From e4741116c27a0a9edf7370860510514ddd9eb572 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Wed, 28 Jun 2017 05:38:27 +0000
Subject: parse.y: add ellipsis

* parse.y (parser_yyerror): add ellipsis properly when error line
  is truncated.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59194 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 parse.y                 | 38 +++++++++++++++++---------------------
 test/ruby/test_parse.rb |  9 +++++++++
 2 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/parse.y b/parse.y
index cb494cc937..ce8a1e5d1c 100644
--- a/parse.y
+++ b/parse.y
@@ -5036,42 +5036,38 @@ parser_yyerror(struct parser_params *parser, const char *msg)
 #ifndef RIPPER
     const int max_line_margin = 30;
     const char *p, *pe;
-    const char *pre = "", *post = "";
+    const char *pre = "", *post = "", *pend;
     const char *code = "", *caret = "", *newline = "";
     const char *lim;
     char *buf;
     long len;
     int i;
 
-    p = parser->tokp;
+    p = lex_p;
     lim = p - lex_pbeg > max_line_margin ? p - max_line_margin : lex_pbeg;
-    while (lim < p) {
-	if (*(p-1) == '\n') break;
-	p--;
-    }
+    while ((lim < p) && (*(p-1) != '\n')) p--;
 
-    pe = lex_p;
-    lim = lex_pend - pe > max_line_margin ? pe + max_line_margin : lex_pend;
-    while (pe < lim) {
-	if (*pe == '\n') break;
-	pe++;
+    pend = lex_pend;
+    if (pend > lex_pbeg && pend[-1] == '\n') {
+	if (--pend > lex_pbeg && pend[-1] == '\r') --pend;
     }
+    pe = lex_p;
+    lim = pend - pe > max_line_margin ? pe + max_line_margin : pend;
+    while ((pe < lim) && (*pe != '\n')) pe++;
 
     len = pe - p;
     if (len > 4) {
 	char *p2;
 
-	if (len > max_line_margin * 2 + 10) {
-	    if (lex_p - p > max_line_margin) {
-		p = rb_enc_prev_char(p, lex_p - max_line_margin, pe, rb_enc_get(lex_lastline));
-		pre = "...";
-	    }
-	    if (pe - lex_p > max_line_margin) {
-		pe = rb_enc_prev_char(lex_p, lex_p + max_line_margin, pe, rb_enc_get(lex_lastline));
-		post = "...";
-	    }
-	    len = pe - p;
+	if (p > lex_pbeg) {
+	    p = rb_enc_prev_char(lex_pbeg, p, lex_p, rb_enc_get(lex_lastline));
+	    if (p > lex_pbeg) pre = "...";
+	}
+	if (pe < pend) {
+	    pe = rb_enc_prev_char(lex_p, pe, pend, rb_enc_get(lex_lastline));
+	    if (pe < pend) post = "...";
 	}
+	len = pe - p;
 	i = (int)(lex_p - p);
 	buf = ALLOCA_N(char, i+2);
 	code = p;
diff --git a/test/ruby/test_parse.rb b/test/ruby/test_parse.rb
index d869fbd7ab..a604d3b193 100644
--- a/test/ruby/test_parse.rb
+++ b/test/ruby/test_parse.rb
@@ -1013,6 +1013,15 @@ x = __ENCODING__
     end
   end
 
+  def test_truncated_source_line
+    e = assert_raise_with_message(SyntaxError, /unexpected tIDENTIFIER/) do
+      eval("'0123456789012345678901234567890123456789' abcdefghijklmnopqrstuvwxyz0123456789 0123456789012345678901234567890123456789")
+    end
+    line = e.message.lines[1]
+    assert_operator(line, :start_with?, "...")
+    assert_operator(line, :end_with?, "...\n")
+  end
+
 =begin
   def test_past_scope_variable
     assert_warning(/past scope/) {catch {|tag| eval("BEGIN{throw tag}; tap {a = 1}; a")}}
-- 
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