vim-patch:8.2.3900: it is not easy to use a script-local function for an option

Problem:    It is not easy to use a script-local function for an option.
Solution:   recognize s: and <SID> at the start of the expression. (Yegappan
            Lakshmanan, closes vim/vim#9401)

https://github.com/vim/vim/commit/8bb65f230d3025037f34021a72616038da0601ee

Omit duplicate docs in fold.txt: removed in a later runtime update.
Cherry-pick test_diffmode.vim changes from patch 8.2.1432.

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

9 files changed, 180 insertions, 9 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index fdb379a682..554771d9c9 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -711,7 +711,7 @@ void eval_patch(const char *const origfile, const char *const difffile, const ch
   set_vim_var_string(VV_FNAME_IN, origfile, -1);
   set_vim_var_string(VV_FNAME_DIFF, difffile, -1);
   set_vim_var_string(VV_FNAME_OUT, outfile, -1);
-  (void)eval_to_bool((char *)p_pex, &err, NULL, false);
+  (void)eval_to_bool(p_pex, &err, NULL, false);
   set_vim_var_string(VV_FNAME_IN, NULL, -1);
   set_vim_var_string(VV_FNAME_DIFF, NULL, -1);
   set_vim_var_string(VV_FNAME_OUT, NULL, -1);
diff --git a/src/nvim/option_defs.h b/src/nvim/option_defs.h
index 40ce022bea..de07327416 100644
--- a/src/nvim/option_defs.h
+++ b/src/nvim/option_defs.h
@@ -622,7 +622,7 @@ EXTERN char *p_opfunc;          // 'operatorfunc'
 EXTERN char_u *p_para;          // 'paragraphs'
 EXTERN int p_paste;             // 'paste'
 EXTERN char *p_pt;              // 'pastetoggle'
-EXTERN char_u *p_pex;           // 'patchexpr'
+EXTERN char *p_pex;             // 'patchexpr'
 EXTERN char *p_pm;              // 'patchmode'
 EXTERN char_u *p_path;          // 'path'
 EXTERN char_u *p_cdpath;        // 'cdpath'
diff --git a/src/nvim/optionstr.c b/src/nvim/optionstr.c
index 61a51532a4..b5dce7ff2a 100644
--- a/src/nvim/optionstr.c
+++ b/src/nvim/optionstr.c
@@ -17,6 +17,7 @@
 #include "nvim/drawscreen.h"
 #include "nvim/eval.h"
 #include "nvim/eval/typval_defs.h"
+#include "nvim/eval/userfunc.h"
 #include "nvim/eval/vars.h"
 #include "nvim/ex_getln.h"
 #include "nvim/fold.h"
@@ -1341,10 +1342,6 @@ char *did_set_string_option(int opt_idx, char **varp, char *oldval, char *errbuf
         newFoldLevel();
       }
     }
-  } else if (varp == &curwin->w_p_fde) {  // 'foldexpr'
-    if (foldmethodIsExpr(curwin)) {
-      foldUpdateAll(curwin);
-    }
   } else if (gvarp == &curwin->w_allbuf_opt.wo_fmr) {  // 'foldmarker'
     p = vim_strchr(*varp, ',');
     if (p == NULL) {
@@ -1484,6 +1481,51 @@ char *did_set_string_option(int opt_idx, char **varp, char *oldval, char *errbuf
         }
       }
     }
+  } else if (varp == &p_dex
+             || varp == &curwin->w_p_fde
+             || gvarp == &p_fex
+             || gvarp == &p_inex
+             || gvarp == &p_inde
+             || varp == &p_pex
+             || varp == &p_pexpr) {  // '*expr' options
+    char **p_opt = NULL;
+
+    // If the option value starts with <SID> or s:, then replace that with
+    // the script identifier.
+
+    if (varp == &p_dex) {  // 'diffexpr'
+      p_opt = &p_dex;
+    }
+    if (varp == &curwin->w_p_fde) {  // 'foldexpr'
+      p_opt = &curwin->w_p_fde;
+    }
+    if (gvarp == &p_fex) {  // 'formatexpr'
+      p_opt = &curbuf->b_p_fex;
+    }
+    if (gvarp == &p_inex) {  // 'includeexpr'
+      p_opt = &curbuf->b_p_inex;
+    }
+    if (gvarp == &p_inde) {  // 'indentexpr'
+      p_opt = &curbuf->b_p_inde;
+    }
+    if (varp == &p_pex) {  // 'patchexpr'
+      p_opt = &p_pex;
+    }
+    if (varp == &p_pexpr) {  // 'printexpr'
+      p_opt = &p_pexpr;
+    }
+
+    if (p_opt != NULL) {
+      char *name = get_scriptlocal_funcname(*p_opt);
+      if (name != NULL) {
+        free_string_option(*p_opt);
+        *p_opt = name;
+      }
+    }
+
+    if (varp == &curwin->w_p_fde && foldmethodIsExpr(curwin)) {
+      foldUpdateAll(curwin);
+    }
   } else if (gvarp == &p_cfu) {  // 'completefunc'
     if (set_completefunc_option() == FAIL) {
       errmsg = e_invarg;
diff --git a/src/nvim/testdir/test_diffmode.vim b/src/nvim/testdir/test_diffmode.vim
index d83cd505a6..0049398776 100644
--- a/src/nvim/testdir/test_diffmode.vim
+++ b/src/nvim/testdir/test_diffmode.vim
@@ -1,4 +1,5 @@
 " Tests for diff mode
+
 source shared.vim
 source screendump.vim
 source check.vim
@@ -681,15 +682,25 @@ func Test_diffexpr()
   set diffexpr=NewDiffFunc()
   call assert_fails('windo diffthis', ['E117:', 'E97:'])
   diffoff!
+
+  " Using a script-local function
+  func s:NewDiffExpr()
+  endfunc
+  set diffexpr=s:NewDiffExpr()
+  call assert_equal(expand('<SID>') .. 'NewDiffExpr()', &diffexpr)
+  set diffexpr=<SID>NewDiffExpr()
+  call assert_equal(expand('<SID>') .. 'NewDiffExpr()', &diffexpr)
+
   %bwipe!
   set diffexpr& diffopt&
+  delfunc DiffExpr
+  delfunc s:NewDiffExpr
 endfunc
 
