Quick script to convert TOML front matter to JSON front matter

tomltojson.py

#!/usr/bin/env python

import json
import os

JSON_CONFIG = {
  "indent": 2,
  "sort_keys": True,
  "ensure_ascii": False,
  "allow_nan": False,
  "separators": (",", ": "),
}

def strip_enclosing_quotes(val):
  if val[:1] == val[-1:] and val[:1] in ("'", '"'):
    val = val[1:-1]
  return val

def convert_toml_to_json(toml_input):
  # Note - this assumes that the input is valid TOML.
  # We don't try to handle invalid markup cases.
  fields = {}
  lines = toml_input.split("\n")
  for line in lines:
    key, equals_sign, value = line.partition("=")
    if not equals_sign:
      continue
    key = key.strip()
    value = value.strip()
    if not (key and value):
      continue
    key = strip_enclosing_quotes(key)
    value = strip_enclosing_quotes(value)
    fields[key] = value
  return json.dumps(fields, **JSON_CONFIG)

def fix_file(path):
  with open(path) as f:
    before = f.read()
  if not before.startswith("+++\n"):
    return False
  front_matter, ok, content = before[4:].partition("\n+++\n")
  if not ok:
    return False
  json_front_matter = convert_toml_to_json(front_matter)
  if json_front_matter is None:
    return False
  with open(path, "w") as f:
    f.write(json_front_matter)
    f.write("\n")
    f.write(content)
  return True


def main():
  fixed_count = 0
  for dirpath, _, filenames in os.walk(os.getcwd()):
    markdown_files = (f for f in filenames if f.endswith(".md"))
    markdown_paths = (os.path.join(dirpath, f) for f in markdown_files)
    fixed_count += sum(1 for p in markdown_paths if fix_file(p))
  print("{} files fixed.".format(fixed_count))

if __name__ == "__main__":
  main()