Feature/add ant support (#2539)

Use ant files to load Java settings too.

ale_linters/java/javac.vim

@@ -21,6 +21,11 @@ function! ale_linters#java#javac#RunWithImportPaths(buffer) abort
         let l:command = ale#gradle#BuildClasspathCommand(a:buffer)
     endif
 
+    " Try to use Ant if Gradle and Maven aren't available
+    if empty(l:command)
+        let l:command = ale#ant#BuildClasspathCommand(a:buffer)
+    endif
+
     if empty(l:command)
         return ale_linters#java#javac#GetCommand(a:buffer, [], {})
     endif

autoload/ale/ant.vim

@@ -0,0 +1,41 @@
+" Author: Andrew Lee <andrewl@mbda.fun>.
+" Inspired by ale/gradle.vim by Michael Pardo <michael@michaelpardo.com>
+" Description: Functions for working with Ant projects.
+
+" Given a buffer number, find an Ant project root
+function! ale#ant#FindProjectRoot(buffer) abort
+    let l:build_xml_path = ale#path#FindNearestFile(a:buffer, 'build.xml')
+
+    if !empty(l:build_xml_path)
+        return fnamemodify(l:build_xml_path, ':h')
+    endif
+
+    return ''
+endfunction
+
+" Given a buffer number, find the path to the `ant` executable. Returns an empty
+" string if cannot find the executable.
+function! ale#ant#FindExecutable(buffer) abort
+    if executable('ant')
+        return 'ant'
+    endif
+
+    return ''
+endfunction
+
+" Given a buffer number, build a command to print the classpath of the root
+" project. Returns an empty string if cannot build the command.
+function! ale#ant#BuildClasspathCommand(buffer) abort
+    let l:executable = ale#ant#FindExecutable(a:buffer)
+    let l:project_root = ale#ant#FindProjectRoot(a:buffer)
+
+    if !empty(l:executable) && !empty(l:project_root)
+        return ale#path#CdString(l:project_root)
+        \   . ale#Escape(l:executable)
+        \   . ' classpath'
+        \   . ' -S'
+        \   . ' -q'
+    endif
+
+    return ''
+endfunction

autoload/ale/java.vim

@@ -16,5 +16,11 @@ function! ale#java#FindProjectRoot(buffer) abort
         return fnamemodify(l:maven_pom_file, ':h')
     endif
 
+    let l:ant_root = ale#ant#FindProjectRoot(a:buffer)
+
+    if !empty(l:ant_root)
+        return l:ant_root
+    endif
+
     return ''
 endfunction

test/test_ant_build_classpath_command.vader

@@ -0,0 +1,29 @@
+Before:
+  call ale#test#SetDirectory('/testplugin/test')
+  runtime ale_linters/java/javac.vim
+
+  Save $PATH
+  let $PATH = ale#path#Simplify(g:dir . '/ant-test-files/bin')
+
+  let g:valid_project = 'ant-test-files/ant-project'
+  let g:invalid_project = 'ant-test-files/non-ant-project'
+  let g:command_tail = ' classpath' . ' -S' . ' -q'
+
+After:
+  Restore
+
+  unlet! g:command_tail
+  unlet! g:valid_project
+  unlet! g:invalid_project
+
+  call ale#test#RestoreDirectory()
+  call ale#linter#Reset()
+
+Execute(Should return `cd '[dir]' && 'ant' classpath -S -q`):
+  call ale#test#SetFilename(valid_project . '/Main.java')
+
+  AssertEqual
+  \ ale#path#CdString(ale#path#Simplify(g:dir . '/ant-test-files/ant-project'))
+  \   . ale#Escape('ant')
+  \   . g:command_tail,
+  \ ale#ant#BuildClasspathCommand(bufnr(''))

test/test_ant_find_project_root.vader

@@ -0,0 +1,35 @@
+Before:
+  call ale#test#SetDirectory('/testplugin/test')
+  runtime ale_linters/java/javac.vim
+
+After:
+  call ale#test#RestoreDirectory()
+  call ale#linter#Reset()
+
+Execute(Should return current directory if called on the project root):
+  call ale#test#SetFilename('ant-test-files/ant-project/Main.java')
+
+  AssertEqual
+  \ ale#path#Simplify(g:dir . '/ant-test-files/ant-project'),
+  \ ale#ant#FindProjectRoot(bufnr(''))
+
+Execute(Should return root directory if called on a deeply nested source file):
+  call ale#test#SetFilename('ant-test-files/ant-project/src/several/namespace/layers/A.java')
+
+  AssertEqual
+  \ ale#path#Simplify(g:dir . '/ant-test-files/ant-project'),
+  \ ale#ant#FindProjectRoot(bufnr(''))
+
+Execute(Should return empty string if called on a non-ant project):
+  call ale#test#SetFilename('ant-test-files/non-ant-project/Main.java')
+
+  AssertEqual
+  \ '',
+  \ ale#ant#FindProjectRoot(bufnr(''))
+
+Execute(Should return empty string if called on a file in a non-ant project):
+  call ale#test#SetFilename('ant-test-files/non-ant-project/several/namespace/layers/A.java')
+
+  AssertEqual
+  \ '',
+  \ ale#ant#FindProjectRoot(bufnr(''))