From 2f9f77cd722a9dad71df46f39c71dca88815c290 Mon Sep 17 00:00:00 2001
From: zeertzjq <zeertzjq@outlook.com>
Date: Tue, 9 Dec 2025 09:08:09 +0800
Subject: [PATCH] vim-patch:9.1.1962: filetype: Erlang application resource
 files are not recognized (#36868)

Problem:  filetype: Erlang application resource files are not recognized
Solution: Add content-based filetype detection for application resource
          files matching extension '*.app' (Doug Kearns)

related: vim/vim#18835
closes:  vim/vim#18842

https://github.com/vim/vim/commit/cf5c25526007a5cc39be317b023f55cb266d5ed2

Co-authored-by: Doug Kearns <dougkearns@gmail.com>
---
 runtime/doc/filetype.txt            |  1 +
 runtime/lua/vim/filetype.lua        |  1 +
 runtime/lua/vim/filetype/detect.lua | 32 +++++++++++++++++++++++++++++
 test/old/testdir/test_filetype.vim  | 30 +++++++++++++++++++++++++++
 4 files changed, 64 insertions(+)

diff --git a/runtime/doc/filetype.txt b/runtime/doc/filetype.txt
index f625b8f84d..5f1471f21c 100644
--- a/runtime/doc/filetype.txt
+++ b/runtime/doc/filetype.txt
@@ -136,6 +136,7 @@ what kind of file it is.  This doesn't always work.  A number of global
 variables can be used to overrule the filetype used for certain extensions:
 
 	file name	variable ~
+	`*.app`		g:filetype_app
 	`*.asa`		g:filetype_asa		|ft-aspperl-syntax|
 						|ft-aspvbs-syntax|
 	`*.asm`		g:asmsyntax		|ft-asm-syntax|
diff --git a/runtime/lua/vim/filetype.lua b/runtime/lua/vim/filetype.lua
index 9230ece5d3..0fbd3f4261 100644
--- a/runtime/lua/vim/filetype.lua
+++ b/runtime/lua/vim/filetype.lua
@@ -212,6 +212,7 @@ local extension = {
   aml = 'aml',
   run = 'ampl',
   g4 = 'antlr4',
+  app = detect.app,
   applescript = 'applescript',
   scpt = 'applescript',
   ino = 'arduino',
diff --git a/runtime/lua/vim/filetype/detect.lua b/runtime/lua/vim/filetype/detect.lua
index 2662b63843..aabb0361ad 100644
--- a/runtime/lua/vim/filetype/detect.lua
+++ b/runtime/lua/vim/filetype/detect.lua
@@ -30,6 +30,38 @@ local matchregex = vim.filetype._matchregex
 -- luacheck: push no unused args
 -- luacheck: push ignore 122
 
+-- Erlang Application Resource Files (*.app.src is matched by extension)
+-- See: https://erlang.org/doc/system/applications
+--- @type vim.filetype.mapfn
+function M.app(path, bufnr)
+  if vim.g.filetype_app then
+    return vim.g.filetype_app
+  end
+  for lnum, line in ipairs(getlines(bufnr, 1, 100)) do
+    -- skip Erlang comments, might be something else
+    if not findany(line, { '^%s*%%', '^%s*$' }) then
+      if line:find('^%s*{') then
+        local name = fn.fnamemodify(path, ':t:r:r')
+        local lines = vim
+          .iter(getlines(bufnr, lnum, lnum + 9))
+          :filter(function(v)
+            return not v:find('^%s*%%')
+          end)
+          :join(' ')
+        if
+          findany(lines, {
+            [[^%s*{%s*application%s*,%s*']] .. name .. [['%s*,]],
+            [[^%s*{%s*application%s*,%s*]] .. name .. [[%s*,]],
+          })
+        then
+          return 'erlang'
+        end
+      end
+      return
+    end
+  end
+end
+
 -- This function checks for the kind of assembly that is wanted by the user, or
 -- can be detected from the beginning of the file.
 --- @type vim.filetype.mapfn
diff --git a/test/old/testdir/test_filetype.vim b/test/old/testdir/test_filetype.vim
index 4a1aaf854e..b014a9bcc4 100644
--- a/test/old/testdir/test_filetype.vim
+++ b/test/old/testdir/test_filetype.vim
@@ -3204,4 +3204,34 @@ func Test_m4_format()
   filetype off
 endfunc
 
+" Erlang Application Resource File
+func Test_app_file()
+  filetype on
+
+  call writefile(['% line comment', '{application, xfile1,'], 'xfile1.app', 'D')
+  split xfile1.app
+  call assert_equal('erlang', &filetype)
+  bwipe!
+
+  call writefile(['% line comment', "{application, 'Xfile2',"], 'Xfile2.app', 'D')
+  split Xfile2.app
+  call assert_equal('erlang', &filetype)
+  bwipe!
+
+  call writefile([' % line comment',
+        \ ' ',
+        \ ' % line comment',
+        \ ' { ',
+        \ ' % line comment ',
+        \ ' application , ',
+        \ ' % line comment ',
+        \ ' xfile3 , '],
+        \ 'xfile3.app', 'D')
+  split xfile3.app
+  call assert_equal('erlang', &filetype)
+  bwipe!
+
+  filetype off
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab