Add JSON output format option to rails stats

Enhance the rails stats command to support JSON formatted output,
enabling easier consumption of architecture metrics by automated systems.
This modification improves the utility of the stats command for continuous
monitoring of application maturity and health.

Example usage:
```
$ bin/rails stats[json] | jq .
{
  "code_statistics": [
    {
      "name": "Controllers",
      "statistic": {
        "lines": 12345,
        "code_lines": 12345,
        "classes": 123,
        "methods": 1234
      }
    },
    ...
  ],
  "total": {
    "lines": 12345,
    "code_lines": 12345,
    "classes": 123,
    "methods": 1234
  }
}
```

railties/CHANGELOG.md

@@ -1,3 +1,33 @@
+*   Add JSON output format to `rails stats` via `format` option.
+
+    Enables JSON formatted output for better integration with automated systems. Maintains default table format unless specified.
+
+    ```shell
+    $ bin/rails stats[json] | jq .
+    {
+      "code_statistics": [
+        {
+          "name": "Controllers",
+          "statistic": {
+            "lines": 12345,
+            "code_lines": 12345,
+            "classes": 123,
+            "methods": 1234
+          }
+        },
+        ...
+      ],
+      "total": {
+        "lines": 12345,
+        "code_lines": 12345,
+        "classes": 123,
+        "methods": 1234
+      }
+    }
+    ```
+
+    *Teppei Shintani*
+
 *   Allow Actionable Errors encountered when running tests to be retried.
 
     ```txt

railties/lib/rails/code_statistics.rb

@@ -35,6 +35,18 @@ def to_s
     print_code_test_stats
   end
 
+  def to_h
+    {
+      code_statistics: @statistics.map do |k, v|
+        {
+          name: k,
+          statistic: v.to_h
+        }
+      end,
+      total: @total&.to_h
+    }
+  end
+
   private
     def calculate_statistics
       Hash[@pairs.map { |pair| [pair.first, calculate_directory_statistics(pair.last)] }]

railties/lib/rails/code_statistics_calculator.rb

@@ -86,6 +86,15 @@ def add_by_io(io, file_type)
     end
   end
 
+  def to_h
+    {
+      lines: lines,
+      code_lines: code_lines,
+      classes: classes,
+      methods: methods
+    }
+  end
+
   private
     def file_type(file_path)
       if file_path.end_with? "_test.rb"

railties/lib/rails/tasks/statistics.rake

@@ -29,10 +29,16 @@ STATS_DIRECTORIES ||= [
 ]
 
 desc "Report code statistics (KLOCs, etc) from the application or engine"
-task :stats do
+task :stats, :format do |_, args|
   require "rails/code_statistics"
   stat_directories = STATS_DIRECTORIES.collect do |name, dir|
     [ name, "#{File.dirname(Rake.application.rakefile_location)}/#{dir}" ]
   end.select { |name, dir| File.directory?(dir) }
-  CodeStatistics.new(*stat_directories).to_s
+  statistics = CodeStatistics.new(*stat_directories)
+  case args[:format]
+  when "json"
+    puts statistics.to_h.to_json
+  else
+    statistics.to_s
+  end
 end

railties/test/code_statistics_calculator_test.rb

@@ -84,6 +84,11 @@ class A; end
     assert_equal 6, @code_statistics_calculator.methods
   end
 
+  test "return statistics as a hash" do
+    code_statistics_calculator = CodeStatisticsCalculator.new(1, 2, 3, 4)
+    assert_equal({ lines: 1, code_lines: 2, classes: 3, methods: 4 }, code_statistics_calculator.to_h)
+  end
+
   test "calculate number of Ruby methods" do
     code = <<-'CODE'
       def foo

railties/test/code_statistics_test.rb

@@ -31,4 +31,59 @@ def foo
       CodeStatistics.new(["hidden file", @tmp_path])
     end
   end
+
+  test "output results in table format" do
+    File.write File.join(@tmp_path, "example.rb"), <<-CODE
+      class Example
+        def foo
+          puts 'foo'
+        end
+      end
+    CODE
+
+    code_statistics = CodeStatistics.new(["tmp dir", @tmp_path])
+    expected = <<~TABLE
+      +----------------------+--------+--------+---------+---------+-----+-------+
+      | Name                 |  Lines |    LOC | Classes | Methods | M/C | LOC/M |
+      +----------------------+--------+--------+---------+---------+-----+-------+
+      | tmp dir              |      5 |      5 |       1 |       1 |   1 |     3 |
+      +----------------------+--------+--------+---------+---------+-----+-------+
+        Code LOC: 5     Test LOC: 0     Code to Test Ratio: 1:0.0
+
+    TABLE
+
+    output, _ = capture_io do
+      code_statistics.to_s
+    end
+
+    assert_equal expected, output
+  end
+
+  test "return results in hash format" do
+    File.write File.join(@tmp_path, "example.rb"), <<-CODE
+      class Example
+        def foo
+          puts 'foo'
+        end
+      end
+    CODE
+
+    code_statistics = CodeStatistics.new(["tmp dir", @tmp_path])
+    expected = {
+      code_statistics: [
+        {
+          name: "tmp dir",
+          statistic: {
+            lines: 5,
+            code_lines: 5,
+            classes: 1,
+            methods: 1
+          }
+        }
+      ],
+      total: nil
+    }
+
+    assert_equal expected, code_statistics.to_h
+  end
 end