clang-format.py

# This file is a minimal clang-format vim-integration. To install:
# - Change 'binary' if clang-format is not on the path (see below).
# - Add to your .vimrc:
#
#   if has('python')
#     map <C-I> :pyf <path-to-this-file>/clang-format.py<cr>
#     imap <C-I> <c-o>:pyf <path-to-this-file>/clang-format.py<cr>
#   elseif has('python3')
#     map <C-I> :py3f <path-to-this-file>/clang-format.py<cr>
#     imap <C-I> <c-o>:py3f <path-to-this-file>/clang-format.py<cr>
#   endif
#
# The if-elseif-endif conditional should pick either the python3 or python2
# integration depending on your vim setup.
#
# The first mapping enables clang-format for NORMAL and VISUAL mode, the second
# mapping adds support for INSERT mode. Change "C-I" to another binding if you
# need clang-format on a different key (C-I stands for Ctrl+i).
#
# With this integration you can press the bound key and clang-format will
# format the current line in NORMAL and INSERT mode or the selected region in
# VISUAL mode. The line or region is extended to the next bigger syntactic
# entity.
#
# You can also pass in the variable "l:lines" to choose the range for
# formatting. This variable can either contain "<start line>:<end line>" or
# "all" to format the full file. So, to format the full file, write a function
# like:
# :function FormatFile()
# :  let l:lines="all"
# :  if has('python')
# :    pyf <path-to-this-file>/clang-format.py
# :  elseif has('python3')
# :    py3f <path-to-this-file>/clang-format.py
# :  endif
# :endfunction
#
# It operates on the current, potentially unsaved buffer and does not create
# or save any files. To revert a formatting, just undo.
from __future__ import absolute_import, division, print_function

import difflib
import json
import os.path
import platform
import subprocess
import sys
import vim

# set g:clang_format_path to the path to clang-format if it is not on the path
# Change this to the full path if clang-format is not on the path.
binary = "clang-format"
if vim.eval('exists("g:clang_format_path")') == "1":
    binary = vim.eval("g:clang_format_path")

# Change this to format according to other formatting styles. See the output of
# 'clang-format --help' for a list of supported styles. The default looks for
# a '.clang-format' or '_clang-format' file to indicate the style that should be
# used.
style = None
fallback_style = None
if vim.eval('exists("g:clang_format_fallback_style")') == "1":
    fallback_style = vim.eval("g:clang_format_fallback_style")


def get_buffer(encoding):
    if platform.python_version_tuple()[0] == "3":
        return vim.current.buffer
    return [line.decode(encoding) for line in vim.current.buffer]


def main():
    # Get the current text.
    encoding = vim.eval("&encoding")
    buf = get_buffer(encoding)
    # Join the buffer into a single string with a terminating newline
    text = ("\n".join(buf) + "\n").encode(encoding)

    # Determine range to format.
    if vim.eval('exists("l:lines")') == "1":
        lines = ["-lines", vim.eval("l:lines")]
    elif vim.eval('exists("l:formatdiff")') == "1" and os.path.exists(
        vim.current.buffer.name
    ):
        with open(vim.current.buffer.name, "r") as f:
            ondisk = f.read().splitlines()
        sequence = difflib.SequenceMatcher(None, ondisk, vim.current.buffer)
        lines = []
        for op in reversed(sequence.get_opcodes()):
            if op[0] not in ["equal", "delete"]:
                lines += ["-lines", "%s:%s" % (op[3] + 1, op[4])]
        if lines == []:
            return
    else:
        lines = [
            "-lines",
            "%s:%s" % (vim.current.range.start + 1, vim.current.range.end + 1),
        ]

    # Convert cursor (line, col) to bytes.
    # Don't use line2byte: https://github.com/vim/vim/issues/5930
    _, cursor_line, cursor_col, _ = vim.eval('getpos(".")')  # 1-based
    cursor_byte = 0
    for line in text.split(b"\n")[: int(cursor_line) - 1]:
        cursor_byte += len(line) + 1
    cursor_byte += int(cursor_col) - 1
    if cursor_byte < 0:
        print("Couldn't determine cursor position. Is your file empty?")
        return

    # Avoid flashing an ugly, ugly cmd prompt on Windows when invoking clang-format.
    startupinfo = None
    if sys.platform.startswith("win32"):
        startupinfo = subprocess.STARTUPINFO()
        startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
        startupinfo.wShowWindow = subprocess.SW_HIDE

    # Call formatter.
    command = [binary, "-cursor", str(cursor_byte)]
    if lines != ["-lines", "all"]:
        command += lines
    if style:
        command.extend(["-style", style])
    if fallback_style:
        command.extend(["-fallback-style", fallback_style])
    if vim.current.buffer.name:
        command.extend(["-assume-filename", vim.current.buffer.name])
    p = subprocess.Popen(
        command,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
        stdin=subprocess.PIPE,
        startupinfo=startupinfo,
    )
    stdout, stderr = p.communicate(input=text)

    # If successful, replace buffer contents.
    if stderr:
        print(stderr)

    if not stdout:
        print(
            "No output from clang-format (crashed?).\n"
            "Please report to bugs.llvm.org."
        )
    else:
        header, content = stdout.split(b"\n", 1)
        header = json.loads(header.decode("utf-8"))
        # Strip off the trailing newline (added above).
        # This maintains trailing empty lines present in the buffer if
        # the -lines specification requests them to remain unchanged.
        lines = content.decode(encoding).split("\n")[:-1]
        sequence = difflib.SequenceMatcher(None, buf, lines)
        for op in reversed(sequence.get_opcodes()):
            if op[0] != "equal":
                vim.current.buffer[op[1] : op[2]] = lines[op[3] : op[4]]
        if header.get("IncompleteFormat"):
            print("clang-format: incomplete (syntax errors)")
        # Convert cursor bytes to (line, col)
        # Don't use goto: https://github.com/vim/vim/issues/5930
        cursor_byte = int(header["Cursor"])
        prefix = content[0:cursor_byte]
        cursor_line = 1 + prefix.count(b"\n")
        cursor_column = 1 + len(prefix.rsplit(b"\n", 1)[-1])
        vim.command("call cursor(%d, %d)" % (cursor_line, cursor_column))


main()