WSO2 IS Custom claim dialect not passed to the Service Provider - wso2

Question

I'm using WSO2 Identity Server version 5.10
I'm facing a strange behaviour. I configured some external IdPs (SAML2 based)
I configured claims returned by these IdPs with WSO2IS local claims. For example, let's suppose that my external IdP returns these SAML attribute name:
a, b and c I configured claim in this way:
External IdP Claim configuration
Identity Provider Claim URI
Local Claim URI
a
http://wso2.org/address
b
http://wso2.org/givenname
c
http://wso2.org/lastname
Then I defined a custom claim dialect in this way; let's call it custom_claim_dialect. I defined in it my claim mapping in this way:
Custom claim dialect
Dialect URI
Claim URI
Mapped Local Claim
custom_claim_dialect
a
http://wso2.org/address
custom_claim_dialect
b
http://wso2.org/givenname
custom_claim_dialect
c
http://wso2.org/lastname
Then I defined a Service Provider (Inbound configuration: SAML2 Web SSO) and I configured it by using these external IdPs
In my Service Provider I configured my claims by adding the custom dialectby specifying it in Service Provider Claim Dialect
Then I tried the access the access to the Service Provider. All worked pretty good just only the first time.
WSO2IS asks to me the consent for the claims and I can land on my authenticated page.
When I close the browser and clent cookies and I try again the access. All works good (no consent ask is showed by WSO2IS) but when I land on my private page no
attribute is contained in the SAML Response.
If i configure my ServiceProvider with WSO2IS local claims, all works good.
Is this correct? Am I missing anything?
Thank you
Angelo
UPDATE
I'm pretty sure it's a kind of bug.
I debugged till the class org.wso2.carbon.identity.application.authentication.framework.handler.claims.impl.DefaultClaimHandler
The org.wso2.carbon.identity.application.authentication.framework.handler.claims.impl.DefaultClaimHandler.handleClaimMappings(StepConfig, AuthenticationContext, Map<String, String>, boolean) returns the correct claims Map In fact I printed the following log:
INFO {org.wso2.carbon.identity.application.authentication.framework.handler.claims.impl.DefaultClaimHandler} - Returning filtered claims {familyName=Surname, name=Example, dateOfBirth=1980-01-01, spidCode=ABCD123456789A, fiscalNumber=TINIT-SRNXPL80A41A662G, MultiAttributeSeparator=,} to SP mySP
In some point during the process WSO2 IS decides that this Map must not be used.
Any tip?
UPDATE 2
This picture shows how I configure my SP claims. As you can see I'm using a defined custom claim. When I define custom claim, I can't make claims mandatory

Answer 1

Did u try making these claims mandatory on the IS SP side? Making claims mandatory will ensure that u always receive the claim for the applications.
If caching is the problem then u can try to JIT provision the user[1]. This way we can save the claims from FIDP on the IS side. "Provision silently" is an easy option to check.
[1] https://is.docs.wso2.com/en/latest/learn/configuring-just-in-time-provisioning-for-an-identity-provider/