fix(buffer): prevent active item extmark accumulation

lua/neogit/lib/buffer.lua

@@ -534,10 +534,6 @@ end
 function Buffer:clear_namespace(name)
   assert(name, "Cannot clear namespace without specifying which")
 
-  if not self:is_focused() then
-    return
-  end
-
   local ns_id = self:get_namespace_id(name)
   if ns_id then
     api.nvim_buf_clear_namespace(self.handle, ns_id, 0, -1)
@@ -955,7 +951,11 @@ function Buffer.create(config)
       on_start = function()
         return buffer:exists() and buffer:is_valid()
       end,
-      on_win = function()
+      on_win = function(_, _, bufnr)
+        if bufnr ~= buffer.handle then
+          return false
+        end
+
         buffer:clear_namespace("ActiveItem")
 
         local active_oid = require("neogit.buffers.commit_view").current_oid()

tests/specs/neogit/lib/buffer_spec.lua

@@ -0,0 +1,105 @@
+local eq = assert.are.same
+local Buffer = require("neogit.lib.buffer")
+local Ui = require("neogit.lib.ui")
+
+describe("buffer decorations", function()
+  local buffer
+  local original_window
+  local unfocused_window
+  local replacement_buffer
+
+  local function extmarks(namespace)
+    return vim.api.nvim_buf_get_extmarks(buffer.handle, buffer:get_namespace_id(namespace), 0, -1, {})
+  end
+
+  before_each(function()
+    original_window = vim.api.nvim_get_current_win()
+  end)
+
+  after_each(function()
+    if original_window and vim.api.nvim_win_is_valid(original_window) then
+      vim.api.nvim_set_current_win(original_window)
+    end
+
+    if unfocused_window and vim.api.nvim_win_is_valid(unfocused_window) then
+      vim.api.nvim_win_close(unfocused_window, true)
+    end
+
+    if buffer then
+      buffer:set_decorations("ActiveItem", {})
+      if vim.api.nvim_buf_is_valid(buffer.handle) then
+        vim.api.nvim_buf_delete(buffer.handle, { force = true })
+      end
+    end
+
+    if replacement_buffer and vim.api.nvim_buf_is_valid(replacement_buffer) then
+      vim.api.nvim_buf_delete(replacement_buffer, { force = true })
+    end
+  end)
+
+  it("does not accumulate active item highlights while unfocused", function()
+    local active_item = { oid = require("neogit.buffers.commit_view").current_oid() }
+    buffer = Buffer.create {
+      name = "NeogitActiveItemHighlightTest",
+      kind = "split",
+      bufhidden = "hide",
+      active_item_highlight = true,
+      render = function()
+        return {
+          Ui.row({ Ui.text("active item") }, { item = active_item }),
+        }
+      end,
+    }
+
+    vim.cmd.vnew()
+    unfocused_window = vim.api.nvim_get_current_win()
+    for _ = 1, 3 do
+      vim.cmd("redraw!")
+
+      local marks = extmarks("ActiveItem")
+      eq(1, #marks)
+      eq({ 0, 0 }, { marks[1][2], marks[1][3] })
+    end
+  end)
+
+  it("only decorates its owning buffer", function()
+    local active_item = { oid = require("neogit.buffers.commit_view").current_oid() }
+    buffer = Buffer.create {
+      name = "NeogitActiveItemOwnerTest",
+      kind = "split",
+      bufhidden = "hide",
+      active_item_highlight = true,
+      render = function()
+        return {
+          Ui.row({ Ui.text("active item") }, { item = active_item }),
+        }
+      end,
+    }
+
+    replacement_buffer = vim.api.nvim_create_buf(false, true)
+    vim.api.nvim_win_set_buf(buffer.win_handle, replacement_buffer)
+    buffer:clear_namespace("ActiveItem")
+    vim.cmd("redraw!")
+
+    eq(0, #extmarks("ActiveItem"))
+  end)
+
+  it("clears a namespace while another buffer is focused", function()
+    buffer = Buffer.create {
+      name = "NeogitUnfocusedNamespaceClearTest",
+      kind = "split",
+      bufhidden = "hide",
+      render = function()
+        return { Ui.text("highlighted line") }
+      end,
+    }
+    buffer:create_namespace("Test")
+    buffer:add_line_highlight(0, "NeogitActiveItem", { namespace = "Test" })
+
+    vim.api.nvim_set_current_win(original_window)
+    assert.is_false(buffer:is_focused())
+    buffer:clear_namespace("Test")
+
+    eq(0, #extmarks("Test"))
+  end)
+end)