feat(exrc): stop searching in parent directories by unsetting 'exrc'

Problem:
No way for a user to limit 'exrc' search in parent directories (compare
editorconfig.root).

Solution:
A configuration file can unset 'exrc', disabling the search for its
parent directories.

runtime/doc/news.txt

@@ -123,6 +123,7 @@ DEFAULTS
 • 'statusline' default is exposed as a statusline expression (previously it
   was implemented as an internal C routine).
 • Project-local configuration ('exrc') is also loaded from parent directories.
+  Unset 'exrc' to stop further search.
 
 DIAGNOSTICS
 

runtime/doc/options.txt

@@ -2416,6 +2416,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 	directories (ordered upwards), if the files are in the |trust| list.
 	Use |:trust| to manage trusted files. See also |vim.secure.read()|.
 
+	Unset 'exrc' to stop further searching of 'exrc' files in parent
+	directories, similar to |editorconfig.root|.
+
 	Compare 'exrc' to |editorconfig|:
 	- 'exrc' can execute any code; editorconfig only specifies settings.
 	- 'exrc' is Nvim-specific; editorconfig works in other editors.

runtime/lua/vim/_defaults.lua

@@ -930,25 +930,29 @@ do
     group = vim.api.nvim_create_augroup('nvim.find_exrc', {}),
     desc = 'Find exrc files in parent directories',
     callback = function()
-      if vim.o.exrc then
+      if not vim.o.exrc then
-        -- Start from parent directory, as exrc file in the current
+        return
-        -- directory is already loaded in do_exrc_initalization().
+      end
-        local files = vim.fs.find({ '.nvim.lua', '.nvimrc', '.exrc' }, {
+      local files = vim.fs.find({ '.nvim.lua', '.nvimrc', '.exrc' }, {
-          type = 'file',
+        type = 'file',
-          upward = true,
+        upward = true,
-          limit = math.huge,
+        limit = math.huge,
-          path = vim.fs.dirname(vim.uv.cwd()),
+        -- exrc in cwd already handled from C, thus start in parent directory.
-        })
+        path = vim.fs.dirname(vim.uv.cwd()),
-        for _, file in ipairs(files) do
+      })
-          local trusted = vim.secure.read(file) --[[@as string|nil]]
+      for _, file in ipairs(files) do
-          if trusted then
+        local trusted = vim.secure.read(file) --[[@as string|nil]]
-            if vim.endswith(file, '.lua') then
+        if trusted then
-              loadstring(trusted)()
+          if vim.endswith(file, '.lua') then
-            else
+            loadstring(trusted)()
-              vim.api.nvim_exec2(trusted, {})
+          else
-            end
+            vim.api.nvim_exec2(trusted, {})
           end
         end
+        -- If the user unset 'exrc' in the current exrc then stop searching
+        if not vim.o.exrc then
+          return
+        end
       end
     end,
   })

runtime/lua/vim/_meta/options.lua

@@ -2080,6 +2080,9 @@ vim.bo.et = vim.bo.expandtab
 --- directories (ordered upwards), if the files are in the `trust` list.
 --- Use `:trust` to manage trusted files. See also `vim.secure.read()`.
 ---
+--- Unset 'exrc' to stop further searching of 'exrc' files in parent
+--- directories, similar to `editorconfig.root`.
+---
 --- Compare 'exrc' to `editorconfig`:
 --- - 'exrc' can execute any code; editorconfig only specifies settings.
 --- - 'exrc' is Nvim-specific; editorconfig works in other editors.

src/nvim/options.lua

@@ -2749,6 +2749,9 @@ local options = {
         directories (ordered upwards), if the files are in the |trust| list.
         Use |:trust| to manage trusted files. See also |vim.secure.read()|.
 
+        Unset 'exrc' to stop further searching of 'exrc' files in parent
+        directories, similar to |editorconfig.root|.
+
         Compare 'exrc' to |editorconfig|:
         - 'exrc' can execute any code; editorconfig only specifies settings.
         - 'exrc' is Nvim-specific; editorconfig works in other editors.

test/functional/core/startup_spec.lua

@@ -1128,6 +1128,10 @@ describe('user config init', function()
     end
 
     before_each(function()
+      for _, file in ipairs({ '.exrc', '.nvimrc', '.nvim.lua' }) do
+        os.remove('../' .. file)
+        os.remove(file)
+      end
       write_file(
         init_lua_path,
         [[
@@ -1139,7 +1143,10 @@ describe('user config init', function()
     end)
 
     after_each(function()
-      os.remove(exrc_path)
+      for _, file in ipairs({ '.exrc', '.nvimrc', '.nvim.lua' }) do
+        os.remove('../' .. file)
+        os.remove(file)
+      end
       rmdir(xstate)
     end)
 
@@ -1188,13 +1195,9 @@ describe('user config init', function()
       end)
     end
 
-    it('exrc from all parent directories', function()
+    it('exrc from parent directories', function()
-      -- make sure that there are not any exrc files left from previous tests
-      for _, file in ipairs({ '.exrc', '.nvimrc', '.nvim.lua', '../.nvim.lua', '../.nvimrc' }) do
-        os.remove(file)
-      end
-      setup_exrc_file('../.exrc')
       setup_exrc_file('.nvim.lua')
+      setup_exrc_file('../.exrc')
       clear { args_rm = { '-u' }, env = xstateenv }
       local screen = Screen.new(50, 8)
       screen._default_attr_ids = nil
@@ -1206,16 +1209,16 @@ describe('user config init', function()
       })
       -- current directory exrc is found first
       screen:expect({ any = '.nvim.lua' })
-      screen:expect({ any = pesc('[i]gnore, (v)iew, (d)eny, (a)llow:') })
+      screen:expect({ any = pesc('[i]gnore, (v)iew, (d)eny, (a)llow:'), unchanged = true })
       feed('ia')
 
       -- after that the exrc in the parent directory
       screen:expect({ any = '.exrc' })
-      screen:expect({ any = pesc('[i]gnore, (v)iew, (d)eny, (a)llow:') })
+      screen:expect({ any = pesc('[i]gnore, (v)iew, (d)eny, (a)llow:'), unchanged = true })
-      feed('ia')
+      feed('a')
-      clear { args_rm = { '-u' }, env = xstateenv }
       -- a total of 2 exrc files are executed
-      eq(2, eval('g:exrc_count'))
+      feed(':echo g:exrc_count<CR>')
+      screen:expect({ any = '2' })
     end)
   end)