Run Svelte preprocessors in the sequence they are declared

sequence.js

import { preprocess } from 'svelte/compiler'

/**
 * @typedef {import("svelte/types/compiler/preprocess").PreprocessorGroup} PreprocessorGroup
 * @param {PreprocessorGroup[]} preprocessors
 * @returns {PreprocessorGroup[]}
 */
export function sequence(preprocessors) {
  return preprocessors.map((preprocessor) => ({
    markup({ content, filename }) {
      return preprocess(content, preprocessor, { filename })
    },
  }))
}

sequence.ts

import { preprocess } from 'svelte/compiler'
import { PreprocessorGroup } from 'svelte/types/compiler/preprocess'

export function sequence(preprocessors: PreprocessorGroup[]): PreprocessorGroup[] {
  return preprocessors.map((preprocessor) => ({
    markup({ content, filename }) {
      return preprocess(content, preprocessor, { filename })
    },
  }))
}

svelte.config.js

// Example usage

import { sequence } from './sequence'

export default {
  preprocess: sequence([sveltePreprocess(), otherPreprocessor()]),
}

Thanks! I've updated the JS version with your jsdocs. Keeping the TS one in case that becomes useful.