feat: add support for Ruby to_s and to_i method conversions

[takaokouji]

Summary

Add support for Ruby's to_s and to_i type conversion methods in the Smalruby editor. These methods should convert to native Scratch operator blocks (operator_join and operator_add) instead of falling through to ruby_expression blocks.

Motivation

Users write Ruby code like:

kakaku = gets.to_i
puts kakaku * 0.7

Currently, to_s and to_i fall through to ruby_expression blocks and are executed via Opal at runtime. Converting them to native Scratch blocks will:

• Make the block view clearer and more visual
• Provide better performance
• Ensure consistent behavior with Scratch's built-in type coercion

Proposed Implementation

Conversion Pattern

• value.to_s → operator_join(value, "") with comment marker @ruby:to_s
• value.to_i → operator_add(value, 0) with comment marker @ruby:to_i

Files to Modify

1. Ruby-to-Blocks Converter (packages/scratch-gui/src/lib/ruby-to-blocks-converter/operators.js)

   • Register to_s method: converts to operator_join block with empty string
   • Register to_i method: converts to operator_add block with zero
   • Attach comment markers using converter._createComment()

2. Code Generator (packages/scratch-gui/src/lib/ruby-generator/operators.js)

   • Update Generator.operator_join: detect @ruby:to_s comment and generate .to_s
   • Update Generator.operator_add: detect @ruby:to_i comment and generate .to_i

3. Unit Tests (packages/scratch-gui/test/unit/lib/ruby-to-blocks-converter/operators.test.js)

   • Test to_s with number literal, string literal, and variables
   • Test to_i with string literal, number literal, and variables

4. Integration Tests (packages/scratch-gui/test/integration/operators.test.js)

   • Test round-trip conversion (Ruby → Blocks → Ruby)
   • Verify comment markers are preserved

Code Snippets

Ruby-to-Blocks Registration (add after line 161 in operators.js):

// to_s method: convert to operator_join with empty string
converter.registerOnSend(['variable', 'number', 'string', 'block'], 'to_s', 0, params => {
    const {receiver} = params;

    const block = converter._createBlock('operator_join', 'value');
    converter._addTextInput(block, 'STRING1', receiver, '');
    converter._addTextInput(block, 'STRING2', '', '');
    block.comment = converter._createComment('@ruby:to_s', block.id);
    return block;
});

// to_i method: convert to operator_add with zero
converter.registerOnSend(['variable', 'number', 'string', 'block'], 'to_i', 0, params => {
    const {receiver} = params;

    const block = converter._createBlock('operator_add', 'value');
    converter._addNumberInput(block, 'NUM1', 'math_number', receiver, '');
    converter._addNumberInput(block, 'NUM2', 'math_number', 0, '');
    block.comment = converter._createComment('@ruby:to_i', block.id);
    return block;
});

Code Generator Enhancement (modify in ruby-generator/operators.js):

Generator.operator_join = function (block) {
    const comment = Generator.getCommentText(block);
    if (comment === '@ruby:to_s') {
        const value = Generator.valueToCode(block, 'STRING1', Generator.ORDER_FUNCTION_CALL) || Generator.quote_('');
        return [`${value}.to_s`, Generator.ORDER_FUNCTION_CALL];
    }

    const order = Generator.ORDER_ADDITIVE;
    const rightStr = Generator.valueToCode(block, 'STRING1', order) || Generator.quote_('');
    const leftStr = Generator.valueToCode(block, 'STRING2', order) || Generator.quote_('');
    return [`${rightStr} + ${leftStr}`, order];
};

Generator.operator_add = function (block) {
    const comment = Generator.getCommentText(block);
    if (comment === '@ruby:to_i') {
        const value = Generator.valueToCode(block, 'NUM1', Generator.ORDER_FUNCTION_CALL) || 0;
        return [`${value}.to_i`, Generator.ORDER_FUNCTION_CALL];
    }

    const order = Generator.ORDER_ADDITIVE;
    const num1 = Generator.valueToCode(block, 'NUM1', order) || 0;
    const num2 = Generator.valueToCode(block, 'NUM2', order) || 0;
    return [`${num1} + ${num2}`, order];
};

Testing

Unit Tests

• Test to_s and to_i with various receiver types (numbers, strings, variables, blocks)
• Verify correct block type and comment marker creation

Integration Tests

• Test complete example code round-trip conversion
• Verify comment markers are preserved through conversion

Manual Verification

docker compose up app
# Visit http://localhost:8601
# Enter Ruby code with to_s and to_i
# Switch to blocks view and verify operator_join/operator_add blocks
# Switch back to Ruby and verify .to_s/.to_i notation

Success Criteria

• ✅ to_s method calls convert to operator_join blocks with empty string
• ✅ to_i method calls convert to operator_add blocks with zero
• ✅ Blocks convert back to Ruby with .to_s and .to_i method notation
• ✅ All tests pass (unit + integration + lint)
• ✅ Example code works correctly: kakaku = gets.to_i; puts kakaku * 0.7
• ✅ Round-trip conversion preserves semantics

Related Files

• packages/scratch-gui/src/lib/ruby-to-blocks-converter/operators.js
• packages/scratch-gui/src/lib/ruby-generator/operators.js
• packages/scratch-gui/test/unit/lib/ruby-to-blocks-converter/operators.test.js
• packages/scratch-gui/test/integration/operators.test.js