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expression.py
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expression.py
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# Copyright (c) Meta Platforms, Inc. and affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
import re
from abc import ABC, abstractmethod
from ast import literal_eval
from contextlib import contextmanager
from dataclasses import dataclass, field
from enum import auto, Enum
from tokenize import (
Floatnumber as FLOATNUMBER_RE,
Imagnumber as IMAGNUMBER_RE,
Intnumber as INTNUMBER_RE,
)
from typing import Callable, Generator, Optional, Sequence, Union
from typing_extensions import Literal
from libcst._add_slots import add_slots
from libcst._maybe_sentinel import MaybeSentinel
from libcst._nodes.base import CSTCodegenError, CSTNode, CSTValidationError
from libcst._nodes.internal import (
CodegenState,
visit_optional,
visit_required,
visit_sentinel,
visit_sequence,
)
from libcst._nodes.op import (
AssignEqual,
BaseBinaryOp,
BaseBooleanOp,
BaseCompOp,
BaseUnaryOp,
Colon,
Comma,
Dot,
In,
Is,
IsNot,
Not,
NotIn,
)
from libcst._nodes.whitespace import BaseParenthesizableWhitespace, SimpleWhitespace
from libcst._visitors import CSTVisitorT
@add_slots
@dataclass(frozen=True)
class LeftSquareBracket(CSTNode):
"""
Used by various nodes to denote a subscript or list section. This doesn't own
the whitespace to the left of it since this is owned by the parent node.
"""
#: Any space that appears directly after this left square bracket.
whitespace_after: BaseParenthesizableWhitespace = SimpleWhitespace.field("")
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "LeftSquareBracket":
return LeftSquareBracket(
whitespace_after=visit_required(
self, "whitespace_after", self.whitespace_after, visitor
)
)
def _codegen_impl(self, state: CodegenState) -> None:
state.add_token("[")
self.whitespace_after._codegen(state)
@add_slots
@dataclass(frozen=True)
class RightSquareBracket(CSTNode):
"""
Used by various nodes to denote a subscript or list section. This doesn't own
the whitespace to the right of it since this is owned by the parent node.
"""
#: Any space that appears directly before this right square bracket.
whitespace_before: BaseParenthesizableWhitespace = SimpleWhitespace.field("")
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "RightSquareBracket":
return RightSquareBracket(
whitespace_before=visit_required(
self, "whitespace_before", self.whitespace_before, visitor
)
)
def _codegen_impl(self, state: CodegenState) -> None:
self.whitespace_before._codegen(state)
state.add_token("]")
@add_slots
@dataclass(frozen=True)
class LeftCurlyBrace(CSTNode):
"""
Used by various nodes to denote a dict or set. This doesn't own the whitespace to
the left of it since this is owned by the parent node.
"""
#: Any space that appears directly after this left curly brace.
whitespace_after: BaseParenthesizableWhitespace = SimpleWhitespace.field("")
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "LeftCurlyBrace":
return LeftCurlyBrace(
whitespace_after=visit_required(
self, "whitespace_after", self.whitespace_after, visitor
)
)
def _codegen_impl(self, state: CodegenState) -> None:
state.add_token("{")
self.whitespace_after._codegen(state)
@add_slots
@dataclass(frozen=True)
class RightCurlyBrace(CSTNode):
"""
Used by various nodes to denote a dict or set. This doesn't own the whitespace to
the right of it since this is owned by the parent node.
"""
#: Any space that appears directly before this right curly brace.
whitespace_before: BaseParenthesizableWhitespace = SimpleWhitespace.field("")
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "RightCurlyBrace":
return RightCurlyBrace(
whitespace_before=visit_required(
self, "whitespace_before", self.whitespace_before, visitor
)
)
def _codegen_impl(self, state: CodegenState) -> None:
self.whitespace_before._codegen(state)
state.add_token("}")
@add_slots
@dataclass(frozen=True)
class LeftParen(CSTNode):
"""
Used by various nodes to denote a parenthesized section. This doesn't own
the whitespace to the left of it since this is owned by the parent node.
