vim-patch:8.2.1297: when a test fails it's often not easy to see where

Problem:    When a test fails it's often not easy to see what the call stack
            is.
Solution:   Add more entries from the call stack in the exception message.
https://github.com/vim/vim/commit/a5d0423fa16f18b4576a2a07e50034e489587a7d

Use docs from latest Vim.

9 files changed, 77 insertions, 43 deletions

diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 291eea7263..0fc8a30c20 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -2010,6 +2010,7 @@ expand({string} [, {nosuf} [, {list}]])				*expand()*
 					a function
 			<SID>		"<SNR>123_"  where "123" is the
 					current script ID  |<SID>|
+			<stack>		call stack
 			<cword>		word under the cursor
 			<cWORD>		WORD under the cursor
 			<client>	the {clientid} of the last received
diff --git a/runtime/doc/cmdline.txt b/runtime/doc/cmdline.txt
index 87f1589ea1..29eff75bfa 100644
--- a/runtime/doc/cmdline.txt
+++ b/runtime/doc/cmdline.txt
@@ -879,12 +879,18 @@ Note: these are typed literally, they are not special keys!
 							*:<sfile>* *<sfile>*
 	<sfile>    When executing a `:source` command, is replaced with the
 		   file name of the sourced file.  *E498*
-		   When executing a function, is replaced with:
-		   "function {function-name}[{lnum}]"
-		   function call nesting is indicated like this:
-		   "function {function-name1}[{lnum}]..{function-name2}[{lnum}]"
+		   When executing a function, is replaced with the call stack,
+		   as with <stack> (this is for backwards compatibility, using
+		   <stack> is preferred).
 		   Note that filename-modifiers are useless when <sfile> is
-		   used inside a function.
+		   not used inside a script.
+							*:<stack>* *<stack>*
+	<stack>	   is replaced with the call stack, using
+		   "function {function-name}[{lnum}]" for a function line
+		   and "script {file-name}[{lnum}]" for a script line, and
+		   ".." in between items.  E.g.:
+		   "function {function-name1}[{lnum}]..{function-name2}[{lnum}]"
+		   If there is no call stack you get error *E489* .
 							*:<slnum>* *<slnum>*
 	<slnum>	   When executing a `:source` command, is replaced with the
 		   line number.  *E842*
diff --git a/src/nvim/debugger.c b/src/nvim/debugger.c
index 76e1caff49..663f4feb08 100644
--- a/src/nvim/debugger.c
+++ b/src/nvim/debugger.c
@@ -99,7 +99,7 @@ void do_debug(char_u *cmd)
     xfree(debug_newval);
     debug_newval = NULL;
   }
-  char *sname = estack_sfile();
+  char *sname = estack_sfile(false);
   if (sname != NULL) {
     msg(sname);
   }
@@ -324,7 +324,7 @@ static void do_checkbacktracelevel(void)
     debug_backtrace_level = 0;
     msg(_("frame is zero"));
   } else {
-    char *sname = estack_sfile();
+    char *sname = estack_sfile(false);
     int max = get_maxbacktrace_level(sname);
 
     if (debug_backtrace_level > max) {
@@ -337,7 +337,7 @@ static void do_checkbacktracelevel(void)
 
 static void do_showbacktrace(char_u *cmd)
 {
-  char *sname = estack_sfile();
+  char *sname = estack_sfile(false);
   int max = get_maxbacktrace_level(sname);
   if (sname != NULL) {
     int i = 0;
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 5ea6a224d6..34768f62a9 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -7912,9 +7912,12 @@ char_u *eval_vars(char_u *src, char_u *srcstart, size_t *usedlen, linenr_T *lnum
       break;
 
