Adding support for including ^ and $ in the middle of an expression

Closes #29

src/js/parser/javascript/anchor.js

@@ -0,0 +1,15 @@
+export default {
+  _render() {
+    return this.renderLabel(this.label).then(label => {
+      return label.addClass('anchor');
+    });
+  },
+
+  setup() {
+    if (this.textValue === '^') {
+      this.label = 'Start of line';
+    } else {
+      this.label = 'End of line';
+    }
+  }
+};

src/js/parser/javascript/grammar.peg

@@ -1,10 +1,9 @@
 grammar JavascriptRegexp
   root <- ( ( "/" regexp "/" flags:[igm]* ) / regexp flags:""? ) <Root>
   regexp <- match:match alternates:( "|" match )* <Regexp>
-  match <- anchor_start:"^"?
-           (!repeat) parts:match_fragment*
-           anchor_end:"$"? <Match>
-  match_fragment <- content:( subexp / charset / terminal ) repeat:repeat? <MatchFragment>
+  match <- (!repeat) parts:match_fragment* <Match>
+  anchor <- ( "^" / "$" ) <Anchor>
+  match_fragment <- content:( anchor / subexp / charset / terminal ) repeat:repeat? <MatchFragment>
   repeat <- spec:( repeat_any / repeat_required / repeat_optional / repeat_spec ) greedy:"?"? <Repeat>
   repeat_any <- "*" <RepeatAny>
   repeat_required <- "+" <RepeatRequired>

src/js/parser/javascript/match.js

@@ -29,39 +29,19 @@ export default {
 
   // Renders the match into the currently set container.
   _render() {
-    var start, end,
-        partPromises,
+    var partPromises,
         items;
 
-    // A `^` at the beginning of the match leads to the "Start of line"
-    // indicator being rendered.
-    if (this.anchorStart) {
-      start = this.renderLabel('Start of line')
-        .then(label => {
-          return label.addClass('anchor');
-        });
-    }
-
-    // A `$` at the end of the match leads to the "End of line" indicator
-    // being rendered.
-    if (this.anchorEnd) {
-      end = this.renderLabel('End of line')
-        .then(label => {
-          return label.addClass('anchor');
-        });
-    }
-
     // Render each of the match fragments.
     partPromises = _.map(this.parts, part => {
       return part.render(this.container.group());
     });
 
-    items = _([start, partPromises, end]).flatten().compact().value();
+    items = _(partPromises).compact().value();
 
     // Handle the situation where a regular expression of `()` is rendered.
-    // This leads to a Match node with no fragments, no start indicator, and
-    // no end indicator. Something must be rendered so that the anchor can be
-    // calculated based on it.
+    // This leads to a Match node with no fragments. Something must be rendered
+    // so that the anchor can be calculated based on it.
     //
     // Furthermore, the content rendered must have height and width or else the
     // anchor calculations fail.
@@ -120,13 +100,8 @@ export default {
       return result;
     }, []);
 
-    // Indicates if the expression starts with a `^`.
-    this.anchorStart = (this.properties.anchor_start.textValue !== '');
-    // Indicates if the expression ends with a `$`.
-    this.anchorEnd = (this.properties.anchor_end.textValue !== '');
-
-    // When there are no anchors and only one part, then proxy to the part.
-    if (!this.anchorStart && !this.anchorEnd && this.parts.length === 1) {
+    // When there is only one part, then proxy to the part.
+    if (this.parts.length === 1) {
       this.proxy = this.parts[0];
     }
   }

src/js/parser/javascript/parser.js

@@ -9,6 +9,7 @@ import Root from './root.js';
 import Regexp from './regexp.js';
 import Match from './match.js';
 import MatchFragment from './match_fragment.js';
+import Anchor from './anchor.js';
 import Subexp from './subexp.js';
 import Charset from './charset.js';
 import CharsetEscape from './charset_escape.js';
@@ -35,6 +36,7 @@ parser.Parser.Root            = { module: Root };
 parser.Parser.Regexp          = { module: Regexp };
 parser.Parser.Match           = { module: Match };
 parser.Parser.MatchFragment   = { module: MatchFragment };
+parser.Parser.Anchor          = { module: Anchor };
 parser.Parser.Subexp          = { module: Subexp };
 parser.Parser.Charset         = { module: Charset };
 parser.Parser.CharsetEscape   = { module: CharsetEscape };