"""
#: Any space that appears directly after this left parenthesis.
whitespace_after: BaseParenthesizableWhitespace = SimpleWhitespace.field("")
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "LeftParen":
return LeftParen(
whitespace_after=visit_required(
self, "whitespace_after", self.whitespace_after, visitor
)
)
def _codegen_impl(self, state: CodegenState) -> None:
state.add_token("(")
self.whitespace_after._codegen(state)
@add_slots
@dataclass(frozen=True)
class RightParen(CSTNode):
"""
Used by various nodes to denote a parenthesized section. This doesn't own
the whitespace to the right of it since this is owned by the parent node.
"""
#: Any space that appears directly after this left parenthesis.
whitespace_before: BaseParenthesizableWhitespace = SimpleWhitespace.field("")
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "RightParen":
return RightParen(
whitespace_before=visit_required(
self, "whitespace_before", self.whitespace_before, visitor
)
)
def _codegen_impl(self, state: CodegenState) -> None:
self.whitespace_before._codegen(state)
state.add_token(")")
@add_slots
@dataclass(frozen=True)
class Asynchronous(CSTNode):
"""
Used by asynchronous function definitions, as well as ``async for`` and
``async with``.
"""
#: Any space that appears directly after this async keyword.
whitespace_after: SimpleWhitespace = SimpleWhitespace.field(" ")
def _validate(self) -> None:
if len(self.whitespace_after.value) < 1:
raise CSTValidationError("Must have at least one space after Asynchronous.")
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "Asynchronous":
return Asynchronous(
whitespace_after=visit_required(
self, "whitespace_after", self.whitespace_after, visitor
)
)
def _codegen_impl(self, state: CodegenState) -> None:
with state.record_syntactic_position(self):
state.add_token("async")
self.whitespace_after._codegen(state)
class _BaseParenthesizedNode(CSTNode, ABC):
"""
We don't want to have another level of indirection for parenthesis in
our tree, since that makes us more of a CST than an AST. So, all the
expressions or atoms that can be wrapped in parenthesis will subclass
this to get that functionality.
"""
__slots__ = ()
lpar: Sequence[LeftParen] = ()
# Sequence of parenthesis for precedence dictation.
rpar: Sequence[RightParen] = ()
def _validate(self) -> None:
if self.lpar and not self.rpar:
raise CSTValidationError("Cannot have left paren without right paren.")
if not self.lpar and self.rpar:
raise CSTValidationError("Cannot have right paren without left paren.")
if len(self.lpar) != len(self.rpar):
raise CSTValidationError("Cannot have unbalanced parens.")
@contextmanager
def _parenthesize(self, state: CodegenState) -> Generator[None, None, None]:
for lpar in self.lpar:
lpar._codegen(state)
with state.record_syntactic_position(self):
yield
for rpar in self.rpar:
rpar._codegen(state)
class ExpressionPosition(Enum):
LEFT = auto()
RIGHT = auto()
class BaseExpression(_BaseParenthesizedNode, ABC):
"""
An base class for all expressions. :class:`BaseExpression` contains no fields.
"""
__slots__ = ()
def _safe_to_use_with_word_operator(self, position: ExpressionPosition) -> bool:
"""
Returns true if this expression is safe to be use with a word operator
such as "not" without space between the operator an ourselves. Examples
where this is true are "not(True)", "(1)in[1,2,3]", etc. This base
function handles parenthesized nodes, but certain nodes such as tuples,
dictionaries and lists will override this to signifiy that they're always
safe.
"""
return len(self.lpar) > 0 and len(self.rpar) > 0
def _check_left_right_word_concatenation_safety(
self,
position: ExpressionPosition,
left: "BaseExpression",
right: "BaseExpression",
) -> bool:
if position == ExpressionPosition.RIGHT:
return left._safe_to_use_with_word_operator(ExpressionPosition.RIGHT)
if position == ExpressionPosition.LEFT:
return right._safe_to_use_with_word_operator(ExpressionPosition.LEFT)
return False
class BaseAssignTargetExpression(BaseExpression, ABC):
"""
An expression that's valid on the left side of an assignment. That assignment may
be part an :class:`Assign` node, or it may be part of a number of other control
structures that perform an assignment, such as a :class:`For` loop.
Python's grammar defines all expression as valid in this position, but the AST
compiler further restricts the allowed types, which is what this type attempts to
express.
This is similar to a :class:`BaseDelTargetExpression`, but it also includes
:class:`StarredElement` as a valid node.
