Improvements and New Features

The Ballerina 0.982.0 release includes new features, improvements and bug fixes including introduction of the new channel type, changes to the main function, improvements to records and objects, and support for HTTP 1.1 piplelining.

An initial version of the Ballerina Native feature that allows simple Ballerina programs with the main function to be compiled into native executables, is also introduced with this release.

Language & Runtime

Introduction of the Channel Type

The channel constrained type is introduced for communication between parallel processes in Ballerina programs. A channel can be defined only as a top level node. Channels can be used for message correlation by sending and receiving messages via different resources to the same channel. Channels can also be used for inter-worker communication and worker synchronization.

Defining a channel constrained by the json type

channel<json> jsonChannel; 

Sending a message to the channel

# One of the receivers waiting on `key` receives the message.
# If there is no receiver, the message is stored and execution continues.
# A receiver can arrive later and fetch the message.
message -> jsonChannel, key; 

Receiving a message from the channel with the given key

# Execution waits here if the message is not available.
json result <- jsonChannel, key;

Introduction of Abstract Objects

An abstract object is identified by the abstract keyword. Abstract objects only describe the type of each field and method, they do not describe the implementation of methods. An abstract object type should not have an object constructor method and cannot be initialized using the object initializer. Abstract objects do not have an implicit initial value.

public type Foo abstract object {
    public string name;
    public int id;

    function getName() returns string;

    function getID() returns int;
};

Introduction of Record Iteration Support

Records are now iterable, and the foreach statement and iterable operations can now be used with records. When iterating a record, one can either iterate over the fields (i.e., field name and value) or iterate only over the field values.

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

The foreach statement can be used with an instance of this record as follows:

foreach field, value in person {
    io:println(field + " : " + <string>value);
}

The foreach statement can be used to iterate only over the field values as follows:

foreach value in person {
    io:println(value);
}

Changes to the "main" Function

Based on the latest changes, the main function has to be marked public and can return an int.

Now it is also possible to execute ballerina run to invoke any public function in the entry package. For example, if you want to invoke the public function add in the calculator package, you can execute ballerina run and specify the integer arguments 4 and 5 as follows:

ballerina run calculator:add 4 5

If a function is not specified, main is considered as the function to run.

The function invoked via ballerina run (including the main function) will be data-binding and can have zero or more parameters of any supported type, including any number of required/defaultable parameters and a single rest parameter. This function can also return a value.

For example, consider the following public function in the package currency:

public function queryChanges(string host, int port = 8080, string… params) returns float {

}

Invoke the function using Ballerina run as follows:

ballerina run --printreturn currency:queryChanges localhost -port=8181 high day

The function invocation results in a value assignment as follows: - host"localhost" - port8181 - params["high", "day"]

When the --printreturn flag is set, the return value is printed to the standard out stream.

New Documentation Syntax

Old syntax:

documentation {
    Adds parameter `x` and parameter `y`.
    P{{x}} one thing to be added
    P{{y}} another thing to be added
    R{{}} the sum of them
}
function add(int x, int y) returns int { return x + y; }

New syntax:

# Adds parameter `x` and parameter `y`.
# + x - one thing to be added
# + y - another thing to be added
# + return - the sum of them
function add(int x, int y) returns int { return x + y; }

Reorder Documentation in Resources

In previous versions, documentation was added after annotation attachments of resources. Now documentation should be added before the annotation attachment.

Old syntax:

service<http:Service> update_token bind { port: 9295 } {

    @http:ResourceConfig {
        methods:["GET"]
    }
    # Updates the access token.
    #
    # + caller - Endpoint
    one_px_image(endpoint caller) {

    }
}

New syntax:

service<http:Service> update_token bind { port: 9295 } {

    # Updates the access token.
    #
    # + caller - Endpoint
    @http:ResourceConfig {
        methods:["GET"]
    }
    one_px_image(endpoint caller) {

    }
}

Changes to Record/Object Field Syntax

Old syntax:

type foo record {
    string a,
    string b,
};

type bar object {
    string a,
    string b,
};

New syntax:

type foo record {
    string a;
    string b;
};

type bar object {
    string a;
    string b;
};

New Anonymous Functions Syntax

The syntax of anonymous functions has been changed to resemble normal function definitions.

