vim-patch:8.1.0515: reloading a script gives errors for existing functions

Problem:    Reloading a script gives errors for existing functions.
Solution:   Allow redefining a function once when reloading a script.
https://github.com/vim/vim/commit/ded5f1bed7ff2d138b3ee0f9610d17290b62692d

9 files changed, 51 insertions, 7 deletions

diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 97ca804c9a..d8c1132906 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -9238,9 +9238,13 @@ See |:verbose-cmd| for more information.
 			deleted if there are no more references to it.
 								*E127* *E122*
 			When a function by this name already exists and [!] is
-			not used an error message is given.  When [!] is used,
-			an existing function is silently replaced.  Unless it
-			is currently being executed, that is an error.
+			not used an error message is given.  There is one
+			exception: When sourcing a script again, a function
+			that was previously defined in that script will be
+			silently replaced.
+			When [!] is used, an existing function is silently
+			replaced.  Unless it is currently being executed, that
+			is an error.
 			NOTE: Use ! wisely.  If used without care it can cause
 			an existing function to be replaced unexpectedly,
 			which is hard to debug.
diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index f15205349b..f8e07a471f 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -5155,6 +5155,7 @@ chk_modeline(
       const int secure_save = secure;
       const sctx_T save_current_sctx = current_sctx;
       current_sctx.sc_sid = SID_MODELINE;
+      current_sctx.sc_seq = 0;
       current_sctx.sc_lnum = 0;
       // Make sure no risky things are executed as a side effect.
       secure = 1;
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 8fa4e23df6..6f7d5ed6e4 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -21504,7 +21504,11 @@ void ex_function(exarg_T *eap)
 
     fp = find_func(name);
     if (fp != NULL) {
-      if (!eap->forceit) {
+      // Function can be replaced with "function!" and when sourcing the
+      // same script again, but only once.
+      if (!eap->forceit
+          && (fp->uf_script_ctx.sc_sid != current_sctx.sc_sid
+              || fp->uf_script_ctx.sc_seq == current_sctx.sc_seq)) {
         emsg_funcname(e_funcexts, name);
         goto erret;
       }
diff --git a/src/nvim/eval/typval.h b/src/nvim/eval/typval.h
index c40585443e..823367560a 100644
--- a/src/nvim/eval/typval.h
+++ b/src/nvim/eval/typval.h
@@ -256,6 +256,7 @@ typedef int scid_T;
 // the line number in the script "sc_sid".
 typedef struct {
   scid_T sc_sid;     // script ID
+  int sc_seq;        // sourcing sequence number
   linenr_T sc_lnum;  // line number
 } sctx_T;
 
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index 96f758805b..964b884460 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -3034,6 +3034,7 @@ int do_source(char_u *fname, int check_other, int is_vimrc)
   char_u                  *firstline = NULL;
   int retval = FAIL;
   static scid_T last_current_SID = 0;
+  static int last_current_SID_seq = 0;
   void                    *save_funccalp;
   int save_debug_break_level = debug_break_level;
   scriptitem_T            *si = NULL;
@@ -3160,7 +3161,9 @@ int do_source(char_u *fname, int check_other, int is_vimrc)
 
   // Check if this script was sourced before to finds its SID.
   // If it's new, generate a new SID.
+  // Always use a new sequence number.
   const sctx_T save_current_sctx = current_sctx;
+  current_sctx.sc_seq = ++last_current_SID_seq;
   current_sctx.sc_lnum = 0;
   FileID file_id;
   bool file_id_ok = os_fileid((char *)fname_exp, &file_id);
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 3eae415719..5237c621f9 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -333,7 +333,7 @@ EXTERN int garbage_collect_at_exit INIT(= false);
 #define SID_API_CLIENT  -8      // for API clients
 
 // Script CTX being sourced or was sourced to define the current function.
-EXTERN sctx_T current_sctx INIT(= { 0 COMMA 0 });
+EXTERN sctx_T current_sctx INIT(= { 0 COMMA 0 COMMA 0 });
 // ID of the current channel making a client API call
 EXTERN uint64_t current_channel_id INIT(= 0);
 
