some more bug fixes and a minor refactoring (#18)

* fix(git): guard LOCAL stat swap when numstat is unavailable
* fix(layout): null COMMIT-side deletions in Diff2
* fix(file-entry): handle should_null errors without nulling files
* fix(file): null missing merge stage blobs
* fix(config,layouts): validate rename threshold and merge null rules
* test(git): cover LOCAL..COMMIT nil-stats binary path
* test(matrix): add merge conflict and null logic coverage
* refactor(file-entry): extract try_should_null helper

Author: dlyongemallo

README.md

@@ -188,7 +188,7 @@ require("diffview").setup({
   enhanced_diff_hl = false, -- See |diffview-config-enhanced_diff_hl|
   git_cmd = { "git" },      -- The git executable followed by default args.
   hg_cmd = { "hg" },        -- The hg executable followed by default args.
-  rename_threshold = nil,   -- Similarity threshold for rename detection (e.g. 40 for 40%). Nil uses git default (50%).
+  rename_threshold = nil,   -- Integer 0-100 for rename detection similarity. Nil uses git default (50%). Invalid values are ignored.
   use_icons = true,         -- Requires nvim-web-devicons or mini.icons
   show_help_hints = true,   -- Show hints for how to open the help panel
   watch_index = true,       -- Update views and index buffers when the git index changes.

doc/diffview.txt

@@ -449,6 +449,7 @@ rename_threshold                                *diffview-config-rename_threshol
 
         Similarity threshold for rename detection (e.g. 40 for 40%). When
         nil, uses the git default (50%).
+        Must be an integer in the range [0, 100]. Invalid values are ignored.
 
 use_icons                                       *diffview-config-use_icons*
         Type: `boolean`, Default: `true`

doc/diffview_defaults.txt

@@ -7,7 +7,7 @@ DEFAULT CONFIG                                  *diffview.defaults*
     enhanced_diff_hl = false, -- See |diffview-config-enhanced_diff_hl|
     git_cmd = { "git" },      -- The git executable followed by default args.
     hg_cmd = { "hg" },        -- The hg executable followed by default args.
-    rename_threshold = nil,   -- Similarity threshold for rename detection (e.g. 40 for 40%). Nil uses git default (50%).
+    rename_threshold = nil,   -- Integer 0-100 for rename detection similarity. Nil uses git default (50%). Invalid values are ignored.
     use_icons = true,         -- Requires nvim-web-devicons or mini.icons
     show_help_hints = true,   -- Show hints for how to open the help panel
     watch_index = true,       -- Update views and index buffers when the git index changes.

lua/diffview/config.lua

@@ -619,6 +619,23 @@ function M.setup(user_config)
     M._config.git_cmd = M.defaults.git_cmd
   end
 
+  do
+    local rename_threshold = M._config.rename_threshold
+
+    if rename_threshold ~= nil then
+      local n = tonumber(rename_threshold)
+
+      if not n or n < 0 or n > 100 or n % 1 ~= 0 then
+        utils.warn(
+          "Invalid value for 'rename_threshold'. Must be an integer between 0 and 100, or nil."
+        )
+        M._config.rename_threshold = M.defaults.rename_threshold
+      else
+        M._config.rename_threshold = n
+      end
+    end
+  end
+
   do
     -- Validate layouts
     local view = M._config.view

lua/diffview/scene/file_entry.lua

@@ -14,6 +14,18 @@ local M = {}
 
 local fstat_cache = {}
 
+---Safely evaluate a layout's should_null predicate. Returns false if the
+---call errors so that a broken predicate never accidentally nulls a file.
+---@param layout Layout (class)
+---@param rev Rev
+---@param status string
+---@param symbol string
+---@return boolean
+local function try_should_null(layout, rev, status, symbol)
+  local ok, res = pcall(layout.should_null, rev, status, symbol)
+  return ok and res or false
+end
+
 ---@class GitStats
 ---@field additions integer
 ---@field deletions integer
@@ -123,7 +135,7 @@ function FileEntry:convert_layout(target_layout)
       commit = self.commit,
       get_data = get_data,
       rev = rev,
-      nulled = select(2, pcall(target_layout.should_null, rev, self.status, symbol)),
+      nulled = try_should_null(target_layout, rev, self.status, symbol),
     }) --[[@as vcs.File ]]
   end
 
@@ -319,7 +331,7 @@ function FileEntry.with_layout(layout_class, opt)
       rev = rev,
       nulled = utils.sate(
         opt.nulled,
-        select(2, pcall(layout_class.should_null, rev, opt.status, symbol))
+        try_should_null(layout_class, rev, opt.status, symbol)
       ),
     }) --[[@as vcs.File ]]
   end

lua/diffview/scene/layouts/diff_2.lua

@@ -74,7 +74,7 @@ function Diff2.should_null(rev, status, sym)
       return vim.tbl_contains({ "?", "A" }, status)
     end
 
