On 5 July 2017 at 18:10, Kohsuke Kawaguchi <[email protected]> wrote:
> FWIW, I've already discussed this offline with Stephen and I'm
> generally +1.
>
> One suggestion I had for him is to consider using a Java method definition
> instead of @StaplerFacet and @StaplerFragment. That is, instead of this:
>
> @StaplerFacets({
> @StaplerFacet("index"),
> @StaplerFacet("config")
> })
> @StaplerFragments({
> @StaplerFragment("main"),
> @StaplerFragment("side-panel"),
> @StaplerFragment(value="tasks",optional=true)
> })
> public class Widget { ... }
>
> Consider that:
>
> public class Widget {
> @StaplerFacet protected void index() {}
> @StaplerFacet protected void config() {}
>
> @StaplerFragment protected abstract void main();
> @StaplerFragment("side-panel") protected abstract void sidepanel();
> @StaplerFragment protected void tasks();
> }
>
>
Well at least this is a better explanation than you gave me verbally ;-)
> I liked this better because ...
>
> - It fits with the original design thinking behind Stapler, which is
> that views are like methods. Their inheritance and override semantics are
> all modeled after methods.
> - It avoids a long list of @StaplerFragment/@StaplerFacet at the top
> of the class declaration. We have some objects in the core that has quite a
> few views.
>
> So let's see:
$ ( cd core/src/main/resources ; find . -name \*.jelly -exec dirname {} \;
; find . -name \*.groovy -exec dirname {} \; ) | sort | uniq -c | grep -v
./lib/ | sort -n | tail -n 10
7 ./hudson/model/AbstractProject
7 ./hudson/slaves/SlaveComputer
7 ./jenkins/install/SetupWizard
9 ./hudson/model/Run
11 ./hudson/PluginManager
11 ./hudson/security/HudsonPrivateSecurityRealm
12 ./hudson/model/Job
13 ./hudson/model/View
14 ./hudson/model/Computer
25 ./jenkins/model/Jenkins
So there are not altogether too many classes in Jenkins having lots of
fragments / facets
I think an argument based on a couple of really big classes like Jenkins
having 25 lines of
@StaplerObject
@StaplerFacet("_restart")
@StaplerFacet("_safeRestart")
@StaplerFacet("_script")
@StaplerFacet("_scriptText")
@StaplerFacet("accessDenied")
@StaplerFacet("configure")
@StaplerFacet("configureExecutors")
@StaplerFacet("fingerprintCheck")
@StaplerFacet("legend")
@StaplerFacet("load-statistics")
@StaplerFacet("login")
@StaplerFacet("loginError")
@StaplerFacet("manag_")
@StaplerFacet("manage")
@StaplerFacet("newView")
@StaplerFacet("noPrincipal")
@StaplerFacet("oops")
@StaplerFacet("opensearch.xml")
@StaplerFacet("projectRelationship-help")
@StaplerFacet("projectRelationship")
@StaplerFacet("systemInfo")
@StaplerFacet("threadDump")
@StaplerFragment("_api")
@StaplerFragment("downgrade")
@StaplerFragment("sidepanel")
public class Jenkins {
...
}
compared with
@StaplerObject
public class Jenkins {
@StaplerFacet protected void _restart() {}
@StaplerFacet protected void _safeRestart() {}
@StaplerFacet protected void _script() {}
@StaplerFacet protected void _scriptText() {}
@StaplerFacet protected void accessDenied() {}
@StaplerFacet protected void configure() {}
@StaplerFacet protected void configureExecutors() {}
@StaplerFacet protected void fingerprintCheck() {}
@StaplerFacet protected void legend() {}
@StaplerFacet @StaplerPath("load-statistics") protected void
loadStatistics() {}
@StaplerFacet protected void login() {}
@StaplerFacet protected void loginError() {}
@StaplerFacet protected void manag_() {}
@StaplerFacet protected void manage() {}
@StaplerFacet protected void newView() {}
@StaplerFacet protected void noPrincipal() {}
@StaplerFacet protected void oops() {}
@StaplerFacet @StaplerPath("opensearch.xml") protected void
opensearchXml() {}
@StaplerFacet @StaplerPath("projectRelationship-help") protected void
projectRelationshipHelp()
@StaplerFacet protected void projectRelationship() {}
@StaplerFacet protected void systemInfo() {}
@StaplerFacet protected void threadDump() {}
@StaplerFragment protected void _api() {}
@StaplerFragment protected void downgrade() {}
@StaplerFragment protected void sidepanel() {}
...
}
just to get the javadoc comments and leverage abstract and final... I
really do not like the extra effort of typing in all those method names...