The set of valid nodes are defined as part of `CPython's AST context computation
<https://github.com/python/cpython/blob/v3.8.0a4/Python/ast.c#L1120>`_.
"""
__slots__ = ()
class BaseDelTargetExpression(BaseExpression, ABC):
"""
An expression that's valid on the right side of a :class:`Del` statement.
Python's grammar defines all expression as valid in this position, but the AST
compiler further restricts the allowed types, which is what this type attempts to
express.
This is similar to a :class:`BaseAssignTargetExpression`, but it excludes
:class:`StarredElement`.
The set of valid nodes are defined as part of `CPython's AST context computation
<https://github.com/python/cpython/blob/v3.8.0a4/Python/ast.c#L1120>`_ and as part
of `CPython's bytecode compiler
<https://github.com/python/cpython/blob/v3.8.0a4/Python/compile.c#L4854>`_.
"""
__slots__ = ()
@add_slots
@dataclass(frozen=True)
class Name(BaseAssignTargetExpression, BaseDelTargetExpression):
"""
A simple variable name. Names are typically used in the context of a variable
access, an assignment, or a deletion.
Dotted variable names (``a.b.c``) are represented with :class:`Attribute` nodes,
and subscripted variable names (``a[b]``) are represented with :class:`Subscript`
nodes.
"""
#: The variable's name (or "identifier") as a string.
value: str
lpar: Sequence[LeftParen] = ()
#: Sequence of parenthesis for precedence dictation.
rpar: Sequence[RightParen] = ()
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "Name":
return Name(
lpar=visit_sequence(self, "lpar", self.lpar, visitor),
value=self.value,
rpar=visit_sequence(self, "rpar", self.rpar, visitor),
)
def _validate(self) -> None:
super(Name, self)._validate()
if len(self.value) == 0:
raise CSTValidationError("Cannot have empty name identifier.")
if not self.value.isidentifier():
raise CSTValidationError(f"Name {self.value!r} is not a valid identifier.")
def _codegen_impl(self, state: CodegenState) -> None:
with self._parenthesize(state):
state.add_token(self.value)
@add_slots
@dataclass(frozen=True)
class Ellipsis(BaseExpression):
"""
An ellipsis ``...``. When used as an expression, it evaluates to the
`Ellipsis constant`_. Ellipsis are often used as placeholders in code or in
conjunction with :class:`SubscriptElement`.
.. _Ellipsis constant: https://docs.python.org/3/library/constants.html#Ellipsis
"""
lpar: Sequence[LeftParen] = ()
#: Sequence of parenthesis for precedence dictation.
rpar: Sequence[RightParen] = ()
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "Ellipsis":
return Ellipsis(
lpar=visit_sequence(self, "lpar", self.lpar, visitor),
rpar=visit_sequence(self, "rpar", self.rpar, visitor),
)
def _safe_to_use_with_word_operator(self, position: ExpressionPosition) -> bool:
return True
def _codegen_impl(self, state: CodegenState) -> None:
with self._parenthesize(state):
state.add_token("...")
class BaseNumber(BaseExpression, ABC):
"""
A type such as :class:`Integer`, :class:`Float`, or :class:`Imaginary` that can be
used anywhere that you need to explicitly take any number type.
"""
__slots__ = ()
def _safe_to_use_with_word_operator(self, position: ExpressionPosition) -> bool:
"""
Numbers are funny. The expression "5in [1,2,3,4,5]" is a valid expression
which evaluates to "True". So, encapsulate that here by allowing zero spacing
with the left hand side of an expression with a comparison operator.
"""
if position == ExpressionPosition.LEFT:
return True
return super(BaseNumber, self)._safe_to_use_with_word_operator(position)
@add_slots
@dataclass(frozen=True)
class Integer(BaseNumber):
#: A string representation of the integer, such as ``"100000"`` or ``100_000``.
