patch 9.0.1773: cannot distinguish Forth and Fortran *.f filesv9.0.1773

Problem:  cannot distinguish Forth and Fortran *.f files
Solution: Add Filetype detection Code

Also add *.4th as a Forth filetype

closes: #12251

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Doug Kearns <dougkearns@gmail.com>

6 files changed, 109 insertions, 19 deletions

diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index 9f53f68460..bc2125754a 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -287,6 +287,37 @@ export def FTe()
   endif
 enddef
 
+def IsForth(): bool
+  var first_line = nextnonblank(1)
+
+  # SwiftForth block comment (line is usually filled with '-' or '=') or
+  # OPTIONAL (sometimes precedes the header comment)
+  if getline(first_line) =~? '^\%({\%(\s\|$\)\|OPTIONAL\s\)'
+    return true
+  endif
+
+  var n = first_line
+  while n < 100 && n <= line("$")
+    # Forth comments and colon definitions
+    if getline(n) =~ '^[:(\\] '
+      return true
+    endif
+    n += 1
+  endwhile
+  return false
+enddef
+
+# Distinguish between Forth and Fortran
+export def FTf()
+  if exists("g:filetype_f")
+    exe "setf " .. g:filetype_f
+  elseif IsForth()
+    setf forth
+  else
+    setf fortran
+  endif
+enddef
+
 export def FTfrm()
   if exists("g:filetype_frm")
     exe "setf " .. g:filetype_frm
@@ -302,21 +333,13 @@ export def FTfrm()
   endif
 enddef
 
-# Distinguish between Forth and F#.
-# Provided by Doug Kearns.
+# Distinguish between Forth and F#
 export def FTfs()
   if exists("g:filetype_fs")
     exe "setf " .. g:filetype_fs
+  elseif IsForth()
+    setf forth
   else
-    var n = 1
-    while n < 100 && n <= line("$")
-      # Forth comments and colon definitions
-      if getline(n) =~ "^[:(\\\\] "
-        setf forth
-        return
-      endif
-      n += 1
-    endwhile
     setf fsharp
   endif
 enddef
diff --git a/runtime/doc/filetype.txt b/runtime/doc/filetype.txt
index 05574eba22..05047224f9 100644
--- a/runtime/doc/filetype.txt
+++ b/runtime/doc/filetype.txt
@@ -146,6 +146,7 @@ variables can be used to overrule the filetype used for certain extensions:
 	*.cls		g:filetype_cls
 	*.csh		g:filetype_csh	|ft-csh-syntax|
 	*.dat		g:filetype_dat
+	*.f		g:filetype_f	|ft-forth-syntax|
 	*.frm		g:filetype_frm	|ft-form-syntax|
 	*.fs		g:filetype_fs	|ft-forth-syntax|
 	*.i		g:filetype_i	|ft-progress-syntax|
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 17f81391a9..29a12396d4 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -1579,9 +1579,10 @@ example, FORM files, use this in your startup vimrc: >
 
 FORTH						*forth.vim* *ft-forth-syntax*
 
-Files matching "*.fs" could be F# or Forth.  If the automatic detection
-doesn't work for you, or you don't edit F# at all, use this in your
-startup vimrc: >
+Files matching "*.f" could be Fortran or Forth and those matching "*.fs" could
+be F# or Forth.  If the automatic detection doesn't work for you, or you don't
+edit F# or Fortran at all, use this in your startup vimrc: >
+   :let filetype_f  = "forth"
    :let filetype_fs = "forth"
 
 
diff --git a/runtime/filetype.vim b/runtime/filetype.vim
index 16d4a131fd..a434503418 100644
--- a/runtime/filetype.vim
+++ b/runtime/filetype.vim
@@ -724,16 +724,19 @@ au BufNewFile,BufRead auto.master		setf conf
 au BufNewFile,BufRead *.mas,*.master		setf master
 
 " Forth
-au BufNewFile,BufRead *.ft,*.fth		setf forth
+au BufNewFile,BufRead *.ft,*.fth,*.4th		setf forth
 