Perhaps the biggest issue for me is that to retrofit that into Jenkins we
would need to take great care that these methods we are adding as facet and
fragment markers do not have names that may potentially conflict with
subclasses...
If we add
@StaplerObject
public abstract class Descriptor ... {
...
@StaplerFragment protected abstract void config(); // doesn't really
matter if abstract or not here
...
}
we may make it impossible for a concrete subclass to have a
public MyDescriptor extends Descriptor ... {
private MyConfig config;
...
public MyConfig config() {
return config.clone();
}
}
as they will be unable to retain binary compatibility with their existing
"config" method when they upgrade...
So that means we will need to do
@StaplerObject
public abstract class Descriptor ... {
...
@StaplerFragment @StaplerPath("config") protected abstract void
_retrofit_config();
...
}
Thinking some more, I see issues with plugin authors being thereby forced
to add implementations when they upgrade core... ok so they are quick and
the IDE will help... but having to add all those
public MyDescriptor extends Descriptor ... {
private MyConfig config;
...
public MyConfig config() {
return config.clone();
}
@StaplerFragment @StaplerPath("config") protected void _retrofit_config()
{}
}
All the while hoping that the IDE has copied the method annotations
(otherwise the method is not annotated) and the plugin author has not opted
into @StaplerObject yet
That, to me, does not make for a compelling developer experience.
WDYT?
I am inclined to reject your method based idea and stick with class level
annotations... there are only 11 classes in all of Jenkins core with more
than 5 facets / fragments
> - It creates a nice to place to describe view as javadoc.
> - 'abstract' and 'final' provides convenient semantics and javac does
> that work for us. One less thing to do for our annotation processor
>
> Obvious downside is that those are not real methods.
>
> On Mon, Jul 3, 2017 at 5:21 AM Stephen Connolly <
> [email protected]> wrote:
>
>> I have been developing Jenkins plugins and changes to Jenkins core for
>> more than 10 years now. As such, I have internalized a lot of the knowledge
>> about how to develop against Jenkins and more specifically against Stapler.
>>
>> When I talk to people trying to start out development against Jenkins,
>> the magic of Stapler seems to be a big source of confusion - at least to
>> the people I have talked to.
>>
>> Prospective developers get confused:
>>
>> - between primary facets and facet fragments.
>> - where to put facets and facet fragments.
>> - which facet fragments are optional and which ones are mandatory
>>
>> (Did you even know that those jelly / groovy views are called facets and
>> that there are two kinds?)
>>
>> Some of those concerns affect me too... but I am a seasoned Jenkins
>> developer CMD+SHIFT+P, *, ENTER and IntelliJ is showing me a full list of
>> facets and facet fragments from the class hierarchy and I can search each
>> one looking for the <st:include page="fragment" optional="true"> to
>> discover that there is an optional facet fragment... and then try and dig
>> through the Jelly / Groovy logic to determine when and why that fragment
>> should be included.
>>
>> It doesn't just stop there... There are those methods that we expect
>> Stapler to invoke for us... typically they are the doFillXYZItems() or
>> doCheckXYZ() methods. I find myself having to mark them up like:
>>
>> @SuppressWarnings("unused") // stapler
>> public FormValidation doCheckWidgetValue(@QueryParameter String value) {
>> ...
>> }
>>
>>
>> So that my IDE stops complaining about the dead code. It's not a big deal
>> in the grand scheme of things, but I'd much rather have an annotation on
>> the method to signify that we expect the method to be used by stapler...
>> Right now I could do that using
>>
>> @WebMethod(name="checkWidgetValue")
>> public FormValidation doCheckWidgetValue(@QueryParameter String value) {
>> ...
>> }
>>
>>
>> If I don't like that, I guess I could use the newer HTTP verb annotations
>> in stapler:
>>
>> @GET // stapler
>> public FormValidation doCheckWidgetValue(@QueryParameter String value) {
>> ...
>> }
>>
>>
>> But the simple @GET is not screaming out stapler to me, so I feel
>> compelled to add a // stapler comment to remind myself that the
>> annotation is used by stapler
>>
>> Then we hit the actual name that stapler exposes things on. There are
>> some conventions that stapler follows... and they are magic conventions...
>> so much so that I just keep http://stapler.kohsuke.org/reference.html as
>> the first bookmark in my bookmark bar.
>>
>> I think we can do better. I think we should do better, and here is my
>> proposal.
>>
>> We should introduce some annotations. Make them available against older
>> versions of Jenkins so that we don't have to wait for everyone to update
>> their plugin baseline. The annotations can be added as a plugin dependency
>> in the parent pom, that everyone can use them just by upgrading the plugin
>> parent pom.
