add @filter syntax (#2037)

Author: fstanis

lib/CodeSection.js

@@ -76,10 +76,12 @@ module.exports = class CodeSection {
     this.storyPageId = '';
     this.currentHint = '';
     this.hints = [];
+    this.filters = null;
   }
 
   appendDoc(doc) {
     doc = doc.replace(/<!--|-->/gm, '') + '\n';
+    doc = this.parseFilters(doc);
     this.extractHeadings(doc);
     this.doc_ += doc;
     this.cachedMarkedDoc = false;
@@ -238,6 +240,18 @@ module.exports = class CodeSection {
     return lines.slice(1, lines.length-1).join('\n');
   }
 
+  parseFilters(line) {
+    const filterMatch = line.match(/@filter\(([^)]+)\)/);
+    if (!filterMatch) {
+      return line;
+    }
+    if (this.filters) {
+      throw new Error('Multiple @filter annotations found in section');
+    }
+    this.filters = filterMatch[1].split(',').map(f => f.trim());
+    return line.replace(filterMatch[0], '');
+  }
+
   extractHeadings(line) {
     const matches = line.match(/^\s*#+\s*(.+)$/m);
     if (!matches) {

spec/compiler/CodeSectionSpec.js

@@ -84,6 +84,13 @@ describe("CodeSection", function() {
       expect(section.doc).toEqual("\nhello\n\n\nworld\n\n");
     });
 
+    it("parses filters", function() {
+      section.appendDoc("<!--hello");
+      section.appendDoc("world! @filter(websites, email)-->");
+      expect(section.doc).toEqual("hello\nworld! \n");
+      expect(section.filters).toEqual(["websites", "email"]);
+    });
+
   });
   describe('hide columns if code section', function() {
     /*