vim-patch:8.2.0578: heredoc for interfaces does not support "trim"

Problem:    Heredoc for interfaces does not support "trim".
Solution:   Update the script heredoc support to be same as the :let command.
            (Yegappan Lakshmanan, closes vim/vim#5916)

https://github.com/vim/vim/commit/6c2b7b8055b96463f78abb70f58c4c6d6d4b9d55

3 files changed, 36 insertions, 19 deletions

diff --git a/src/nvim/eval/userfunc.c b/src/nvim/eval/userfunc.c
index 0e22cf54cf..1f5a6eaec4 100644
--- a/src/nvim/eval/userfunc.c
+++ b/src/nvim/eval/userfunc.c
@@ -2571,11 +2571,18 @@ void ex_function(exarg_T *eap)
                   && (!ASCII_ISALPHA(p[2]) || p[2] == 's')))) {
         // ":python <<" continues until a dot, like ":append"
         p = skipwhite(arg + 2);
+        if (strncmp(p, "trim", 4) == 0) {
+          // Ignore leading white space.
+          p = skipwhite(p + 4);
+          heredoc_trimmed = xstrnsave(theline, (size_t)(skipwhite(theline) - theline));
+        }
         if (*p == NUL) {
           skip_until = xstrdup(".");
         } else {
-          skip_until = xstrdup(p);
+          skip_until = xstrnsave(p, (size_t)(skiptowhite(p) - p));
         }
+        do_concat = false;
+        is_heredoc = true;
       }
 
       // Check for ":let v =<< [trim] EOF"
diff --git a/src/nvim/eval/vars.c b/src/nvim/eval/vars.c
index 593ba9f6c3..dee3867a5a 100644
--- a/src/nvim/eval/vars.c
+++ b/src/nvim/eval/vars.c
@@ -155,14 +155,19 @@ char *eval_all_expr_in_str(char *str)
 /// marker, then the leading indentation before the lines (matching the
 /// indentation in the 'cmd' line) is stripped.
 ///
+/// When getting lines for an embedded script (e.g. python, lua, perl, ruby,
+/// tcl, mzscheme), "script_get" is set to true. In this case, if the marker is
+/// missing, then '.' is accepted as a marker.
+///
 /// @return  a List with {lines} or NULL on failure.
-static list_T *heredoc_get(exarg_T *eap, char *cmd)
+list_T *heredoc_get(exarg_T *eap, char *cmd, bool script_get)
 {
   char *marker;
   char *p;
   int marker_indent_len = 0;
   int text_indent_len = 0;
   char *text_indent = NULL;
+  char dot[] = ".";
 
   if (eap->getline == NULL) {
     emsg(_("E991: cannot use =<< here"));
@@ -214,8 +219,14 @@ static list_T *heredoc_get(exarg_T *eap, char *cmd)
       return NULL;
     }
   } else {
-    emsg(_("E172: Missing marker"));
-    return NULL;
+    // When getting lines for an embedded script, if the marker is missing,
+    // accept '.' as the marker.
+    if (script_get) {
+      marker = dot;
+    } else {
+      emsg(_("E172: Missing marker"));
+      return NULL;
+    }
   }
 
   char *theline = NULL;
@@ -353,7 +364,7 @@ void ex_let(exarg_T *eap)
 
   if (expr[0] == '=' && expr[1] == '<' && expr[2] == '<') {
     // HERE document
-    list_T *l = heredoc_get(eap, expr + 3);
+    list_T *l = heredoc_get(eap, expr + 3, false);
     if (l != NULL) {
       tv_list_set_ret(&rettv, l);
       if (!eap->skip) {
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index c0c8a5605b..5018c9268b 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -29,6 +29,7 @@
 #include "nvim/edit.h"
 #include "nvim/eval.h"
 #include "nvim/eval/typval.h"
+#include "nvim/eval/vars.h"
 #include "nvim/ex_cmds.h"
 #include "nvim/ex_cmds_defs.h"
 #include "nvim/ex_docmd.h"
@@ -4561,39 +4562,37 @@ bool is_in_cmdwin(void)
 char *script_get(exarg_T *const eap, size_t *const lenp)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_MALLOC
 {
-  const char *const cmd = eap->arg;
+  char *cmd = eap->arg;
 
   if (cmd[0] != '<' || cmd[1] != '<' || eap->getline == NULL) {
     *lenp = strlen(eap->arg);
     return eap->skip ? NULL : xmemdupz(eap->arg, *lenp);
   }
+  cmd += 2;
 
   garray_T ga = { .ga_data = NULL, .ga_len = 0 };
+
+  list_T *const l = heredoc_get(eap, cmd, true);
+  if (l == NULL) {
+    return NULL;
+  }
+
   if (!eap->skip) {
     ga_init(&ga, 1, 0x400);
   }
 
-  const char *const end_pattern = (cmd[2] != NUL ? skipwhite(cmd + 2) : ".");
-  while (true) {
-    char *const theline = eap->getline(eap->cstack->cs_looplevel > 0 ? -1 : NUL, eap->cookie, 0,
-                                       true);
-
-    if (theline == NULL || strcmp(end_pattern, theline) == 0) {
-      xfree(theline);
-      break;
-    }
-
+  TV_LIST_ITER_CONST(l, li, {
     if (!eap->skip) {
-      ga_concat(&ga, theline);
+      ga_concat(&ga, tv_get_string(TV_LIST_ITEM_TV(li)));
       ga_append(&ga, '\n');
     }
-    xfree(theline);
-  }
+  });
   *lenp = (size_t)ga.ga_len;  // Set length without trailing NUL.
   if (!eap->skip) {
     ga_append(&ga, NUL);
   }
 
+  tv_list_free(l);
   return (char *)ga.ga_data;
 }