>>
>> Here are the class annotations I think we need:
>>
>> - An annotation (I propose @StaplerObject) that says "This object is
>> expected to bound to a URL by Stapler, the Stapler annotations are
>> complete, check that there are no facets / fragments without a
>> corresponding annotation and no magic on this class please" (so if there
>> is, say a rename.jelly but no @StaplerFacet("rename") or
>> @StaplerFragment("rename") then you get an error)
>> - An annotation (I propose @StaplerFacet and the repeatable container
>> @StaplerFacets) that says "Here are the facets that this object is
>> expected to have" (doesn't have to be on a @StaplerObject but when
>> not on a @StaplerObject we can only check for missing expected
>> facets, we cannot check for "unexpected" facets - i.e. I created a facet
>> with a spelling mistake or typo in the name)
>> - An annotation (I propose @StaplerFragment and the repeatable
>> container @StaplerFragments) that says "Here are the facet fragments
>> that this object is required or may optionally have" (quite often will not
>> be on a @StaplerObject)
>>
>>
>> So I envision something like this (pre-Java 8):
>>
>> @StaplerObject
>> @StaplerFacets({
>> @StaplerFacet("index"),
>> @StaplerFacet("config")
>> })
>> @StaplerFragments({
>> @StaplerFragment("main"),
>> @StaplerFragment("side-panel"),
>> @StaplerFragment(value="tasks",optional=true)
>> })
>> public class Widget { ... }
>>
>>
>> When compiled targeting Java 8 this would become:
>>
>> @StaplerObject
>> @StaplerFacet("index")
>> @StaplerFacet("config")
>> @StaplerFragment("main")
>> @StaplerFragment("side-panel")
>> @StaplerFragment(value="tasks",optional=true)
>> public class Widget { ... }
>>
>>
>> There would be an annotation processor that could do some checks:
>>
>> - If you add @StaplerFragment(..., optional=false) then any
>> non-abstract class must have that fragment somewhere in the class
>> hierarchy
>> - If you add @StaplerFacet then any non-abstract class must have that
>> fragment somewhere in the class hierarchy
>> - If you add @StaplerObject then only the named facets and facet
>> fragments must be present for that class (to catch somebody calling the
>> facet resource with an incorrect name - it should be side-panel2.jelly
>> but they called it sidepanel2.jelly)
>>
>>
>> Then, while we are at it, I'd also like to add method / field annotations:
>>
>> - An annotation (I propose @StaplerPath and the repeatable container
>> @StaplerPaths) that says "here is the URL segment names that this
>> method / field matches when Stapler is binding the URL". This annotation
>> can be used to enable easier refactoring without risk of breaking the URLs
>> because we can rename the getters and keep the URL scheme as before or
>> even
>> keep the legacy URLs but direct to the new URLs via the UI.
>> - Annotations (I propose @StaplerHEAD / @StaplerGET / @StaplerPOST /
>> @StaplerPUT / @StaplerPATCH / @StaplerDELETE plus non standard
>> methods supported with @StaplerMethod("...") and then a repeatable
>> container of @StaplerMethods - the repeatable container would only
>> take @StaplerMethod annotations though) that cover the different HTTP
>> methods (a.k.a. verbs) - we have some existing, but they need some
>> extensions and I think it might be a good idea to consolidate the names,
>> especially if we want to allow consumption on older baseline versions of
>> Jenkins
>>
>>
>> So this could be something like this (Pre Java 8):
>>
>> public class Widget {
>> @StaplerPath
>> public Manchu manchu;
>>
>> @StaplerPaths({@StaplerPath,@StaplerPath("fu")})
>> public Foo foo;
>>
>> @StaplerPath
>> public Bar getBar() { ... }
>>
>> @StaplerPath(StaplerPath.DYNAMIC)
>> public Object getDynamic(StaplerRequest req) { ... }
>>
>> @StaplerPOST
>> public HttpResponse doActivate(StaplerRequest req) { ... }
>>
>> @StaplerPath(StaplerPath.DYNAMIC)
>> @StaplerPUT
>> public HttpResponse doDynamic(StaplerRequest req) { ... }
>> }
>>
>>
>> Or targeting Java 8:
>>
>> public class Widget {
>> @StaplerPath
>> public Manchu manchu;
>>
>> @StaplerPath
>> @StaplerPath("fu")
>> public Foo foo;
>>
>> @StaplerPath
>> public Bar getBar() { ... }
>>
>> @StaplerPath(StaplerPath.DYNAMIC)
>> public Object getDynamic(StaplerRequest req) { ... }
>>
>> @StaplerPOST
>> public HttpResponse doActivate(StaplerRequest req) { ... }
>>
>> @StaplerPath(StaplerPath.DYNAMIC)
>> @StaplerPUT
>> public HttpResponse doDynamic(StaplerRequest req) { ... }
>> }
>>
>>
>> The annotation processor can then give additional checks:
>>
>>
>> - @StaplerPath annotated fields must be public
>> - @StaplerPath(altName) annotated fields are only allowed if
>> targeting a new version Stapler that adds support for that (unless the
>> name
>> is the inferred name)
>> - @StaplerPath annotated methods must be public and either match one
>> of the allowed getter signatures or also have a HTTP method annotation and
>> match the allowed action method signatures.
