Mini Shell

import ast
import inspect
import textwrap
import tokenize
import types
import warnings
from bisect import bisect_right
from typing import Iterable
from typing import Iterator
from typing import List
from typing import Optional
from typing import overload
from typing import Tuple
from typing import Union


class Source:
    """An immutable object holding a source code fragment.

    When using Source(...), the source lines are deindented.
    """

    def __init__(self, obj: object = None) -> None:
        if not obj:
            self.lines: List[str] = []
        elif isinstance(obj, Source):
            self.lines = obj.lines
        elif isinstance(obj, (tuple, list)):
            self.lines = deindent(x.rstrip("\n") for x in obj)
        elif isinstance(obj, str):
            self.lines = deindent(obj.split("\n"))
        else:
            try:
                rawcode = getrawcode(obj)
                src = inspect.getsource(rawcode)
            except TypeError:
                src = inspect.getsource(obj)  # type: ignore[arg-type]
            self.lines = deindent(src.split("\n"))

    def __eq__(self, other: object) -> bool:
        if not isinstance(other, Source):
            return NotImplemented
        return self.lines == other.lines

    # Ignore type because of https://github.com/python/mypy/issues/4266.
    __hash__ = None  # type: ignore

    @overload
    def __getitem__(self, key: int) -> str:
        ...

    @overload
    def __getitem__(self, key: slice) -> "Source":
        ...

    def __getitem__(self, key: Union[int, slice]) -> Union[str, "Source"]:
        if isinstance(key, int):
            return self.lines[key]
        else:
            if key.step not in (None, 1):
                raise IndexError("cannot slice a Source with a step")
            newsource = Source()
            newsource.lines = self.lines[key.start : key.stop]
            return newsource

    def __iter__(self) -> Iterator[str]:
        return iter(self.lines)

    def __len__(self) -> int:
        return len(self.lines)

    def strip(self) -> "Source":
        """Return new Source object with trailing and leading blank lines removed."""
        start, end = 0, len(self)
        while start < end and not self.lines[start].strip():
            start += 1
        while end > start and not self.lines[end - 1].strip():
            end -= 1
        source = Source()
        source.lines[:] = self.lines[start:end]
        return source

    def indent(self, indent: str = " " * 4) -> "Source":
        """Return a copy of the source object with all lines indented by the
        given indent-string."""
        newsource = Source()
        newsource.lines = [(indent + line) for line in self.lines]
        return newsource

    def getstatement(self, lineno: int) -> "Source":
        """Return Source statement which contains the given linenumber
        (counted from 0)."""
        start, end = self.getstatementrange(lineno)
        return self[start:end]

    def getstatementrange(self, lineno: int) -> Tuple[int, int]:
        """Return (start, end) tuple which spans the minimal statement region
        which containing the given lineno."""
        if not (0 <= lineno < len(self)):
            raise IndexError("lineno out of range")
        ast, start, end = getstatementrange_ast(lineno, self)
        return start, end

    def deindent(self) -> "Source":
        """Return a new Source object deindented."""
        newsource = Source()
        newsource.lines[:] = deindent(self.lines)
        return newsource

    def __str__(self) -> str:
        return "\n".join(self.lines)


#
# helper functions
#


def findsource(obj) -> Tuple[Optional[Source], int]:
    try:
        sourcelines, lineno = inspect.findsource(obj)
    except Exception:
        return None, -1
    source = Source()
    source.lines = [line.rstrip() for line in sourcelines]
    return source, lineno


def getrawcode(obj: object, trycall: bool = True) -> types.CodeType:
    """Return code object for given function."""
    try:
        return obj.__code__  # type: ignore[attr-defined,no-any-return]
    except AttributeError:
        pass
    if trycall:
        call = getattr(obj, "__call__", None)
        if call and not isinstance(obj, type):
            return getrawcode(call, trycall=False)
    raise TypeError(f"could not get code object for {obj!r}")


def deindent(lines: Iterable[str]) -> List[str]:
    return textwrap.dedent("\n".join(lines)).splitlines()


def get_statement_startend2(lineno: int, node: ast.AST) -> Tuple[int, Optional[int]]:
    # Flatten all statements and except handlers into one lineno-list.
    # AST's line numbers start indexing at 1.
    values: List[int] = []
    for x in ast.walk(node):
        if isinstance(x, (ast.stmt, ast.ExceptHandler)):
            # Before Python 3.8, the lineno of a decorated class or function pointed at the decorator.
            # Since Python 3.8, the lineno points to the class/def, so need to include the decorators.
            if isinstance(x, (ast.ClassDef, ast.FunctionDef, ast.AsyncFunctionDef)):
                for d in x.decorator_list:
                    values.append(d.lineno - 1)
            values.append(x.lineno - 1)
            for name in ("finalbody", "orelse"):
                val: Optional[List[ast.stmt]] = getattr(x, name, None)
                if val:
                    # Treat the finally/orelse part as its own statement.
                    values.append(val[0].lineno - 1 - 1)
    values.sort()
    insert_index = bisect_right(values, lineno)
    start = values[insert_index - 1]
    if insert_index >= len(values):
        end = None
    else:
        end = values[insert_index]
    return start, end


def getstatementrange_ast(
    lineno: int,
    source: Source,
    assertion: bool = False,
    astnode: Optional[ast.AST] = None,
) -> Tuple[ast.AST, int, int]:
    if astnode is None:
        content = str(source)
        # See #4260:
        # Don't produce duplicate warnings when compiling source to find AST.
        with warnings.catch_warnings():
            warnings.simplefilter("ignore")
            astnode = ast.parse(content, "source", "exec")

    start, end = get_statement_startend2(lineno, astnode)
    # We need to correct the end:
    # - ast-parsing strips comments
    # - there might be empty lines
    # - we might have lesser indented code blocks at the end
    if end is None:
        end = len(source.lines)

    if end > start + 1:
        # Make sure we don't span differently indented code blocks
        # by using the BlockFinder helper used which inspect.getsource() uses itself.
        block_finder = inspect.BlockFinder()
        # If we start with an indented line, put blockfinder to "started" mode.
        block_finder.started = source.lines[start][0].isspace()
        it = ((x + "\n") for x in source.lines[start:end])
        try:
            for tok in tokenize.generate_tokens(lambda: next(it)):
                block_finder.tokeneater(*tok)
        except (inspect.EndOfBlock, IndentationError):
            end = block_finder.last + start
        except Exception:
            pass

    # The end might still point to a comment or empty line, correct it.
    while end:
        line = source.lines[end - 1].lstrip()
        if line.startswith("#") or not line:
            end -= 1
        else:
            break
    return astnode, start, end