Overview of Ballerina 0.991.0

Ballerina 0.991.0 consists of improvements to the language syntax and semantics based on the language specification and new features and improvements to the standard library modules, extensions, and tooling.

Highlights

Improved error handling with new checkpanic expression. Now, error values cannot be ignored using "_".
Improved type checking with the union type.
Improved syntax for the closed record, closed arrays, and string/XML interpolation etc.
Additionally, this release includes several fixes to address Ballerina language specification deviations from the Ballerina 0.990 specification.

Breaking Language Changes

Closed record syntax was updated to use the {| and |} delimiters to indicate that the record is closed.

Previous syntax

type Person record {
    string name;
    int age;
    !...;
};

New syntax

type Person record {|
    string name;
    int age;
|};

The syntax for destructure binding pattern for closed records was also updated to use the {| and |} delimiters.

Previous syntax

Person p = { name: "John Doe", age: 25 };
Person { name: pName, age: pAge, !... } = p;

New syntax

Person p = { name: "John Doe", age: 25 };
Person {| name: pName, age: pAge |} = p;

The syntax for closed arrays with inferred length was changed as follows.

Previous syntax

string[!...] array = ["a", "b", "c"];

New syntax

string[*] array = ["a", "b", "c"];

It is now mandatory for list element types to have an implicit initial value. Where a type T does not have an implicit initial value, a T?[] could be used.
Use of the null literal is now restricted to JSON contexts.

json response = null; // Allowed
string? name = null; // Compile error

String template expression interpolation syntax was updated.

Previous syntax

string s = string `Hello {{name}}!`;

New syntax

string s = string `Hello ${name}!`;

XML literal interpolation syntax was updated.

Previous syntax

xml x = xml `<Person name={{name}}>{{content}}</Person>`;

New syntax

xml x = xml `<Person name=${name}>${content}</Person>`;

Interpolating XML elements and attribute names are no longer supported.
The XML attribute expression now directly returns the attributes of a singleton xml element as a map<string> or () if the operand is not a singleton xml.

Previous syntax

map<anydata> attributeMap = map<anydata>.convert(x1@);

New syntax

map<string>? attributeMap = x1@;

Error values can no longer be ignored using “”. If the result of an expression is an error type or is a union that contains an error type, the result cannot be ignored using “”. This is to enforce the user to handle all possible errors.
The capability to consider (run) any public function as an entry point to a Ballerina program was removed.
The types of the parameters and the return type of the main function were restricted to subtypes of anydata and error? respectively.
The diamond operator was updated to perform type-casting as follows:

Foo f = <Foo> value;

If value belongs to Foo, casting will be successful and value will be assigned to f. Else, casting will result in a panic.

The type of the error detail is now restricted to be a mapping that could only have fields of types that are subtypes of anydata|error.
The default record rest field type was changed to anydata|error from anydata.
anydata was updated to include structures of pure values (values whose types are subtypes of anydata|error). anydata is now the union of the following:

() | boolean | int | float | decimal | string | (anydata|error)[] | map<anydata|error> | xml | table

Module variable declarations are not allowed to be public now and also require an assignment.
The syntax for functions with external implementations has been changed as follows:

Previous syntax

extern function externFunction();

New syntax

function externFunction() = external;

The signature of the __attach() method of AbstractListener has been changed as follows:

Previous signature

public function __attach(service s, map<any> annotationData) returns error?

New signature

public function __attach(service s, string? name = ()) returns error?;

Type narrowing does not apply to global variables now.

Breaking Standard Library Changes

Crypto Library Changes

Ballerina crypto stdlib was made flexible enough to introduce new features and algorithms in future.

Previous syntax

string input = "Hello Ballerina";
crypto:hash(input, crypto:MD5)

New syntax

string input = "Hello Ballerina";
byte[] inputArr = input.toByteArray("UTF-8");
byte[] output = crypto:hashMd5(inputArr);

gRPC Library Changes

Ballerina gRPC client initialization in the generated code is changed. Generated file(*.pb.bal) from previous versions of Ballerina distributions will not be worked with this release. Regenerate the client stub using proto to Ballerina tool and replace the previously generated file with the new one.

