From 753f248eb30350eb9ba6ca108e466be8e54a51c8 Mon Sep 17 00:00:00 2001
From: Jackson Moore <jacksonmoore@tuta.io>
Date: Fri, 4 Sep 2026 11:35:32 +0200
Subject: Apply missing default label fallback

---
 lua/clever_f/capabilities.lua        |  6 +++++-
 lua/clever_f/feedback_service.lua    | 19 +++++++++++++++++--
 lua/clever_f/testing/memory_host.lua | 32 ++++++++++++++++++++++++++++++++
 tests/run.lua                        | 24 ++++++++++++++++++++++++
 4 files changed, 78 insertions(+), 3 deletions(-)

diff --git a/lua/clever_f/capabilities.lua b/lua/clever_f/capabilities.lua
index 194de0b..3e770bd 100644
--- a/lua/clever_f/capabilities.lua
+++ b/lua/clever_f/capabilities.lua
@@ -22,7 +22,11 @@ M.effect_methods = {
   prompt = { "show_prompt" },
   redraw = { "redraw" },
   diagnostics = { "emit_diagnostic" },
-  highlights = { "create_highlight", "remove_highlight" },
+  highlights = {
+    "define_highlight_group",
+    "create_highlight",
+    "remove_highlight",
+  },
   cursor_presentation = {
     "suppress_cursor_presentation",
     "restore_cursor_presentation",
diff --git a/lua/clever_f/feedback_service.lua b/lua/clever_f/feedback_service.lua
index f7e1dd6..d1fa9d6 100644
--- a/lua/clever_f/feedback_service.lua
+++ b/lua/clever_f/feedback_service.lua
@@ -52,7 +52,10 @@ local function normalize_options(options)
 end
 
 local function require_host(host)
-  if type(host) ~= "table" or type(host.read_highlight_group) ~= "function" then
+  if type(host) ~= "table"
+    or type(host.read_highlight_group) ~= "function"
+    or type(host.define_highlight_group) ~= "function"
+  then
     fail("FeedbackService host must provide highlight groups", 3)
   end
   return host
@@ -86,7 +89,19 @@ function FeedbackService:ensure_default_label()
       applied = false,
     }
   end
-  return nil
+
+  local definition = M.default_label_definition()
+  service_records[self].host:define_highlight_group(
+    M.DEFAULT_LABEL_GROUP,
+    definition,
+    { default = true }
+  )
+  return {
+    group = M.DEFAULT_LABEL_GROUP,
+    definition = definition,
+    source = "fallback",
+    applied = true,
+  }
 end
 
 function M.new(options)
diff --git a/lua/clever_f/testing/memory_host.lua b/lua/clever_f/testing/memory_host.lua
index 459c9a8..0f8fc2d 100644
--- a/lua/clever_f/testing/memory_host.lua
+++ b/lua/clever_f/testing/memory_host.lua
@@ -663,6 +663,38 @@ function MemoryHost:highlight_groups()
   return copy(self._highlight_groups)
 end
 
+function MemoryHost:define_highlight_group(name, definition, options)
+  if type(name) ~= "string" or name == "" then
+    error("highlight group name must be a nonempty string", 2)
+  end
+  if type(definition) ~= "table" then
+    error("highlight group definition must be a table", 2)
+  end
+  options = options or {}
+  if type(options) ~= "table" then
+    error("highlight group options must be a table", 2)
+  end
+  if options.default ~= nil and type(options.default) ~= "boolean" then
+    error("highlight group default option must be a Boolean", 2)
+  end
+  if options.force ~= nil and type(options.force) ~= "boolean" then
+    error("highlight group force option must be a Boolean", 2)
+  end
+
+  local exists = self._highlight_groups[name] ~= nil
+  local applied = not (exists and options.default)
+  if applied then
+    self._highlight_groups[name] = copy(definition)
+  end
+  self:_record("define_highlight_group", {
+    name = name,
+    definition = definition,
+    options = options,
+    applied = applied,
+  })
+  return applied
+end
+
 function MemoryHost:create_highlight(specification)
   if type(specification) ~= "table" then
     error("highlight specification must be a table", 2)
diff --git a/tests/run.lua b/tests/run.lua
index 696026e..de48f0b 100644
--- a/tests/run.lua
+++ b/tests/run.lua
@@ -4257,6 +4257,30 @@ test("Default label evaluation preserves a colorscheme definition", function()
   same("read_highlight_group", operations[1].operation)
 end)
 
+test("Default label evaluation defines the fallback when absent", function()
+  local host = MemoryHost.new()
+  local feedback = feedback_service.new(host)
+
+  local result = feedback:ensure_default_label()
+  same("fallback", result.source)
+  truthy(result.applied)
+  local definition = host:highlight_groups().CleverFDefaultLabel
+  same("red", definition.guifg)
+  same("NONE", definition.guibg)
+  truthy(definition.gui.bold)
+  truthy(definition.gui.underline)
+  same("red", definition.ctermfg)
+  same("NONE", definition.ctermbg)
+  truthy(definition.cterm.bold)
+  truthy(definition.cterm.underline)
+
+  local operations = host:operations()
+  same(2, #operations)
+  same("read_highlight_group", operations[1].operation)
+  same("define_highlight_group", operations[2].operation)
+  truthy(operations[2].options.default)
+end)
+
 for _, item in ipairs(tests) do
   local ok, failure = xpcall(item.body, debug.traceback)
   if not ok then
-- 
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