Export static site

[Rich-Harris]

For static sites (e.g. svelte.technology), it might be nice to have an equivalent of next export. Could be done like so:

// scripts/export.js
const exporter = require('sapper/export');

const pages = [
  '/',
  '/guide',
  '/repl',
  '/blog'
].concat(getListOfBlogPostsSomehow());

exporter.export(pages, 'dist').then(() => {
  console.log('done');
});

That would run server.js in a separate process and basically just curl those URLs into dist, and copy over the assets folder and the files generated by the compiler.

[EmilTholin]

Oh, this would be such an awesome addition.

Maybe export could take an object with some additional optional settings:

// scripts/export.js
const exporter = require('sapper/export');
const axios = require('axios');

const exportOpts = {
  getPages: async () => {
    const { data: posts } = await axios.get('https://jsonplaceholder.typicode.com/posts');
    
    return [
      '/',
      {
        page: '/blog',
        getParams: async () => ({
          posts: posts.map(post => ({ id: post.id, title: post.title }))
        }),
        // Array of "child" pages?
        children: posts.map(post => ({
          page: '/:slug',
          getParams: async () => ({
            post,
            // Used to give a value to :slug
            slug: post.id
          })
        }))
      },
      {
        page: '/repl',
        // Optional values for automatic sitemap.xml generation?
        index: false,
        lastModified: '2018-01-04',
        priority: 0.5
      }
    ]
  },
  dist: 'dist',
  // Optional automatic sitemap.xml generation?
  sitemap: true
}

exporter.export(exportOpts).then(() => {
  console.log('done');
});

[Rich-Harris]

I had a thought about this — had assumed you would need config for this to work, but what if instead we started at / and other known static routes and crawled the site looking for those dynamic links, and monitored which network requests (e.g. to /api/blog/some-post) were being made? As long as you could reach a given page from known static routes, it seems plausible that the whole thing could be config free, which would be cool.

I haven't studied Next and Nuxt's implementation, it's possible they're already doing something similar.

[freedmand]

I've created a hacky but workable implementation of this idea using node-spider. You can see the implementation running on Netlify here.

I feel like there should be a clean way to extract all these routes and URLs without doing what I've done (combing through links, src attributes, and manually parsing service-worker.js) -- but it's probably a lot more work to do this nicely in the middle stages of generation. Hopefully this serves as a good starting point.

I'll try to clean this up tomorrow and merge into master, but for now I've added an "extract" config in my package.json scripts that looks like npm run build && cross-env NODE_ENV=production node extract.js. I'm still familiarizing myself with the source code, but let me know if it seems right to add the following extract.js to the Sapper template code, or if some version of it should be added to the main Sapper repo.

extract.js:

const fs = require('fs');
const app = require('express')();
const compression = require('compression');
const sapper = require('sapper');
const static = require('serve-static');

// New requirements.
const Spider = require('node-spider');
const path = require('path');

const { PORT = 3000 } = process.env;
// TODO(freedmand): un-hardcode
const outputDir = 'dist';

// File manipulation functions:
// TODO(freedmand): use established packages or move into separate file.

/**
 * Deletes the specified directory if it exists.
 * @param {string} dir The directory to delete.
 */
function rmdir(dir) {
  const list = fs.readdirSync(dir);
  for(const f of list) {
      const filename = path.join(dir, f);
      const stat = fs.statSync(filename);

      if (filename == '.' || filename == '..') {
        continue;
      } else if(stat.isDirectory()) {
        rmdir(filename);
      } else {
        fs.unlinkSync(filename);
      }
  }
  fs.rmdirSync(dir);
};

/**
 * Creates parent directories recursively for the given file path if they do not
 * exist.
 * @param {string} filePath The file path to clear the way for.
 */
function makeDirectories(filePath) {
  const dirname = path.dirname(filePath);
  if (fs.existsSync(dirname)) return true;
  makeDirectories(dirname);
  fs.mkdirSync(dirname);
}

/**
 * Writes the specified contents to the specified file asynchronously.
 * @param {string} fn The file name to write to.
 * @param {string} contents The contents to write to the file in binary.
 */
function writeFile(fn, contents) {
  makeDirectories(fn);
  const stream = fs.createWriteStream(fn, {encoding: 'binary'});
  stream.once('open', () => {
    stream.write(contents);
    stream.end();
  });
}

