Add a dash of awesome to your SBT shell prompt

If you're anything like me, you probably spent just as much, if not more, time in the SBT shell as you do in your normal shell. So why not make it look just as awesome?

This is the plugin for you if you would like to have a fancy SBT prompt but you don't feel like spending the same insane amount of time as me researching ANSI color escape codes and SBT internals. All you have to do is pick one of the existing prompt themes or, if they're not awesome enough, just use an easy mini-DSL to create your own custom theme.

Here's an example of the "Scalapenos" prompt theme, which I created to exactly match my zsh prompt (which is why this plugin was built):

That example prompt consists of three promptlets:

• a label to indicate that we are in the SBT shell
• the current Git branch name and whether the branch is clean (green) or dirty (yellow)
• the current sbt project and, if applicable, subproject.

All promptlets can be styled with foreground and background colors and you can customize them even further with prefixes, suffixes, and other text transformers. See below for all customization options.

Getting Started

You will need to be using SBT 0.13.5 or higher for this plugin to work correctly. It was created for SBT 0.13.6 and has been tested with every public release of SBT since (up to and including 0.13.16, 1.0.0, and 1.0.1).

Add the following line to your plugins.sbt file (or ~/.sbt/0.13/plugins/plugin.sbt/~/.sbt/1.0/plugins/plugin.sbt to enable it for all projects):

addSbtPlugin("com.scalapenos" % "sbt-prompt" % "1.0.2")

For normal build.sbt projects, this will automatically enable the default prompt theme, which looks like this (green for a clean Git repo, yellow for a dirty one):

If you want to use one of the existing themes, like the "Scalapenos" theme shown at the top of this README, just add the following import and setting to your build.sbt file (or to any sbt file in ~/.sbt/0.13//~/.sbt/1.0/):

import com.scalapenos.sbt.prompt.SbtPrompt.autoImport._

promptTheme := com.scalapenos.sbt.prompt.PromptThemes.ScalapenosTheme

Note: The Scalapenos theme uses some fancy unicode symbols as separators but these are not usually supported by the average console font. You will need to configure your terminal with a Powerline-patched font or things will look a bit weird.

If you are using a Build.scala definition or when using custom themes, please add these alternative imports:

import com.scalapenos.sbt.prompt._
import SbtPrompt.autoImport._

The source code contains a number of small, self-contained example projects that show you how to enable the plugin with the default theme, how to enable the Scalapenos theme, and how to configure a custom theme.

Customization

Writing your own prompt theme is prety easy. Let's start with some definitions.

Definitions

A prompt theme is a sequence of so-called promptlets that together represent the entire prompt.

A promptlet is a function that takes the current project State and produces some styled text.

Styled text is some static text combined with a style.

A style is a combination of a foregound color and a background color with a little builder API for combining two colors into a style.

A color is a little wrapper around a color code from the ANSI 256 color space (i.e. a number from 0 up to and including 255) plus the ability to produce the correct escape codes for rendering themselves to any terminal configured to emulate xterm-256color (or one compatible with it). There is a handy list of links to color references at the bottom of this README.

Advanced prompt themes, like the builtin Scalapenos theme, might want to create some kind of styled transition between promptlets based on their separate styles. To enable this, a prompt theme can be configured with an optional separator, which is a function that takes the styled output of two promptlets to produce some styled text that will be rendered in between those two promptlets.

Available promptlets

The list of builtin promptlets is relatively small but it should cover all the basics.

Promplet: currentProject(style)

Renders the current project name, including the current sub-project when applicable. Example:

currentProject(fg(green))

Promplet: gitBranch(cleanStyle, dirtyStyle)

Renders the current Git branch name, with configurable styles for clean and dirty states. Example:

gitBranch(clean = fg(green), dirty = fg(red))

If the current project is not a Git repository, this promptlet will produce StyledText.Empty.

Promplet: gitPromptlet(render: Option[GitInfo] ⇒ StyledText)

The more powerful form of gitBranch, which lets you use more specific Git status information to produce some styled text. If the current project is not a Git repository, the Option[GitInfo] parameter to the render function will be None.

