'
if len(self._line_prefix) + len(single_line) <= MAX_LINE_WIDTH:
self._add_line(single_line)
return
self._add_line(open_token)
with self._indent():
for v in obj:
with self._append_at_end(','):
self.add(v)
self._add_line(close_token)
def add(self, obj: Any) -> None:
"""Adds an object to the formatted output."""
if _is_all_simple((obj,)):
self._add_line(repr(obj))
elif dataclasses.is_dataclass(obj):
self._add_dataclass(obj)
elif isinstance(obj, Mapping):
self._add_dict(obj)
elif isinstance(obj, Sequence):
self._add_sequence(obj)
else:
raise NotImplementedError
def __str__(self):
lines = []
for line in self._lines:
if len(line) > MAX_LINE_WIDTH:
lines.append(f'{line} # pylint: disable=line-too-long')
else:
lines.append(line)
return '\n'.join(lines)
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