// Specialized URL functions.
const prefix = `http://localhost:${PORT}`;

/**
 * Returns the full URL of the specified relative path in the server.
 * @param {string} url The path for which to get the complete URL.
 * @return {string} The full URL.
 */
function getFullUrl(url) {
  return `${prefix}${url}`;
}

/**
 * Returns the extension on the URL or '' if there is none.
 * @param {string} url The URL.
 * @return {string} The URL's extension or the empty string if the URL has no
 *     extension.
 */
function getExtension(url) {
  const splits = url.split('.');
  let extension = splits[splits.length - 1].trim();
  // Assume that an extension cannot be longer than 10 characters.
  if (!/^[a-zA-Z0-9]+$/.test(extension) || extension.length > 10) {
    // Clear the extension if it is not alphanumeric or is long enough to
    // signify it may just be a hash value or something.
    extension = '';
  }
  return extension;
}

/**
 * Returns the relative path for the specified URL, adding index.html if the URL
 * ends in `/`.
 * @param {string} url The URL for which to retrieve the relative path.
 * @return {string} A URL that starts with / that is relative to the server
 *     root. The URL will add index.html if it ends with `/`.
 */
function relativePath(url) {
  if (url.startsWith(prefix)) return relativePath(url.substr(prefix.length));
  if (url.endsWith('/')) url += 'index.html';
  if (getExtension(url) == '') url += '/index.html';
  if (url.startsWith('/')) return url;
  throw new Error('Bad url');
}

/**
 * Returns the Sapper API route for the specified URL path.
 * @param {string} url The absolute or relative URL.
 * @return {string} The URL with /api/ in front.
 */
function apiPath(url) {
  if (url.startsWith(prefix)) {
    return `${prefix}/api${url.substr(prefix.length)}`;
  }
  return `/api${url}`;
}

/**
 * Returns whether the specified URL is on the server or an external link.
 * @param {string} url The URL.
 * @return {boolean} True if the URL is on the server.
 */
function filter(url) {
  return url.startsWith('/') || url.startsWith(getFullUrl('/'));
}

// Normal server.js stuff.

// this allows us to do e.g. `fetch('/api/blog')` on the server
const fetch = require('node-fetch');
global.fetch = (url, opts) => {
	if (url[0] === '/') url = getFullUrl(url);
	return fetch(url, opts);
};

app.use(compression({ threshold: 0 }));

app.use(static('assets'));

app.use(sapper());

// Clean the output directory.

// Remove the output directory.
rmdir(outputDir);

// Create a clean output directory.
if (!fs.existsSync(outputDir)){
  fs.mkdirSync(outputDir);
}

// The crux of the scrape, chaining the traditional server call with a web
// scraper. The program automatically exits after all the static pages have been
// scraped from the server that are accessible from the root page (`/`).
let server;
new Promise((resolve) => {
  server = app.listen(PORT, () => {
    console.log(`listening on port ${PORT}`);
    resolve();
  });
}).then(() => {
  return new Promise((resolve, reject) => {
    const spider = new Spider({
      // Most of these config options are copied from node-spider's usage
      // example.
      concurrent: 5,
      delay: 0,
      logs: process.stderr,
      allowDuplicates: false,
      catchErrors: true,
      addReferrer: false,
      xhr: false,
      keepAlive: false,
      error: (err, url) => {
        console.error(`ERROR ${err} at ${url}`);
        reject();
      },
      // Called when there are no more requests
      done: () => {
        console.log('Done!');
        resolve();
      },

      headers: { 'user-agent': 'node-spider' },
      // Use a binary encoding to preserve image files.
      encoding: 'binary'
    });

    // The primary logic to handle a scraped page.
    const handleRequest = (doc) => {
      // Only deal with the page if it is on the server.
      if (!filter(doc.url)) return;

      // Grab the page's relative path and write the page contents to a local
      //file.
      const relPath = relativePath(doc.url);
      console.log(`GOT ${relPath}`); // page url
      writeFile(path.join(outputDir, relPath), doc.res.body);

