I wish there was a getv equivalent that accepted a default value

[larsks]

My templates often end up being far too verbose because of things like this:

option = {{if exists "/example/app/option"}}{{getv "/example/app/option"}}{{else}}default_value{{end}}

That makes it quite hard to visually parse the config files. Much easier would be something like:

option = {{getv "/example/app/option" "default_value"}}

[kelseyhightower]

@larsks I wonder if we can do this on a way that backwards compatible.

[bacongobbler]

does {{ or (getv "/example/app/option") "default_value"}} accomplish the same thing?

[bacongobbler]

kelseyhightower/memkv#4

[larsks]

@bacongobbler While that expression accomplishes the same thing, for someone coming from a different background where things like ${somevar:-value} or {{somevar|default('value')}} are possible it seems needlessly verbose.

That linked patch looks like a step in the right direction, although it could use some documentation to go with it.

[bacongobbler]

@larsks that expression actually doesn't work; tried it myself today. However, with the proposed function it would look like {{ getord "/example/key" "default" }}.

[kelseyhightower]

@bacongobbler @larsks I wish go template function took optional params. Some people want thing to error if the key does not exist, some one a default value, some want a default empty value.

I guess we could solve this with more template functions, or figure out new functions that take options.

[bacongobbler]

Alternatively, a function which returns an empty string instead of an error would allow us to take advantage of the builtin or func. For example, {{ or (funcName "/example/app/option") "default_value"}} would default to "default_value" if the key did not exist and returned an empty string. This is thanks to how or works:

Returns the boolean OR of its arguments by returning the first non-empty argument or the last argument, that is, "or x y" behaves as "if x then x else y". All the arguments are evaluated.

That should minimize it down to 2 different functions while covering all use cases: one to return an empty string and one returning an error when the key does not exist.

[Dynom]

Highly desired feature from my part. Due to the limited scoping flexibility it's very hard to produce default values when dealing with single-line properties (such as some HAProxy configuration lines).

[technosophos]

Could adding a default function accomplish this?

getv "foo" | default "bar"

Where default is basically backed by func Default(def interface{}, given interface{}) interface{}. The Default func then evaluates given to see if it's "empty" (however you want to define that), and returns either given if non-empty, or def if empty.

[technosophos]

Here's an example from Sprig. I'd be happy to port to Confd if others think this fits the bill:

https://github.com/Masterminds/sprig/blob/master/functions.go#L44

https://github.com/Masterminds/sprig/blob/master/functions.go#L231

[Dynom]

I don't have a particular preference for syntax, so whatever fits the convention is fine by me. The proposed .. | default "value" sounds excellent 👍

[mishak87]

👍 Any progress?

[fruch]

👍

it's a bit confusing that the documetion mention this now, and the version 0.11.0 doesn't have it,
maybe adding a link in the documetion to 0.12.0-alpha3, or add a comment add in version.

[bacongobbler]

@fruch I'd accept a PR to remove that documentation.

[estahn]

Any progress?

[bacongobbler]

none.

[qvdk]

The documentation should be fixed since the default value is not available as described in the documentation.

[okushchenko]

Fixed in 4388e4b