Halon 4.1 “teamy" with scripting modules


We shipped the 4.1 “teamy” release, and we’re happy to see that the majority of our users have already updated. The 4.0 release brought several major changes, and 4.1 includes many improvements to it. The web administration in general, and the script editor in particular, have received lots of attention. The new live staging functionality that was introduced in 4.0 now extends to queue (pre- and post-delivery) scripts as well, using the _stageid metadata field. You can employ even more aggressive caching now that the API includes a hslCacheClear() function, and we’re opened up a wide range of possibilities via the new setBody function in the DATA script’s MIME class, such as URL rewriting.

The most anticipated addition however, is a new language feature often referred to as modules. The Halon scripting language is highly email-centric. We strive towards keeping it as simple as possible, which is a great recipe for stability and high, predictable performance. At the same time, we’re designing it after the principle of least astonishment, and consequently it shares many characteristics with established languages. Having researched both namespaces (found in languages such as C++ and PHP) and modules (found in for example Python and Perl), we decided that modules was the best fit for our language and its users. It’s great when working in larger teams, since it introduces file-wide symbol (variable and function) scoping. Modules are regular script files, which becomes modules the moment you import them. It’s similar to include, except an imported file has its own scope. You explicitly choose which symbols to “import” to the parent file using the syntax

import { Foo as X, $bar as $y } from "test";

Variables are imported by reference, hence all changes to the variable in the module will be reflected by the imported variable. As modules have their own global scope, variables referenced in a module’s function by global or closure points at the module’s scope, as per the example below

$x = "hello";
function foo($bar) {
    global $x;
    echo $x;

imported by

import { foo } from "test";
$x = "world";
echo foo(function() closure ($x) { echo $x; });

which will echo


We hope that the modules concept will be helpful in both smaller and larger projects, and we promise that much more is to come as Halon 4.2 “classy” hits the servers.

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