#:
#: To convert this string representation to an ``int``, use the calculated
#: property :attr:`~Integer.evaluated_value`.
value: str
lpar: Sequence[LeftParen] = ()
#: Sequence of parenthesis for precedence dictation.
rpar: Sequence[RightParen] = ()
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "Integer":
return Integer(
lpar=visit_sequence(self, "lpar", self.lpar, visitor),
value=self.value,
rpar=visit_sequence(self, "rpar", self.rpar, visitor),
)
def _validate(self) -> None:
super(Integer, self)._validate()
if not re.fullmatch(INTNUMBER_RE, self.value):
raise CSTValidationError("Number is not a valid integer.")
def _codegen_impl(self, state: CodegenState) -> None:
with self._parenthesize(state):
state.add_token(self.value)
@property
def evaluated_value(self) -> int:
"""
Return an :func:`ast.literal_eval` evaluated int of :py:attr:`value`.
"""
return literal_eval(self.value)
@add_slots
@dataclass(frozen=True)
class Float(BaseNumber):
#: A string representation of the floating point number, such as ``"0.05"``,
#: ``".050"``, or ``"5e-2"``.
#:
#: To convert this string representation to an ``float``, use the calculated
#: property :attr:`~Float.evaluated_value`.
value: str
lpar: Sequence[LeftParen] = ()
#: Sequence of parenthesis for precedence dictation.
rpar: Sequence[RightParen] = ()
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "Float":
return Float(
lpar=visit_sequence(self, "lpar", self.lpar, visitor),
value=self.value,
rpar=visit_sequence(self, "rpar", self.rpar, visitor),
)
def _validate(self) -> None:
super(Float, self)._validate()
if not re.fullmatch(FLOATNUMBER_RE, self.value):
raise CSTValidationError("Number is not a valid float.")
def _codegen_impl(self, state: CodegenState) -> None:
with self._parenthesize(state):
state.add_token(self.value)
@property
def evaluated_value(self) -> float:
"""
Return an :func:`ast.literal_eval` evaluated float of :py:attr:`value`.
"""
return literal_eval(self.value)
@add_slots
@dataclass(frozen=True)
class Imaginary(BaseNumber):
#: A string representation of the imaginary (complex) number, such as ``"2j"``.
#:
#: To convert this string representation to an ``complex``, use the calculated
#: property :attr:`~Imaginary.evaluated_value`.
value: str
lpar: Sequence[LeftParen] = ()
#: Sequence of parenthesis for precedence dictation.
rpar: Sequence[RightParen] = ()
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "Imaginary":
return Imaginary(
lpar=visit_sequence(self, "lpar", self.lpar, visitor),
value=self.value,
rpar=visit_sequence(self, "rpar", self.rpar, visitor),
)
def _validate(self) -> None:
super(Imaginary, self)._validate()
if not re.fullmatch(IMAGNUMBER_RE, self.value):
raise CSTValidationError("Number is not a valid imaginary.")
def _codegen_impl(self, state: CodegenState) -> None:
with self._parenthesize(state):
state.add_token(self.value)
@property
def evaluated_value(self) -> complex:
"""
Return an :func:`ast.literal_eval` evaluated complex of :py:attr:`value`.
"""
return literal_eval(self.value)
class BaseString(BaseExpression, ABC):
"""
A type that can be used anywhere that you need to take any string. This includes
:class:`SimpleString`, :class:`ConcatenatedString`, and :class:`FormattedString`.
"""
__slots__ = ()
StringQuoteLiteral = Literal['"', "'", '"""', "'''"]
class _BasePrefixedString(BaseString, ABC):
__slots__ = ()
@property
def prefix(self) -> str:
"""
Returns the string's prefix, if any exists.
See `String and Bytes literals
<https://docs.python.org/3.7/reference/lexical_analysis.html#string-and-bytes-literals>`_
for more information.
"""
...
@property
def quote(self) -> StringQuoteLiteral:
"""
Returns the quotation used to denote the string. Can be either ``'``,
``"``, ``'''`` or ``\"\"\"``.
"""
...
def _safe_to_use_with_word_operator(self, position: ExpressionPosition) -> bool:
"""
``"a"in"abc`` is okay, but if you add a prefix, (e.g. ``b"a"inb"abc"``), the string
is no longer valid on the RHS of the word operator, because it's not clear where
the keyword ends and the prefix begins, unless it's parenthesized.