      /**
       * Resolves and checks if a given URL is local; if so, adds it to the
       * scraping queue.
       * @param {string} url The URL to process.
       */
      const process = (url) => {
        // Remove trailing hash if relevant.
        url = url.split('#')[0];
        // Resolve URL relative to server root.
        url = doc.resolve(url);
        // Crawl more if the URL is on the server.
        if (filter(url)) spider.queue(url, handleRequest);
      };

      const extension = getExtension(doc.url);
      if (extension == 'html' || extension == '') {
        // Grab src and href attributes from html pages.
        doc.$('[src]').each((i, elem) => {
          process(doc.$(elem).attr('src'));
        });
        doc.$('[href]').each((i, elem) => {
          process(doc.$(elem).attr('href'));
        });
      }

      // TODO(freedmand): find a cleaner way to do this.
      if (doc.url.endsWith('/service-worker.js')) {
        // Grab to_cache URLs from the service-worker. This is messy since the
        // contents of service-worker.js could be prone to change on
        // minification.
        const match = /const to_cache = (\[.*?;)/.exec(doc.res.body);
        // Use a hacky eval to process the array.
        const additionalUrls = eval(match[1]);
        for (const additionalUrl of additionalUrls) {
          // Queue the resulting URLs.
          spider.queue(doc.resolve(additionalUrl), handleRequest);
        }
      }

      if (relPath.endsWith('/index.html') && !relPath.startsWith('/api/')) {
        // Attempt to grab the /api/ version of a page that seems to be a basic
        // route.
        spider.queue(apiPath(doc.url), handleRequest);
      }
    };

    // Start crawling with the document root and the service worker.
    spider.queue(getFullUrl('/'), handleRequest);
    spider.queue(getFullUrl('/service-worker.js'), handleRequest);
  });
}).then(() => {
  server.close();
});

[zzolo]

For reference, here's how next does their export:
https://github.com/zeit/next.js/blob/canary/server/export.js

I don't really have much context on next, but though I would help with the link.

[lukeed]

Most tools like this take a config with a "routes" definition array, similar to what @EmilTholin described.

I would reckon that Sapper should (begin to) include some CLI tasks baked in, so that devs don't have to redefine the base exporter script every time.

[kosirm]

Hi, I'm just learning Svelte/Sapper so so I have practically no experience with it but I've been using static site generators like Jekyll, Hugo, Gatsby, etc. so I can recommend some design decisions which imo should be baked in, if you decide to make it. From user standpoint following is important (imo):

• incremental build (generators which doesn't implement it from beginning, later struggle with partial/buggy implementations, huge user demand and unsatisfaction). Suppose that someone has huge site with thousands of articles/products/posts and is regularly adding/updating just some pages (not something sitewide like haeder, footer, style, etc). If there is no incremental build, it is a no-go.
• HTML from data - that's common demand. Suppose you have some data somewhere (huge list of users, products, whatever) and you want to make two templates to produce HTML - one for list of data and one for product from list (it should be linked from list). If this is not possible, your generator will be usable for blogging/portfolio and nothing else really.
• remote content - this should be outlined, microservices are huge demand. Gatsby made Solomon's solution with graphql imo (pull data instead of push).

Please let me know if I forgot something 😄

[niksurff]

✋

Based on @Rich-Harris' and @freedmand's ideas I built an exporter prototype which can be pulled into sapper-template.

Check out the README for details on how it works.

☠️ sapper-pirate-export ☠️

[EmilTholin]

sapper export works extremely well, and is ridiculously fast. Awesome work!

Is there still room for a "config-like" export within Sapper, or is that best pursued in a separate package?

Imagine that I have a WordPress site and I want to get all the pages and posts as data with WordPress REST API, and then bake a lean and mean static Sapper site, and finally host it on Netlify. In that case it would be great with a data driven export config of sorts, so I don't have to keep the file system of pages up to date when I e.g. change the permalink of a WordPress page in the CMS.

[freedmand]

This current export solution is experimental, so I would definitely imagine room for a config-like export. In the first comment of #88, @Rich-Harris alluded to having more options in the CLI when exporting the site, thus necessitating a more detailed CLI help interface. In addition to being able to specify options via the command line, I agree it would be nice to have the possibility for a Sapper export config file down the road.