Add linter for Scala Metals

https://scalameta.org/metals/

ale_linters/scala/metals.vim

@@ -0,0 +1,48 @@
+" Author: Jeffrey Lau - https://github.com/zoonfafer
+" Description: Metals Language Server for Scala https://scalameta.org/metals/
+
+call ale#Set('scala_metals_executable', 'metals-vim')
+call ale#Set('scala_metals_project_root', '')
+
+function! ale_linters#scala#metals#GetProjectRoot(buffer) abort
+    let l:project_root = ale#Var(a:buffer, 'scala_metals_project_root')
+
+    if !empty(l:project_root)
+        return l:project_root
+    endif
+
+    let l:potential_roots = [
+    \   'build.sc',
+    \   'build.sbt',
+    \   '.bloop',
+    \   '.metals',
+    \]
+
+    for l:root in l:potential_roots
+        let l:project_root = ale#path#ResolveLocalPath(
+        \   a:buffer,
+        \   l:root,
+        \   ''
+        \)
+
+        if !empty(l:project_root)
+            return fnamemodify(
+            \   l:project_root,
+            \   ':h',
+            \)
+        endif
+    endfor
+endfunction
+
+function! ale_linters#scala#metals#GetCommand(buffer) abort
+    return '%e' . ale#Pad('stdio')
+endfunction
+
+call ale#linter#Define('scala', {
+\   'name': 'metals',
+\   'lsp': 'stdio',
+\   'language': 'scala',
+\   'executable': {b -> ale#Var(b, 'scala_metals_executable')},
+\   'command': function('ale_linters#scala#metals#GetCommand'),
+\   'project_root': function('ale_linters#scala#metals#GetProjectRoot'),
+\})

doc/ale-scala.txt

@@ -2,6 +2,32 @@
 ALE Scala Integration                                       *ale-scala-options*
 
 
+===============================================================================
+metals                                                       *ale-scala-metals*
+
+`metals` requires either an SBT project, a Mill project, or a running Bloop
+server.
+
+
+g:ale_scala_metals_executable                    *g:ale_scala_metals_executable*
+                                                 *b:ale_scala_metals_executable*
+  Type: |String|
+  Default: `'metals-vim'`
+
+  Override the invoked `metals` binary.
+
+
+g:ale_scala_metals_project_root                *g:ale_scala_metals_project_root*
+                                               *b:ale_scala_metals_project_root*
+  Type: |String|
+  Default: `''`
+
+  By default the project root is found by searching upwards for `build.sbt`,
+  `build.sc`, `.bloop` or `.metals`.
+  If the project root is elsewhere, you can override the project root
+  directory.
+
+
 ===============================================================================
 sbtserver                                                 *ale-scala-sbtserver*
 

doc/ale-supported-languages-and-tools.txt

@@ -406,6 +406,7 @@ Notes:
   * `stylelint`
 * Scala
   * `fsc`
+  * `metals`
   * `sbtserver`
   * `scalac`
   * `scalafmt`

doc/ale.txt

@@ -2298,6 +2298,7 @@ documented in additional help files.
     sasslint..............................|ale-sass-sasslint|
     stylelint.............................|ale-sass-stylelint|
   scala...................................|ale-scala-options|
+    metals................................|ale-scala-metals|
     sbtserver.............................|ale-scala-sbtserver|
     scalafmt..............................|ale-scala-scalafmt|
     scalastyle............................|ale-scala-scalastyle|

supported-tools.md

@@ -415,6 +415,7 @@ formatting.
   * [stylelint](https://github.com/stylelint/stylelint)
 * Scala
   * [fsc](https://www.scala-lang.org/old/sites/default/files/linuxsoft_archives/docu/files/tools/fsc.html)
+  * [metals](https://scalameta.org/metals/)
   * [sbtserver](https://www.scala-sbt.org/1.x/docs/sbt-server.html)
   * [scalac](http://scala-lang.org)
   * [scalafmt](https://scalameta.org/scalafmt/)

test/command_callback/test_scala_metals.vader

@@ -0,0 +1,20 @@
+" Author: Jeffrey Lau https://github.com/zoonfafer
+" Description: Tests for the Scala Metals linter
+
+Before:
+  call ale#assert#SetUpLinterTest('scala', 'metals')
+
+After:
+  call ale#assert#TearDownLinterTest()
+Execute(should set metals for sbt project with build.sbt):
+  call ale#test#SetFilename('../scala_fixtures/valid_sbt_project/Main.scala')
+  AssertLSPLanguage 'scala'
+  AssertLSPOptions {}
+  AssertLSPConfig {}
+  AssertLSPProject ale#path#Simplify(g:dir . 'command_callback/../scala_fixtures/valid_sbt_project')
+Execute(should not set metals for sbt project without build.sbt):
+  call ale#test#SetFilename('../scala_fixtures/invalid_sbt_project/Main.scala')
+  AssertLSPLanguage 'scala'
+  AssertLSPOptions {}
+  AssertLSPConfig {}
+  AssertLSPProject ''