     case SPEC_SFILE:            // file name for ":so" command
-      result = estack_sfile();
+    case SPEC_STACK:            // call stack
+      result = estack_sfile(spec_idx == SPEC_SFILE);
       if (result == NULL) {
-        *errormsg = _("E498: no :source file name to substitute for \"<sfile>\"");
+        *errormsg = spec_idx == SPEC_SFILE
+          ? _("E498: no :source file name to substitute for \"<sfile>\"")
+          : _("E489: no call stack to substitute for \"<stack>\"");
         return NULL;
       }
       resultbuf = result;  // remember allocated string
diff --git a/src/nvim/ex_eval.c b/src/nvim/ex_eval.c
index 66c782d12e..61456acc2a 100644
--- a/src/nvim/ex_eval.c
+++ b/src/nvim/ex_eval.c
@@ -278,7 +278,7 @@ bool cause_errthrow(const char *mesg, bool severe, bool *ignore)
 
       // Get the source name and lnum now, it may change before
       // reaching do_errthrow().
-      elem->sfile = estack_sfile();
+      elem->sfile = estack_sfile(false);
       elem->slnum = SOURCING_LNUM;
     }
     return true;
@@ -490,7 +490,7 @@ static int throw_exception(void *value, except_type_T type, char *cmdname)
     entry->sfile = NULL;
     excp->throw_lnum = entry->slnum;
   } else {
-    excp->throw_name = estack_sfile();
+    excp->throw_name = estack_sfile(false);
     if (excp->throw_name == NULL) {
       excp->throw_name = xstrdup("");
     }
diff --git a/src/nvim/message.c b/src/nvim/message.c
index c97e68207b..62827ffabc 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -555,7 +555,7 @@ static char *get_emsg_source(void)
   FUNC_ATTR_MALLOC FUNC_ATTR_WARN_UNUSED_RESULT
 {
   if (SOURCING_NAME != NULL && other_sourcing_name()) {
-    char *sname = estack_sfile();
+    char *sname = estack_sfile(false);
     char *tofree = sname;
 
     if (sname == NULL) {
diff --git a/src/nvim/runtime.c b/src/nvim/runtime.c
index 8299f8ec45..1cafd22b0a 100644
--- a/src/nvim/runtime.c
+++ b/src/nvim/runtime.c
@@ -100,42 +100,55 @@ void estack_pop(void)
 }
 
 /// Get the current value for <sfile> in allocated memory.
-char *estack_sfile(void)
+/// @param is_sfile  true for <sfile> itself.
+char *estack_sfile(bool is_sfile)
 {
   estack_T *entry = ((estack_T *)exestack.ga_data) + exestack.ga_len - 1;
-  if (entry->es_name == NULL) {
-    return NULL;
-  }
-  if (entry->es_info.ufunc == NULL) {
+  if (is_sfile && entry->es_type != ETYPE_UFUNC) {
+    if (entry->es_name == NULL) {
+      return NULL;
+    }
     return xstrdup(entry->es_name);
   }
 
+  // Give information about each stack entry up to the root.
   // For a function we compose the call stack, as it was done in the past:
   //   "function One[123]..Two[456]..Three"
-  size_t len = STRLEN(entry->es_name) + 10;
-  int idx;
-  for (idx = exestack.ga_len - 2; idx >= 0; idx--) {
+  garray_T ga;
+  ga_init(&ga, sizeof(char), 100);
+  etype_T last_type = ETYPE_SCRIPT;
+  for (int idx = 0; idx < exestack.ga_len; idx++) {
     entry = ((estack_T *)exestack.ga_data) + idx;
-    if (entry->es_name == NULL || entry->es_info.ufunc == NULL) {
-      idx++;
-      break;
+    if (entry->es_name != NULL) {
+      size_t len = strlen(entry->es_name) + 15;
+      char *type_name = "";
+      if (entry->es_type != last_type) {
+        switch (entry->es_type) {
+        case ETYPE_SCRIPT:
+          type_name = "script "; break;
+        case ETYPE_UFUNC:
+          type_name = "function "; break;
+        default:
+          type_name = ""; break;
+        }
+        last_type = entry->es_type;
+      }
+      len += strlen(type_name);
+      ga_grow(&ga, (int)len);
+      if (idx == exestack.ga_len - 1 || entry->es_lnum == 0) {
+        // For the bottom entry: do not add the line number, it is used
+        // in <slnum>.  Also leave it out when the number is not set.
+        vim_snprintf((char *)ga.ga_data + ga.ga_len, len, "%s%s%s",
+                     type_name, entry->es_name, idx == exestack.ga_len - 1 ? "" : "..");
+      } else {
+        vim_snprintf((char *)ga.ga_data + ga.ga_len, len, "%s%s[%" PRIdLINENR "]..",
+                     type_name, entry->es_name, entry->es_lnum);
+      }
+      ga.ga_len += (int)strlen((char *)ga.ga_data + ga.ga_len);
     }
-    len += STRLEN(entry->es_name) + 15;
   }
 
