CSS now records its provenance and can be rebuilt

The site serves HTML and CSS from the database. The compiler, however, read the files in the repository. Anyone editing a page in the panel changed the HTML in the database, and the CSS remained the one from the old file: new classes reached the visitor with no rule at all.

The decision

HTML and CSS written by someone are authored. Compiled CSS is derived: it can be regenerated at any time and should not be preserved as if it were the user's work.

What landed

• Provenance signature: each resource stores the signature of the content its CSS was generated from. With no signature, or a different one, the CSS counts as stale.
• Invalidate, never delete: an update that touches the content marks the CSS as stale but does not remove it. Deleting it would leave the page unstyled until someone recompiled.
• c2f css:audit: measures, per table, how much CSS is stale and how many classes have no rule.
• c2f css:rebuild: recompiles from the HTML in the database. With --url, it also uses the HTML the page actually returns, which removes the need to declare where classes come from.

The same batch fixed an old defect: content written in the text editor depended on CSS the public page never loaded. Indents and alignments worked or not depending on the button used. The content stylesheet now loads whenever the page has text from that editor.

In a measured batch of 80 pages, classes with no rule dropped from 1,538 to 291.