`@ConditionalOnProperty` does not handle lists properly

[snicoll]

We use a List<String> instead of a String in many places to allow YAML to configure the property with nested structure. spring.couchbase.bootstrap-hosts is one of these.

In CouchbaseAutoConfiguration we check if that property is set to auto-configure a Bucket. The following works: spring.couchbase.bootstrap-hosts=localhost but the following does not spring.couchbase.bootstrap-hosts[0]=localhost

[snicoll]

I've tried to fix this in 1bfd245 which works for most cases but breaks the case where no prefix is specified for a composite.

Basically what the code does now is effectively binding the environment for the given prefix (if the prefix is not set, it binds the full environment (!) ). That way, we get what the binder would do on the pojo. The rest of code looks pretty much the same.

Unfortunately it does so in a generic way and any element in the map leads to a new list. So for instance, @ConditionalOnProperty("some.property") does not work anymore as the map contains an entry for some that is a map with the content of property). So when the (unchanged) code checks for a key in some.property it does not find it.

Arguably that would be the same problem with any property that defines a dot in it (@ConditionalOnProperty(prefix = "foo", value = "bar.biz")).

We could fix that with a regex matching if there is no match. Having said that, if PropertyResolver was supporting that use case, no change in OnPropertyCondition would be required.

[philwebb]

I'm worried about speed issues trying to make @ConditionalOnProperty too smart. I'd love to rationalize all this stuff in 2.0 when we revisit properties.

[snicoll]

Discussing this a bit more with @jhoeller, I am not sure that rationalizing the properties stuff is going to change anything. Those two worlds aren't asymmetrical. You have properties on one hand and there's nothing special about spring.couchbase.bootstrap-hosts[0] for the PropertyResolver (its contract is to check if a property is available, it has no notion of binding). On the other hand you have the binder that knows [0] is an indexed property.

If we truly want this to be asymmetrical, we need a PropertyResolver of some kind that knows about binding. It should also have a property à la ValueWrapper that tells you in one go if a property is present and its value if it is. Right now, RelaxedPropertyResolver does its magic twice (one to check that the property exists and one to get its value).