Task Library Changes

Redesigned the Task library to function as a service. The previous task implementation of task:Timer and task:Appointment will be deferred and new task:Listener and task:Scheduler objects are introduced to create task timers and appointments.

Tasks now can be defined as a service and as an object. Both the previously existed Timer and Appointment functionalities can be used by new Listener and/or Scheduler.

Timer

Timer was previously created by providing onTrigger and onError functions along with the interval and delay parameters. Now interval and delay parameters are provided through a task:TimerConfiguration record type, while onTrigger function should be implemented as a resource function inside the attaching service. Service can be created on top of a task:Listener or can be manually attached to a task:Scheduler object.

Previous Syntax

function startTimer() {
    ((function) returns error?) onTriggerFunction = cleanup;
    function (error) onErrorFunction = cleanupError;
    timer = new task:Timer(onTriggerFunction, onErrorFunction, 1000, delay = 500);
    timer.start();
}

function cleanup() returns error? {
    // onTriggerFunction
}

function cleanupError(error e) {
    // handle error
}

New Syntax

function startTimer() {
    task:TimerConfiguration timerConfiguration = {
        interval: 1000,
        initialDelay: 500
    }
    task:Scheduler timer = new(timerConfguration);
    var attachResult = timer.attach(timerService);
    if (attachResult is error) {
        // handle error
    } else {
        var startResult = timer.start();
        if (startResult is error) {
            // handle error
        } else {
            // successfully started timer
        }
    }
}

Service timerService = service {
    resource function onTrigger() {
        // onTrigger function
    }
}

task:TimerConfiguration timerConfiguration = {
   interval: 1000,
   initialDelay: 3000
};
listener task:Listener timer = new(timerConfiguration);
Service timerService on timer {
    resource function onTrigger() {
        // onTrigger function
    }
}

Appointment

task:Appointment functionality can be implemented using task:Listener and the task:Scheduler objects. Previously the cronExpression used for the appointment given as a parameter, along with the onTrigger and onError functions. Now the cronExpression should be provided using appointmentDetails field inside the task:AppointmentConfiguration record type. Alternatively, task:AppointmentData record can also be provided as the appointmentDetails field (see below examples). onTrigger function should be implemented inside a service, and the service can be created on top a task:Listener or the service can be attached to a task:Scheduler object, manually.

Previous Syntax

function startAppointment() {
    ((function) returns error?) onTriggerFunction = cleanup;
    function (error) onErrorFunction = cleanupError;
    appointment = new task:Appointment(onTriggerFunction, onErrorFunction, "0/2 * * * * ?");
    appointment.schedule();
}

function cleanup() returns error? {
    // onTrigger function
}

function cleanupError(error e) {
    // handle error
}

New Syntax

task:AppointmentData appointmentData = {
    seconds: "0/2",
    minutes: "*",
    hours: "*",
    daysOfMonth: "?",
    months: "*",
    daysOfWeek: "*",
    year: "*"
};

task:AppointmentConfiguration appointmentConfiguration = {
    appointmentDetails: appointmentData
};

listener task:Listener appointment = new(appointmentConfiguration);

service appointmentService on appointment {
    resource function onTrigger() {
        // onTriggerFunction
    }
}

function startAppointment() {
    task:AppointmentConfiguration appointmentConfiguration = {
        appointmentDetails: “0/2 * * * * ?”
    };
    task:Scheduler appointment = new(appointmentConfiguration);
    var attachResult = appointment.attach(appointmentService);
    if (attachResult is error) {
        // handle error
    } else {
        var startResult = appointment.start();
        if (startResult is error) {
            // handle error
        } else {
            // successfully started the appointment
        }
    }
}

service appointmentService = service {
    resource function onTrigger() {
        // onTrigger function
    }
}

Time Library Changes

The format, parse, createTimeand toTimeZone functions are changed to return errors when there is an issue.

