feat: deduplicate repeated messages (close #162)

README.md

@@ -215,6 +215,10 @@ Available options are shown below:
       group_separator = "---",    -- Separator between notification groups
       group_separator_hl =        -- Highlight group used for group separator
         "Comment",
+      render_message =            -- How to render notification messages
+        function(msg, cnt)
+          return cnt == 1 and msg or string.format("(%dx) %s", cnt, msg)
+        end,
     },
 
     -- Options related to the notification window and buffer

lua/fidget/notification.lua

@@ -70,7 +70,8 @@ local logger                = require("fidget.logger")
 --- Notification element containing a message and optional annotation.
 ---
 ---@class Item
----@field key           Key         Used to distinguish this item from others
+---@field key           Key         Identity of this item (for in-place updates)
+---@field content_key   Key         What to deduplicate items by (do not deduplicate if `nil`)
 ---@field message       string      Displayed message for the item
 ---@field annote        string|nil  Optional title that accompanies the message
 ---@field style         string      Style used to render the annote/title, if any
@@ -121,6 +122,11 @@ local state                 = {
 --- :lua print(vim.inspect(require("fidget.notification").default_config))
 ---<
 ---
+--- Note that the default `update_hook` function performs a few book-keeping
+--- tasks, e.g., calling |fidget.notification.set_content_key| to keep its
+--- `content_key` up to date. You may want to do the same if writing your own;
+--- check the source code to see what it's doing.
+---
 --- See also:~
 ---     |fidget.notification.Config|
 ---
@@ -140,9 +146,42 @@ notification.default_config = {
   info_annote = "INFO",
   warn_annote = "WARN",
   error_annote = "ERROR",
-  update_hook = false,
+  update_hook = function(item)
+    notification.set_content_key(item)
+  end,
 }
 
+--- Sets a |fidget.notification.Item|'s `content_key`, for deduplication.
+---
+--- This default implementation sets an item's `content_key` to its `message`,
+--- appended with its `annote` (or a null byte if it has no `annote`), a rough
+--- "hash" of its contents. You can write your own `update_hook` that "hashes"
+--- the message differently, e.g., only considering the `message`, or taking the
+--- `data` or style fields into account.
+---
+--- If you would like to disable message deduplication, don't call this
+--- function, leaving the `content_key` field as `nil`. Assuming you're not
+--- using the `update_hook` for anything else, you can achieve this by simply
+--- the option to `false`, e.g.:
+---
+--->lua
+--- { -- In options table
+---   notification = {
+---     configs = {
+---       -- Opt out of deduplication by default, i.e., in default config
+---       default = vim.tbl_extend("force", require('fidget.notification').default_config, {
+---         update_hook = false,
+---       },
+---     },
+---   },
+--- }
+---<
+---
+---@param item Item
+function notification.set_content_key(item)
+    item.content_key = item.message .. " " .. (item.annote and item.annote or string.char(0))
+end
+
 ---@options notification [[
 ---@protected
 --- Notification options

lua/fidget/notification/view.lua

@@ -49,6 +49,23 @@ M.options = {
   ---
   ---@type string|false
   group_separator_hl = "Comment",
+
+  --- How to render notification messages
+  ---
+  --- Messages that appear multiple times (have the same `content_key`) will
+  --- only be rendered once, with a `cnt` greater than 1. This hook provides an
+  --- opportunity to customize how such messages should appear.
+  ---
+  --- Note that if this returns an empty string, the notification will not be
+  --- rendered.
+  ---
+  --- See also:~
+  ---     |fidget.notification.Config|
+  ---     |fidget.notification.default_config|
+  ---     |fidget.notification.set_content_key|
+  ---
+  ---@type fun(msg: string, cnt: number): string
+  render_message = function(msg, cnt) return cnt == 1 and msg or string.format("(%dx) %s", cnt, msg) end,
 }
 ---@options ]]
 
@@ -160,15 +177,17 @@ end
 ---
 ---@param item   Item
 ---@param config Config
+---@param count  number
 ---@return       NotificationRenderItem|nil render_item
-function M.render_item(item, config)
+function M.render_item(item, config, count)
   if item.hidden then
     return nil
   end
 
   local lines, highlights = {}, {}
 
-  for line in vim.gsplit(item.message, "\n", { plain = true, trimempty = true }) do
+  local msg = M.options.render_message(item.message, count)
+  for line in vim.gsplit(msg, "\n", { plain = true, trimempty = true }) do
     table.insert(lines, line)
   end
 
@@ -178,16 +197,17 @@ function M.render_item(item, config)
   end
 
   if item.annote then
-    local msg = lines[1] -- Append annote to first line of message
+    local line1 = lines[1] -- Append annote to first line
+    local col_start = #line1
     local sep = config.annote_separator or " "
-    local line = string.format("%s%s%s", msg, sep, item.annote)
-    lines[1] = line
+    line1 = string.format("%s%s%s", line1, sep, item.annote)
+    lines[1] = line1
 
     -- Insert highlight for annote
     table.insert(highlights, {
       hl_group = item.style,
-      line = 0,         -- 0-indexed
-      col_start = #msg, -- byte-indexed
+      line = 0,              -- 0-indexed
+      col_start = col_start, -- byte-indexed
       col_end = -1,
     })
   end
@@ -217,16 +237,37 @@ function M.render(now, groups)
       table.insert(render_items, group_header)
     end
 
+    local counts = {}
+    for _, item in ipairs(group.items) do
+      local content_key = item.content_key
+      if content_key ~= nil then
+        if counts[content_key] then
+          counts[content_key] = counts[content_key] + 1
+        else
+          counts[content_key] = 1
+        end
+      end
+    end
+
     local i = 1
     for _, item in ipairs(group.items) do
       if group.config.render_limit and i > group.config.render_limit then
         -- Don't bother rendering the rest (though they still exist)
         break
       end
-      local render_item = M.render_item(item, group.config)
-      if render_item then
-        table.insert(render_items, render_item)
-        i = i + 1
+      local content_key = item.content_key
+      if content_key == nil or counts[content_key] then
+        local count = 1
+        if content_key ~= nil then
+          count = counts[content_key]
+          counts[content_key] = nil
+        end
+
+        local render_item = M.render_item(item, group.config, count)
+        if render_item then
+          table.insert(render_items, render_item)
+          i = i + 1
+        end
       end
     end
   end