Watch mode

yassb watch builds the site, serves it, and rebuilds whenever a file changes. Your browser reloads by itself, and errors show up on the page.

What is watched

The whole project, except the output folder, node_modules, .git and temporary files of editors. That includes the configuration, your renderers and directives, package.json and tsconfig.json.

Every build is fresh

Each rebuild runs in a new process. Nothing is cached between builds, so:

• changes to the configuration and to the code it imports are always picked up;
• if your code throws, the error is printed and shown in the browser, and the server keeps running: fix the file and save.

Only what changed is rebuilt

Changes made while a build is running are queued into one more build.

Live reload and the error overlay

Pages get a small script, injected before </body>, connected to the dev server:

• a badge shows while a rebuild runs;
• the page reloads when it is done (or only the CSS is swapped);
• the errors of the last build appear in an overlay at the bottom of the page, with code, file and line, and disappear when fixed.

The Content-Security-Policy meta tag is removed in watch mode so that the script can run. Pages are not minified.

The dev server

http://localhost:3000, or devServerPort, or --port; if the port is busy the next one is used.

• /<lang>/… serves <out>/<lang>/…; other paths are looked up in the first language, then in the output root;
• folders redirect to a trailing slash and serve their index.html;
• unknown paths serve the home page.

One process per output folder

Two YASSB processes writing the same output folder would overwrite each other's files and leave empty or mixed pages. So only one at a time may write it: build and check hold a lock during the build, watch for its whole session.

Start a second one on the same folder and it stops at once, writes nothing and exits with code 1:

error OUTPUT_LOCKED
  Another YASSB process is writing …/dist/public: `yassb watch` (pid 35695 since 20:18:02, in …/my-site).
  Two processes writing the same folder corrupt each other's pages, so nothing was written.
  hint: Stop it (Ctrl+C in its terminal, or `kill 35695`), or build into another folder with --out <dir>. If no YASSB process is running, delete …/yassb-locks/….lock.

• The lock lives in the temporary folder of the system, never in the output, so it is never deployed.
• A lock left by a process that no longer exists (a crash, kill -9) is taken over automatically.
• Different folders never conflict: yassb build --out preview works while watch runs.