[Fix #10241] Fix last_column value for JSONFormatter

changelog/fix_last_column_number_for_json_formatter.md

@@ -0,0 +1 @@
+* [#10242](https://github.com/rubocop/rubocop/pull/10242): Fix `last_column` value for `JSONFormatter`. ([@koic][])

lib/rubocop/formatter/json_formatter.rb

@@ -59,12 +59,15 @@ def hash_for_offense(offense)
       end
 
       # TODO: Consider better solution for Offense#real_column.
+      #       The minimum value of `start_column: real_column` is 1.
+      #       So, the minimum value of `last_column` should be 1.
+      #       And non-zero value of `last_column` should be used as is.
       def hash_for_location(offense)
         {
           start_line:   offense.line,
           start_column: offense.real_column,
           last_line:    offense.last_line,
-          last_column:  offense.last_column,
+          last_column:  offense.last_column.zero? ? 1 : offense.last_column,
           length:       offense.location.length,
           # `line` and `column` exist for compatibility.
           # Use `start_line` and `start_column` instead.

spec/rubocop/formatter/json_formatter_spec.rb

@@ -166,7 +166,7 @@
                              start_line: 1,
                              start_column: 1,
                              last_line: 1,
-                             last_column: 0,
+                             last_column: 1,
                              length: 0,
                              line: 1,
                              column: 1