"""
if position == ExpressionPosition.LEFT:
return True
elif self.prefix == "": # and position == ExpressionPosition.RIGHT
return True
else:
return super(_BasePrefixedString, self)._safe_to_use_with_word_operator(
position
)
@add_slots
@dataclass(frozen=True)
class SimpleString(_BasePrefixedString):
"""
Any sort of literal string expression that is not a :class:`FormattedString`
(f-string), including triple-quoted multi-line strings.
"""
#: The texual representation of the string, including quotes, prefix characters, and
#: any escape characters present in the original source code , such as
#: ``r"my string\n"``. To remove the quotes and interpret any escape characters,
#: use the calculated property :attr:`~SimpleString.evaluated_value`.
value: str
lpar: Sequence[LeftParen] = ()
#: Sequence of parenthesis for precidence dictation.
rpar: Sequence[RightParen] = ()
def _validate(self) -> None:
super(SimpleString, self)._validate()
# Validate any prefix
prefix = self.prefix
if prefix not in ("", "r", "u", "b", "br", "rb"):
raise CSTValidationError("Invalid string prefix.")
prefixlen = len(prefix)
# Validate wrapping quotes
if len(self.value) < (prefixlen + 2):
raise CSTValidationError("String must have enclosing quotes.")
if (
self.value[prefixlen] not in ['"', "'"]
or self.value[prefixlen] != self.value[-1]
):
raise CSTValidationError("String must have matching enclosing quotes.")
# Check validity of triple-quoted strings
if len(self.value) >= (prefixlen + 6):
if self.value[prefixlen] == self.value[prefixlen + 1]:
# We know this isn't an empty string, so there needs to be a third
# identical enclosing token.
if (
self.value[prefixlen] != self.value[prefixlen + 2]
or self.value[prefixlen] != self.value[-2]
or self.value[prefixlen] != self.value[-3]
):
raise CSTValidationError(
"String must have matching enclosing quotes."
)
# We should check the contents as well, but this is pretty complicated,
# partially due to triple-quoted strings.
@property
def prefix(self) -> str:
"""
Returns the string's prefix, if any exists. The prefix can be ``r``,
``u``, ``b``, ``br`` or ``rb``.
"""
prefix: str = ""
for c in self.value:
if c in ['"', "'"]:
break
prefix += c
return prefix.lower()
@property
def quote(self) -> StringQuoteLiteral:
"""
Returns the quotation used to denote the string. Can be either ``'``,
``"``, ``'''`` or ``\"\"\"``.
"""
quote: str = ""
for char in self.value[len(self.prefix) :]:
if char not in {"'", '"'}:
break
if quote and char != quote[0]:
# This is no longer the same string quote
break
quote += char
if len(quote) == 2:
# Let's assume this is an empty string.
quote = quote[:1]
elif 3 < len(quote) <= 6:
# Let's assume this can be one of the following:
# >>> """"foo"""
# '"foo'
# >>> """""bar"""
# '""bar'
# >>> """"""
# ''
quote = quote[:3]
if len(quote) not in {1, 3}:
# We shouldn't get here due to construction validation logic,
# but handle the case anyway.
raise Exception(f"Invalid string {self.value}")
# pyre-ignore We know via the above validation that we will only
# ever return one of the four string literals.
return quote
@property
def raw_value(self) -> str:
"""
Returns the raw value of the string as it appears in source, without
the beginning or end quotes and without the prefix. This is often
useful when constructing transforms which need to manipulate strings
in source code.
"""
prefix_len = len(self.prefix)
quote_len = len(self.quote)
return self.value[(prefix_len + quote_len) : (-quote_len)]
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "SimpleString":
return SimpleString(
lpar=visit_sequence(self, "lpar", self.lpar, visitor),
value=self.value,
rpar=visit_sequence(self, "rpar", self.rpar, visitor),
)
def _codegen_impl(self, state: CodegenState) -> None:
with self._parenthesize(state):
state.add_token(self.value)
@property
def evaluated_value(self) -> str:
"""
Return an :func:`ast.literal_eval` evaluated str of :py:attr:`value`.
"""
return literal_eval(self.value)
class BaseFormattedStringContent(CSTNode, ABC):
"""
The base type for :class:`FormattedStringText` and
:class:`FormattedStringExpression`. A :class:`FormattedString` is composed of a
sequence of :class:`BaseFormattedStringContent` parts.
