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Maximilian Wolff 1e5cdfeedc
[scala] Avoid depending on abandoned ensime backend 
Ensime seems to be finally dead, as ensime-mode is not longer
available on melpa. The same applies to ob-scala the package
which delivered scala support for org babel.

I have changed the layers default to metals and took care that
ensime is not tried to be installed until it is really selected
as a package.

In addition I have also fixed some smaller issues in the layer
which caused ensime specific settings to be forced even when
metals was selected as a backend.

I have also removed the not longer existing org-babel support
for scala as it requires ob-scala which in turn is based on ensime.

See https://github.com/hvesalai/emacs-scala-mode/issues/155 for details.
2020-03-12 23:59:31 +01:00

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#+TITLE: Scala layer
#+TAGS: general|layer|multi-paradigm|programming
[[file:img/scala.png]] with [[file:img/ensime.png]]
* Table of Contents :TOC_5_gh:noexport:
- [[#description][Description]]
- [[#features][Features:]]
- [[#layer-installation][Layer Installation]]
- [[#backends][Backends]]
- [[#metals][Metals]]
- [[#ensime][Ensime]]
- [[#installation-when-using-sbt][Installation when using SBT]]
- [[#installation-when-using-gradle][Installation when using Gradle]]
- [[#configuration][Configuration]]
- [[#usage][Usage]]
- [[#scalastyle][Scalastyle]]
- [[#use-java-doc-style][Use Java doc-style]]
- [[#automatically-show-the-type-of-the-symbol-under-the-cursor][Automatically show the type of the symbol under the cursor]]
- [[#automatically-insert-asterisk-in-multiline-comments][Automatically insert asterisk in multiline comments]]
- [[#automatically-replace-arrows-with-unicode-ones][Automatically replace arrows with unicode ones]]
- [[#auto-start][Auto-start]]
- [[#key-bindings][Key bindings]]
- [[#ensime-1][Ensime]]
- [[#search][Search]]
- [[#ensime-search-mode][Ensime Search Mode]]
- [[#sbt][sbt]]
- [[#typecheck][Typecheck]]
- [[#debug][Debug]]
- [[#errors][Errors]]
- [[#goto][Goto]]
- [[#print-and-yank-types][Print and yank types]]
- [[#documentation-inspect][Documentation, Inspect]]
- [[#server][Server]]
- [[#refactoring][Refactoring]]
- [[#tests][Tests]]
- [[#repl][REPL]]
* Description
This layer adds support for the Scala language to Spacemacs.
** Features:
- Syntax highlighting
- Support for language backend. Either using [[https://ensime.github.io/][ENSIME]] or [[https://scalameta.org/metals/][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.
* Backends
The currently supported language backends are:
- scala-metals
- scala-ensime (deprecated)
To set your choice of backend, configure the layer variable =scala-backend=.
#+BEGIN_SRC emacs-lisp
(setq-default dotspacemacs-configuration-layers
'((scala :variables scala-backend 'scala-metals))) ;or 'scala-ensime
#+END_SRC
** 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,
where =0.7.6= can be replaced with the current version of [[https://github.com/scalameta/metals/][Metals]]:
#+BEGIN_SRC bash
./coursier bootstrap \
--java-opt -Xss4m \
--java-opt -Xms100m \
--java-opt -Dmetals.client=emacs \
org.scalameta:metals_2.12:0.7.6 \
-r bintray:scalacenter/releases \
-r sonatype:snapshots \
-o /usr/local/bin/metals-emacs -f
#+END_SRC
You will then have the common LSP key bindings; see
[[https://github.com/syl20bnr/spacemacs/tree/develop/layers/%2Btools/lsp#key-bindings][LSP#key-bindings]] for more details.
** Ensime (deprecated)
This package is mainly unmaintained today and should only be used as a last resort.
[[https://ensime.github.io/][ENSIME]] provides IDE-like features, such as refactoring, incremental compilation
and project-wide type-checking.
You will also need to modify your =dotspacemacs/user-init= to pull the recommended Ensime
version (Stable):
#+BEGIN_SRC emacs-lisp
(add-to-list 'configuration-layer-elpa-archives '("melpa-stable" . "stable.melpa.org/packages/"))
(add-to-list 'package-pinned-packages '(ensime . "melpa-stable"))
#+END_SRC
ENSIME requires a configuration file at the root of each Scala project. It
provides an SBT plugin, a gradle plugin and others (see [[https://web.archive.org/web/20190427005241/https://ensime.github.io/build_tools/][ensime.org]] for a full
list) to generate these files.
*** Installation when using SBT
Find it with your favourite package manager, eg:
#+BEGIN_SRC shell
nix-env --install sbt
#+END_SRC
or refer to [[http://www.scala-sbt.org/download.html][the sbt installation instructions]].
