=title module Zef::Utils::SystemQuery

=subtitle Utility subroutines for resolving declarative logic based dependencies

Synopsis

    use Zef::Utils::SystemQuery;
    my @depends = (
        {
            "name" => {
                "by-distro.name" => {
                    "mswin32" => "Windows::Dependency",
                    ""        => "NonWindows::Dependency"
                },
            },
        },
    );
    my @resolved-depends := system-collapse(@depends);
    say @resolved-depends.raku;
    # [{:name("Windows::Dependency")},]    # on windows systems
    # [{:name("NonWindows::Dependency")},] # on non-windows systems

Description

Provides facilities for resolving dependencies that use declarative logic.

Subroutines

sub system-collapse

our sub system-collapse($data)

Traverses an Array or Hash $data, collapsing the blocks of declarative logic and returns the otherwise same data structure.

Declarative logic current supports three main query forms:

# by-env-exists.$FOO - selects "yes" key %*ENV{$FOO} exists, else the "no" key
        "by-env-exists.FOO" : {
            "yes" : "Env::Exists",
            "no"  : "Env::DoesNotExists"
        }

# by-env.$FOO - selects the value of %*ENV{$FOO} as the key, else the "" key if there is no matching key
        "by-env.FOO" : {
            "SomeValue" : "Env::FOO::SomeValue",
            ""          : "Env::FOO::DefaultValue"
        }

# by-[distro|kernel|raku|vm].$FOO - selects the value of e.g. $*DISTRO.name as the key, else the "" key if there is no matching key
        # where $FOO is e.g. $*DISTRO.^methods (or $*KERNEL.^methods, $*RAKU.^methods, $*VM.^methods)
        "by-distro.name" : {
            "macosx" : "OSX::Dependency",
            ""       : "NonOSX::Dependency"
        }

Note that e.g. $*DISTRO.name (and thus the by-[distro|kernel|raku|vm].$FOO form) depends on potentially Raku backend specific stuff -- for instance libuv based backends would have similar e.g. $*DISTRO values, but on the JVM $*DISTRO.name might return "linux" when MoarVM returns "debian". When using this query form you will want to test on multiple systems.