Allow running eclipselsp as installed by system package on GNU/Linux (#2523)

* Search eclipselsp jar and config files within system package path
* Allow setting an alternate eclipselsp configuration directory
* Add test for ale_java_eclipselsp_config_path

ale_linters/java/eclipselsp.vim

@@ -4,6 +4,7 @@
 let s:version_cache = {}
 
 call ale#Set('java_eclipselsp_path', ale#path#Simplify($HOME . '/eclipse.jdt.ls'))
+call ale#Set('java_eclipselsp_config_path', '')
 call ale#Set('java_eclipselsp_executable', 'java')
 
 function! ale_linters#java#eclipselsp#Executable(buffer) abort
@@ -32,11 +33,23 @@ function! ale_linters#java#eclipselsp#JarPath(buffer) abort
         return l:files[0]
     endif
 
+    " Search jar file within system package path
+    let l:files = globpath('/usr/share/java/jdtls/plugins', 'org.eclipse.equinox.launcher_\d\.\d\.\d\d\d\.*\.jar', 1, 1)
+
+    if len(l:files) == 1
+        return l:files[0]
+    endif
+
     return ''
 endfunction
 
 function! ale_linters#java#eclipselsp#ConfigurationPath(buffer) abort
     let l:path = fnamemodify(ale_linters#java#eclipselsp#JarPath(a:buffer), ':p:h:h')
+    let l:config_path = ale#Var(a:buffer, 'java_eclipselsp_config_path')
+
+    if !empty(l:config_path)
+        return ale#path#Simplify(l:config_path)
+    endif
 
     if has('win32')
         let l:path = l:path . '/config_win'

doc/ale-java.txt

@@ -141,6 +141,19 @@ g:ale_java_eclipselsp_executable                *g:ale_java_eclipse_executable*
   This variable can be set to change the executable path used for java.
 
 
+g:ale_java_eclipselsp_config_path                *g:ale_java_eclipse_config_path*
+                                                 *b:ale_java_eclipse_config_path*
+  Type: |String|
+  Default: `''`
+
+  Set this variable to change the configuration directory path used by
+  eclipselsp (e.g. `$HOME/.jdtls` in Linux).
+  By default ALE will attempt to use the configuration within the installation
+  directory.
+  This setting is particularly useful when eclipselsp is installed in a
+  non-writable directory like `/usr/share/java/jdtls`, as is the case when
+  installed via system package.
+
 ===============================================================================
 uncrustify                                                *ale-java-uncrustify*
 

test/command_callback/test_eclipselsp_command_callback.vader

@@ -85,3 +85,20 @@ Execute(The eclipselsp callback should allow custom executable):
     \]
   AssertLinter '/bin/foobar', join(cmd, ' ')
 
+Execute(The eclipselsp callback should allow custom configuration path):
+  let b:ale_java_eclipselsp_config_path='/home/config'
+  let cmd = [ ale#Escape('java'),
+    \ '-Declipse.application=org.eclipse.jdt.ls.core.id1',
+    \ '-Dosgi.bundles.defaultStartLevel=4',
+    \ '-Declipse.product=org.eclipse.jdt.ls.core.product',
+    \ '-Dlog.level=ALL',
+    \ '-noverify',
+    \ '-Xmx1G',
+    \ '-jar',
+    \ '',
+    \ '-configuration',
+    \ b:ale_java_eclipselsp_config_path,
+    \ '-data',
+    \ ''
+    \]
+  AssertLinter 'java', join(cmd, ' ')