*** Installation when using Gradle
Refer to the [[https://web.archive.org/web/20190324005432/http://ensime.github.io/build_tools/gradle/][Ensime installation instructions]] to install the =ensime-gradle=
plugin.
*** Configuration
Follow [[https://web.archive.org/web/20190417132406/http://ensime.github.io/build_tools/sbt/][the ENSIME configuration instructions]]. Spacemacs uses
the development version of Ensime so follow the appropriate steps.
To use the build functions under ~SPC m b~ you need to use version =0.13.5= or
newer of =sbt=, and specify that in your project's =project/build.properties=.
For example,
#+BEGIN_SRC scala
sbt.version=0.13.11
#+END_SRC
*** Usage
~SPC SPC spacemacs/ensime-gen-and-restart~ or ~SPC m D r~ generates a new config
for a project and starts the server. Afterwards ~SPC SPC ensime~ or ~SPC m D s~
will suffice do the trick.
* Scalastyle
[[http://www.scalastyle.org/][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=.
- macOS 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:
#+BEGIN_SRC bash
$ scalastyle
scalastyle 0.8.0
Usage: scalastyle [options] <source directory>
...
#+END_SRC
Finally, enable the =syntax-checking= layer and set the =flycheck-scalastylerc=
variable to a valid location.
#+BEGIN_SRC emacs-lisp
(setq-default flycheck-scalastylerc "/usr/local/etc/scalastyle_config.xml")
#+END_SRC
See the [[http://www.flycheck.org/en/latest/languages.html?highlight=scala#syntax-checker-scala-scalastyle][flycheck documentation]] and [[http://www.scalastyle.org/configuration.html][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=
#+BEGIN_SRC emacs-lisp
(setq-default dotspacemacs-configuration-layers '(
(scala :variables scala-indent:use-javadoc-style t)))
#+END_SRC
* 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=.
#+BEGIN_SRC emacs-lisp
(setq-default dotspacemacs-configuration-layers '(
(scala :variables scala-enable-eldoc t)))
#+END_SRC
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=.
#+BEGIN_SRC emacs-lisp
(setq-default dotspacemacs-configuration-layers '(
(scala :variables scala-auto-insert-asterisk-in-comments t)))
#+END_SRC
* 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.
#+BEGIN_SRC emacs-lisp
(setq-default dotspacemacs-configuration-layers '(
(scala :variables scala-use-unicode-arrows t)))
#+END_SRC
* Auto-start
If you prefer to have the backend start when you load a scala file, you can enable it
with
#+BEGIN_SRC emacs-lisp
(setq-default dotspacemacs-configuration-layers '(
(scala :variables scala-auto-start-backend t)))
#+END_SRC
* Key bindings
** Ensime
*** Search
| Key binding | Description |
|-------------+-----------------------------------------------------|
| ~SPC m /~ | incremental search using =ensime-scalex= major mode |
| ~SPC m ?~ | incremental search in all live buffers |
*** Ensime Search Mode
| Key binding | Description |
|-------------+-------------------------------------------------------------------|
| ~C-j~ | Move to next match |
| ~C-k~ | Move to previous match |
| ~C-i~ | Insert at point import of current result |
| ~RET~ | Jump to the target of the currently selected ensime-search-result |
| ~C-q~ | Quit ensime search |
*** sbt
| Key binding | Description |
|-------------+---------------------|
| ~SPC m b .~ | sbt transient state |
| ~SPC m b b~ | sbt command |
| ~SPC m b c~ | compile |
| ~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 |
*** 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 i~ | inspect value at point |
| ~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 s~ | switch to buffer containing the stack trace parser |
*** Goto
| Key binding | Description |
|-------------+------------------|
| ~SPC m g g~ | go to definition |
*** Print and yank types
|-------------+--------------------------------|
| ~SPC m h T~ | print full type name at point |
| ~SPC m h t~ | print short type name at point |
| ~SPC m y T~ | yank full type name at point |
| ~SPC m y t~ | yank short type name at point |
*** 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 |
*** Server
| Key binding | Description |
|-------------+--------------------------------------------------------|
| ~SPC m D f~ | reload open files |
| ~SPC m D r~ | regenerate the =.ensime= and restart the ensime server |
| ~SPC m D s~ | start ensime server |
*** Refactoring
| Key binding | Description |
|-------------+----------------------------------------------------------------------|
| ~SPC m r a~ | add type annotation |
| ~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= |
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