Add alternate receive bbe

[poorna2152]

Purpose

$subject

Part of ballerina-platform/ballerina-dev-website#8856

[MaryamZi]

Is the "error is not an expected static type" part correct?

Also, with

import ballerina/io;
import ballerina/lang.runtime;

public function main() {
    worker w4 returns error? {
        int value = 10;
        if value == 10 {
            return error("Error in worker 1");
        }
        value -> w6;
    }

    worker w5 returns error? {
        runtime:sleep(2);
        boolean b = true;
        if b {
            return error("x");
        }
        3 -> w6;
    }

    worker w6 returns int|error? {
        // Alternate receive action waits until a message that is not an error is received 
        // when error is not an expected static type. Since `w4` returns an error it 
        // waits further and sets the value that is received from `w5`.
        int|error a = <- w4 | w5;
        return a;
    }

    int|error? valueW6 = wait w6;
    io:println(valueW6);
}

when error is in the expected type, we still wait for the second error?

@lochana-chathura

[lochana-chathura]

when error is in the expected type, we still wait for the second error?

I think no.

@HindujaB can u confirm the behavior here?

[HindujaB]

Currently, we don't evaluate the error return type when passing the message.
The alternate wait will wait until a message that is not an error is received. Or if errors are received in all the channels, then the result is the last such error.
In the above case, the int|error a = <- w4 | w5; will return error("x").

[lochana-chathura]

when error is in the expected type, we still wait for the second error?

I think no.

@HindujaB can u confirm the behavior here?

[lochana-chathura]

LGTM

[lochana-chathura]

LGTM

[MaryamZi]

Suggested change

	function fetch(string url) returns json|error {
	http:Client cl = check new (url);
	map<json> payload = check cl->get("");
	return payload["args"];
	}
	function getJsonProperty(json|error data) returns json|error? =>
	data is error ? data.message() : data.'worker;
	function fetch(string url) returns map<json>|error {
	http:Client cl = check new (url);
	record {| map<json> args; |} payload = check cl->/;
	return payload.args;
	}
	function getJsonProperty(map<json>|error data) returns json|error =>
	data is error ? data.message() : data.'worker;

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[github-actions]

This PR has been open for more than 15 days with no activity. This will be closed in 3 days unless the stale label is removed or commented.

[github-actions]

This PR has been open for more than 15 days with no activity. This will be closed in 3 days unless the stale label is removed or commented.