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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
/** * {@linkcode parse} function for parsing * {@link https://code.visualstudio.com/docs/languages/json#_json-with-comments | JSONC} * (JSON with Comments) strings. * * This module is browser compatible. * * @module */
import { assert } from "../assert/assert.ts";
import type { JsonValue } from "../json/common.ts";export type { JsonValue } from "../json/common.ts";
/** Options for {@linkcode parse}. */export interface ParseOptions {  /** Allow trailing commas at the end of arrays and objects.   *   * @default {true}   */  allowTrailingComma?: boolean;}
/** * Converts a JSON with Comments (JSONC) string into an object. * If a syntax error is found, throw a {@linkcode SyntaxError}. * * @example * ```ts * import { parse } from "https://deno.land/std@$STD_VERSION/jsonc/mod.ts"; * * parse('{"foo": "bar", } // comment'); // { foo: "bar" } * parse('{"foo": "bar", } /* comment *\/'); // { foo: "bar" } * parse('{"foo": "bar" } // comment', { *   allowTrailingComma: false, * }); // { foo: "bar" } * ``` * * @param text A valid JSONC string. */export function parse(  text: string,  { allowTrailingComma = true }: ParseOptions = {},): JsonValue {  if (new.target) {    throw new TypeError("parse is not a constructor");  }  return new JSONCParser(text, { allowTrailingComma }).parse();}
type TokenType =  | "BeginObject"  | "EndObject"  | "BeginArray"  | "EndArray"  | "NameSeparator"  | "ValueSeparator"  | "NullOrTrueOrFalseOrNumber"  | "String";
type Token = {  type: Exclude<    TokenType,    "String" | "NullOrTrueOrFalseOrNumber"  >;  sourceText?: undefined;  position: number;} | {  type: "String";  sourceText: string;  position: number;} | {  type: "NullOrTrueOrFalseOrNumber";  sourceText: string;  position: number;};
const originalJSONParse = globalThis.JSON.parse;
// First tokenize and then parse the token.class JSONCParser {  readonly #whitespace = new Set(" \t\r\n");  readonly #numberEndToken = new Set([..."[]{}:,/", ...this.#whitespace]);  #text: string;  #length: number;  #tokenized: Generator<Token, void>;  #options: ParseOptions;  constructor(text: string, options: ParseOptions) {    this.#text = `${text}`;    this.#length = this.#text.length;    this.#tokenized = this.#tokenize();    this.#options = options;  }  parse(): JsonValue {    const token = this.#getNext();    const res = this.#parseJsonValue(token);
    // make sure all characters have been read    const { done, value } = this.#tokenized.next();    if (!done) {      throw new SyntaxError(buildErrorMessage(value));    }
    return res;  }  /** Read the next token. If the token is read to the end, it throws a SyntaxError. */  #getNext(): Token {    const { done, value } = this.#tokenized.next();    if (done) {      throw new SyntaxError("Unexpected end of JSONC input");    }    return value;  }  /** Split the JSONC string into token units. Whitespace and comments are skipped. */  *#tokenize(): Generator<Token, void> {    for (let i = 0; i < this.#length; i++) {      // skip whitespace      if (this.#whitespace.has(this.#text[i]!)) {        continue;      }
      // skip multi line comment (`/*...*/`)      if (this.#text[i] === "/" && this.#text[i + 1] === "*") {        i += 2;        let hasEndOfComment = false;        for (; i < this.#length; i++) { // read until find `*/`          if (this.#text[i] === "*" && this.#text[i + 1] === "/") {            hasEndOfComment = true;            break;          }        }        if (!hasEndOfComment) {          throw new SyntaxError("Unexpected end of JSONC input");        }        i++;        continue;      }
      // skip single line comment (`//...`)      if (this.#text[i] === "/" && this.#text[i + 1] === "/") {        i += 2;        for (; i < this.#length; i++) { // read until find `\n` or `\r`          if (this.#text[i] === "\n" || this.#text[i] === "\r") {            break;          }        }        continue;      }
      switch (this.#text[i]) {        case "{":          yield { type: "BeginObject", position: i };          break;        case "}":          yield { type: "EndObject", position: i };          break;        case "[":          yield { type: "BeginArray", position: i };          break;        case "]":          yield { type: "EndArray", position: i };          break;        case ":":          yield { type: "NameSeparator", position: i };          break;        case ",":          yield { type: "ValueSeparator", position: i };          break;        case '"': { // parse string token          const startIndex = i;          // Need to handle consecutive backslashes correctly          // '"\\""' => '"'          // '"\\\\"' => '\\'          // '"\\\\\\""' => '\\"'          // '"\\\\\\\\"' => '\\\\'          let shouldEscapeNext = false;          i++;          for (; i < this.#length; i++) { // read until find `"`            if (this.#text[i] === '"' && !shouldEscapeNext) {              break;            }            shouldEscapeNext = this.#text[i] === "\\" && !shouldEscapeNext;          }          yield {            type: "String",            sourceText: this.#text.substring(startIndex, i + 1),            position: startIndex,          };          break;        }        default: { // parse null, true, false or number token          const startIndex = i;          for (; i < this.