improve error message for unknown formatters

lua/conform/health.lua

@@ -101,12 +101,15 @@ M.show_window = function()
   ---@param formatter conform.FormatterInfo
   local function append_formatter_info(formatter)
     if not formatter.available then
-      local line = string.format("%s unavailable: %s", formatter.name, formatter.available_msg)
+      local type_label = formatter.error and "error" or "unavailable"
+
+      local line = string.format("%s %s: %s", formatter.name, type_label, formatter.available_msg)
+
       table.insert(lines, line)
-      table.insert(
-        highlights,
-        { "DiagnosticWarn", #lines, formatter.name:len(), formatter.name:len() + 12 }
-      )
+
+      local hl = formatter.error and "DiagnosticError" or "DiagnosticWarn"
+      local hl_start = formatter.name:len() + 1
+      table.insert(highlights, { hl, #lines, hl_start, hl_start + type_label:len() })
     else
       local filetypes = get_formatter_filetypes(formatter.name)
       local filetypes_list = table.concat(filetypes, ", ")

lua/conform/init.lua

@@ -766,7 +766,8 @@ M.get_formatter_info = function(formatter, bufnr)
       name = formatter,
       command = formatter,
       available = false,
-      available_msg = "Formatter config missing or incomplete",
+      available_msg = "Unknown formatter. Formatter config missing or incomplete",
+      error = true,
     }
   end
 

lua/conform/types.lua

@@ -4,6 +4,7 @@
 ---@field cwd? string
 ---@field available boolean
 ---@field available_msg? string
+---@field error? boolean
 
 ---@class (exact) conform.JobFormatterConfig
 ---@field command string|fun(self: conform.JobFormatterConfig, ctx: conform.Context): string

tests/api_spec.lua

@@ -12,13 +12,15 @@ describe("api", function()
     assert.equal("stylua", info.name)
     assert.equal("stylua", info.command)
     assert.equal("boolean", type(info.available))
+    assert.is_nil(info.error)
   end)
 
   it("retrieves unavailable info if formatter does not exist", function()
     local info = conform.get_formatter_info("asdf")
     assert.equal("asdf", info.name)
     assert.equal("asdf", info.command)
     assert.falsy(info.available)
+    assert.truthy(info.error)
   end)
 
   describe("list_formatters", function()