OK thanks for the info. Well I'd say coming up with an approximate solution for one shell is easy -- but that's the state of the art. That's what bash, zsh, a

OK thanks for the info. Well I'd say coming up with an approximate solution for one shell is easy -- but that's the state of the art. That's what bash, zsh, and fish do. (Not they are the same -- I'd like something closer to fish, not bash.) The goal was to improve on the state of the art, which is hard. The original motivation for Shellac is here and I discussed it with many people. The Ion shell author wrote some code toward it, and so did a zsh dev. https://github.com/oilshell/oil/wiki/Shellac-Protocol-Proposal https://github.com/oilshell/oil/wiki/Shellac-Protocol-Propos... But it didn't really go anywhere for a variety of reasons. One is the "bootstrapping" problem. That is, there's no incentive for anyone to implement shellac if there's no corpus of completions. Likewise there's no incentive for the author of new-popular-tool to use it if no shells implement it. The other problem is whether the completion is declarative or imperative, which you hinted at. If it's more imperative then you've automatically coupled it to a language like Murex. If not then I think the UI will be limited and it will break some of the invariants I wanted (but are maybe not strictly necessary). I think that most people on the #shell-autocompletion Zulip wanted it to be declarative. I was one of the few people who said that declarative isn't enough, mainly because the ACTUAL command lines are written in imperative languages. It's sort of an argument around computational power. To me the fact that all the popular systems are imperative is evidence in favor of that, until reality shows the opposite :) I also wanted to push the burden of developing the logic on the people who write the tools -- THEY know what its syntax is. This also solves versioning problems. So the idea was that EITHER the shell or the TOOL ITSELF would be a Shellac server. In the latter case, it would never get out of sync, which does happen in bash, zsh, and fish. (Although to be fair if you dynamically scrape --help, that also solves the versioning problem, but not if you bake it in. bash-completion actually DOES the dynamic execution and scraping of 'ls --help' on TAB, which I didn't know before implementing Oil's autocompletion )