Class DictionaryCompleter

src/ptpython/completer.py:297–612

Experimental completer for Python dictionary keys. Warning: This does an `eval` and `repr` on some Python expressions before the cursor, which is potentially dangerous. It doesn't match on function calls, so it only triggers attribute access.

class DictionaryCompleter(Completer):
    """
    Experimental completer for Python dictionary keys.

    Warning: This does an `eval` and `repr` on some Python expressions before
             the cursor, which is potentially dangerous. It doesn't match on
             function calls, so it only triggers attribute access.
    """

    def __init__(
        self,
        get_globals: Callable[[], dict[str, Any]],
        get_locals: Callable[[], dict[str, Any]],
    ) -> None:
        super().__init__()

        self.get_globals = get_globals
        self.get_locals = get_locals

        # Pattern for expressions that are "safe" to eval for auto-completion.
        # These are expressions that contain only attribute and index lookups.
        varname = r"[a-zA-Z_][a-zA-Z0-9_]*"

        expression = rf"""
            # Any expression safe enough to eval while typing.
            # No operators, except dot, and only other dict lookups.
            # Technically, this can be unsafe of course, if bad code runs
            # in `__getattr__` or ``__getitem__``.
            (
                # Variable name
                {varname}

                \s*

                (?:
                    # Attribute access.
                    \s* \. \s* {varname} \s*

                    |

                    # Item lookup.
                    # (We match the square brackets. The key can be anything.
                    # We don't care about matching quotes here in the regex.
                    # Nested square brackets are not supported.)
                    \s* \[ [^\[\]]+ \] \s*
                )*
            )
        """

        # Pattern for recognizing for-loops, so that we can provide
        # autocompletion on the iterator of the for-loop. (According to the
        # first item of the collection we're iterating over.)
        self.for_loop_pattern = re.compile(
            rf"""
                for \s+ ([a-zA-Z0-9_]+) \s+ in \s+ {expression} \s* :
            """,
            re.VERBOSE,
        )