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1'use strict'
2
3const INDENT = Symbol.for('indent')
4const NEWLINE = Symbol.for('newline')
5
6const DEFAULT_NEWLINE = '\n'
7const DEFAULT_INDENT = '  '
8const BOM = /^\uFEFF/
9
10// only respect indentation if we got a line break, otherwise squash it
11// things other than objects and arrays aren't indented, so ignore those
12// Important: in both of these regexps, the $1 capture group is the newline
13// or undefined, and the $2 capture group is the indent, or undefined.
14const FORMAT = /^\s*[{[]((?:\r?\n)+)([\s\t]*)/
15const EMPTY = /^(?:\{\}|\[\])((?:\r?\n)+)?$/
16
17// Node 20 puts single quotes around the token and a comma after it
18const UNEXPECTED_TOKEN = /^Unexpected token '?(.)'?(,)? /i
19
20const hexify = (char) => {
21  const h = char.charCodeAt(0).toString(16).toUpperCase()
22  return `0x${h.length % 2 ? '0' : ''}${h}`
23}
24
25// Remove byte order marker. This catches EF BB BF (the UTF-8 BOM)
26// because the buffer-to-string conversion in `fs.readFileSync()`
27// translates it to FEFF, the UTF-16 BOM.
28const stripBOM = (txt) => String(txt).replace(BOM, '')
29
30const makeParsedError = (msg, parsing, position = 0) => ({
31  message: `${msg} while parsing ${parsing}`,
32  position,
33})
34
35const parseError = (e, txt, context = 20) => {
36  let msg = e.message
37
38  if (!txt) {
39    return makeParsedError(msg, 'empty string')
40  }
41
42  const badTokenMatch = msg.match(UNEXPECTED_TOKEN)
43  const badIndexMatch = msg.match(/ position\s+(\d+)/i)
44
45  if (badTokenMatch) {
46    msg = msg.replace(
47      UNEXPECTED_TOKEN,
48      `Unexpected token ${JSON.stringify(badTokenMatch[1])} (${hexify(badTokenMatch[1])})$2 `
49    )
50  }
51
52  let errIdx
53  if (badIndexMatch) {
54    errIdx = +badIndexMatch[1]
55  } else if (msg.match(/^Unexpected end of JSON.*/i)) {
56    errIdx = txt.length - 1
57  }
58
59  if (errIdx == null) {
60    return makeParsedError(msg, `'${txt.slice(0, context * 2)}'`)
61  }
62
63  const start = errIdx <= context ? 0 : errIdx - context
64  const end = errIdx + context >= txt.length ? txt.length : errIdx + context
65  const slice = `${start ? '...' : ''}${txt.slice(start, end)}${end === txt.length ? '' : '...'}`
66
67  return makeParsedError(
68    msg,
69    `${txt === slice ? '' : 'near '}${JSON.stringify(slice)}`,
70    errIdx
71  )
72}
73
74class JSONParseError extends SyntaxError {
75  constructor (er, txt, context, caller) {
76    const metadata = parseError(er, txt, context)
77    super(metadata.message)
78    Object.assign(this, metadata)
79    this.code = 'EJSONPARSE'
80    this.systemError = er
81    Error.captureStackTrace(this, caller || this.constructor)
82  }
83
84  get name () {
85    return this.constructor.name
86  }
87
88  set name (n) {}
89
90  get [Symbol.toStringTag] () {
91    return this.constructor.name
92  }
93}
94
95const parseJson = (txt, reviver) => {
96  const result = JSON.parse(txt, reviver)
97  if (result && typeof result === 'object') {
98    // get the indentation so that we can save it back nicely
99    // if the file starts with {" then we have an indent of '', ie, none
100    // otherwise, pick the indentation of the next line after the first \n If the
101    // pattern doesn't match, then it means no indentation. JSON.stringify ignores
102    // symbols, so this is reasonably safe. if the string is '{}' or '[]', then
103    // use the default 2-space indent.
104    const match = txt.match(EMPTY) || txt.match(FORMAT) || [null, '', '']
105    result[NEWLINE] = match[1] ?? DEFAULT_NEWLINE
106    result[INDENT] = match[2] ?? DEFAULT_INDENT
107  }
108  return result
109}
110
111const parseJsonError = (raw, reviver, context) => {
112  const txt = stripBOM(raw)
113  try {
114    return parseJson(txt, reviver)
115  } catch (e) {
116    if (typeof raw !== 'string' && !Buffer.isBuffer(raw)) {
117      const msg = Array.isArray(raw) && raw.length === 0 ? 'an empty array' : String(raw)
118      throw Object.assign(
119        new TypeError(`Cannot parse ${msg}`),
120        { code: 'EJSONPARSE', systemError: e }
121      )
122    }
123    throw new JSONParseError(e, txt, context, parseJsonError)
124  }
125}
126
127module.exports = parseJsonError
128parseJsonError.JSONParseError = JSONParseError
129parseJsonError.noExceptions = (raw, reviver) => {
130  try {
131    return parseJson(stripBOM(raw), reviver)
132  } catch {
133    // no exceptions
134  }
135}
136