[Bug]: Cannot Read Annotation Value at Runtime When a Function Pointer is Passed to an Object Defined at the Module Level or Service Level

[MohamedSabthar]

Description

In the ballerinax/ai.agent package, there's a requirement to read the annotation value of a function at runtime. However, when the agent is defined at the module level, it is not possible to retrieve the annotation value at runtime.

Steps to Reproduce

The following stripped-down version of the code illustrates the problem:

import ballerina/io;

type ToolConfig record {|
    string name?;
|};

annotation ToolConfig Tool on function;

class Agent {
    private (isolated function)[] tools = [];
    isolated function init((isolated function)[] tools) {
        self.tools = tools;
    }

    isolated function run() returns ToolConfig|error {
        typedesc<isolated function> typedesVal = typeof self.tools.pop();
        ToolConfig toolConfig = check typedesVal.@Tool.ensureType();
        return toolConfig;
    }
}

@Tool{name: "name"}
isolated function sum(int a, int b) returns int {
    return a + b;
}

Agent agent = new([sum]); // This doesn't work

public function main() {
    // Agent agent = new(sum); // This works
    io:println(agent.run());
}

service on new http:Listener(9090) {
    private final Agent agent;

    function init() {
       self.agent = new([sum]);
    }

    resource function get .() returns ToolConfig|error {
        return self.agent.run();
    }
}

The issue is also reproducible when the agent defined as a field in service class.

Affected Version(s)

No response

OS, DB, other environment details and versions

No response

Related area

-> Runtime

Related issue(s) (optional)

No response

Suggested label(s) (optional)

No response

Suggested assignee(s) (optional)

No response

[MaryamZi]

For different function pointers referring to the same function we have different BFunctionTypes (annotations are bound the type atm) and therefore, we set the annotations whenever an FPValue is created - codegen to io.ballerina.runtime.internal.utils.AnnotationUtils#processFPValueAnnotations. Here, the annotation map isn't populated when processFPValueAnnotations is called for the function pointer at module-level.

Related to the known ordering/typedesc + annotation resolution issue we have.