Support HTML attributes without starting quotes

This allows the lexer to process input such as:

    <a href=foo"></a>

For XML input the lexer still expects properly opened/closed attribute
values.

Fixes #109

ext/ragel/base_lexer.rl

@@ -422,9 +422,9 @@
     # Characters that can be used for unquoted HTML attribute values.
     # See https://html.spec.whatwg.org/multipage/introduction.html#intro-early-example
     # for more info.
-    html_unquoted_value = ^(
-        squote | dquote | '`' | '=' | '<' | '>' | whitespace_or_newline
-    )+;
+    html_unquoted_value =
+        ^(squote | dquote | whitespace_or_newline)
+        ^('`' | '=' | '<' | '>' | whitespace_or_newline)+;
 
     # Machine used after matching the "=" of an attribute and just before moving
     # into the actual attribute value.

spec/oga/html/lexer/attributes_spec.rb

@@ -58,6 +58,28 @@ describe Oga::XML::Lexer do
       ]
     end
 
+    it 'lexes an attribute with a value without a starting double quote' do
+      lex_html('<a href=foo"></a>').should == [
+        [:T_ELEM_NAME, 'a', 1],
+        [:T_ATTR, 'href', 1],
+        [:T_STRING_SQUOTE, nil, 1],
+        [:T_STRING_BODY, 'foo"', 1],
+        [:T_STRING_SQUOTE, nil, 1],
+        [:T_ELEM_END, nil, 1]
+      ]
+    end
+
+    it 'lexes an attribute with a value without a starting single quote' do
+      lex_html("<a href=foo'></a>").should == [
+        [:T_ELEM_NAME, 'a', 1],
+        [:T_ATTR, 'href', 1],
+        [:T_STRING_SQUOTE, nil, 1],
+        [:T_STRING_BODY, "foo'", 1],
+        [:T_STRING_SQUOTE, nil, 1],
+        [:T_ELEM_END, nil, 1]
+      ]
+    end
+
     it 'lexes an element with spaces around the attribute equal sign' do
       lex_html('<p foo = "bar"></p>').should == [
         [:T_ELEM_NAME, 'p', 1],