 " Reva Forth
 au BufNewFile,BufRead *.frt			setf reva
 
 " Fortran
 if has("fname_case")
-  au BufNewFile,BufRead *.F,*.FOR,*.FPP,*.FTN,*.F77,*.F90,*.F95,*.F03,*.F08	 setf fortran
+  au BufNewFile,BufRead *.F,*.FOR,*.FPP,*.FTN,*.F77,*.F90,*.F95,*.F03,*.F08	setf fortran
 endif
-au BufNewFile,BufRead   *.f,*.for,*.fortran,*.fpp,*.ftn,*.f77,*.f90,*.f95,*.f03,*.f08  setf fortran
+au BufNewFile,BufRead *.for,*.fortran,*.fpp,*.ftn,*.f77,*.f90,*.f95,*.f03,*.f08	setf fortran
+
+" Fortran or Forth
+au BufNewFile,BufRead *.f			call dist#ft#FTf()
 
 " Framescript
 au BufNewFile,BufRead *.fsl			setf framescript
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 778736b36c..a8ce88cca0 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -246,7 +246,7 @@ def s:GetFilenameChecks(): dict<list<string>>
     fish: ['file.fish'],
     focexec: ['file.fex', 'file.focexec'],
     form: ['file.frm'],
-    forth: ['file.ft', 'file.fth'],
+    forth: ['file.ft', 'file.fth', 'file.4th'],
     fortran: ['file.f', 'file.for', 'file.fortran', 'file.fpp', 'file.ftn', 'file.f77', 'file.f90', 'file.f95', 'file.f03', 'file.f08'],
     fpcmake: ['file.fpc'],
     framescript: ['file.fsl'],
@@ -1265,6 +1265,54 @@ func Test_ex_file()
   filetype off
 endfunc
 
+func Test_f_file()
+  filetype on
+
+  call writefile(['looks like Fortran'], 'Xfile.f', 'D')
+  split Xfile.f
+  call assert_equal('fortran', &filetype)
+  bwipe!
+
+  let g:filetype_f = 'forth'
+  split Xfile.f
+  call assert_equal('forth', &filetype)
+  bwipe!
+  unlet g:filetype_f
+
+  " Test dist#ft#FTf()
+
+  " Forth
+
+  call writefile(['( Forth inline comment )'], 'Xfile.f')
+  split Xfile.f
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  call writefile(['\ Forth line comment'], 'Xfile.f')
+  split Xfile.f
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  call writefile([': squared ( n -- n^2 )', 'dup * ;'], 'Xfile.f')
+  split Xfile.f
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  " SwiftForth
+
+  call writefile(['{ ================', 'Header comment', '================ }'], 'Xfile.f')
+  split Xfile.f
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  call writefile(['OPTIONAL Maybe Descriptive text'], 'Xfile.f')
+  split Xfile.f
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  filetype off
+endfunc
+
 func Test_foam_file()
   filetype on
   call assert_true(mkdir('0', 'pR'))
@@ -1355,7 +1403,7 @@ func Test_fs_file()
 
   " Test dist#ft#FTfs()
 
-  " Forth (Gforth)
+  " Forth
 
   call writefile(['( Forth inline comment )'], 'Xfile.fs')
   split Xfile.fs
@@ -1372,6 +1420,18 @@ func Test_fs_file()
   call assert_equal('forth', &filetype)
   bwipe!
 
+  " SwiftForth
+
+  call writefile(['{ ================', 'Header comment', '================ }'], 'Xfile.fs')
+  split Xfile.fs
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  call writefile(['OPTIONAL Maybe Descriptive text'], 'Xfile.fs')
+  split Xfile.fs
+  call assert_equal('forth', &filetype)
+  bwipe!
+
   filetype off
 endfunc
 
diff --git a/src/version.c b/src/version.c
index 13d27f4afd..ffecee9e17 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@ static char *(features[]) =
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1773,
+/**/
     1772,
 /**/
     1771,