Hi Tomas,


It’s bug 10662, but I haven’t posted the revised patches with the parameter 
validation yet.


After reviewing bug 17425 and the documentation for Class::Exception, I see 
what you’re saying.


These two sections are the part that explain it for me best:




However, I think there’s still room for convention.


For instance:


try {


} catch {

                ok( $_->isa('Koha::Exceptions::Object::MethodNotFound'),

                'Calling a non-existent method should raise a 
Koha::Exceptions::Object::MethodNotFound exception' );



This is a basic example… I’d want to see “which” method was not found. Of 
course, Object.pm defines that in the exception:


Koha::Exceptions::Object::MethodNotFound->throw( "No method $method for " . 
ref($self) );

Koha::Exceptions::Object::PropertyNotFound->throw( "No property $p for " . 
ref($self) );


However, that’s more human readable than machine readable. Let’s say we’re 
doing a CRUD form for the web UI, and we have something like 
Koha::Exceptions::Object::ValueInvalid. I think we’d want an error code or 
error message that would be easy to catch in the code, and then we relay that 
to the template in a way which allows for translation. 


In my code, I’ve been doing it like in my .pm/.pl:


$errors->{url}->{invalid_scheme} = 1;


Then in the template:


[% IF ( errors.url.invalid_scheme ) %]

                Your url must start with http:// or https://

[% END %]


While my approach works, I don’t know that I’ve seen it elsewhere in Koha, and 
it just feels a bit… suboptimal to me. I don’t know why.


I suppose if I were using exceptions… it might be something like 
Koha::Exceptions::URI::InvalidScheme, and I’d probably be manually throwing 
that error in my processing of the CRUD form (since different forms might 
accept URIs with different schemes). I suppose in this case I don’t necessarily 
need the URI scheme that they did use… I just need to tell them the one that 
they “need to use” and I know that based on my controller’s logic and display 
it with the view. I suppose if they did use a scheme like “ftp”, I would know 
about it since I’m trying to catch that exception… and then pass it to the view 
if necessary.


So I guess in the end my questions are a bit irrelevant in terms of exceptions 
per se and relate to how we surface errors for users in a consistent way…


David Cook

Systems Librarian

Prosentient Systems

72/330 Wattle St

Ultimo, NSW 2007



Office: 02 9212 0899

Direct: 02 8005 0595


From: Tomas Cohen Arazi [mailto:tomasco...@gmail.com] 
Sent: Wednesday, 12 October 2016 6:17 PM
To: David Cook <dc...@prosentient.com.au>; koha-devel 
Subject: Re: [Koha-devel] Marseille16 / REST api



El mié., 12 oct. 2016 a las 7:26, David Cook (<dc...@prosentient.com.au 
<mailto:dc...@prosentient.com.au> >) escribió:

Really curious to see how this plays out!


I’ve just added parameter validation to a Koha::Object, and while it works well 
enough, I’m hoping for a more generalized solution. I haven’t looked at 
Koha::Exceptions::* yet, but maybe that will help.


I don't know how that would work, what bug number is it?


Peeking at Koha::Exceptions::MissingParameter, I hope that there’s more 
specificity than just “A required parameter is missing”. I’d want to know which 
required parameter is missing.


Is there a document somewhere saying how to use Koha::Exceptions?


Well, we are not baking our own exception system, we are just using 
Class::Exception so it is pretty documented!


Look at bug 17425, you will notice when we throw an exception we can add a 





David Cook

Systems Librarian

Prosentient Systems

72/330 Wattle St

Ultimo, NSW 2007



Office: 02 9212 0899 <tel:02%2092%2012%2008%2099> 

Direct: 02 8005 0595 <tel:02%2080%2005%2005%2095> 


From: koha-devel-boun...@lists.koha-community.org 
<mailto:koha-devel-boun...@lists.koha-community.org> ] On Behalf Of Tomas Cohen 
Sent: Wednesday, 12 October 2016 2:39 AM
To: koha-devel <koha-devel@lists.koha-community.org 
<mailto:koha-devel@lists.koha-community.org> >
Subject: [Koha-devel] Marseille16 / REST api


During the first couple Hackfest days, Jonathan, Benjamin and I worked on a 
reference implementation of CRUD code for a REST endpoint, so others can read 
it, discuss it and use it as a reference for their own developments.


We worked on Koha::Cit(y|ies) because it was a really simple class. All our 
work is now on bug 17428.


The main goals/concepts we tried to apply were:

* Controller class (Koha::REST::V1::Cities) should be as simple as possible. No 
business logic on it. All business logic is expected to be put on the 
Koha::Cit(ies|y) classes. And fully tested.

* All verbs/use cases should be covered by tests 
(t/db_dependent/api/v1/cities.t). We did it, and this file could be used (with 
little adjustments) as the basis for new endpoint tests.

* Heavy use of exceptions. I wouldn't say we heavily use them, but the point is 
that we pass everything to the business object, and catch exceptions it might 
raise. Martin pointed out that he would help us further simplify it, making 
heavier use of the Swagger plugin's facilities. Specially on parameters sanity 
check. More on this tomorrow!

* Koha::Exceptions got per-class files so the exceptions file is more 
manageable. Bug 17425 introduced Koha/Exceptions/Object.pm, and we propose 
that's the way to go (Koha/Exceptions.pm still has Virtualshelves-related 
exceptions that should be moved).

* Make use of Try::Tiny for try/catch blocks. On the process we wrote bug 
17425, which introduces new exceptions, we added the dependency for Try::Tiny 
(no worries, it is packaged for Jessie/Ubuntu) and Mirko was here to validate.

* Moving business-logic to Koha:: namespace and write REST endpoints on top of 
that business objects. We picked a simple object, Koha::Patron(s) will be a 
more complex one of course. This is what Jonathan has been doing, and people 
willing to write REST endpoints should check with him, and probably help moving 
business logic into Koha:: namespace.


There are several patches on bugzilla introducing endpoints. We will try to 
contact patch authors to help them make their work match this proposed 


We are sticking to the 'patches speak' approach, so feel free to criticize this 
implementation, to improve it or even provide a counter-proposal. We are 
otherwise moving on, trying to get a functional complete REST api ASAP.




Tomas, Jonathan, Benjamin





Tomás Cohen Arazi

Theke Solutions (https://theke.io <http://theke.io/> )
✆ +54 9351 3513384 <tel:+54%209%20351%20351-3384> 


Tomás Cohen Arazi

Theke Solutions (https://theke.io <http://theke.io/> )
✆ +54 9351 3513384

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