>> - @StaplerPath(altName) annotated methods are only allowed if
>> targeting a new version Stapler that adds support for that (unless the
>> name
>> is the inferred name)
>> - @StaplerHEAD / @StaplerGET / @StaplerPOST / @StaplerPUT /
>> @StaplerPATCH / @StaplerDELETE annotated methods must be public and
>> match one of the allowed action method signatures. The method name must
>> match the convention for action method inference (subject to
>> @WebMethod(name="...") overriding when *compiling against older
>> versions of Stapler* - but it would be an error to use @WebMethod if
>> compiling against newer versions of Stapler because we can move to the new
>> annotations in those cases)
>> - If the class is @StaplerObject annotated we can do additional
>> checks for overlapping facets, for example where an action method or a
>> getter will hide a facet (it's ok to hide the facet for non HEAD/GET
>> requests though)
>>
>> There are probably additional checks that we can add as we figure them
>> out.
>>
>>
>> Now there are some open questions:
>>
>> - Does it make sense to start all these annotations with Stapler? My
>> initial stab at this was to use @Staple in place of @StaplerPath and
>> to re-use the @GET / @POST / @PUT / @DELETE verbs but mandating the
>> @Staple annotation so that you would have:
>>
>> @Staple @POST
>>
>> public HttpResponse doActivate(StaplerRequest req) { ... }
>>
>>
>> rather than
>>
>> @StaplerPOST
>>
>> public HttpResponse doActivate(StaplerRequest req) { ... }
>>
>>
>> One of the issues I found with that is class conflicts when back-porting
>> the @GET / @POST / etc annotations, so we could only use those if we
>> were prepared to mark 2.7 as the oldest core that could use the
>> annotations, whereas we can make new annotations in a separate package
>> available as far back as Stapler 1.180 == Jenkins 1.455 (or worst case
>> Stapler 1.237 == Jenkins 1.651)
>>
>> Now we could introduce new annotations without the @Stapler prefix, but
>> then your code complete would confuse you between @org.kohsuke.stapler.
>> annotations.GET and @org.kohsuke.stapler.verbs.GET plus we still need
>> something to give a hint that the annotation is implying Stapler's
>> involvement (at least from my perspective)
>>
>>
>> - I had thought about saying that the class level @StaplerObject
>> should be enough of a flag that you should expect the other annotations...
>> but the class annotation will be inherited, so you may not see it until
>> you
>> look at the super-class... and @Path will conflict with
>> java.nio.file.Path... that might work with @Staple (and @Staples as
>> the container) but while cute they do not scream to the new developers
>> that
>> these are involved in url binding.
>>
>> NOTE: In this context I see this change as being entirely opt-in. Plugin
>> developers should not have to go adding the annotations - though we would
>> probably apply them in Jenkins core to assist new developers.
>>
>>
>> - If we go with the Stapler prefix, would it make sense to
>> consolidate all the annotations with that prefix?
>>
>> - I am not convinced for the case of @ExportedBean and @Exported,
>> these reflect a different cross-cutting concern and as such the pair
>> seem
>> named well from my PoV
>> - The @JavaScriptMethod / @WithWellKnownURL annotations might be
>> worthy of consolidation if we can determine better names.
>> - The parameter binding annotations such as @AncestorInPath,
>> @Header, @QueryParameter and @InjectedParameter I think are fine
>> where they are as they will only be on an action method which already
>> has
>> the @StaplerPOST etc indicator.
>> - The meta-annotation @InterceptorAnnotation should not be
>> consolidated, in any case we could not consolidate it and retain usage
>> against older cores
>> - The other annotations are likely rarely used, but if we can find
>> good names and people think they are generically useful rather than
>> single
>> use-case hacks added into the stapler API, I think consolidation might
>> make
>> the features more widely used.
>>
>> So, over to you the community of Jenkins developers:
>>
>> 1. Would this change have helped you get started quicker?
>> 2. Would this change help you even now?
>> 3. How ugly are my proposed annotation names? Can you provide a less
>> ugly scheme of names?
>> 4. Anything else?
>>
>> Stephen
>>
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> --
> Kohsuke Kawaguchi
>
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