 func Test_diffpatch()
   " The patch program on MS-Windows may fail or hang.
-  if !executable('patch') || !has('unix')
-    return
-  endif
+  CheckExecutable patch
+  CheckUnix
   new
   insert
 ***************
@@ -1250,10 +1261,19 @@ func Test_patchexpr()
   call assert_equal(2, winnr('$'))
   call assert_true(&diff)
 
+  " Using a script-local function
+  func s:NewPatchExpr()
+  endfunc
+  set patchexpr=s:NewPatchExpr()
+  call assert_equal(expand('<SID>') .. 'NewPatchExpr()', &patchexpr)
+  set patchexpr=<SID>NewPatchExpr()
+  call assert_equal(expand('<SID>') .. 'NewPatchExpr()', &patchexpr)
+
   call delete('Xinput')
   call delete('Xdiff')
   set patchexpr&
   delfunc TPatch
+  delfunc s:NewPatchExpr
   %bwipe!
 endfunc
 
diff --git a/src/nvim/testdir/test_edit.vim b/src/nvim/testdir/test_edit.vim
index 89e597f401..fd54f77ccb 100644
--- a/src/nvim/testdir/test_edit.vim
+++ b/src/nvim/testdir/test_edit.vim
@@ -330,6 +330,16 @@ func Test_edit_11_indentexpr()
   set cinkeys&vim indentkeys&vim
   set nocindent indentexpr=
   delfu Do_Indent
+
+  " Using a script-local function
+  func s:NewIndentExpr()
+  endfunc
+  set indentexpr=s:NewIndentExpr()
+  call assert_equal(expand('<SID>') .. 'NewIndentExpr()', &indentexpr)
+  set indentexpr=<SID>NewIndentExpr()
+  call assert_equal(expand('<SID>') .. 'NewIndentExpr()', &indentexpr)
+  set indentexpr&
+
   bw!
 endfunc
 
diff --git a/src/nvim/testdir/test_fold.vim b/src/nvim/testdir/test_fold.vim
index 2215166cd6..bc8364a80e 100644
--- a/src/nvim/testdir/test_fold.vim
+++ b/src/nvim/testdir/test_fold.vim
@@ -1273,6 +1273,32 @@ func Test_fold_jump()
   bw!
 endfunc
 
+" Test for using a script-local function for 'foldexpr'
+func Test_foldexpr_scriptlocal_func()
+  func! s:FoldFunc()
+    let g:FoldLnum = v:lnum
+  endfunc
+  new | only
+  call setline(1, 'abc')
+  let g:FoldLnum = 0
+  set foldmethod=expr foldexpr=s:FoldFunc()
+  redraw!
+  call assert_equal(expand('<SID>') .. 'FoldFunc()', &foldexpr)
+  call assert_equal(1, g:FoldLnum)
+  set foldmethod& foldexpr=
+  bw!
+  new | only
+  call setline(1, 'abc')
+  let g:FoldLnum = 0
+  set foldmethod=expr foldexpr=<SID>FoldFunc()
+  redraw!
+  call assert_equal(expand('<SID>') .. 'FoldFunc()', &foldexpr)
+  call assert_equal(1, g:FoldLnum)
+  set foldmethod& foldexpr=
+  delfunc s:FoldFunc
+  bw!
+endfunc
+
 " Make sure a fold containing a nested fold is split correctly when using
 " foldmethod=indent
 func Test_fold_split()
diff --git a/src/nvim/testdir/test_gf.vim b/src/nvim/testdir/test_gf.vim
index b2bb189688..e369645328 100644
--- a/src/nvim/testdir/test_gf.vim
+++ b/src/nvim/testdir/test_gf.vim
@@ -226,6 +226,32 @@ func Test_gf_includeexpr()
   delfunc IncFunc
 endfunc
 
