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 #9401)

runtime/doc/diff.txt

@@ -398,6 +398,11 @@ mode, so that a CTRL-Z doesn't end the text on DOS.
 The `redraw!` command may not be needed, depending on whether executing a
 shell command shows something on the display or not.
 
+If the 'diffexpr' expression starts with s: or |<SID>|, then it is replaced
+with the script ID (|local-function|). Example: >
+		set diffexpr=s:MyDiffExpr()
+		set diffexpr=<SID>SomeDiffExpr()
+<
 						*E810* *E97*
 Vim will do a test if the diff output looks alright.  If it doesn't, you will
 get an error message.  Possible causes:
@@ -449,4 +454,9 @@ evaluating 'patchexpr'.  This hopefully avoids that files in the current
 directory are accidentally patched.  Vim will also delete files starting with
 v:fname_in and ending in ".rej" and ".orig".
 
+If the 'patchexpr' expression starts with s: or |<SID>|, then it is replaced
+with the script ID (|local-function|). Example: >
+		set patchexpr=s:MyPatchExpr()
+		set patchexpr=<SID>SomePatchExpr()
+<
  vim:tw=78:ts=8:noet:ft=help:norl:

runtime/doc/fold.txt

@@ -121,6 +121,11 @@ method can be very slow!
 Try to avoid the "=", "a" and "s" return values, since Vim often has to search
 backwards for a line for which the fold level is defined.  This can be slow.
 
+If the 'foldexpr' expression starts with s: or |<SID>|, then it is replaced
+with the script ID (|local-function|). Example: >
+		set foldexpr=s:MyFoldExpr()
+		set foldexpr=<SID>SomeFoldExpr()
+<
 An example of using "a1" and "s1": For a multi-line C comment, a line
 containing "/*" would return "a1" to start a fold, and a line containing "*/"
 would return "s1" to end the fold after that line: >
@@ -543,6 +548,8 @@ A closed fold is indicated with a '+'.
 
 These characters can be changed with the 'fillchars' option.
 
+These characters can be changed with the 'fillchars' option.
+
 Where the fold column is too narrow to display all nested folds, digits are
 shown to indicate the nesting level.
 

runtime/doc/options.txt

@@ -1225,6 +1225,11 @@ A jump table for the options with a short description can be found at |Q_op|.
 	Vim does not try to send a message to an external debugger (Netbeans
 	or Sun Workshop).
 
+	If the expression starts with s: or |<SID>|, then it is replaced with
+	the script ID (|local-function|). Example: >
+		set bexpr=s:MyBalloonExpr()
+		set bexpr=<SID>SomeBalloonExpr()
+<
 	The expression will be evaluated in the |sandbox| when set from a
 	modeline, see |sandbox-option|.
 	This option cannot be set in a modeline when 'modelineexpr' is off.
@@ -3596,6 +3601,11 @@ A jump table for the options with a short description can be found at |Q_op|.
 	When the expression evaluates to non-zero Vim will fall back to using
 	the internal format mechanism.
 
+	If the expression starts with s: or |<SID>|, then it is replaced with
+	the script ID (|local-function|). Example: >
+		set formatexpr=s:MyFormatExpr()
+		set formatexpr=<SID>SomeFormatExpr()
+<
 	The expression will be evaluated in the |sandbox| when set from a
 	modeline, see |sandbox-option|.  That stops the option from working,
 	since changing the buffer text is not allowed.
@@ -4438,6 +4448,11 @@ A jump table for the options with a short description can be found at |Q_op|.
 	found.  Allows doing "gf" on the name after an 'include' statement.
 	Also used for |<cfile>|.
 
+	If the expression starts with s: or |<SID>|, then it is replaced with
+	the script ID (|local-function|). Example: >
+		set includeexpr=s:MyIncludeExpr(v:fname)
+		set includeexpr=<SID>SomeIncludeExpr(v:fname)
+<
 	The expression will be evaluated in the |sandbox| when set from a
 	modeline, see |sandbox-option|.
 	This option cannot be set in a modeline when 'modelineexpr' is off.
@@ -4511,6 +4526,11 @@ A jump table for the options with a short description can be found at |Q_op|.
 	The expression is evaluated with |v:lnum| set to the line number for
 	which the indent is to be computed.  The cursor is also in this line
 	when the expression is evaluated (but it may be moved around).
+	If the expression starts with s: or |<SID>|, then it is replaced with
+	the script ID (|local-function|). Example: >
+		set indentexpr=s:MyIndentExpr()
+		set indentexpr=<SID>SomeIndentExpr()
+<
 	The expression must return the number of spaces worth of indent.  It
 	can return "-1" to keep the current indent (this means 'autoindent' is
 	used for the indent).

runtime/doc/print.txt

@@ -174,6 +174,11 @@ an error message.  In that case Vim will delete the file.  In the default
 value for non-MS-Windows a trick is used: Adding "v:shell_error" will result
 in a non-zero number when the system() call fails.
 
