Mike Drob created CURATOR-148:
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Summary: Order of modifiers on framework commands matters
Key: CURATOR-148
URL: https://issues.apache.org/jira/browse/CURATOR-148
Project: Apache Curator
Issue Type: Improvement
Components: Client
Reporter: Mike Drob
I only tested this with the {{CreateBuilder}}, but visual inspection makes me
think that it is present on other operations as well.
If I want to create a ZK node, using a bunch of the features that curator
provides, I have to do it in a specific order. (Arguments removed for clarity)
{code}
client.create()
.compressed()
.withMode()
.withACL()
.inBackground()
.forPath();
{code}
If I unknowingly call {{inBackground()}} first, then the only methods available
to me are the {{forPath()}} variants. Similarly, if I call
{{create().withMode()}}, then there is longer a way for me to call
{{compressed()}} on that object.
Even more concerning is that it is impossible to call {{compressed()}} and
{{withProtection()}} on the same chain, regardless of order.
Since each of the fluent-style methods already returns {{this}}, it might make
sense to modify each method as implemented on {{CreateBuilder}} to have a
declared return type of {{CreateBuilder}}, taking advantage of covariant return
types.
Another option, with similar results, would be to remove many of the
intermediate interfaces from {{CreateBuilder}} like
{{ACLCreateModeBackgroundPathAndBytesable<String>}} and declare it to be:
{code}
interface CreateBuilder extends Pathable<String>,
Backgroundable<CreateBuilder>,
Compressible<CreateBuilder>,
ACLable<CreateBuilder>,
CreateModable<CreateBuilder>,
....
{code}
This option is very verbose, however.
A disadvantage of both of these options is that it allows users to call methods
multiple times. In some cases, like {{inBackground()}}, it won't matter. In
other cases, like {{withACLs()}} we'd have to make a decision on taking an
intersection or "last call wins" approach. That might even differ per call, so
we'd have to have careful documentation on each.
Another option is to simply document the behavior (probably on the {{create()}}
method) and hope that users will see it. Maybe the best solution is to document
in a minor release line, and then make breaking changes in a major version?
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