Capture snippets

It is possible to include pieces of code in your documentation with the org.specs2.specification.Snippets trait using the snippet method to capture a block code with marker comments to delimit the parts you want to show.

What does this look like?

Snippet

Here is an example of using the snippet method:

s2"""
This is a multi-line string with a code snippet: ${ snippet {
def factorial(n: Int): Int = if (n == 1) n else (n * factorial(n - 1))
factorial(3) == 6
}}
"""

When you use the snippet method, the reports will show:

This is a multi-line string with a code snippet:

def factorial(n: Int): Int = if (n == 1) n else (n * factorial(n - 1))
factorial(3) == 6

Cuts

Since snippets are compiled code, you might have to include many declarations, like imports or variables definitions to make the code compile. This can make your documentation more verbose than necessary so you can hide those definitions by delimiting the code to show with some comments of the form // 8<--:

s2"""
This is a snippet of code with one relevant line: ${ snippet {
// 8<--
def factorial(n: Int): Int = if (n == 1) n else (n * factorial(n - 1))
// 8<--
factorial(3) == 6
// 8<--
}}
"""

The snippet above will only show factorial(3) == 6. You can repeat this pattern several times:

s2"""
This is a snippet of code with 2 relevant lines: ${ snippet {
// 8<--
def factorial(n: Int): Int = if (n == 1) n else (n * factorial(n - 1))
// 8<--
factorial(3) == 6
// 8<--
val n = 4
// 8<--
factorial(n) == 24
}}
"""

This just displays:

factorial(3) == 6
factorial(n) == 24

Evaluation

By default the last value of a Snippet is not shown but you can display it with the eval method:

s2"""
This is a snippet of code with a result: ${ snippet {
factorial(3)
}.eval}
"""

This displays:

factorial(3)

> 6

Offsets

It is possible to adjust the margin of captured source code by adding or removing whitespace:

s2"""
This is a snippet of code with a negative offset to align the code to the border of the screen: ${ snippet {
   def factorial(n: Int): Int = if (n == 1) n else (n * factorial(n - 1))
   factorial(3)
}.offsetIs(-3)}
"""

This displays:

factorial(3)

Parameters

All of the settings above: cuts, offset,… are coming from an implicit SnippetParams object that is changing the behavior of the created Snippets. You can choose, for a given scope, to replace these parameters with other ones and simply shadow the default parameters with your own, for example to always evaluate the snippets results:

implicit def snippetParams[T]: SnippetParams[T] = SnippetParams(evalCode = true)

The parameters you can set are:

name	description
trimExpression	function that is trimming the expression from newlines or accolades
cutter	function to remove parts which must not be shown
asCode	function to render the resulting text (as Markdown for example)
prompt	function to display the evaluated result with a prompt
evalCode	boolean indicating if a snippet must be evaluated
verify	function checking the snippet value