+" Test for using a script-local function for 'includeexpr'
+func Test_includeexpr_scriptlocal_func()
+  func! s:IncludeFunc()
+    let g:IncludeFname = v:fname
+    return ''
+  endfunc
+  set includeexpr=s:IncludeFunc()
+  call assert_equal(expand('<SID>') .. 'IncludeFunc()', &includeexpr)
+  new | only
+  call setline(1, 'TestFile1')
+  let g:IncludeFname = ''
+  call assert_fails('normal! gf', 'E447:')
+  call assert_equal('TestFile1', g:IncludeFname)
+  bw!
+  set includeexpr=<SID>IncludeFunc()
+  call assert_equal(expand('<SID>') .. 'IncludeFunc()', &includeexpr)
+  new | only
+  call setline(1, 'TestFile2')
+  let g:IncludeFname = ''
+  call assert_fails('normal! gf', 'E447:')
+  call assert_equal('TestFile2', g:IncludeFname)
+  set includeexpr&
+  delfunc s:IncludeFunc
+  bw!
+endfunc
+
 " Check that expanding directories can handle more than 255 entries.
 func Test_gf_subdirs_wildcard()
   let cwd = getcwd()
diff --git a/src/nvim/testdir/test_hardcopy.vim b/src/nvim/testdir/test_hardcopy.vim
index e390bd5cc8..be83728b4f 100644
--- a/src/nvim/testdir/test_hardcopy.vim
+++ b/src/nvim/testdir/test_hardcopy.vim
@@ -125,6 +125,14 @@ func Test_printexpr()
   set printexpr=PrintFails(v:fname_in)
   call assert_fails('hardcopy', 'E365:')
 
+  " Using a script-local function
+  func s:NewPrintExpr()
+  endfunc
+  set printexpr=s:NewPrintExpr()
+  call assert_equal(expand('<SID>') .. 'NewPrintExpr()', &printexpr)
+  set printexpr=<SID>NewPrintExpr()
+  call assert_equal(expand('<SID>') .. 'NewPrintExpr()', &printexpr)
+
   set printexpr&
   bwipe
 endfunc
diff --git a/src/nvim/testdir/test_normal.vim b/src/nvim/testdir/test_normal.vim
index 9c5cc51f79..7e8b8c5eef 100644
--- a/src/nvim/testdir/test_normal.vim
+++ b/src/nvim/testdir/test_normal.vim
@@ -255,6 +255,45 @@ func Test_normal_formatexpr_returns_nonzero()
   close!
 endfunc
 
+" Test for using a script-local function for 'formatexpr'
+func Test_formatexpr_scriptlocal_func()
+  func! s:Format()
+    let g:FormatArgs = [v:lnum, v:count]
+  endfunc
+  set formatexpr=s:Format()
+  call assert_equal(expand('<SID>') .. 'Format()', &formatexpr)
+  new | only
+  call setline(1, range(1, 40))
+  let g:FormatArgs = []
+  normal! 2GVjgq
+  call assert_equal([2, 2], g:FormatArgs)
+  bw!
+  set formatexpr=<SID>Format()
+  call assert_equal(expand('<SID>') .. 'Format()', &formatexpr)
+  new | only
+  call setline(1, range(1, 40))
+  let g:FormatArgs = []
+  normal! 4GVjgq
+  call assert_equal([4, 2], g:FormatArgs)
+  bw!
+  let &formatexpr = 's:Format()'
+  new | only
+  call setline(1, range(1, 40))
+  let g:FormatArgs = []
+  normal! 6GVjgq
+  call assert_equal([6, 2], g:FormatArgs)
+  bw!
+  let &formatexpr = '<SID>Format()'
+  new | only
+  call setline(1, range(1, 40))
+  let g:FormatArgs = []
+  normal! 8GVjgq
+  call assert_equal([8, 2], g:FormatArgs)
+  setlocal formatexpr=
+  delfunc s:Format
+  bw!
+endfunc
+
 " basic test for formatprg
 func Test_normal06_formatprg()
   " only test on non windows platform