1 files changed, 85 insertions, 16 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index e1f9fe0253..0a83c3a586 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -5552,19 +5552,18 @@ void prepare_assert_error(garray_T *gap)
   }
 }
 
-// Append "str" to "gap", escaping unprintable characters.
+// Append "p[clen]" to "gap", escaping unprintable characters.
 // Changes NL to \n, CR to \r, etc.
-static void ga_concat_esc(garray_T *gap, char_u *str)
+static void ga_concat_esc(garray_T *gap, const char_u *p, int clen)
+  FUNC_ATTR_NONNULL_ALL
 {
-  char_u *p;
   char_u buf[NUMBUFLEN];
 
-  if (str == NULL) {
-    ga_concat(gap, (char_u *)"NULL");
-    return;
-  }
-
-  for (p = str; *p != NUL; p++) {
+  if (clen > 1) {
+    memmove(buf, p, clen);
+    buf[clen] = NUL;
+    ga_concat(gap, buf);
+  } else {
     switch (*p) {
       case BS: ga_concat(gap, (char_u *)"\\b"); break;
       case ESC: ga_concat(gap, (char_u *)"\\e"); break;
@@ -5585,6 +5584,41 @@ static void ga_concat_esc(garray_T *gap, char_u *str)
   }
 }
 
+// Append "str" to "gap", escaping unprintable characters.
+// Changes NL to \n, CR to \r, etc.
+static void ga_concat_shorten_esc(garray_T *gap, const char_u *str)
+  FUNC_ATTR_NONNULL_ARG(1)
+{
+  char_u buf[NUMBUFLEN];
+
+  if (str == NULL) {
+    ga_concat(gap, (char_u *)"NULL");
+    return;
+  }
+
+  for (const char_u *p = str; *p != NUL; p++) {
+    int same_len = 1;
+    const char_u *s = p;
+    const int c = mb_ptr2char_adv(&s);
+    const int clen = s - p;
+    while (*s != NUL && c == utf_ptr2char(s)) {
+      same_len++;
+      s += clen;
+    }
+    if (same_len > 20) {
+      ga_concat(gap, (char_u *)"\\[");
+      ga_concat_esc(gap, p, clen);
+      ga_concat(gap, (char_u *)" occurs ");
+      vim_snprintf((char *)buf, NUMBUFLEN, "%d", same_len);
+      ga_concat(gap, buf);
+      ga_concat(gap, (char_u *)" times]");
+      p = s - 1;
+    } else {
+      ga_concat_esc(gap, p, clen);
+    }
+  }
+}
+
 // Fill "gap" with information about an assert error.
 void fill_assert_error(garray_T *gap, typval_T *opt_msg_tv,
                        char_u *exp_str, typval_T *exp_tv,
@@ -5609,10 +5643,10 @@ void fill_assert_error(garray_T *gap, typval_T *opt_msg_tv,
 
   if (exp_str == NULL) {
     tofree = (char_u *)encode_tv2string(exp_tv, NULL);
-    ga_concat_esc(gap, tofree);
+    ga_concat_shorten_esc(gap, tofree);
     xfree(tofree);
   } else {
-    ga_concat_esc(gap, exp_str);
+    ga_concat_shorten_esc(gap, exp_str);
   }
 
   if (atype != ASSERT_NOTEQUAL) {
@@ -5624,7 +5658,7 @@ void fill_assert_error(garray_T *gap, typval_T *opt_msg_tv,
       ga_concat(gap, (char_u *)" but got ");
     }
     tofree = (char_u *)encode_tv2string(got_tv, NULL);
-    ga_concat_esc(gap, tofree);
+    ga_concat_shorten_esc(gap, tofree);
     xfree(tofree);
   }
 }
@@ -5674,6 +5708,9 @@ int assert_equalfile(typval_T *argvars)
 
   IObuff[0] = NUL;
   FILE *const fd1 = os_fopen(fname1, READBIN);
+  char line1[200];
+  char line2[200];
+  ptrdiff_t lineidx = 0;
   if (fd1 == NULL) {
     snprintf((char *)IObuff, IOSIZE, (char *)e_notread, fname1);
   } else {
@@ -5682,6 +5719,7 @@ int assert_equalfile(typval_T *argvars)
       fclose(fd1);
       snprintf((char *)IObuff, IOSIZE, (char *)e_notread, fname2);
     } else {
+      int64_t linecount = 1;
       for (int64_t count = 0; ; count++) {
         const int c1 = fgetc(fd1);
         const int c2 = fgetc(fd2);
@@ -5693,10 +5731,24 @@ int assert_equalfile(typval_T *argvars)
         } else if (c2 == EOF) {
           STRCPY(IObuff, "second file is shorter");
           break;
-        } else if (c1 != c2) {
-          snprintf((char *)IObuff, IOSIZE,
-                   "difference at byte %" PRId64, count);
-          break;
+        } else {
+          line1[lineidx] = c1;
+          line2[lineidx] = c2;
+          lineidx++;
+          if (c1 != c2) {
+            snprintf((char *)IObuff, IOSIZE,
+                     "difference at byte %" PRId64 ", line %" PRId64,
+                     count, linecount);
+            break;
+          }
+        }
+        if (c1 == NL) {
+          linecount++;
+          lineidx = 0;
+        } else if (lineidx + 2 == (ptrdiff_t)sizeof(line1)) {
+          memmove(line1, line1 + 100, lineidx - 100);
+          memmove(line2, line2 + 100, lineidx - 100);
+          lineidx -= 100;
         }
       }
       fclose(fd1);
@@ -5705,7 +5757,24 @@ int assert_equalfile(typval_T *argvars)
   }
   if (IObuff[0] != NUL) {
     prepare_assert_error(&ga);
+    if (argvars[2].v_type != VAR_UNKNOWN) {
+      char *const tofree = encode_tv2echo(&argvars[2], NULL);
+      ga_concat(&ga, (char_u *)tofree);
+      xfree(tofree);
+      ga_concat(&ga, (char_u *)": ");
+    }
     ga_concat(&ga, IObuff);
+    if (lineidx > 0) {
+      line1[lineidx] = NUL;
+      line2[lineidx] = NUL;
+      ga_concat(&ga, (char_u *)" after \"");
+      ga_concat(&ga, (char_u *)line1);
+      if (STRCMP(line1, line2) != 0) {
+        ga_concat(&ga, (char_u *)"\" vs \"");
+        ga_concat(&ga, (char_u *)line2);
+      }
+      ga_concat(&ga, (char_u *)"\"");
+    }
     assert_error(&ga);
     ga_clear(&ga);
     return 1;