"""
__slots__ = ()
@add_slots
@dataclass(frozen=True)
class FormattedStringText(BaseFormattedStringContent):
"""
Part of a :class:`FormattedString` that is not inside curly braces (``{`` or ``}``).
For example, in::
f"ab{cd}ef"
``ab`` and ``ef`` are :class:`FormattedStringText` nodes, but ``{cd}`` is a
:class:`FormattedStringExpression`.
"""
#: The raw string value, including any escape characters present in the source
#: code, not including any enclosing quotes.
value: str
def _visit_and_replace_children(
self, visitor: CSTVisitorT
) -> "FormattedStringText":
return FormattedStringText(value=self.value)
def _codegen_impl(self, state: CodegenState) -> None:
state.add_token(self.value)
@add_slots
@dataclass(frozen=True)
class FormattedStringExpression(BaseFormattedStringContent):
"""
Part of a :class:`FormattedString` that is inside curly braces (``{`` or ``}``),
including the surrounding curly braces. For example, in::
f"ab{cd}ef"
``{cd}`` is a :class:`FormattedStringExpression`, but ``ab`` and ``ef`` are
:class:`FormattedStringText` nodes.
An f-string expression may contain ``conversion`` and ``format_spec`` suffixes that
control how the expression is converted to a string. See `Python's language
reference
<https://docs.python.org/3/reference/lexical_analysis.html#formatted-string-literals>`__
for details.
"""
#: The expression we will evaluate and render when generating the string.
expression: BaseExpression
#: An optional conversion specifier, such as ``!s``, ``!r`` or ``!a``.
conversion: Optional[str] = None
#: An optional format specifier following the `format specification mini-language
#: <https://docs.python.org/3/library/string.html#formatspec>`_.
format_spec: Optional[Sequence[BaseFormattedStringContent]] = None
#: Whitespace after the opening curly brace (``{``), but before the ``expression``.
whitespace_before_expression: BaseParenthesizableWhitespace = (
SimpleWhitespace.field("")
)
#: Whitespace after the ``expression``, but before the ``conversion``,
#: ``format_spec`` and the closing curly brace (``}``). Python does not
#: allow whitespace inside or after a ``conversion`` or ``format_spec``.
whitespace_after_expression: BaseParenthesizableWhitespace = SimpleWhitespace.field(
""
)
#: Equal sign for formatted string expression uses self-documenting expressions,
#: such as ``f"{x=}"``. See the `Python 3.8 release notes
#: <https://docs.python.org/3/whatsnew/3.8.html#f-strings-support-for-self-documenting-expressions-and-debugging>`_.
equal: Optional[AssignEqual] = None
def _validate(self) -> None:
if self.conversion is not None and self.conversion not in ("s", "r", "a"):
raise CSTValidationError("Invalid f-string conversion.")
def _visit_and_replace_children(
self, visitor: CSTVisitorT
) -> "FormattedStringExpression":
format_spec = self.format_spec
return FormattedStringExpression(
whitespace_before_expression=visit_required(
self,
"whitespace_before_expression",
self.whitespace_before_expression,
visitor,
),
expression=visit_required(self, "expression", self.expression, visitor),
equal=visit_optional(self, "equal", self.equal, visitor),
whitespace_after_expression=visit_required(
self,
"whitespace_after_expression",
self.whitespace_after_expression,
visitor,
),
conversion=self.conversion,
format_spec=(
visit_sequence(self, "format_spec", format_spec, visitor)
if format_spec is not None
else None
),
)
def _codegen_impl(self, state: CodegenState) -> None:
state.add_token("{")
self.whitespace_before_expression._codegen(state)
self.expression._codegen(state)
equal = self.equal
if equal is not None:
equal._codegen(state)
self.whitespace_after_expression._codegen(state)
conversion = self.conversion
if conversion is not None:
state.add_token("!")
state.add_token(conversion)
format_spec = self.format_spec
if format_spec is not None:
state.add_token(":")
for spec in format_spec:
spec._codegen(state)
state.add_token("}")
@add_slots
@dataclass(frozen=True)
class FormattedString(_BasePrefixedString):
"""
An "f-string". These formatted strings are string literals prefixed by the letter
"f". An f-string may contain interpolated expressions inside curly braces (``{`` and
``}``).
