XPrudence: The Prudence Customizer

The downloadable distribution of Prudence contains a ready-to-use prudence executable that is bundled with all the basic types, APIs, cache backends, renderers, and JST tags. However, if you want to extend Prudence then you’ll need to make a custom build of prudence with your plugins.

That’s what xprudence, which is also included in the distribution, is for.

It’s a rather simple program! It requires you to have Go installed, but otherwise has no dependencies. All it does is create custom builds of prudence.

Background

This necessity might seem strange to you if you’re familiar with web frameforks or indeed other platforms built on interpreted languages such as Python, Ruby, or Node.js’s JavaScript. In those cases your code would simply “pick up” any other code if it’s in the right path and you could use some kind of package manager (pip, gem, npm, etc.) to add libraries. Even Java, a compiled language, picks up JAR files on-the-fly and can install them using Maven.

But Go is different, in a good way. Instead of a mess of dependencies scattered all over your operating system, everything a Go program normally needs is in one executable. That’s just one single file that you need to distribute.

In recognizing this advantage, xprudence is inspired by xcaddy.

Note that Go does have support for plugins, which are dynamically-linked libraries provided as separate files. Unfortunately it’s limited to just a few platforms and breaks the straigtforward advantage of having just one executable.

Example

Here’s how you would build Prudence with the plugin example:

xprudence build -v --directory=examples/plugin

The first time you build it may take some time, but note that most of this time is spent downloading (and caching) the Go source code of the dependencies. The Go compiler/linker itself is very fast and subsequent builds will use the cached downloads.

A common flag to use with xprudence build is --directory, which you can specify several times to include all the plugin directories that you want to add to your build. These directories are Go modules and thus must have a go.mod file. The extension guide goes into more detail about their structure.

Or, you can use the --module flag to specify plugins as Go module names, which is useful if you keep your module code in a git repository. As is usual with Go modules, you can append a specific version or tag after a @.

Another useful flag is --replace, which lets you insert a replace directive.

To get help on the additional build flags:

xprudence build -h