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 9ea856a0c4..50e495c1e6 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -1665,6 +1665,7 @@ static void exe_commands(mparm_T *parmp)
     curwin->w_cursor.lnum = 0;
   sourcing_name = (char_u *)"command line";
   current_sctx.sc_sid = SID_CARG;
+  current_sctx.sc_seq = 0;
   for (i = 0; i < parmp->n_commands; i++) {
     do_cmdline_cmd(parmp->commands[i]);
     if (parmp->cmds_tofree[i])
@@ -1862,6 +1863,7 @@ static int execute_env(char *env)
     sourcing_lnum = 0;
     const sctx_T save_current_sctx = current_sctx;
     current_sctx.sc_sid = SID_ENV;
+    current_sctx.sc_seq = 0;
     current_sctx.sc_lnum = 0;
     do_cmdline_cmd((char *)initstr);
     sourcing_name = save_sourcing_name;
diff --git a/src/nvim/option.c b/src/nvim/option.c
index c7d2dcb602..ae75644794 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -200,7 +200,7 @@ typedef struct vimoption {
                                 // local option: indirect option index
   char_u      *def_val[2];      // default values for variable (vi and vim)
   LastSet last_set;             // script in which the option was last set
-# define SCTX_INIT , { 0, 0 }
+# define SCTX_INIT , { 0, 0, 0 }
 } vimoption_T;
 
 #define VI_DEFAULT  0       // def_val[VI_DEFAULT] is Vi default value
@@ -2423,6 +2423,7 @@ set_string_option_direct(
         script_ctx = current_sctx;
       } else {
         script_ctx.sc_sid = set_sid;
+        script_ctx.sc_seq = 0;
         script_ctx.sc_lnum = 0;
       }
       set_option_sctx_idx(idx, opt_flags, script_ctx);
@@ -3798,7 +3799,8 @@ static void set_option_sctx_idx(int opt_idx, int opt_flags, sctx_T script_ctx)
   int both = (opt_flags & (OPT_LOCAL | OPT_GLOBAL)) == 0;
   int indir = (int)options[opt_idx].indir;
   const LastSet last_set = { .script_ctx =
-    { script_ctx.sc_sid, script_ctx.sc_lnum + sourcing_lnum },
+    { script_ctx.sc_sid, script_ctx.sc_seq,
+      script_ctx.sc_lnum + sourcing_lnum },
     current_channel_id };
 
   // Remember where the option was set.  For local options need to do that
diff --git a/src/nvim/testdir/test_functions.vim b/src/nvim/testdir/test_functions.vim
index 6c3d944ad5..a36c51f56f 100644
--- a/src/nvim/testdir/test_functions.vim
+++ b/src/nvim/testdir/test_functions.vim
@@ -1067,6 +1067,33 @@ func Test_func_range_with_edit()
   bwipe!
 endfunc
 
+func Test_func_exists_on_reload()
+  call writefile(['func ExistingFunction()', 'echo "yes"', 'endfunc'], 'Xfuncexists')
+  call assert_equal(0, exists('*ExistingFunction'))
+  source Xfuncexists
+  call assert_equal(1, exists('*ExistingFunction'))
+  " Redefining a function when reloading a script is OK.
+  source Xfuncexists
+  call assert_equal(1, exists('*ExistingFunction'))
+
+  " But redefining in another script is not OK.
+  call writefile(['func ExistingFunction()', 'echo "yes"', 'endfunc'], 'Xfuncexists2')
+  call assert_fails('source Xfuncexists2', 'E122:')
+
+  delfunc ExistingFunction
+  call assert_equal(0, exists('*ExistingFunction'))
+  call writefile([
+	\ 'func ExistingFunction()', 'echo "yes"', 'endfunc',
+	\ 'func ExistingFunction()', 'echo "no"', 'endfunc',
+	\ ], 'Xfuncexists')
+  call assert_fails('source Xfuncexists', 'E122:')
+  call assert_equal(1, exists('*ExistingFunction'))
+
+  call delete('Xfuncexists2')
+  call delete('Xfuncexists')
+  delfunc ExistingFunction
+endfunc
+
 sandbox function Fsandbox()
   normal ix
 endfunc