Old syntax:

var lambda = (int b) => (int) {
    int x = b * b;
    return x;
};

New syntax:

var lambda = function (int b) returns int {
    int x = b * b;
    return x;
};

A new "Arrow Function Expression" is introduced as a simple alternative to anonymous functions that only have a return statement as the body:

function (int, string) returns string lambdaVar = (param1, param2) => param2.toUpper();

Removal of Implicit Cast from int to float

Now it is necessary to explicitly define a float with a decimal point.

float x = 0; // Compile Error
float x = 0.0; // Working Code

Tracking Tainted State Changes of Function Parameters

The taint analyzer keeps track of the tainted state of parameters in different execution conditions. This information is used to update the tainted state of the arguments used in a function invocation, and to make sure that the tainted state is propagated correctly when the parameter is an out parameter or an in-out parameter.

Option/Param Order Enforcement with the Run Command

Option vs parameter ordering has been enforced with the Ballerina run command. All options now need to be specified before the file or package to run.

Any and all arguments specified after the file or package are now considered program arguments.

A config file can be specified with the run command as follows:

ballerina run --config myConfig.conf calculator 4 5

Specifying the --config argument as follows, after the package calculator would not result in it being identified as an option:

ballerina run calculator --config myConfig.conf 4 5

Ballerina Native

The Ballerina Native feature is the introduction of an LLVM-based backend for the Ballerina compiler. It allows Ballerina programs to be compiled into native executables.

Prerequisites

  • Unix based (Linux/MacOS) operating system to run the initial version. Other operating systems will be supported in future versions.
  • GCC compiler (it is possible to use clang or ld. However, the current recommended option is gcc)

Supported language constructs

  • main function (arguments are ignored)
  • int and boolean types
  • if condition
  • while loop
  • Function calls and return values
  • Partial support for println for int values

How to run

  • Build a Ballerina program with the native option ballerina build --native -o myballerinamain myballerinamain.bal

  • Run the created executable ./myballerinamain

Command line flags

The following additional options are valid when the --native option is provided: --dump-bir prints the Ballerina intermediate representation --dump-llvm-ir prints the LLVM intermediate representation assembly code

Standard Library

  • Support for HTTP 1.1 pipelining
  • Enhanced support for compression/decompression
  • Change of status code and reason to be optional parameters for the close action of the WebSocket endpoint
  • Support to directly configure SSL certificates and keys without keystores
  • Support to define enum type in gRPC request/response messages

Build & Package Management

Mandating Build on Ballerina Push and Install

By default, the sources are built before pushing the package to Ballerina Central and before installing the package in the home repository.

The --no-build flag could be used to skip building before pushing or installing.

ballerina push <package-name> --no-build
ballerina install <package-name> --no-build

Introduction of the Uninstall Command

Packages that are installed in the home repository can now be uninstalled or removed using the uninstall command.

ballerina uninstall <org-name>/<package-name>:<version>

IDE Plugins

  • Diagram editing support in VSCode
  • Language Server integration support in IDEA plugin: this results in providing all language intellisense support through the Language Server
  • Variable definition auto generation code action
  • Attached function’s implementation snippet
  • Object constructor auto generation code action

Extensions

Kubernetes

  • Support is now introduced for Helm Chart generation

Performance Results

From Ballerina 0.982.0 onward, a performance test result summary would also be made available with each release.

Bug Fixes

Please refer the GitHub milestone 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 the [Quick Tour] (https://ballerina.io/learn/quick-tour/) to get started. We encourage you to report issues, improvements, and suggestions at the Ballerina Github Repository.