+If the expression starts with s: or |<SID>|, then it is replaced with the
+script ID (|local-function|). Example: >
+		set printexpr=s:MyPrintFile()
+		set printexpr=<SID>SomePrintFile()
+<
 This option cannot be set from a |modeline| or in the |sandbox|, for security
 reasons.
 

src/optionstr.c

@@ -2026,14 +2026,6 @@ ambw_end:
 		newFoldLevel();
 	}
     }
-# ifdef FEAT_EVAL
-    // 'foldexpr'
-    else if (varp == &curwin->w_p_fde)
-    {
-	if (foldmethodIsExpr(curwin))
-	    foldUpdateAll(curwin);
-    }
-# endif
     // 'foldmarker'
     else if (gvarp == &curwin->w_allbuf_opt.wo_fmr)
     {
@@ -2307,6 +2299,89 @@ ambw_end:
 # endif
 #endif
 
+#ifdef FEAT_EVAL
+    // '*expr' options
+    else if (
+# ifdef FEAT_BEVAL
+	    varp == &p_bexpr ||
+# endif
+# ifdef FEAT_DIFF
+	    varp == &p_dex ||
+# endif
+# ifdef FEAT_FOLDING
+	    varp == &curwin->w_p_fde ||
+# endif
+	    gvarp == &p_fex ||
+# ifdef FEAT_FIND_ID
+	    gvarp == &p_inex ||
+# endif
+# ifdef FEAT_CINDENT
+	    gvarp == &p_inde ||
+# endif
+# ifdef FEAT_DIFF
+	    varp == &p_pex ||
+# endif
+# ifdef FEAT_POSTSCRIPT
+	    varp == &p_pexpr ||
+# endif
+	    FALSE
+	    )
+    {
+	char_u	**p_opt = NULL;
+	char_u	*name;
+
+	// If the option value starts with <SID> or s:, then replace that with
+	// the script identifier.
+# ifdef FEAT_BEVAL
+	if (varp == &p_bexpr)		// 'balloonexpr'
+	    p_opt = (opt_flags & OPT_LOCAL) ? &curbuf->b_p_bexpr : &p_bexpr;
+# endif
+# ifdef FEAT_DIFF
+	if (varp == &p_dex)	// 'diffexpr'
+	    p_opt = &p_dex;
+# endif
+# ifdef FEAT_FOLDING
+	if(varp == &curwin->w_p_fde)	// 'foldexpr'
+	    p_opt = &curwin->w_p_fde;
+# endif
+	if (gvarp == &p_fex)	// 'formatexpr'
+	    p_opt = &curbuf->b_p_fex;
+# ifdef FEAT_FIND_ID
+	if (gvarp == &p_inex)	// 'includeexpr'
+	    p_opt = &curbuf->b_p_inex;
+# endif
+# ifdef FEAT_CINDENT
+	if (gvarp == &p_inde)	// 'indentexpr'
+	    p_opt = &curbuf->b_p_inde;
+# endif
+# ifdef FEAT_DIFF
+	if (varp == &p_pex)	// 'patchexpr'
+	    p_opt = &p_pex;
+# endif
+# ifdef FEAT_POSTSCRIPT
+	if (varp == &p_pexpr)	// 'printexpr'
+	    p_opt = &p_pexpr;
+# endif
+
+	if (p_opt != NULL)
+	{
+	    name = get_scriptlocal_funcname(*p_opt);
+	    if (name != NULL)
+	    {
+		if (new_value_alloced)
+		    free_string_option(*p_opt);
+		*p_opt = name;
+		new_value_alloced = TRUE;
+	    }
+	}
+
+# ifdef FEAT_FOLDING
+	if (varp == &curwin->w_p_fde && foldmethodIsExpr(curwin))
+	    foldUpdateAll(curwin);
+# endif
+    }
+#endif
+
 #ifdef FEAT_COMPL_FUNC
     // 'completefunc'
     else if (gvarp == &p_cfu)

src/testdir/test_diffmode.vim

@@ -681,8 +681,19 @@ 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()
@@ -1216,10 +1227,19 @@ 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
 

src/testdir/test_edit.vim

@@ -324,6 +324,16 @@ 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
 

src/testdir/test_fold.vim

@@ -1382,4 +1382,30 @@ 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
+
 " vim: shiftwidth=2 sts=2 expandtab

src/testdir/test_gf.vim

@@ -217,4 +217,30 @@ 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
+
 " vim: shiftwidth=2 sts=2 expandtab

src/testdir/test_gui.vim

@@ -258,6 +258,15 @@ func Test_set_balloonexpr()
   setl balloonexpr&
   call assert_equal('', &balloonexpr)
   delfunc MyBalloonExpr
+
+  " Using a script-local function
+  func s:NewBalloonExpr()
+  endfunc
+  set balloonexpr=s:NewBalloonExpr()
+  call assert_equal(expand('<SID>') .. 'NewBalloonExpr()', &balloonexpr)
+  set balloonexpr=<SID>NewBalloonExpr()
+  call assert_equal(expand('<SID>') .. 'NewBalloonExpr()', &balloonexpr)
+  delfunc s:NewBalloonExpr
   bwipe!
 
   " Multiline support

src/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

src/testdir/test_normal.vim

@@ -253,6 +253,45 @@ 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

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3900,
 /**/
     3899,
 /**/