1 files changed, 59 insertions, 2 deletions

diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 5e700dea8a..6a50264e0f 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -85,6 +85,9 @@
 # include "buffer.c.generated.h"
 #endif
 
+// Determines how deeply nested %{} blocks will be evaluated in statusline.
+#define MAX_STL_EVAL_DEPTH 100
+
 static char *msg_loclist = N_("[Location List]");
 static char *msg_qflist = N_("[Quickfix List]");
 static char *e_auabort = N_("E855: Autocommands caused command to abort");
@@ -3572,6 +3575,7 @@ int build_stl_str_hl(
   }
 
   int groupdepth = 0;
+  int evaldepth  = 0;
 
   int curitem = 0;
   bool prevchar_isflag = true;
@@ -3909,6 +3913,13 @@ int build_stl_str_hl(
       continue;
     }
 
+    // Denotes end of expanded %{} block
+    if (*fmt_p == '}' && evaldepth > 0) {
+        fmt_p++;
+        evaldepth--;
+        continue;
+    }
+
     // An invalid item was specified.
     // Continue processing on the next character of the format string.
     if (vim_strchr(STL_ALL, *fmt_p) == NULL) {
@@ -3950,18 +3961,30 @@ int build_stl_str_hl(
     }
     case STL_VIM_EXPR:     // '{'
     {
+      char_u *block_start = fmt_p - 1;
+      int reevaluate = (*fmt_p == '%');
       itemisflag = true;
 
+      if (reevaluate) {
+        fmt_p++;
+      }
+
       // Attempt to copy the expression to evaluate into
       // the output buffer as a null-terminated string.
       char_u *t = out_p;
-      while (*fmt_p != '}' && *fmt_p != NUL && out_p < out_end_p)
+      while ((*fmt_p != '}' || (reevaluate && fmt_p[-1] != '%'))
+             && *fmt_p != NUL && out_p < out_end_p) {
         *out_p++ = *fmt_p++;
+      }
       if (*fmt_p != '}') {          // missing '}' or out of space
         break;
       }
       fmt_p++;
-      *out_p = 0;
+      if (reevaluate) {
+        out_p[-1] = 0;  // remove the % at the end of %{% expr %}
+      } else {
+        *out_p = 0;
+      }
 
       // Move our position in the output buffer
       // to the beginning of the expression
@@ -4007,6 +4030,40 @@ int build_stl_str_hl(
           itemisflag = false;
         }
       }
+
+
+      // If the output of the expression needs to be evaluated
+      // replace the %{} block with the result of evaluation
+      if (reevaluate && str != NULL && *str != 0
+          && strchr((const char *)str, '%') != NULL
+          && evaldepth < MAX_STL_EVAL_DEPTH) {
+        size_t parsed_usefmt = (size_t)(block_start - usefmt);
+        size_t str_length = strlen((const char *)str);
+        size_t fmt_length = strlen((const char *)fmt_p);
+        size_t new_fmt_len = parsed_usefmt
+          + str_length + fmt_length + 3;
+        char_u *new_fmt = (char_u *)xmalloc(new_fmt_len * sizeof(char_u));
+        char_u *new_fmt_p = new_fmt;
+
+        new_fmt_p = (char_u *)memcpy(new_fmt_p, usefmt, parsed_usefmt)
+          + parsed_usefmt;
+        new_fmt_p = (char_u *)memcpy(new_fmt_p , str, str_length)
+          + str_length;
+        new_fmt_p = (char_u *)memcpy(new_fmt_p, "%}", 2) + 2;
+        new_fmt_p = (char_u *)memcpy(new_fmt_p , fmt_p, fmt_length)
+          + fmt_length;
+        *new_fmt_p = 0;
+        new_fmt_p = NULL;
+
+        if (usefmt != fmt) {
+          xfree(usefmt);
+        }
+        XFREE_CLEAR(str);
+        usefmt = new_fmt;
+        fmt_p = usefmt + parsed_usefmt;
+        evaldepth++;
+        continue;
+      }
       break;
     }