script-mime-types.ts

import type { BuiltInParserName } from 'prettier';
import type { AttributeToken } from 'pug-lexer';

// NOTE: XML would be useful, but it's not a default parser.
//       YAML is not official, but it costs nothing to support it right now.
const jsonSuffixRe: RegExp = /\+(json|yaml)$/i;
const wrappingQuotesRe: RegExp = /(^(["'`]))|((["'`])$)/g;

// Matches IANA media types to the required parser for them
// https://iana.org/assignments/media-types/media-types.xhtml
// Note: Don't need to put any suffixed types (+json, +xml) in here as it
//       will be handled separately
// Why using a Map: https://github.com/prettier/plugin-pug/pull/248#discussion_r663854854
const scriptTypeToParserMap: Map<string, BuiltInParserName> = new Map([
  ['application/ecmascript', 'babel'],
  ['application/javascript', 'babel'],
  ['application/json', 'json'],
  ['text/ecmascript', 'babel'],
  ['text/javascript', 'babel'],
  ['text/markdown', 'markdown'],
  ['text/typescript', 'typescript'],
  ['module', 'babel'],
]);

/**
 * Decides which parser to format script contents with.
 *
 * @param typeAttrToken Type token of the.
 * @returns Parser name to parse contents with.
 */
export function getScriptParserName(
  typeAttrToken?: AttributeToken,
): BuiltInParserName | undefined {
  // Omission means Javascript
  if (!typeAttrToken) {
    return 'babel';
  }

  const typeRaw: string | boolean = typeAttrToken.val;
  // If it's not a string, best not do anything
  if (typeof typeRaw !== 'string') {
    return;
  }

  const type: string = typeRaw.replaceAll(wrappingQuotesRe, '');

  // Empty type is equivalent to omission
  if (!type) {
    return 'babel';
  }

  const suffixExec: RegExpExecArray | null = jsonSuffixRe.exec(type);
  if (suffixExec) {
    return suffixExec[1] as unknown as 'json' | 'yaml';
  }

  return scriptTypeToParserMap.get(type);
}