-  char *res = (char *)xmalloc(len);
-  STRCPY(res, "function ");
-  size_t done;
-  while (idx < exestack.ga_len - 1) {
-    done = STRLEN(res);
-    entry = ((estack_T *)exestack.ga_data) + idx;
-    vim_snprintf(res + done, len - done, "%s[%" PRIdLINENR "]..", entry->es_name, entry->es_lnum);
-    idx++;
-  }
-  done = STRLEN(res);
-  entry = ((estack_T *)exestack.ga_data) + idx;
-  vim_snprintf(res + done, len - done, "%s", entry->es_name);
-  return res;
+  return (char *)ga.ga_data;
 }
 
 static bool runtime_search_path_valid = false;
diff --git a/src/nvim/testdir/test_expand_func.vim b/src/nvim/testdir/test_expand_func.vim
index b48c2e8a19..388620f87e 100644
--- a/src/nvim/testdir/test_expand_func.vim
+++ b/src/nvim/testdir/test_expand_func.vim
@@ -37,17 +37,28 @@ func Test_expand_sflnum()
   delcommand Flnum
 endfunc
 
-func Test_expand_sfile()
+func Test_expand_sfile_and_stack()
   call assert_match('test_expand_func\.vim$', s:sfile)
-  call assert_match('^function .*\.\.Test_expand_sfile$', expand('<sfile>'))
+  let expected = 'script .*testdir/runtest.vim\[\d\+\]\.\.function RunTheTest\[\d\+\]\.\.Test_expand_sfile_and_stack$'
+  call assert_match(expected , expand('<sfile>'))
+  call assert_match(expected , expand('<stack>'))
 
   " Call in script-local function
-  call assert_match('^function .*\.\.Test_expand_sfile\[5\]\.\.<SNR>\d\+_expand_sfile$', s:expand_sfile())
+  call assert_match('script .*testdir/runtest.vim\[\d\+\]\.\.function RunTheTest\[\d\+\]\.\.Test_expand_sfile_and_stack\[7\]\.\.<SNR>\d\+_expand_sfile$', s:expand_sfile())
 
   " Call in command
   command Sfile echo expand('<sfile>')
-  call assert_match('^function .*\.\.Test_expand_sfile$', trim(execute('Sfile')))
+  call assert_match('script .*testdir/runtest.vim\[\d\+\]\.\.function RunTheTest\[\d\+\]\.\.Test_expand_sfile_and_stack$', trim(execute('Sfile')))
   delcommand Sfile
+
+  " Use <stack> from sourced script.
+  let lines =<< trim END
+    let g:stack_value = expand('<stack>')
+  END
+  call writefile(lines, 'Xstack')
+  source Xstack
+  call assert_match('\<Xstack$', g:stack_value)
+  call delete('Xstack')
 endfunc
 
 func Test_expand_slnum()
diff --git a/src/nvim/testing.c b/src/nvim/testing.c
index de6d445ba3..97bc690363 100644
--- a/src/nvim/testing.c
+++ b/src/nvim/testing.c
@@ -18,7 +18,7 @@
 static void prepare_assert_error(garray_T *gap)
 {
   char buf[NUMBUFLEN];
-  char *sname = estack_sfile();
+  char *sname = estack_sfile(false);
 
   ga_init(gap, 1, 100);
   if (sname != NULL) {