svelte-docgen.ts

import type { PluginOption } from 'vite';
import MagicString from 'magic-string';
import path from 'path';
import fs from 'fs';
import svelteDoc from 'sveltedoc-parser';
import type { SvelteParserOptions } from 'sveltedoc-parser';
import { logger } from '@storybook/node-logger';
import { preprocess } from 'svelte/compiler';
import { createFilter } from 'vite';

// Most of the code here should probably be exported by @storybook/svelte and reused here.
// See: https://github.com/storybookjs/storybook/blob/next/app/svelte/src/server/svelte-docgen-loader.ts

// From https://github.com/sveltejs/svelte/blob/8db3e8d0297e052556f0b6dde310ef6e197b8d18/src/compiler/compile/utils/get_name_from_filename.ts
// Copied because it is not exported from the compiler
function getNameFromFilename(filename: string) {
  if (!filename) return null;

  const parts = filename.split(/[/\\]/).map(encodeURI);

  if (parts.length > 1) {
    const indexMatch = parts[parts.length - 1].match(/^index(\.\w+)/);
    if (indexMatch) {
      parts.pop();
      parts[parts.length - 1] += indexMatch[1];
    }
  }

  const base = parts
    .pop()
    ?.replace(/%/g, 'u')
    .replace(/\.[^.]+$/, '')
    .replace(/[^a-zA-Z_$0-9]+/g, '_')
    .replace(/^_/, '')
    .replace(/_$/, '')
    .replace(/^(\d)/, '_$1');

  if (!base) {
    throw new Error(`Could not derive component name from file ${filename}`);
  }

  return base[0].toUpperCase() + base.slice(1);
}

export function svelteDocgen(svelteOptions: Record<string, any> = {}): PluginOption {
  const cwd = process.cwd();
  const { preprocess: preprocessOptions, logDocgen = false } = svelteOptions;
  const include = /\.(svelte)$/;
  const filter = createFilter(include);

  return {
    name: 'storybook:svelte-docgen-plugin',
    async transform(src: string, id: string) {
      if (!filter(id)) return undefined;

      const resource = path.relative(cwd, id);

      let docOptions;
      if (preprocessOptions) {
        // eslint-disable-next-line @typescript-eslint/no-shadow
        const src = fs.readFileSync(resource).toString();

        const { code: fileContent } = await preprocess(src, preprocessOptions, {
          filename: resource,
        });

        docOptions = {
          fileContent,
        };
      } else {
        docOptions = { filename: resource };
      }

      // set SvelteDoc options
      const options: SvelteParserOptions = {
        ...docOptions,
        version: 3,
      };

      const s = new MagicString(src);

      try {
        const componentDoc = await svelteDoc.parse(options);
        // get filename for source content
        const file = path.basename(resource);

        componentDoc.name = path.basename(file);

        const componentName = getNameFromFilename(resource);
        s.append(`;${componentName}.__docgen = ${JSON.stringify(componentDoc)}`);
      } catch (error: any) {
        if (logDocgen) {
          logger.error(error);
        }
      }

      return {
        code: s.toString(),
        map: s.generateMap({ hires: true, source: id }),
      };
    },
  };
}