Support declare for checking for function definition about oil

[andychu]

Thanks, I think this should be pretty easy, and I should be able to get it for the next release!

[travisbhartwell]

Looking through code I've written recently, I've also seen the following uses of declare:

1. Declaring a variable as an array, with or without setting the value:

# filenames is an array
declare -a filenames
# foo is an array with one element, b
declare -a foo=( b )

2. Declaring a variable read-only and an array:

declare -ar foo=( b )

3. Declare a string as only upper case or only lower case:

declare -u upper_region_name="${region}"
declare -l lower_region_name="${region}"

Related, I've used local and readonly similarly:

function() {
    local src="$1"
    local -r read_only_src="$2"
}

# Read only file-level variable
readonly [email protected]

# Only set ENV_NAME if it isn't already
: "${ENV_NAME:='MyEnvironment'}"
# Make it read-only
readonly ENV_NAME

[andychu]

Hi Travis, I'm starting to look at this now. Just curious what you use -u and -l for?

It shouldn't be hard to implement them. But I'm a little wary about checking extra flags on every assignment, since it could more or less be written:

$ foo=xyz
$ foo=${foo^^}
$ echo $foo
XYZ

Or is there a reason that -u and -l are preferable for your use case?

[travisbhartwell]

No, no reason they are preferable. I didn't know about case modification as part of parameter expansion. I can't remember where I saw the flag. These are not variables that are set more than once, so making the variable always be upper or lower aren't requirements, I can use the parameter expansion versions instead.

[andychu]

OK great thanks for letting me know! I landed these changes on the master branch. If you want to try it on your code, you can clone and make a "dev build", which should take 30 seconds if you have an Ubuntu machine:

https://github.com/oilshell/oil/wiki/Contributing

It's somewhat dependent on the environment, there are few dependencies.

Still aiming for a 0.4 release by the end of the month, maybe early next month. I've been working on trap as well.

[andychu]

0.4.alpha1 release is here: http://www.oilshell.org/releases.html

I'm closing this for now -- please test and reopen if there are issues :)