Notes from Book Sbt in Action
http://www.manning.com/suereth2/
Chapter 1
Maven concepts
Maven has set of lifecycles
Lifecycle
Phases
Goals ( Tasks in Ant)
Maven has following lifecycles
default ( build and deployment )
clean ( used to clean )
site ( used for documentation )
Each phase can have number of goals
Phases are executed in sequence
All previous phases ( and goals ) are executed if you call some phase
You can assign goals to phases via plugins goals
e.g Maven syntax
SBT is better for
Type safety
Ease of making new tasks
Test and development features for incremental builds
SBT concepts
Sbt just has tasks
Tasks can have dependency with each other.
Tasks with no dependency are executed in parallel
Tasks output can be passed on to next output
Settings
Settings are values ( e.g ) Project name
Plugins
If something is reusable tasks which is done again and again in different projects , we can abstract it as plugin.
This plugin can be used in different projects and can be sourced by build file of projects.
Chapter 2
Download and add sbt to your path
http://www.scala-sbt.org/download.html
Every project using sbt should have two files:
• project/build.properties
• build.sbt
build.properties tell which version of sbt to use
build.sbt tells which all settings are applicable for this project , including the library dependencies
start sbt by typing sbt at command prompt
After sbt starts , you can see the help by typing
> help
This will show all of the help topics
> help
help Displays this help message or prints detailed help on requested commands (run 'help <command>').
about Displays basic information about sbt and the build.
tasks Lists the tasks defined for the current project.
settings Lists the settings defined for the current project.
reload (Re)loads the project in the current directory
projects Lists the names of available projects or temporarily adds/removes extra builds to the session.
project Displays the current project or changes to the provided `project`.
set [every] <setting> Evaluates a Setting and applies it to the current project.
session Manipulates session settings. For details, run 'help session'.
inspect [uses|tree|definitions] <key> Prints the value for 'key', the defining scope, delegates, related definitions, and dependencies.
<log-level> Sets the logging level to 'log-level'. Valid levels: debug, info, warn, error
; <command> (; <command>)* Runs the provided semicolon-separated commands.
~ <command> Executes the specified command whenever source files change.
last Displays output from a previous command or the output from a specific task.
last-grep Shows lines from the last output for 'key' that match 'pattern'.
export <tasks>+ Executes tasks and displays the equivalent command lines.
exit Terminates the build.
--<command> Schedules a command to run before other commands on startup.
show <key> Displays the result of evaluating the setting or task associated with 'key'.
> tasks
This will show which all tasks are defined for this project
> settings
This will show which all settings are applicable for this project
For example which is sScalaversion etc
> settings
This is a list of settings defined for the current project.
It does not list the scopes the settings are defined in; use the 'inspect' command for that.
autoCompilerPlugins If true, enables automatically generating -Xplugin arguments to the compiler based on the classpath for the plugin configuration.
autoScalaLibrary Adds a dependency on scala-library if true.
baseDirectory The base directory. Depending on the scope, this is the base directory for the build, project, configuration, or task.
classDirectory Directory for compiled classes and copied resources.
crossPaths If true, enables cross paths, which distinguish output directories for cross-building.
fork If true, forks a new JVM when running. If false, runs in the same JVM as the build.
initialCommands Initial commands to execute when starting up the Scala interpreter.
javaHome Selects the Java installation used for compiling and forking. If None, uses the Java installation running the build.
javaSource Default Java source directory.
libraryDependencies Declares managed dependencies.
managedResourceDirectories List of managed resource directories.
maxErrors The maximum number of errors, such as compile errors, to list.
name Project name.
offline Configures sbt to work without a network connection where possible.
organization Organization/group ID.
publishArtifact Enables (true) or disables (false) publishing an artifact.
publishTo The resolver to publish to.
resourceDirectory Default unmanaged resource directory, used for user-defined resources.
scalaHome If Some, defines the local Scala installation to use for compilation, running, and testing.
scalaSource Default Scala source directory.
scalaVersion The version of Scala used for building.
sourceDirectories List of all source directories, both managed and unmanaged.
sourceDirectory Default directory containing sources.
target Main directory for files generated by the build.
unmanagedBase The default directory for manually managed libraries.
unmanagedResourceDirectories Unmanaged resource directories, containing resources manually created by the user.
unmanagedSourceDirectories Unmanaged source directories, which contain manually created sources.
version The version/revision of the current module.
More settings may be viewed by increasing verbosity. See 'help settings'.
> settings name
Project name.
More settings may be searched by increasing verbosity. See 'help settings'.
> settings scalaVersion
The version of Scala used for building.
More settings may be searched by increasing verbosity. See 'help settings'.
> name
[info] learn_sbt
> scalaVersion
[info] 2.10.3
>
Starting Scala console
> console
This will start scala console where you can run scala code
> scala
To exist the scala console type
:q
If you change build.sbt ( or Build.scala) you have to reload the settings using
> reload
To run tests
> test
To continuously run tasks
Prefix them by ~
e.g
> ~comple
This will keep on compiling code with each change
Auto completion works in sbt
> test<TAB>
This will show set of possible options with tasks similar to test
To run only particular test in sbt
> testOnly <TESTNAME>
Chapter 8
When sbt reads your project description,
it reads the .sbt files in the root directory,
the .sbt files in /project and
.scala files in /project.
It compiles everything that it finds and this gives you your build definition. sbt then runs this build and creates your artifact, your jar or whatever.
Difference between dependency and plugin
A plugin is simply a jar which contains settings or tasks. The jar contains a definition
file which sbt reads to work out what settings and tasks are available.
To include a plugin in your build, add the following lines to project/plugins.sbt:
project/plugins.sbt
addSbtPlugin("org.scalastyle" %% "scalastyle-sbt-plugin" % "0.4.0")
resolvers += "sonatype-releases" at
"https://oss.sonatype.org/content/repositories/releases/"
Repositories of plugins and dependeicies are different from each other , it means If you've a repository which contains both plugins and dependencies of your artifact, you'll need to include in both project/plugins.sbt and build.sbt.
Version
When sbt resolves the plugin, it appends both the scala version and the sbt version. But the
appended scala version number is not the scala version that you've declared in the build.sbt,
but the version of scala which is used by sbt.
Example
build.sbt
scalaVersion := "2.9.2"
and you are running sbt version 0.13, then the version appended by addSbtPlugin will be
2.10, not 2.9.2, because sbt 0.13 uses version 2.10 of scala. Similarly, if you are running
sbt version 0.12 and you have scalaVersion := "2.10", then the version appended will be
2.9.
Create your own plugin
Define the code in
project/MyPlugin.scala
In build.sbt
Declare the plugin
Call the plugin defined in project/MyPlugin.scala
Credentials
To add credentials for some repo
Use the file
$HOME/.sbt/0.13/credentials.sbt
