Python tool to add entries to an LLVM compilation database

llvm-ccdb-add

#! /usr/bin/env python

import sys
import os
import fcntl
import argparse
import json

# the default location for the compilation database is the file 'compile_commands.json' in the current directory
def_dbname = 'compile_commands.json'

# arguments and options
parser = argparse.ArgumentParser(
    description = '''Add an entry to an LLVM Compilation Database.
See http://clang.llvm.org/docs/JSONCompilationDatabase.html for details.''')
parser.add_argument('--path', '-p',
    metavar = 'PATH',
    dest = 'dbname',
    default = def_dbname,
    help = '''path to the compilation database (directory or json file).
PATH can be a file or directory; if it is a directory, PATH/compile_commands.json will be used.
The default is to use the file "compile_commands.json" in the current directory.''')
parser.add_argument('--replace', '-r',
    action = 'store_true',
    default = False,
    help = 'replace any existing record with the same FILE entry. The default is to allow duplicates with a different COMMAND or DIRECTORY.')
parser.add_argument('--directory', '-d',
    metavar = 'DIRECTORY',
    default = os.getcwd(),
    help = 'set the "directory" entry for the new record. The default is the current directory.')
parser.add_argument('file',
    metavar = 'FILE',
    help = 'set the "file" entry for the new record')
parser.add_argument('command',
    metavar = 'COMMAND',
    help = 'set the "command" entry for the new record')
args = parser.parse_args()

# open the file for read/append, so it is not truncated
dbname = args.dbname
if os.path.isdir(dbname):
    dbname = os.path.join(dbname, def_dbname)
dbfile = open(dbname, 'a+')

# acquire an advisory exclusive lock on the file
fcntl.flock(dbfile, fcntl.LOCK_EX)

# read the content of the file
dbfile.seek(0)
dbjson = dbfile.read()
try:
    dbdata = json.loads(dbjson)
except ValueError as e:
    # if the file is empty or the content s not valid json, start from an empty database
    dbdata = []

# add the new record, if not present already
record = { 'directory': args.directory, 'file': args.file, 'command': args.command }
if args.replace:
    for r in list(dbdata):
        if r['file'] == record['file']:
            dbdata.remove(r)
    dbdata.append(record)
else:
    if not record in dbdata:
        dbdata.append(record)

# truncate the file and replace its content
dbfile.seek(0)
dbfile.truncate()
dbfile.write(json.dumps(dbdata, indent=2, separators=(',', ': ')))
dbfile.write('\n')
# the lock is automatically release when the file is closed
dbfile.close()