Implement Hamlit::SyntaxChecker.string_literal?

lib/hamlit/syntax_checker.rb

@@ -11,6 +11,17 @@ module Hamlit
       true
     end
 
+    def self.string_literal?(code)
+      return false if syntax_error?(code)
+
+      type, instructions = Ripper.sexp(code)
+      return false if type != :program
+      return false if instructions.size > 1
+
+      type, _ = instructions.first
+      type == :string_literal
+    end
+
     private
 
     def on_parse_error(*)

test/hamlit/syntax_checker_test.rb

@@ -0,0 +1,44 @@
+describe Hamlit::SyntaxChecker do
+  describe '.syntax_error?' do
+    it { assert_equal(true,  Hamlit::SyntaxChecker.syntax_error?('{ hash }')) }
+    it { assert_equal(false, Hamlit::SyntaxChecker.syntax_error?('{ a: b }')) }
+  end
+
+  describe '.string_literal?' do
+    def assert_literal(expected, code)
+      actual = Hamlit::SyntaxChecker.string_literal?(code)
+      assert_equal expected, actual
+    end
+
+    describe 'invalid expressions' do
+      it { assert_literal(false, %q|{ hash }|) }
+      it { assert_literal(false, %q|"hello".|) }
+    end
+
+    describe 'string literal' do
+      it { assert_literal(true, %q|''|) }
+      it { assert_literal(true, %q|""|) }
+      it { assert_literal(true, %Q|'\n'|) }
+      it { assert_literal(true, %q|'';   |) }
+      it { assert_literal(true, %q|  ""  |) }
+      it { assert_literal(true, %q|'hello world'|) }
+      it { assert_literal(true, %q|"hello world"|) }
+      it { assert_literal(true, %q|"h#{ %Q[e#{ "llo wor" }l] }d"|) }
+      it { assert_literal(true, %q|%Q[nya]|) }
+      it { assert_literal(true, %q|%Q[#{123}]|) }
+    end
+
+    describe 'not string literal' do
+      it { assert_literal(false, %q|123|) }
+      it { assert_literal(false, %q|'hello' + ''|) }
+      it { assert_literal(false, %q|'hello'.to_s|) }
+      it { assert_literal(false, %Q|'' \\ \n ''|) }
+      it { assert_literal(false, %q|['']|) }
+      it { assert_literal(false, %q|return ''|) }
+    end
+
+    describe 'multiple instructions' do
+      it { assert_literal(false, %Q|''\n''|) }
+    end
+  end
+end