Issue #48: improve handling of special chars

spec/fixtures/attribute-wrappers.slang

@@ -3,4 +3,6 @@ div(hello="world" foo="bar")
 div[hello="world" foo="bar"]
 div(hello=Process.pid)
 div{hello="world" foo="bar"}
-div{hello="#{"world"}" foo="bar"}
+div{hello="world\u0021" foo="bar"}
+div{hello="#{"world"}" foo="bar"}
+div{hello="#{"world\u0021"}" foo="bar"}

spec/fixtures/script.slang

@@ -14,4 +14,9 @@ javascript:
         something
       </div>
     `
-  })
+  })
+
+javascript:
+  let twoLines = "bar\nbaz";
+  let hello = "#{"Hello, " + "world!"}";
+  let obj = #{{:a => 17, "b" => "foo"}.to_json};

spec/fixtures/with_html.slang

@@ -1,2 +1,3 @@
 table
-  <tr><td>#{Process.pid}</td></tr>
+  <tr><td>#{Process.pid}</td></tr>
+  <tr><td>"hello\u0021"</td></tr>

spec/slang_spec.cr

@@ -1,4 +1,5 @@
 require "./spec_helper"
+require "json"
 
 def evaluates_to_true
   1 == 1
@@ -172,6 +173,7 @@ describe Slang do
       res.should eq <<-HTML
       <table>
         <tr><td>#{Process.pid}</td></tr>
+        <tr><td>"hello\\u0021"</td></tr>
       </table>
       HTML
     end
@@ -279,6 +281,11 @@ describe Slang do
           `
         })
       </script>
+      <script>
+        let twoLines = "bar\\nbaz";
+        let hello = "Hello, world!";
+        let obj = {"a":17,"b":"foo"};
+      </script>
       HTML
     end
     it "renders stylesheets" do
@@ -335,7 +342,9 @@ describe Slang do
       <div hello="world" foo="bar"></div>
       <div hello="#{Process.pid}"></div>
       <div hello="world" foo="bar"></div>
+      <div hello="world\\u0021" foo="bar"></div>
       <div hello="world" foo="bar"></div>
+      <div hello="world!" foo="bar"></div>
       HTML
     end
   end

src/slang/lexer.cr

@@ -206,7 +206,7 @@ module Slang
       @token.type = :CONTROL
       next_char
       next_char if current_char == ' '
-      @token.value = consume_line
+      @token.value = consume_line(escape_double_quotes=false)
     end
 
     private def consume_output
@@ -228,7 +228,7 @@ module Slang
       end
 
       skip_whitespace
-      @token.value = consume_line.strip
+      @token.value = consume_line(escape_double_quotes=false).strip
       @token.value = " #{@token.value}" if prepend_whitespace
       @token.value = "#{@token.value} " if append_whitespace
     end
@@ -257,14 +257,14 @@ module Slang
             cc = STRING_OPEN_CLOSE_CHARS_MAP[current_char]
             str << current_char
             next_char
-            str << consume_string open_char: oc, close_char: cc
+            str << consume_string open_char: oc, close_char: cc, crystal: true
             next
           end
           if current_char == '"' || current_char == '\''
             ch = current_char
             str << current_char
             next_char
-            str << consume_string open_char: ch, close_char: ch
+            str << consume_string open_char: ch, close_char: ch, crystal: true
             next
           end
           if current_char == '}'
@@ -283,7 +283,7 @@ module Slang
       end
     end
 
-    private def consume_string(open_char = '"', close_char = '"', escape_double_quotes = false)
+    private def consume_string(open_char = '"', close_char = '"', escape_double_quotes = false, crystal = false)
       level = 0
       escaped = false
       maybe_string_interpolation = false
@@ -326,10 +326,11 @@ module Slang
             maybe_string_interpolation = true
           end
 
-          if current_char == '\\' && !escaped
-            escaped = true
-          else
+          if escaped
             escaped = false
+            str << '\\' unless crystal
+          elsif current_char == '\\'
+            escaped = true
           end
 
           if current_char == '\n' || current_char == '\0'
@@ -348,12 +349,16 @@ module Slang
       @token.value = "\"#{consume_line}\""
     end
 
-    private def consume_line
+    private def consume_line(escape_double_quotes=true)
       String.build do |str|
         loop do
           if current_char == '\n' || current_char == '\0'
             break
           else
+            if escape_double_quotes && (current_char == '"' || current_char == '\\')
+              str << '\\'
+            end
+
             str << current_char
             next_char
           end