Add experimental rbminify tool for .rb minification

Author: kateinoigakukun

tools/exe/rbminify

@@ -0,0 +1,12 @@
+#!/usr/bin/env ruby
+
+$LOAD_PATH << File.join(File.dirname(__FILE__), "../lib")
+
+require "syntax_tree"
+require "syntax_tree/cli"
+require "syntax_tree/minify_ruby"
+
+# Override the default formatter with our own.
+SyntaxTree.register_handler(".rb", SyntaxTree::MinifyRuby)
+
+exit(SyntaxTree::CLI.run(ARGV))

tools/lib/syntax_tree/minify_ruby.rb

@@ -0,0 +1,63 @@
+require "syntax_tree"
+
+module SyntaxTree
+  module MinifyRuby
+
+    # This is a required API for syntax tree which just delegates to SyntaxTree.parse.
+    def self.parse(source)
+      ::SyntaxTree.parse(source)
+    end
+
+    # This is the main entrypoint for the formatter. It parses the source,
+    # builds a formatter, then prints the result.
+    def self.format(source, _maxwidth = nil)
+      formatter = Formatter.new(source)
+      program = parse(source)
+      CommentStrippingVisitor.new.visit(program)
+      program.format(formatter)
+
+      formatter.flush
+      formatter.output.join
+    end
+
+    # This is a required API for syntax tree which just delegates to SyntaxTree.read.
+    def self.read(filepath)
+      ::SyntaxTree.read(filepath)
+    end
+
+    class CommentStrippingVisitor < SyntaxTree::Visitor
+      def visit(node)
+        if node and node.comments.any?
+          node.comments.clear
+        end
+        super(node)
+      end
+
+      def visit_statements(node)
+        node.body.delete_if { _1.is_a?(SyntaxTree::Comment) }
+        super(node)
+      end
+    end
+
+    class Formatter < SyntaxTree::Formatter
+      def initialize(source)
+        super(source, [], Float::INFINITY) do |n|
+          # This block, called `genspace`, is used to generate indentation for `n` depth.
+          ""
+        end
+      end
+
+      def breakable(
+        separator = " ",
+        _width = separator.length,
+        indent: nil,
+        force: nil
+      )
+        # Don't break when already broken
+        return if target.last.is_a?(PrettierPrint::BreakParent)
+        return if not force and separator == ""
+        super(separator, _width, indent: indent, force: force)
+      end
+    end
+  end
+end