F-strings are defined in `PEP 498`_ and documented in `Python's language
reference
<https://docs.python.org/3/reference/lexical_analysis.html#formatted-string-literals>`__.
>>> import libcst as cst
>>> cst.parse_expression('f"ab{cd}ef"')
FormattedString(
parts=[
FormattedStringText(
value='ab',
),
FormattedStringExpression(
expression=Name(
value='cd',
lpar=[],
rpar=[],
),
conversion=None,
format_spec=None,
whitespace_before_expression=SimpleWhitespace(
value='',
),
whitespace_after_expression=SimpleWhitespace(
value='',
),
),
FormattedStringText(
value='ef',
),
],
start='f"',
end='"',
lpar=[],
rpar=[],
)
.. _PEP 498: https://www.python.org/dev/peps/pep-0498/#specification
"""
#: A formatted string is composed as a series of :class:`FormattedStringText` and
#: :class:`FormattedStringExpression` parts.
parts: Sequence[BaseFormattedStringContent]
#: The string prefix and the leading quote, such as ``f"``, ``F'``, ``fr"``, or
#: ``f"""``.
start: str = 'f"'
#: The trailing quote. This must match the type of quote used in ``start``.
end: Literal['"', "'", '"""', "'''"] = '"'
lpar: Sequence[LeftParen] = ()
#: Sequence of parenthesis for precidence dictation.
rpar: Sequence[RightParen] = ()
def _validate(self) -> None:
super(FormattedString, self)._validate()
# Validate any prefix
prefix = self.prefix
if prefix not in ("f", "fr", "rf"):
raise CSTValidationError("Invalid f-string prefix.")
# Validate wrapping quotes
starttoken = self.start[len(prefix) :]
if starttoken != self.end:
raise CSTValidationError("f-string must have matching enclosing quotes.")
# Validate valid wrapping quote usage
if starttoken not in ('"', "'", '"""', "'''"):
raise CSTValidationError("Invalid f-string enclosing quotes.")
@property
def prefix(self) -> str:
"""
Returns the string's prefix, if any exists. The prefix can be ``f``,
``fr``, or ``rf``.
"""
prefix = ""
for c in self.start:
if c in ['"', "'"]:
break
prefix += c
return prefix.lower()
@property
def quote(self) -> StringQuoteLiteral:
"""
Returns the quotation used to denote the string. Can be either ``'``,
``"``, ``'''`` or ``\"\"\"``.
"""
return self.end
def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "FormattedString":
return FormattedString(
lpar=visit_sequence(self, "lpar", self.lpar, visitor),
start=self.start,
parts=visit_sequence(self, "parts", self.parts, visitor),
end=self.end,
rpar=visit_sequence(self, "rpar", self.rpar, visitor),
)
def _codegen_impl(self, state: CodegenState) -> None:
with self._parenthesize(state):
state.add_token(self.start)
for part in self.parts:
part._codegen(state)
state.add_token(self.end)
@add_slots
@dataclass(frozen=True)
class ConcatenatedString(BaseString):
"""
Represents an implicitly concatenated string, such as::
"abc" "def" == "abcdef"
.. warning::
This is different from two strings joined in a :class:`BinaryOperation` with an
:class:`Add` operator, and is `sometimes viewed as an antifeature of Python
<https://lwn.net/Articles/551426/>`_.
"""
#: String on the left of the concatenation.
left: Union[SimpleString, FormattedString]
#: String on the right of the concatenation.
right: Union[SimpleString, FormattedString, "ConcatenatedString"]
lpar: Sequence[LeftParen] = ()
#: Sequence of parenthesis for precidence dictation.
rpar: Sequence[RightParen] = ()
#: Whitespace between the ``left`` and ``right`` substrings.
whitespace_between: BaseParenthesizableWhitespace = SimpleWhitespace.field("")
def _safe_to_use_with_word_operator(self, position: ExpressionPosition) -> bool:
if super(ConcatenatedString, self)._safe_to_use_with_word_operator(position):
# if we have parenthesis, we're safe.
return True
return self._check_left_right_word_concatenation_safety(
position, self.left, self.right
)
def _validate(self) -> None:
super(ConcatenatedString, self)._validate()
# Strings that are concatenated cannot have parens.
if bool(self.left.lpar) or bool(self.left.rpar):