patch 9.1.0602: filetype: Prolog detection can be improved

Problem:  filetype: Prolog detection can be improved
Solution: update the prolog detection regex
          (igna_martinoli)

related: #10835
related: #15206
closes: #15253

Co-authored-by: clason <c.clason@uni-graz.at>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: igna_martinoli <ignamartinoli@protonmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/autoload/dist/ft.vim

@@ -9,6 +9,8 @@ vim9script
 # These functions are moved here from runtime/filetype.vim to make startup
 # faster.
 
+var prolog_pattern = '^\s*\(:-\|%\+\(\s\|$\)\|\/\*\)\|\.\s*$'
+
 export def Check_inp()
   if getline(1) =~ '%%'
     setf tex
@@ -465,7 +467,7 @@ export def ProtoCheck(default: string)
     # recognize Prolog by specific text in the first non-empty line
     # require a blank after the '%' because Perl uses "%list" and "%translate"
     var lnum = getline(nextnonblank(1))
-    if lnum =~ '\<prolog\>' || lnum =~ '^\(:-\|%\|\/\*\)\|\.$'
+    if lnum =~ '\<prolog\>' || lnum =~ prolog_pattern
       setf prolog
     else
       exe 'setf ' .. default
@@ -644,7 +646,7 @@ export def FTpl()
     # recognize Prolog by specific text in the first non-empty line
     # require a blank after the '%' because Perl uses "%list" and "%translate"
     var line = getline(nextnonblank(1))
-    if line =~ '\<prolog\>' || line =~ '^\s*\(%\+\(\s\|$\)\|/\*\)' || line =~ ':-'
+    if line =~ '\<prolog\>' || line =~ prolog_pattern
       setf prolog
     else
       setf perl

runtime/filetype.vim

@@ -1719,7 +1719,7 @@ au BufNewFile,BufRead *.pcmk				setf pcmk
 " PEM (Privacy-Enhanced Mail)
 au BufNewFile,BufRead *.pem,*.cer,*.crt,*.csr		setf pem
 
-" Perl
+" Perl or Prolog
 if has("fname_case")
   au BufNewFile,BufRead *.pl,*.PL			call dist#ft#FTpl()
 else

src/testdir/test_filetype.vim

@@ -2603,6 +2603,44 @@ func Test_pro_file()
   call assert_equal('prolog', &filetype)
   bwipe!
 
+  " IDL
+  call writefile(['x = findgen(100)/10'], 'Xfile.pro', 'D')
+  split Xfile.pro
+  call assert_equal('idlang', &filetype)
+
+  filetype off
+endfunc
+
+
+func Test_pl_file()
+  filetype on
+
+  "Prolog
+  call writefile([':-module(test/1,'], 'Xfile.pl', 'D')
+  split Xfile.pl
+  call assert_equal('prolog', &filetype)
+  bwipe!
+
+  call writefile(['% comment'], 'Xfile.pl', 'D')
+  split Xfile.pl
+  call assert_equal('prolog', &filetype)
+  bwipe!
+
+  call writefile(['/* multiline comment'], 'Xfile.pl', 'D')
+  split Xfile.pl
+  call assert_equal('prolog', &filetype)
+  bwipe!
+
+  call writefile(['rule(test, 1.7).'], 'Xfile.pl', 'D')
+  split Xfile.pl
+  call assert_equal('prolog', &filetype)
+  bwipe!
+
+  " Perl
+  call writefile(['%data = (1, 2, 3);'], 'Xfile.pl', 'D')
+  split Xfile.pl
+  call assert_equal('perl', &filetype)
+
   filetype off
 endfunc
 

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    602,
 /**/
     601,
 /**/