spacemacs/layers/+lang/scala

Scala layer

• Description
• Layer Installation
• Ensime
  • Installation
  • Usage
• Scalastyle
• Automatically show the type of the symbol under the cursor
• Automatically insert asterisk in multiline comments
• Automatically replace arrows with unicode ones
• Key bindings
  • Ensime key bindings
    • Search
    • sbt
    • Typecheck
    • Debug
    • Errors
    • Goto
    • Documentation, Inspect
    • Server
    • Refactoring
    • Tests
    • REPL

with

Description

This layer adds support for the Scala language using the excellent ENSIME client/server.

Layer Installation

To use this configuration layer, add it to your ~/.spacemacs. You will need to add scala to the existing dotspacemacs-configuration-layers list in this file.

Ensime

ENSIME provides IDE-like features, such as refactoring, incremental compilation and project-wide type-checking.

ENSIME requires a configuration file at the root of each Scala project. It provides an SBT plugin to generate these files.

Installation

Configure the ENSIME sbt plugin by adding the following to ~/.sbt/0.13/plugins/plugins.sbt:

  addSbtPlugin("org.ensime" % "ensime-sbt" % "0.2.3")

Please go to ensime-sbt Github Page to check the latest version of ensime-sbt plugin.

Please note your projects' project/build.properties need to use a version newer that 0.13.5 of sbt.

  sbt.version=0.13.9

Usage

1. Create a .ensime file at the root of your Scala project using sbt gen-ensime at the shell.
2. Run M-x ensime within Emacs to start an ENSIME session.

Each Scala project uses a dedicated ENSIME session, so you only need to run M-x ensime once per project. Any Scala files you create or visit within the project will automatically use ENSIME for the remainder of your editing session.

Scalastyle

Scalastyle provides style-checking and linting. The Emacs functionality is provided by Flycheck.

To use scalastyle,

1. Download the scalastyle jar and put it somewhere sensible
2. Customise the flycheck-scalastyle-jar variable and set it to the path of the jar.

See the flycheck documentation for up-to-date configuration instructions.

Automatically show the type of the symbol under the cursor

To enable the feature ensime-print-type-at-point when cursor moves, set the variable scala-enable-eldoc to t.

  (setq-default dotspacemacs-configuration-layers '(
    (scala :variables scala-enable-eldoc t)))

Enabling this option can cause slow editor performance.

Automatically insert asterisk in multiline comments

To insert a leading asterisk in multiline comments automatically, set the variable scala-auto-insert-asterisk-in-comments to t.

  (setq-default dotspacemacs-configuration-layers '(
    (scala :variables scala-auto-insert-asterisk-in-comments t)))

Automatically replace arrows with unicode ones

To replace =>, -> and <- with unicode arrows ⇒, → and ←, set the variable scala-use-unicode-arrows to t.

If in some occasions you don't want the arrows replaced (for example when defining compound operators like =>>), you can always undo the change and get the ascii arrows back.

  (setq-default dotspacemacs-configuration-layers '(
    (scala :variables scala-use-unicode-arrows t)))

* Disable auto-start

If you prefer not to have Ensime start when you load a scala file, you can
disable it with

#+BEGIN_SRC emacs-lisp
(setq-default dotspacemacs-configuration-layers '(
    (scala :variables scala-auto-start-ensime nil)))

Key bindings

Ensime key bindings

Search

Key Binding	Description
SPC m /	incremental search using ensime-scalex major mode
SPC m ?	incremental search in all live buffers

sbt

Key Binding	Description
SPC m b c	compile command
SPC m b C	clean command
SPC m b i	switch to sbt shell
SPC m b p	package command
SPC m b r	run command

Typecheck

Key Binding	Description
SPC m c t	type check the current file
SPC m c T	type check all the open buffers

Debug

Key Binding	Description
SPC m d A	Attach to a remote debugger
SPC m d b	set breakpoint
SPC m d B	clear breakpoint
SPC m d C	clear all breakpoints
SPC m d c	continue
SPC m d d	start a debug session
SPC m d i	inspect value at point
SPC m d l	list local variables
SPC m d n	next
SPC m d o	step out
SPC m d q	quit
SPC m d r	run
SPC m d s	step
SPC m d t	backtrace

Note: These key bindings need a transient-state, PR welcome :-)

Errors

Key Binding	Description
SPC m e e	print error at point
SPC m e l	show all errors and warnings
SPC m e s	switch to buffer containing the stack trace parser

Goto

Key Binding	Description
SPC m g g	go to definition
SPC m g i	go to implementation
SPC m g t	go to test

Documentation, Inspect

Key Binding	Description
SPC m h h	show documentation for symbol at point
SPC m h u	show uses for symbol at point
SPC m h t	print type at point
SPC m i i	inspect type at point
SPC m i I	inspect type in other frame
SPC m i p	inspect project package
SPC m i y	yank type at point

Server

Key Binding	Description
SPC m n F	reload open files
SPC m n s	start ensime server
SPC m n S	regenerate the .ensime and restart the ensime server

Refactoring

Key Binding	Description
SPC m r a	add type annotation
SPC m r f	format source
SPC m r d	get rid of an intermediate variable (ensime-refactor-inline-local)
SPC m r D	get rid of an intermediate variable (ensime-undo-peek)
SPC m r i	organize imports
SPC m r m	extract a range of code into a method
SPC m r r	rename a symbol project wide
SPC m r t	import type at point
SPC m r v	extract a range of code into a variable
SPC m z	expand/contract region

Tests

Key Binding	Description
SPC m t a	test command (sbt)
SPC m t r	test quick command (sbt)
SPC m t t	test only (sbt)

REPL

Key Binding	Description
SPC m s a	ask for a file to be loaded in the REPL
SPC m s b	send buffer to the REPL
SPC m s B	send buffer to the REPL and focus the REPL buffer in insert state
SPC m s i	start or switch to the REPL inferior process
SPC m s r	send region to the REPL
SPC m s R	send region to the REPL and focus the REPL buffer in insert state