and/or followed by let results in command not found

Reproduction:

echo "This does not have a bad exit status"; and let x = "something"

Expected behavior: x is set to something

Actual behavior:

ion: command not found: let

Build information:

A git bisect showed that this started at 7d9584ee

Fix should be to check if the first argument is a builtin command / keyword or not, and handling it accordingly.

Created by: AgustinCB

Would this make sense in the first place? Why not just echo "This does not have a bad exit status"; and eval let x = "something"? (Which works as expected)

Not excited about forcing the use of eval in this case, but it certainly reasonable.

In other shells, the and, not, and or commands are not builtins, but keywords (like let).

Then again, it seems Fish has them as builtins?

Funny how that works, but their source code looks similar-ish to ours https://github.com/fish-shell/fish-shell/blob/master/src/builtin.cpp#L409:L464

Then again, maybe not? Is confusing that they have control flow keywords listed as builtins.

Created by: AgustinCB

I don't use fish, what happens when you do a similar command there?

On the other hand, when I think of those boolean operations (and, not and or) I think of boolean operations. let doesn't return a value, so it wouldn't make sense to use it in this kind of operations. For example, why would you support not let x = "something";? If the idea is to do a conditional... Well, you can just use if. In that sense, I prefer an strong well defined syntax over a flexible one.

I guess this will require solve some question first:

• Should and, not and or be just boolean operations or some kind of control flow?
• If they should be boolean, but we want to support that syntax, what should be the return value of let or how should they treat that return value?
• Should they be keywords or bultins?

We should probably implement them as keywords in our shell, because let requires special parsing rules (hence the need for let to be a keyword). Keywords have the highest level of control over their execution.

Created by: AgustinCB

I just tried echo 'hola'; and set x "something" in https://tio.run/#fish-shell and it works as suggested here. I think the difference is that set is a builtin: https://github.com/fish-shell/fish-shell/blob/master/src/builtin.cpp#L454 and it handles status codes: https://github.com/fish-shell/fish-shell/blob/master/src/builtin_set.cpp#L155.

Maybe that's the way to go?

Created by: AgustinCB

Oh, sorry, I didn't see your last message:

Yeah, that makes sense. And what should be the behavior of things like:

let x = "something"; and echo "hola"

When should echo be executed? Every time?

In the above example, the let command would exit with a SUCCESS exit status, which would thereby continue to print hola. There are cases where a let operation can fail though. For example, the and condition that follows will not execute:

let x:int = something; and echo "hola"

Created by: AgustinCB

Perfect. Can you point me out to the code that handles let, please? I'll be happy to start working on this.

@AgustinCB Look for Statement::Time as an example of how And/Or/Not could be implemented. Their implementation would be similar, but rather than computing times, you'd just execute based on the current exit status stored in the shell.

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