Merge pull request #15786 from gpanders/diagnostic-signs-unique-severity

runtime/doc/diagnostic.txt

@@ -201,7 +201,52 @@ DiagnosticsChanged	After diagnostics have changed.
 Example: >
 	autocmd User DiagnosticsChanged lua vim.diagnostic.setqflist({open = false })
 <
+==============================================================================
+CUSTOMIZATION						*diagnostic-config*
 
+If you need more customization over the way diagnostics are displayed than the
+built-in configuration options provide, you can override the display handler
+explicitly. For example, use the following to only show a sign for the highest
+severity diagnostic on a given line: >
+
+	-- Disable the default signs handler
+	vim.diagnostic.config({signs = false})
+
+	-- Create a namespace. This won't be used to add any diagnostics,
+	-- only to display them.
+	local ns = vim.api.nvim_create_namespace("my_namespace")
+
+	-- Create a reference to the original function
+	local orig_show = vim.diagnostic.show
+
+	local function set_signs(bufnr)
+	  -- Get all diagnostics from the current buffer
+	  local diagnostics = vim.diagnostic.get(bufnr)
+
+	  -- Find the "worst" diagnostic per line
+	  local max_severity_per_line = {}
+	  for _, d in pairs(diagnostics) do
+	    local m = max_severity_per_line[d.lnum]
+	    if not m or d.severity < m.severity then
+	      max_severity_per_line[d.lnum] = d
+	    end
+	  end
+
+	  -- Show the filtered diagnostics using the custom namespace. Use the
+	  -- reference to the original function to avoid a loop.
+	  local filtered_diagnostics = vim.tbl_values(max_severity_per_line)
+	  orig_show(ns, bufnr, filtered_diagnostics, {
+	    virtual_text=false,
+	    underline=false,
+	    signs=true
+	  })
+	end
+
+	function vim.diagnostic.show(namespace, bufnr, ...)
+	  orig_show(namespace, bufnr, ...)
+	  set_signs(bufnr)
+	end
+<
 ==============================================================================
 Lua module: vim.diagnostic                                    *diagnostic-api*
 

runtime/lua/vim/diagnostic.lua

@@ -620,23 +620,22 @@ function M.set(namespace, bufnr, diagnostics, opts)
   }
 
   if vim.tbl_isempty(diagnostics) then
-    return M.reset(namespace, bufnr)
+    clear_diagnostic_cache(namespace, bufnr)
+  else
+    if not diagnostic_cleanup[bufnr][namespace] then
+      diagnostic_cleanup[bufnr][namespace] = true
+
+      -- Clean up our data when the buffer unloads.
+      vim.api.nvim_buf_attach(bufnr, false, {
+        on_detach = function(_, b)
+          clear_diagnostic_cache(b, namespace)
+          diagnostic_cleanup[b][namespace] = nil
+        end
+      })
+    end
+    set_diagnostic_cache(namespace, bufnr, diagnostics)
   end
 
-  if not diagnostic_cleanup[bufnr][namespace] then
-    diagnostic_cleanup[bufnr][namespace] = true
-
-    -- Clean up our data when the buffer unloads.
-    vim.api.nvim_buf_attach(bufnr, false, {
-      on_detach = function(_, b)
-        clear_diagnostic_cache(b, namespace)
-        diagnostic_cleanup[b][namespace] = nil
-      end
-    })
-  end
-
-  set_diagnostic_cache(namespace, bufnr, diagnostics)
-
   if vim.api.nvim_buf_is_loaded(bufnr) then
     M.show(namespace, bufnr, diagnostics, opts)
   elseif opts then

test/functional/lua/diagnostic_spec.lua

@@ -874,6 +874,26 @@ describe('vim.diagnostic', function()
         return count_extmarks(diagnostic_bufnr, diagnostic_ns)
       ]])
     end)
+
+    it('sets signs', function()
+      local result = exec_lua [[
+        vim.diagnostic.config({
+          signs = true,
+        })
+
+        local diagnostics = {
+          make_error('Error', 1, 1, 1, 2),
+          make_warning('Warning', 3, 3, 3, 3),
+        }
+
+        vim.diagnostic.set(diagnostic_ns, diagnostic_bufnr, diagnostics)
+
+        return vim.fn.sign_getplaced(diagnostic_bufnr, {group = '*'})[1].signs
+      ]]
+
+      eq({2, 'DiagnosticSignError'}, {result[1].lnum, result[1].name})
+      eq({4, 'DiagnosticSignWarn'}, {result[2].lnum, result[2].name})
+    end)
   end)
 
   describe('show_line_diagnostics()', function()
@@ -995,37 +1015,6 @@ describe('vim.diagnostic', function()
     end)
   end)
 
-  describe('set_signs()', function()
-    -- TODO(tjdevries): Find out why signs are not displayed when set from Lua...??
-    pending('sets signs by default', function()
-      exec_lua [[
-        vim.diagnostic.config({
-          update_in_insert = true,
-          signs = true,
-        })
-
-        local diagnostics = {
-          make_error('Delayed Diagnostic', 1, 1, 1, 2),
-          make_error('Delayed Diagnostic', 3, 3, 3, 3),
-        }
-
-        vim.api.nvim_win_set_buf(0, diagnostic_bufnr)
-        vim.diagnostic.set(diagnostic_ns, diagnostic_bufnr, diagnostics)
-
-        vim.diagnostic._set_signs(diagnostic_ns, diagnostic_bufnr, diagnostics)
-        -- return vim.fn.sign_getplaced()
-      ]]
-
-      nvim("input", "o")
-      nvim("input", "<esc>")
-
-      -- TODO(tjdevries): Find a way to get the signs to display in the test...
-      eq(nil, exec_lua [[
-        return im.fn.sign_getplaced()[1].signs
-      ]])
-    end)
-  end)
-
   describe('setloclist()', function()
     it('sets diagnostics in lnum order', function()
       local loc_list = exec_lua [[