-    return false
+    return status == "D"
 
   elseif rev.type == RevType.STAGE then
     if sym == "a" then

lua/diffview/scene/layouts/diff_3.lua

@@ -106,13 +106,38 @@ function Diff3:to_diff4(layout)
   })
 end
 
----FIXME
 ---@override
 ---@param rev Rev
 ---@param status string Git status symbol.
 ---@param sym Diff3.WindowSymbol
 function Diff3.should_null(rev, status, sym)
-  return false
+  assert(sym == "a" or sym == "b" or sym == "c")
+
+  if rev.type == RevType.LOCAL then
+    return status == "D"
+
+  elseif rev.type == RevType.COMMIT then
+    if sym == "a" then
+      return vim.tbl_contains({ "?", "A" }, status)
+    end
+
+    return status == "D"
+
+  elseif rev.type == RevType.STAGE then
+    if rev.stage == 0 then
+      if sym == "a" then
+        return vim.tbl_contains({ "?", "A" }, status)
+      end
+
+      return status == "D"
+    end
+
+    -- Merge stages (1..3) can be absent depending on conflict type.
+    -- This is resolved at file load time by checking stage blob existence.
+    return false
+  end
+
+  error(("Unexpected state! %s, %s, %s"):format(rev, status, sym))
 end
 
 M.Diff3 = Diff3

lua/diffview/scene/layouts/diff_4.lua

@@ -6,6 +6,7 @@ local oop = require("diffview.oop")
 
 local Diff1 = lazy.access("diffview.scene.layouts.diff_1", "Diff1") ---@type Diff1|LazyModule
 local Diff3 = lazy.access("diffview.scene.layouts.diff_3", "Diff3") ---@type Diff3|LazyModule
+local RevType = lazy.access("diffview.vcs.rev", "RevType") ---@type RevType|LazyModule
 
 local await = async.await
 
@@ -103,13 +104,38 @@ function Diff4:to_diff3(layout)
   })
 end
 
----FIXME
 ---@override
 ---@param rev Rev
 ---@param status string Git status symbol.
 ---@param sym Diff4.WindowSymbol
 function Diff4.should_null(rev, status, sym)
-  return false
+  assert(sym == "a" or sym == "b" or sym == "c" or sym == "d")
+
+  if rev.type == RevType.LOCAL then
+    return status == "D"
+
+  elseif rev.type == RevType.COMMIT then
+    if sym == "a" then
+      return vim.tbl_contains({ "?", "A" }, status)
+    end
+
+    return status == "D"
+
+  elseif rev.type == RevType.STAGE then
+    if rev.stage == 0 then
+      if sym == "a" then
+        return vim.tbl_contains({ "?", "A" }, status)
+      end
+
+      return status == "D"
+    end
+
+    -- Merge stages (1..3) can be absent depending on conflict type.
+    -- This is resolved at file load time by checking stage blob existence.
+    return false
+  end
+
+  error(("Unexpected state! %s, %s, %s"):format(rev, status, sym))
 end
 
 M.Diff4 = Diff4

lua/diffview/tests/functional/config_spec.lua

@@ -0,0 +1,26 @@
+local config = require("diffview.config")
+local utils = require("diffview.utils")
+
+describe("diffview.config", function()
+  it("validates rename_threshold", function()
+    local original = vim.deepcopy(config.get_config())
+    local old_warn = utils.warn
+    utils.warn = function() end
+
+    local ok, err = pcall(function()
+      config.setup({ rename_threshold = "40" })
+      assert.equals(40, config.get_config().rename_threshold)
+
+      config.setup({ rename_threshold = 101 })
+      assert.is_nil(config.get_config().rename_threshold)
+
+      config.setup({ rename_threshold = 12.5 })
+      assert.is_nil(config.get_config().rename_threshold)
+    end)
+
+    utils.warn = old_warn
+    config.setup(original)
+
+    if not ok then error(err) end
+  end)
+end)

lua/diffview/tests/functional/file_entry_spec.lua

@@ -0,0 +1,37 @@
+local FileEntry = require("diffview.scene.file_entry").FileEntry
+local RevType = require("diffview.vcs.rev").RevType
+local GitRev = require("diffview.vcs.adapters.git.rev").GitRev
+
+describe("diffview.file_entry", function()
+  it("does not treat should_null errors as truthy null markers", function()
+    local captured
+    local layout_class = setmetatable({
+      should_null = function()
+        error("boom")
+      end,
+    }, {
+      __call = function(_, opt)
+        captured = opt
+        return {
+          files = function()
+            return { opt.b }
+          end,
+        }
+      end,
+    })
+
+    local rev = GitRev(RevType.STAGE, 0)
+    local adapter = { ctx = { toplevel = vim.uv.cwd() } }
+
+    FileEntry.with_layout(layout_class, {
+      adapter = adapter,
+      path = "README.md",
+      status = "M",
+      kind = "working",
+      revs = { a = rev, b = rev },
+    })
+
+    assert.is_not_nil(captured)
+    assert.False(captured.b.nulled)
+  end)
+end)