#1428 Start implementing LSP hover support

test/lsp/test_lsp_client_messages.vader

@@ -159,6 +159,20 @@ Execute(ale#lsp#message#References() should return correct messages):
   \ ],
   \ ale#lsp#message#References(bufnr(''), 12, 34)
 
+Execute(ale#lsp#message#Hover() should return correct messages):
+  AssertEqual
+  \ [
+  \   0,
+  \   'textDocument/hover',
+  \   {
+  \     'textDocument': {
+  \         'uri': ale#path#ToURI(g:dir . '/foo/bar.ts'),
+  \     },
+  \     'position': {'line': 11, 'character': 34},
+  \   }
+  \ ],
+  \ ale#lsp#message#Hover(bufnr(''), 12, 34)
+
 Execute(ale#lsp#tsserver_message#Open() should return correct messages):
   AssertEqual
   \ [

test/test_hover.vader

@@ -0,0 +1,107 @@
+Before:
+  call ale#test#SetDirectory('/testplugin/test')
+  call ale#test#SetFilename('dummy.txt')
+
+  let g:Callback = 0
+  let g:message_list = []
+  let g:item_list = []
+  let g:echo_list = []
+
+  runtime autoload/ale/linter.vim
+  runtime autoload/ale/lsp.vim
+  runtime autoload/ale/util.vim
+
+  function! ale#linter#StartLSP(buffer, linter, callback) abort
+    let g:Callback = a:callback
+
+    return {
+    \ 'connection_id': 347,
+    \ 'project_root': '/foo/bar',
+    \}
+  endfunction
+
+  function! ale#lsp#Send(conn_id, message, root) abort
+    call add(g:message_list, a:message)
+
+    return 42
+  endfunction
+
+  function! ale#util#Echo(string) abort
+      call add(g:echo_list, a:string)
+  endfunction
+
+  function! HandleValidLSPResult(result) abort
+    " The cursor is beyond the length of the line.
+    " We will clamp the cursor position with the line length.
+    call setpos('.', [bufnr(''), 1, 5, 0])
+
+    call ale#hover#SetMap({3: {
+    \ 'buffer': bufnr(''),
+    \ 'line': 1,
+    \ 'column': 5,
+    \}})
+    call ale#hover#HandleLSPResponse(
+    \ 1,
+    \ {
+    \   'id': 3,
+    \   'result': a:result,
+    \ }
+    \)
+  endfunction
+
+After:
+  call ale#hover#SetMap({})
+  call ale#test#RestoreDirectory()
+  call ale#linter#Reset()
+
+  unlet! g:Callback
+  unlet! g:message_list
+  unlet! b:ale_linters
+  unlet! g:echo_list
+
+  delfunction HandleValidLSPResult
+
+  runtime autoload/ale/linter.vim
+  runtime autoload/ale/lsp.vim
+  runtime autoload/ale/util.vim
+
+Given python(Some Python file):
+  foo
+  somelongerline
+  bazxyzxyzxyz
+
+Execute(LSP hover responses with just a string should be handled):
+  call HandleValidLSPResult({'contents': 'foobar'})
+
+  AssertEqual ['foobar'], g:echo_list
+  AssertEqual {}, ale#hover#GetMap()
+
+Execute(LSP hover null responses should be handled):
+  call HandleValidLSPResult(v:null)
+
+  AssertEqual [], g:echo_list
+  AssertEqual {}, ale#hover#GetMap()
+
+Execute(LSP hover responses with markup content should be handled):
+  call HandleValidLSPResult({'contents': {'kind': 'something', 'value': 'markup'}})
+
+  AssertEqual ['markup'], g:echo_list
+  AssertEqual {}, ale#hover#GetMap()
+
+Execute(LSP hover response with lists of strings should be handled):
+  call HandleValidLSPResult({'contents': [
+  \  "foo\n",
+  \  "bar\n",
+  \]})
+
+  AssertEqual ['foo bar'], g:echo_list
+  AssertEqual {}, ale#hover#GetMap()
+
+Execute(LSP hover response with lists of strings and marked strings should be handled):
+  call HandleValidLSPResult({'contents': [
+  \  {'language': 'rust', 'value': 'foo'},
+  \  "bar\n",
+  \]})
+
+  AssertEqual ['foo bar'], g:echo_list
+  AssertEqual {}, ale#hover#GetMap()