'use strict'
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const hexify = char => {
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const h = char.charCodeAt(0).toString(16).toUpperCase()
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return '0x' + (h.length % 2 ? '0' : '') + h
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}
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const parseError = (e, txt, context) => {
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if (!txt) {
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return {
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message: e.message + ' while parsing empty string',
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position: 0,
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}
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}
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const badToken = e.message.match(/^Unexpected token (.) .*position\s+(\d+)/i)
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const errIdx = badToken ? +badToken[2]
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: e.message.match(/^Unexpected end of JSON.*/i) ? txt.length - 1
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: null
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const msg = badToken ? e.message.replace(/^Unexpected token ./, `Unexpected token ${
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JSON.stringify(badToken[1])
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} (${hexify(badToken[1])})`)
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: e.message
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if (errIdx !== null && errIdx !== undefined) {
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const start = errIdx <= context ? 0
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: errIdx - context
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const end = errIdx + context >= txt.length ? txt.length
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: errIdx + context
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const slice = (start === 0 ? '' : '...') +
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txt.slice(start, end) +
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(end === txt.length ? '' : '...')
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const near = txt === slice ? '' : 'near '
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return {
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message: msg + ` while parsing ${near}${JSON.stringify(slice)}`,
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position: errIdx,
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}
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} else {
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return {
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message: msg + ` while parsing '${txt.slice(0, context * 2)}'`,
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position: 0,
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}
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}
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}
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class JSONParseError extends SyntaxError {
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constructor (er, txt, context, caller) {
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context = context || 20
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const metadata = parseError(er, txt, context)
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super(metadata.message)
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Object.assign(this, metadata)
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this.code = 'EJSONPARSE'
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this.systemError = er
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Error.captureStackTrace(this, caller || this.constructor)
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}
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get name () { return this.constructor.name }
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set name (n) {}
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get [Symbol.toStringTag] () { return this.constructor.name }
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}
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const kIndent = Symbol.for('indent')
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const kNewline = Symbol.for('newline')
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// only respect indentation if we got a line break, otherwise squash it
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// things other than objects and arrays aren't indented, so ignore those
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// Important: in both of these regexps, the $1 capture group is the newline
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// or undefined, and the $2 capture group is the indent, or undefined.
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const formatRE = /^\s*[{\[]((?:\r?\n)+)([\s\t]*)/
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const emptyRE = /^(?:\{\}|\[\])((?:\r?\n)+)?$/
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const parseJson = (txt, reviver, context) => {
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const parseText = stripBOM(txt)
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context = context || 20
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try {
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// get the indentation so that we can save it back nicely
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// if the file starts with {" then we have an indent of '', ie, none
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// otherwise, pick the indentation of the next line after the first \n
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// If the pattern doesn't match, then it means no indentation.
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// JSON.stringify ignores symbols, so this is reasonably safe.
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// if the string is '{}' or '[]', then use the default 2-space indent.
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const [, newline = '\n', indent = ' '] = parseText.match(emptyRE) ||
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parseText.match(formatRE) ||
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[, '', '']
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const result = JSON.parse(parseText, reviver)
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if (result && typeof result === 'object') {
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result[kNewline] = newline
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result[kIndent] = indent
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}
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return result
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} catch (e) {
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if (typeof txt !== 'string' && !Buffer.isBuffer(txt)) {
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const isEmptyArray = Array.isArray(txt) && txt.length === 0
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throw Object.assign(new TypeError(
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`Cannot parse ${isEmptyArray ? 'an empty array' : String(txt)}`
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), {
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code: 'EJSONPARSE',
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systemError: e,
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})
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}
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throw new JSONParseError(e, parseText, context, parseJson)
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}
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}
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// Remove byte order marker. This catches EF BB BF (the UTF-8 BOM)
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// because the buffer-to-string conversion in `fs.readFileSync()`
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// translates it to FEFF, the UTF-16 BOM.
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const stripBOM = txt => String(txt).replace(/^\uFEFF/, '')
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module.exports = parseJson
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parseJson.JSONParseError = JSONParseError
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parseJson.noExceptions = (txt, reviver) => {
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try {
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return JSON.parse(stripBOM(txt), reviver)
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} catch (e) {}
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}
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