[ruby/prism] Truncate source lines in errors messages when too long

https://github.com/ruby/prism/commit/72518f5716

2 files changed, 39 insertions, 4 deletions

diff --git a/test/prism/format_errors_test.rb b/test/prism/format_errors_test.rb
index a1edbef2e8..63206d5765 100644
--- a/test/prism/format_errors_test.rb
+++ b/test/prism/format_errors_test.rb
@@ -6,19 +6,53 @@ return if Prism::BACKEND == :FFI
 
 module Prism
   class FormatErrorsTest < TestCase
-    def test_format_errors
-      assert_equal <<~ERROR, Debug.format_errors("<>", false)
+    def test_basic
+      expected = <<~ERROR
         > 1 | <>
             | ^ unexpected '<', ignoring it
             |  ^ unexpected '>', ignoring it
       ERROR
 
-      assert_equal <<~'ERROR', Debug.format_errors('"%W"\u"', false)
-        > 1 | "%W"\u"
+      assert_equal expected, Debug.format_errors("<>", false)
+    end
+
+    def test_multiple
+      expected = <<~ERROR
+        > 1 | "%W"\\u"
             |     ^ unexpected backslash, ignoring it
             |      ^ unexpected local variable or method, expecting end-of-input
             |        ^ unterminated string meets end of file
       ERROR
+
+      assert_equal expected, Debug.format_errors('"%W"\u"', false)
+    end
+
+    def test_truncate_start
+      expected = <<~ERROR
+        > 1 | ... <>
+            |     ^ unexpected '<', ignoring it
+            |      ^ unexpected '>', ignoring it
+      ERROR
+
+      assert_equal expected, Debug.format_errors("#{" " * 30}<>", false)
+    end
+
+    def test_truncate_end
+      expected = <<~ERROR
+        > 1 | <#{" " * 30} ...
+            | ^ unexpected '<', ignoring it
+      ERROR
+
+      assert_equal expected, Debug.format_errors("<#{" " * 30}a", false)
+    end
+
+    def test_truncate_both
+      expected = <<~ERROR
+        > 1 | ... <#{" " * 30} ...
+            |     ^ unexpected '<', ignoring it
+      ERROR
+
+      assert_equal expected, Debug.format_errors("#{" " * 30}<#{" " * 30}a", false)
     end
   end
 end
diff --git a/test/prism/newline_test.rb b/test/prism/newline_test.rb
index d31fb89bc6..f7511f665c 100644
--- a/test/prism/newline_test.rb
+++ b/test/prism/newline_test.rb
@@ -10,6 +10,7 @@ module Prism
     filepaths = Dir["*.rb", base: base] - %w[
       encoding_test.rb
       errors_test.rb
+      format_errors_test.rb
       parser_test.rb
       regexp_test.rb
       static_literals_test.rb