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Sharing like Google Docs: private, shared with people, anyone with the link, public ​

A document starts private. Its owner shares it with people, hands out a link, or makes it public.

authz
type document = app.documents
  owner  : user = owner_id
  viewer : user, link shared by share
  editor : user shared by share

  can share = owner
  can edit  = share or editor
  can view  = edit or viewer or {visibility = 'public'}

rules app.documents
  select                      : view
  insert                      : owner
  update                      : edit
  update owner_id, visibility : share
  delete                      : share
  • Private is the absence of everything else: only owner holds.
  • Shared with people: authz.share('document', 7, 'viewer', 'user', 4), or 'editor'.
  • Anyone with the link: viewer may be given to link. authz.create_link('document', 7, 'viewer') returns a token, and a request that carries it sets authz_ctx.links to it for its transaction. authz.list_links shows a document's links and authz.revoke_link turns one off.
  • Public: {visibility = 'public'} is a condition on the row, true for everyone, signed in or not.
  • update owner_id, visibility : share: an editor changes the text, and only the owner changes who sees it.

Tested ​

anyone in a test asks as nobody signed in:

authz
test "private, shared with a person, public"
  user $bo cannot view document $diary
  anyone cannot view document $diary
  anyone can view document $blog
  user $bo cannot edit document $blog
  as user $ann allowed {SELECT authz.share('document', $diary, 'editor', 'user', $bo)}
  user $bo can edit document $diary
  as user $bo refused {UPDATE app.documents SET visibility = 'public' WHERE id = $diary}
  as user $ann allowed {UPDATE app.documents SET visibility = 'public' WHERE id = $diary}
  anyone can view document $diary
authz
test "anyone with the link"
  as user $bo refused {SELECT authz.create_link('document', $d, 'viewer')}
  as user $ann allowed {SELECT authz.create_link('document', $d, 'viewer')}
  as user $ann sees 1 {SELECT FROM authz.list_links('document', $d)}

Try it ​

Open it in the playground: the tables, the policy and the tests, in your browser, with nothing to install. Or take the files of docs/cookbook/google-docs-sharing/ (schema.sql, policy.authz, tests.authz) and run rowstile dev. CI applies and tests them on every change (core/tests/cookbook.sh), and every line shown here is in those files.

More: sharing with teams, and shares that end, links from app code, the other recipes.