#length; i++) { // read until find numberEndToken            if (this.#numberEndToken.has(this.#text[i]!)) {              break;            }          }          i--;          yield {            type: "NullOrTrueOrFalseOrNumber",            sourceText: this.#text.substring(startIndex, i + 1),            position: startIndex,          };        }      }    }  }  #parseJsonValue(value: Token): JsonValue {    switch (value.type) {      case "BeginObject":        return this.#parseObject();      case "BeginArray":        return this.#parseArray();      case "NullOrTrueOrFalseOrNumber":        return this.#parseNullOrTrueOrFalseOrNumber(value);      case "String":        return this.#parseString(value);      default:        throw new SyntaxError(buildErrorMessage(value));    }  }  #parseObject(): { [key: string]: JsonValue | undefined } {    const target: { [key: string]: JsonValue | undefined } = {};    //   ┌─token1    // { }    //      ┌─────────────token1    //      │   ┌─────────token2    //      │   │   ┌─────token3    //      │   │   │   ┌─token4    //  { "key" : value }    //      ┌───────────────token1    //      │   ┌───────────token2    //      │   │   ┌───────token3    //      │   │   │   ┌───token4    //      │   │   │   │ ┌─token1    //  { "key" : value , }    //      ┌─────────────────────────────token1    //      │   ┌─────────────────────────token2    //      │   │   ┌─────────────────────token3    //      │   │   │   ┌─────────────────token4    //      │   │   │   │   ┌─────────────token1    //      │   │   │   │   │   ┌─────────token2    //      │   │   │   │   │   │   ┌─────token3    //      │   │   │   │   │   │   │   ┌─token4    //  { "key" : value , "key" : value }    for (let isFirst = true;; isFirst = false) {      const token1 = this.#getNext();      if (        (isFirst || this.#options.allowTrailingComma) &&        token1.type === "EndObject"      ) {        return target;      }      if (token1.type !== "String") {        throw new SyntaxError(buildErrorMessage(token1));      }      const key = this.#parseString(token1);
      const token2 = this.#getNext();      if (token2.type !== "NameSeparator") {        throw new SyntaxError(buildErrorMessage(token2));      }
      const token3 = this.#getNext();      Object.defineProperty(target, key, {        value: this.#parseJsonValue(token3),        writable: true,        enumerable: true,        configurable: true,      });
      const token4 = this.#getNext();      if (token4.type === "EndObject") {        return target;      }      if (token4.type !== "ValueSeparator") {        throw new SyntaxError(buildErrorMessage(token4));      }    }  }  #parseArray(): JsonValue[] {    const target: JsonValue[] = [];    //   ┌─token1    // [ ]    //      ┌─────────────token1    //      │   ┌─────────token2    //  [ value ]    //      ┌───────token1    //      │   ┌───token2    //      │   │ ┌─token1    //  [ value , ]    //      ┌─────────────token1    //      │   ┌─────────token2    //      │   │   ┌─────token1    //      │   │   │   ┌─token2    //  [ value , value ]    for (let isFirst = true;; isFirst = false) {      const token1 = this.#getNext();      if (        (isFirst || this.#options.allowTrailingComma) &&        token1.type === "EndArray"      ) {        return target;      }      target.push(this.#parseJsonValue(token1));
      const token2 = this.#getNext();      if (token2.type === "EndArray") {        return target;      }      if (token2.type !== "ValueSeparator") {        throw new SyntaxError(buildErrorMessage(token2));      }    }  }  #parseString(value: {    type: "String";    sourceText: string;    position: number;  }): string {    let parsed;    try {      // Use JSON.parse to handle `\u0000` etc. correctly.      parsed = originalJSONParse(value.sourceText);    } catch {      throw new SyntaxError(buildErrorMessage(value));    }    assert(typeof parsed === "string");    return parsed;  }  #parseNullOrTrueOrFalseOrNumber(value: {    type: "NullOrTrueOrFalseOrNumber";    sourceText: string;    position: number;  }): null | boolean | number {    if (value.sourceText === "null") {      return null;    }    if (value.sourceText === "true") {      return true;    }    if (value.sourceText === "false") {      return false;    }    let parsed;    try {      // Use JSON.parse to handle `+100`, `Infinity` etc. correctly.      parsed = originalJSONParse(value.sourceText);    } catch {      throw new SyntaxError(buildErrorMessage(value));    }    assert(typeof parsed === "number");    return parsed;  }}
function buildErrorMessage({ type, sourceText, position }: Token): string {  let token = "";  switch (type) {    case "BeginObject":      token = "{";      break;    case "EndObject":      token = "}";      break;    case "BeginArray":      token = "[";      break;    case "EndArray":      token = "]";      break;    case "NameSeparator":      token = ":";      break;    case "ValueSeparator":      token = ",";      break;    case "NullOrTrueOrFalseOrNumber":    case "String":      // Truncate the string so that it is within 30 lengths.      token = 30 < sourceText.length        ? `${sourceText.slice(0, 30)}...`        : sourceText;      break;    default:      throw new Error("unreachable");  }  return `Unexpected token ${token} in JSONC at position ${position}`;}