spacemacs/layers/+lang/scala

Scala layer

• Description
  • Features:
• Layer Installation
• Backends
  • Ensime
  • Metals
• Scalastyle
  • Use Java doc-style
• Automatically show the type of the symbol under the cursor
• Automatically insert asterisk in multiline comments
• Automatically replace arrows with unicode ones
• Auto-start
• Key bindings

with

Description

This layer adds support for the Scala language to Spacemacs.

Features:

• Syntax highlighting
• Support for language backend. Either using ENSIME or Metals
• Auto-completion
• Syntax-checking
• Refactoring
• Incremental compilation
• Scala Repl
• Style linting
• Eldoc integration
• Test execution directly from Emacs
• Automatic replacement of ASCII arrows with unicode ones

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.

Then, you should modify your ~/.spacemacs to use the recommended Ensime version (Stable). Please add the following lines to dotspacemacs/user-init:

  (add-to-list 'configuration-layer-elpa-archives '("melpa-stable" . "stable.melpa.org/packages/"))
  (add-to-list 'package-pinned-packages '(ensime . "melpa-stable"))

Backends

The currently supported language backends are:

• scala-ensime (default)
• scala-metals

To set your choice of backend, configure the layer variable scala-backend.

  (setq-default dotspacemacs-configuration-layers
                '((scala :variables scala-backend 'scala-ensime))) ;or 'scala-metals

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, a gradle plugin and others (see ensime.org for a full list) to generate these files.

Installation instructions and usage can be found in the Java layer README.org.

Metals

Currently, you must manually install the metals server. It is possible to do so via coursier; the latest version can be built using the following commands:

  ./coursier bootstrap \
    --java-opt -Xss4m \
    --java-opt -Xms100m \
    --java-opt -Dmetals.client=emacs \
    org.scalameta:metals_2.12:0.5.1 \
    -r bintray:scalacenter/releases \
    -r sonatype:snapshots \
    -o /usr/local/bin/metals-emacs -f

You will then have the common LSP key bindings; see http://develop.spacemacs.org/layers/+tools/lsp/README.html#key-bindings for more details.

Scalastyle

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

To use scalastyle, it must be present as an executable in your PATH.

• OSX users: brew install scalastyle
• Linux, please see http://www.scalastyle.org/command-line.html

To test if scalastyle executable is in your path, run scalastyle in a new terminal, it should output something like:

  $ scalastyle
  scalastyle 0.8.0
  Usage: scalastyle [options] <source directory>
  ...

Finally, enable the syntax-checking layer and set the flycheck-scalastylerc variable to a valid location.

  (setq-default flycheck-scalastylerc "/usr/local/etc/scalastyle_config.xml")

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

Use Java doc-style

To enable java-doc-style, set the variable scala-indent:use-javadoc-style to t

  (setq-default dotspacemacs-configuration-layers '(
    (scala :variables scala-indent:use-javadoc-style t)))

Automatically show the type of the symbol under the cursor

To enable the feature ensime-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)))

Auto-start

If you prefer to have the backend start when you load a scala file, you can enable it with

  (setq-default dotspacemacs-configuration-layers '(
      (scala :variables scala-auto-start-backend t)))

Key bindings

All ensime key bindings are listed in the java layer README.org.