ADR-237: An empty field is filled after the save 

Context 

Editors leave the teaser and the meta description empty. An installation wants those fields written when a record is saved, for the fields it chooses.

A save is a bad place to call a model. It would take seconds, a provider failure would have to be handled inside the editor's request, and a failed call must not cost the editor the save. Two questions follow, and they are product decisions: what happens when the model fails during a save, and who waits for it.

Decision 

Nobody waits, and a model failure touches nothing. A hook after the database write stores one tool-free background run per empty, opted-in field (ADR-234) and the save ends. No model is called in the request. Whatever fails in the hook is logged and stops there, and the hook builds the agent runtime only when a field of the table is opted in. The worker runs the model and writes the answer.

The field is written only while it is empty. The worker reads the field immediately before the write. A text somebody added in the meantime stands, and the history says so. The DataHandler has no compare-and-set, so a save in the few milliseconds between the read and the write is overwritten by the fill; the window is that of two editors saving the same record, which TYPO3 accepts.

An editor who empties a field keeps it empty. A save that changes a field to empty is an answer, and the field is left alone in that save. A later save that does not touch the field fills it.

Opting in is the confirmation. "Nothing is saved without confirmation" is the rule of the chat tours, and ADR-236 keeps it for a batch: a run there produces a draft. This run writes directly, because an administrator listed the field in fieldFill.fields, and the list is the explicit opt-in. It is empty by default. The write is an ordinary edit of an empty field: it is in the record history, and nothing was there to lose. This is no exception to ADR-134, which is about tools a model chooses. The run has no tools, the model chooses neither the record nor the field, and its only output is the text of one field.

The writer is the editor who saved. The worker resolves that user and writes through ToolDataHandler as them, so their rights decide. Live only: a user who moved to a draft workspace since the save gets no write, because the DataHandler would write into a version. An editor whose group may not use the default configuration queues nothing. _cli_ queues nothing either: an import or a scheduled task saving records is nobody's choice to spend money, and neither is a copy, a translation or an AI write. Core makes copies and translations as new records, so a copied page tree would otherwise queue a run per page. It writes them through a DataHandler of its own with dontProcessTransformations set, which is how they are told from a save.

The worker sets the backend environment for this one write. ADR-135 refuses a write in a process without $GLOBALS['LANG'] and $GLOBALS['BE_USER'], and does not set them, because they would stay behind for every later hook in the process. The tools keep that rule: their writes happen after an approval, in a backend request. This write has no request to wait for, so the writer sets both around the DataHandler call and restores them in finally. What ADR-135 feared is the leak, and the leak is closed.

The model gets named text, not the row. For a page that is its descriptive columns and the text of its content elements in its language; for another table the label and its prose columns. A page row also holds its TSconfig and its author. Under FieldFillPlanner::MIN_SOURCE_LENGTH characters there is nothing to summarise, and a model would invent the text, so no run is queued. The text ends at RecordTextReader::MAX_LENGTH characters.

Only plain text fields of content tables. A listed field counts when its TCA type is input or text without rich text. A slug, a relation or a rich text field stays out whatever the list says, and so do accounts and sys_ tables.

The answer is checked, and a bad one is not written. Tags and surrounding quotes are removed. An empty answer, the word NOTHING the prompt offers for a record with nothing to say, in any case, and an answer over fieldFill.maxLength or the TCA max leave the field empty.

The history says what became of the answer. A model failure is a failed run. A finished run stays completed, and a new column outcome says written, the field was filled meanwhile or not written, on the detail page of the Agent Runs module. Withdrawing the opt-in stops queued runs: they are cancelled before the model is asked.

Consequences 

• Filling needs a worker: nrllm:agent:work from cron or the scheduler, or a Messenger consumer. Without one, runs stay queued and the fields stay empty.
• The field fills some time after the save. A form left open across the fill still holds the empty field, and saving it empties the field again, like any two edits of one record. That save reads as the editor emptying the field, so nothing is queued; the next save fills it again.
• A save that fails to queue is not repeated. The next save tries again.
• A save that changes nothing fills nothing, and existing records are not filled in bulk. Pressing save on an old page without an edit does nothing.
• A queued run keeps the text of the save that queued it. Text rewritten while it waits is not read, and a later save queues nothing for that field until the run ended.
• A record whose fill keeps failing costs one model call per save that leaves the field empty, as long as no run for that field is open. The budget applies as for any run of that user.
• Content elements are read, but saving one does not fill the page. The fill follows the save of the record that holds the field.
• The opt-in is per installation, not per page tree. A site that needs less can not say so; that is a setting nobody has asked for yet.
• A field filled for a translated record follows the language of that record's text. A translation made by core is not filled, as a copy is not, and neither is a translation that only inherited a value from a save of its default record. The save of the translation itself fills it. A save that changes only a slug or a value translations inherit, such as a stop time, fills nothing, which also keeps the pages EXT:redirects rewrites below a changed slug out of it.
• Whether the form of a record type shows the field is not asked. Listing a field some types do not show fills it on those types too.
• A reply cut off by the token limit of the configuration is written if it fits. The default of 1000 tokens is far above 300 characters.