Previous Syntax

time:Time timeVal = time:parse("2016-03-01T09:46:22.444", yyyy-MM-dd'T'HH:mm:ss.SSS");

New Syntax

time:Time|error timeVal = time:parse("2016-03-01T09:46:22.444", yyyy-MM-dd'T'HH:mm:ss.SSS");

What's new in Ballerina 0.991.0

Language & Runtime

Introduction of the checkpanic unary expression
- checkpanic is a unary expression that is used to handle errors. The checkpanic expression checks the result of the sub-expression and panics if the result is error.
- The only difference between the checkpanic expression and the check expression is that, if the result of the sub-expression is of type error, the checkpanic expression results in a panic while the check expression returns the error value.
Error values can now be destructured using binding patterns and typed binding patterns as follows,

// Usage of error typed binding pattern.
var error (reasonString, detailMap) = getErrorValue();

// Usage of error binding pattern.
string reasonString;
map<anydata|error> detailMap;
error (reasonString, detailMap) = getErrorValue();

Value equality checks (==, !=) are now allowed with error values.
The return signature of the initializer of an object can now be error? (sub types of error allowed) or ().

type Person object {
    string name;

    function __init(string name) returns error? {
        self.name = check fnWithPotentialErrorReturn(name);
    };
}

// Usage
Person|error person = new("John Doe");

Tuple type is now iterable via the foreach statement.
Patterns in the static value match statement now support const values.
String can concatenate into XML values and the string part is automatically converted to an XML character sequence, resulting in XML concatenation. This supports both '+' and '+=' operators.

xml xValue = xml `<name>John</name>`;
xml yValue = xValue + "suf";
yValue += "fix";
io:println(yValue);

Standard Library

Introduced NATS connector.
Introduced Artemis connector.
Introduced RabbitMQ connector.
Introduced OAuth2 password grant type and client credentials grant type along with the direct token mode for outbound authentication.
Added support for password hashing techniques for basic auth authentication.
Introduced filepath module with a set of utility functions to manipulate the file path in a way that is compatible with the target operating system.
Introduced an "encoding" API to perform byte[] to string conversions using different encoding mechanisms.
Introduced RSA and AES encryption/decryption capabilities to the crypto API.
Introduced RSA signing operations to the crypto API.
Improved h2/mysql/jdbc database clients to share a single, global connection pool for interacting with the same database with same connection properties. The option to use an unshared or a locally shared custom pool is provided.
Introduced a shared global connection pool for HTTP client connectors. Per-client pools are also possible with http:PoolConfiguration.
Improved the HTTP/2 client connection pool to distribute the request load among I/O threads properly.

IDEs & Language Server

The Language Server Extension API to contribute custom completions.
Improvements to the Go-To definition, Find all references and Rename features.
Diagram view function collapsing capability. This feature allows you to expand functions in a sequence diagram to view its internal logic.

IDEA Plugin

Improved performance, stability, and reduced plugin size with “Lsp4IntelliJ” language client support.
Ballerina language server-based code formatting.
Minor bug fixes and improvements.

Compiler Extensions

Support for generating OpenShift artifacts.

Performance Results

See Ballerina performance test results, which is available in the repository.

Bug Fixes

See Github milestone issues to view bug fixes.

Getting Started

You can download the Ballerina distributions, try samples, and read the documentation at https://ballerina.io. You can also visit Quick Tour to get started.

We encourage you to report issues, improvements, and suggestions at the Ballerina Github Repository.

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Overview of Ballerina 0.991.0

Highlights

Breaking Language Changes

Breaking Standard Library Changes

Crypto Library Changes

gRPC Library Changes

Task Library Changes

Timer

Appointment

Time Library Changes

What's new in Ballerina 0.991.0

Language & Runtime

Standard Library

IDEs & Language Server

IDEA Plugin

Compiler Extensions

Performance Results

Bug Fixes

Getting Started