The available Git information is encoded in these two case classes:

case class GitInfo(branch: String, status: GitStatus)
case class GitStatus(nrModified: Int, nrUntracked: Int) {
  val dirty = nrModified > 0 || nrUntracked > 0
}

The gitBranch promptlet is built using gitPromptlet:

def gitBranch(clean: Style = NoStyle, dirty: Style = NoStyle): Promptlet = gitPromptlet {
  case Some(git) ⇒ StyledText(git.branch, if (git.status.dirty) dirty else clean)
  case None      ⇒ StyledText.Empty
}

Promptlet: currentScalaVersion(style)

Renders the current scala version in the project. Example:

currentScalaVersion(fg(red))

Promptlet: currentSbtVersion(style)

Renders the current SBT version. Example:

currentSbtVersion(fg(26))

Promptlet: currentSbtKey(settingKey, style)

Renders the current value for the SBT key. Example:

currentSbtKey(version, fg(26))

That will generate a promptlet with the current version of the project. In fact, currentScalaVersion and currentSbtVersion are short-hands for currentSbtKey(scalaVersion) and currentSbtKey(sbtVersion).

Promplet: hostName(style)

Renders the current system hostname. Example:

hostName(fg(blue))

Promplet: userName(style)

Renders your current system username. Example:

userName(fg(white).bg(blue))

Promplet: text(text: String, style)

Renders the specified static text. Example:

text(fg(235).bg(26)) // using raw ANSI 256 color codes

Promptlet: text(text: State ⇒ String, style)

Allows you to extract whatever information you want from the current project State and render it as dynamic text every time the prompt gets re-drawn.

As an example, this is how the projectName promptlet is implemented:

def currentProject(style: Style = NoStyle): Promptlet = text(state ⇒ {
  val extracted = Project.extract(state)
  val project = extracted.currentRef.project
  val root = extracted.rootProject(extracted.currentRef.build)

  if (project == root) project else s"${root}/${project}"
}, style)

Post-processing styled text with mapText

Sometimes you want to take an existing promptlet like gitBranch and add some extra text to it in the same style. Enter the mapText(String ⇒ String) function, available on all promptlets, which allows you to post-process the raw text any way you want. For your convenience some common post-processors like padLeft and padRight have alrady been defined.

Example:

gitBranch(clean = fg(green), dirty = fg(yellow)).mapText(_.toUpperCase).padLeft("[").padRight("]")

Combining promptlets into a theme

To define a theme you simply call its apply method with a sequence of promptlets and an optional separator. Here's a few examples:

The default theme

PromptTheme(List(
  gitBranch(clean = fg(green), dirty = fg(yellow)).padLeft("[").padRight("] "),
  currentProject(),
  text(": ", NoStyle)
))

A custom theme

PromptTheme(List(
  text("[SBT] ", fg(green)),
  userName(fg(26)),
  text("@", fg(green)),
  hostName(fg(26)),
  text(" on ", fg(red)),
  gitBranch(clean = fg(green), dirty = fg(yellow)),
  text(" in ", fg(red)),
  currentProject(fg(magenta)),
  text(" ⇒  ", fg(red))
))

The Scalapenos theme

The Scalapenos theme uses a separator and some fancy unicode symbols that are not supported by your average font. You will need to configure your terminal with a Powerline-patched font.

PromptTheme(
  List(
    text(" SBT ", fg(235).bg(26)),
    gitBranch(clean = fg(235).bg(34), dirty = fg(235).bg(214)).padLeft("  ").padRight(" "),
    currentProject(fg(250).bg(235)).pad(" "),
    text(" ", NoStyle)
  ),
  (previous, next) ⇒ StyledText("", fg(previous.style.background).bg(next.style.background))
)

Examples

• How to enable the plugin with the default theme
• How to enable the Scalapenos theme
• How to configure a custom theme

Questions, issues, pull requests, cool themes, etc.

Yes please!

Color references

• Graphical overview of the Ansi 256 color codes
• Ansi escape code reference

License

This plugin is licensed under the MIT license.