fix(highlight): handle nil Normal.bg in blending logic (#175)

Co-authored-by: Barrett Ruth <br.barrettruth@gmail.com>

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -68,10 +68,26 @@ body:
         load(vim.fn.system('curl -s https://raw.githubusercontent.com/folke/lazy.nvim/main/bootstrap.lua'))()
         require('lazy.nvim').setup({
           spec = {
-            'tpope/vim-fugitive',
+            { 'barrettruth/midnight.nvim', lazy = false, config = function() vim.cmd.colorscheme('midnight') end },
+            { 'tpope/vim-fugitive' },
+            { 'NeogitOrg/neogit', dependencies = { 'nvim-lua/plenary.nvim' } },
+            { 'lewis6991/gitsigns.nvim', config = true },
+            { 'rhysd/committia.vim' },
+            { 'nvim-telescope/telescope.nvim', dependencies = { 'nvim-lua/plenary.nvim' } },
             {
               'barrettruth/diffs.nvim',
-              opts = {},
+              init = function()
+                vim.g.diffs = {
+                  debug = '/tmp/diffs.log',
+                  integrations = {
+                    fugitive = true,
+                    neogit = true,
+                    gitsigns = true,
+                    committia = true,
+                    telescope = true,
+                  },
+                }
+              end,
             },
           },
         })

lua/diffs/init.lua

@@ -510,7 +510,6 @@ local function compute_highlight_groups()
   if not normal.bg and not hl_retry_pending then
     hl_retry_pending = true
     vim.schedule(function()
-      hl_retry_pending = false
       compute_highlight_groups()
       for bufnr, _ in pairs(attached_buffers) do
         invalidate_cache(bufnr)
@@ -1115,6 +1114,13 @@ M._test = {
   process_pending_clear = process_pending_clear,
   ft_retry_pending = ft_retry_pending,
   compute_hunk_context = compute_hunk_context,
+  compute_highlight_groups = compute_highlight_groups,
+  get_hl_retry_pending = function()
+    return hl_retry_pending
+  end,
+  set_hl_retry_pending = function(v)
+    hl_retry_pending = v
+  end,
 }
 
 return M

spec/init_spec.lua

@@ -527,4 +527,77 @@ describe('diffs', function()
       end)
     end)
   end)
+
+  describe('compute_highlight_groups', function()
+    local saved_get_hl, saved_set_hl, saved_schedule
+    local set_calls, schedule_cbs
+
+    before_each(function()
+      saved_get_hl = vim.api.nvim_get_hl
+      saved_set_hl = vim.api.nvim_set_hl
+      saved_schedule = vim.schedule
+      set_calls = {}
+      schedule_cbs = {}
+      vim.api.nvim_set_hl = function(_, group, opts)
+        set_calls[group] = opts
+      end
+      vim.schedule = function(cb)
+        table.insert(schedule_cbs, cb)
+      end
+      diffs._test.set_hl_retry_pending(false)
+    end)
+
+    after_each(function()
+      vim.api.nvim_get_hl = saved_get_hl
+      vim.api.nvim_set_hl = saved_set_hl
+      vim.schedule = saved_schedule
+      diffs._test.set_hl_retry_pending(false)
+    end)
+
+    it('sets DiffsClear.bg to a number when Normal.bg is nil', function()
+      vim.api.nvim_get_hl = function(ns, opts)
+        if opts.name == 'Normal' then
+          return { fg = 0xc0c0c0 }
+        end
+        return saved_get_hl(ns, opts)
+      end
+      diffs._test.compute_highlight_groups()
+      assert.is_number(set_calls.DiffsClear.bg)
+      assert.is_table(set_calls.DiffsAdd)
+      assert.is_table(set_calls.DiffsDelete)
+    end)
+
+    it('retries once then stops when Normal.bg stays nil', function()
+      vim.api.nvim_get_hl = function(ns, opts)
+        if opts.name == 'Normal' then
+          return { fg = 0xc0c0c0 }
+        end
+        return saved_get_hl(ns, opts)
+      end
+      diffs._test.compute_highlight_groups()
+      assert.are.equal(1, #schedule_cbs)
+      schedule_cbs[1]()
+      assert.are.equal(1, #schedule_cbs)
+      assert.is_true(diffs._test.get_hl_retry_pending())
+    end)
+
+    it('picks up bg on retry when colorscheme loads late', function()
+      local call_count = 0
+      vim.api.nvim_get_hl = function(ns, opts)
+        if opts.name == 'Normal' then
+          call_count = call_count + 1
+          if call_count <= 1 then
+            return { fg = 0xc0c0c0 }
+          end
+          return { fg = 0xc0c0c0, bg = 0x1e1e2e }
+        end
+        return saved_get_hl(ns, opts)
+      end
+      diffs._test.compute_highlight_groups()
+      assert.are.equal(1, #schedule_cbs)
+      schedule_cbs[1]()
+      assert.is_number(set_calls.DiffsClear.bg)
+      assert.are.equal(1, #schedule_cbs)
+    end)
+  end)
 end)