path: root/src/flake8/formatting/base.py

"""The base class and interface for all formatting plugins."""
import argparse
import os
import sys
from typing import IO
from typing import List
from typing import Optional
from typing import Tuple
from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from flake8.statistics import Statistics
    from flake8.style_guide import Violation


class BaseFormatter:
    """Class defining the formatter interface.

    .. attribute:: options

        The options parsed from both configuration files and the command-line.

    .. attribute:: filename

        If specified by the user, the path to store the results of the run.

    .. attribute:: output_fd

        Initialized when the :meth:`start` is called. This will be a file
        object opened for writing.

    .. attribute:: newline

        The string to add to the end of a line. This is only used when the
        output filename has been specified.
    """

    def __init__(self, options: argparse.Namespace) -> None:
        """Initialize with the options parsed from config and cli.

        This also calls a hook, :meth:`after_init`, so subclasses do not need
        to call super to call this method.

        :param options:
            User specified configuration parsed from both configuration files
            and the command-line interface.
        :type options:
            :class:`argparse.Namespace`
        """
        self.options = options
        self.filename = options.output_file
        self.output_fd: Optional[IO[str]] = None
        self.newline = "\n"
        self.after_init()

    def after_init(self) -> None:
        """Initialize the formatter further."""

    def beginning(self, filename: str) -> None:
        """Notify the formatter that we're starting to process a file.

        :param str filename:
            The name of the file that Flake8 is beginning to report results
            from.
        """

    def finished(self, filename: str) -> None:
        """Notify the formatter that we've finished processing a file.

        :param str filename:
            The name of the file that Flake8 has finished reporting results
            from.
        """

    def start(self) -> None:
        """Prepare the formatter to receive input.

        This defaults to initializing :attr:`output_fd` if :attr:`filename`
        """
        if self.filename:
            dirname = os.path.dirname(os.path.abspath(self.filename))
            os.makedirs(dirname, exist_ok=True)
            self.output_fd = open(self.filename, "a")

    def handle(self, error: "Violation") -> None:
        """Handle an error reported by Flake8.

        This defaults to calling :meth:`format`, :meth:`show_source`, and
        then :meth:`write`. To extend how errors are handled, override this
        method.

        :param error:
            This will be an instance of
            :class:`~flake8.style_guide.Violation`.
        :type error:
            flake8.style_guide.Violation
        """
        line = self.format(error)
        source = self.show_source(error)
        self.write(line, source)

    def format(self, error: "Violation") -> Optional[str]:
        """Format an error reported by Flake8.

        This method **must** be implemented by subclasses.

        :param error:
            This will be an instance of
            :class:`~flake8.style_guide.Violation`.
        :type error:
            flake8.style_guide.Violation
        :returns:
            The formatted error string.
        :rtype:
            str
        """
        raise NotImplementedError(
            "Subclass of BaseFormatter did not implement" " format."
        )

    def show_statistics(self, statistics: "Statistics") -> None:
        """Format and print the statistics."""
        for error_code in statistics.error_codes():
            stats_for_error_code = statistics.statistics_for(error_code)
            statistic = next(stats_for_error_code)
            count = statistic.count
            count += sum(stat.count for stat in stats_for_error_code)
            self._write(f"{count:<5} {error_code} {statistic.message}")

    def show_benchmarks(self, benchmarks: List[Tuple[str, float]]) -> None:
        """Format and print the benchmarks."""
        # NOTE(sigmavirus24): The format strings are a little confusing, even
        # to me, so here's a quick explanation:
        # We specify the named value first followed by a ':' to indicate we're
        # formatting the value.
        # Next we use '<' to indicate we want the value left aligned.
        # Then '10' is the width of the area.
        # For floats, finally, we only want only want at most 3 digits after
        # the decimal point to be displayed. This is the precision and it
        # can not be specified for integers which is why we need two separate
        # format strings.
        float_format = "{value:<10.3} {statistic}".format
        int_format = "{value:<10} {statistic}".format
        for statistic, value in benchmarks:
            if isinstance(value, int):
                benchmark = int_format(statistic=statistic, value=value)
            else:
                benchmark = float_format(statistic=statistic, value=value)
            self._write(benchmark)

    def show_source(self, error: "Violation") -> Optional[str]:
        """Show the physical line generating the error.

        This also adds an indicator for the particular part of the line that
        is reported as generating the problem.

        :param error:
            This will be an instance of
            :class:`~flake8.style_guide.Violation`.
        :type error:
            flake8.style_guide.Violation
        :returns:
            The formatted error string if the user wants to show the source.
            If the user does not want to show the source, this will return
            ``None``.
        :rtype:
            str
        """
        if not self.options.show_source or error.physical_line is None:
            return ""

        # Because column numbers are 1-indexed, we need to remove one to get
        # the proper number of space characters.
        indent = "".join(
            c if c.isspace() else " "
            for c in error.physical_line[: error.column_number - 1]
        )
        # Physical lines have a newline at the end, no need to add an extra
        # one
        return f"{error.physical_line}{indent}^"

    def _write(self, output: str) -> None:
        """Handle logic of whether to use an output file or print()."""
        if self.output_fd is not None:
            self.output_fd.write(output + self.newline)
        if self.output_fd is None or self.options.tee:
            sys.stdout.buffer.write(output.encode() + self.newline.encode())

    def write(self, line: Optional[str], source: Optional[str]) -> None:
        """Write the line either to the output file or stdout.

        This handles deciding whether to write to a file or print to standard
        out for subclasses. Override this if you want behaviour that differs
        from the default.

        :param str line:
            The formatted string to print or write.
        :param str source:
            The source code that has been formatted and associated with the
            line of output.
        """
        if line:
            self._write(line)
        if source:
            self._write(source)

    def stop(self) -> None:
        """Clean up after reporting is finished."""
        if self.output_fd is not None:
            self.output_fd.close()
            self.output_fd = None