Add support for custom link resolver (issue #2).

README.md

@@ -75,6 +75,38 @@ void main() {
 }
 ```
 
+Custom reference resolver
+-------------------------
+
+Custom reference resolver may be required when parsing document without implicit defined references, for example 
+Dartdoc.
+
+```dart
+/**
+ * Throws a [StateError] if ...
+ * similar to [anotherMethod], but ...
+ */
+```
+
+In that case you could supply parser with resolver, which should provide all missing links.
+
+```dart
+String library = "md_proc";
+String version = "0.4.0";
+Target linkResolver(String normalizedReference, String reference) {
+  if (reference.startsWith("new ")) {
+    String className = reference.substring(4);
+    return new Target("http://www.dartdocs.org/documentation/$library/$version/index.html#$library/$library.$className@id_$className-", null);
+  } else {
+    return null;
+  }
+}
+
+CommonMarkParser parser = new CommonMarkParser(new Options(linkResolver: linkResolver));
+Document doc = parser.parse('Hello world!\n===');
+String res = HtmlWriter.DEFAULT.write(doc);
+```
+
 High-level plan for development
 ===============================
 

lib/md_proc.dart

@@ -4,8 +4,8 @@ import 'src/html_writer.dart';
 import 'src/markdown_parser.dart';
 
 export 'src/definitions.dart';
-export 'src/markdown_parser.dart';
 export 'src/html_writer.dart';
+export 'src/markdown_parser.dart';
 export 'src/markdown_writer.dart';
 export 'src/options.dart';
 

lib/src/markdown_parser.dart

@@ -747,11 +747,15 @@ class CommonMarkParser {
     if (refRes.isSuccess) {
       String reference = refRes.value == "" ? labelRes.value : refRes.value;
       String normalizedReference = _normalizeReference(reference);
-      if (_references.containsKey(normalizedReference)) {
+      Target target = _references[normalizedReference];
+      if (target == null) {
+        target = _options.linkResolver(normalizedReference, reference);
+      }
+      if (target != null) {
         if (isLink) {
-          return refRes.copy(value: [new ReferenceLink(reference, linkInlines, _references[normalizedReference])]);
+          return refRes.copy(value: [new ReferenceLink(reference, linkInlines, target)]);
         } else {
-          return refRes.copy(value: [new ReferenceImage(reference, linkInlines, _references[normalizedReference])]);
+          return refRes.copy(value: [new ReferenceImage(reference, linkInlines, target)]);
         }
       }
     } else {
@@ -761,11 +765,15 @@ class CommonMarkParser {
         return labelRes;
       }
       String normalizedReference = _normalizeReference(labelRes.value);
-      if (_references.containsKey(normalizedReference)) {
+      Target target = _references[normalizedReference];
+      if (target == null) {
+        target = _options.linkResolver(normalizedReference, labelRes.value);
+      }
+      if (target != null) {
         if (isLink) {
-          return labelRes.copy(value: [new ReferenceLink(labelRes.value, linkInlines, _references[normalizedReference])]);
+          return labelRes.copy(value: [new ReferenceLink(labelRes.value, linkInlines, target)]);
         } else {
-          return labelRes.copy(value: [new ReferenceImage(labelRes.value, linkInlines, _references[normalizedReference])]);
+          return labelRes.copy(value: [new ReferenceImage(labelRes.value, linkInlines, target)]);
         }
       }
     }

lib/src/options.dart

@@ -1,9 +1,30 @@
 library md_proc.options;
 
+import 'definitions.dart';
+
+/**
+ * Link resolver accepts two references and should return [Target] with correspondent link.
+ * If link doesn't exists link resolver should return `null`.
+ *
+ * CommonMark defines reference as case insensitive. Use [normalizedReference] when you need reference
+ * normalized according to CommonMark rules, or just [reference] if you want to get reference as it
+ * written in document.
+ */
+typedef Target LinkResolver(String normalizedReference, String reference);
+
+/**
+ * Default resolver doesn't return any link, so be default parser parses only explicitly written references.
+ */
+Target DEFAULT_LINK_RESOLVER(String normalizedReference, String reference) => null;
+
 class Options {
   bool smartPunctuation;
+  LinkResolver linkResolver;
 
-  Options({this.smartPunctuation: false});
+  Options({
+          this.smartPunctuation: false,
+          this.linkResolver: DEFAULT_LINK_RESOLVER
+          });
 
   static Options DEFAULT = new Options(smartPunctuation: true);
   static Options STRICT = new Options();

test/library_test.dart

@@ -2,7 +2,7 @@ import 'package:md_proc/src/options.dart';
 
 import 'parser.dart';
 import 'service.dart';
-
+import 'reference_resolver.dart';
 
 void main() {
   serviceTests();
@@ -16,4 +16,6 @@ void main() {
   fileTest("SmartPunct", "smart_punct.txt", mdToHtmlTest(Options.DEFAULT));
   // Markdown to markdown tests
   fileTest("md2md", "markdownToMarkdown.txt", mdToMdTest(Options.STRICT));
+  // Custom resolver
+  referenceResolverTests();
 }

test/markdownToMarkdown.txt

@@ -295,3 +295,28 @@ Lists formatting
 
 3. b
 .
+
+Links
+=====
+
+.
+[reference][reference]
+
+[reference]: reference
+.
+[reference]
+
+
+[reference]: reference
+.
+
+.
+[reference][reference][reference]
+
+[reference]: reference
+.
+[reference][reference]
+
+
+[reference]: reference
+.

test/reference_resolver.dart

@@ -0,0 +1,67 @@
+library referenceResolverTest;
+
+import 'package:test/test.dart' as t;
+
+import 'package:md_proc/md_proc.dart';
+
+Target linkResolver(String normalizedReference, String reference) {
+  if (reference == "reference") {
+    return new Target(reference, null);
+  } else {
+    return null;
+  }
+}
+
+
+String md1Test = r'''
+This is a [reference].
+
+[reference]: reference2
+''';
+
+String md1Pattern = r'''
+This is a [reference].
+
+[reference]: reference2
+''';
+
+String md2Test = r'''
+This is a [reference].
+''';
+
+String md2Pattern = r'''
+This is a [reference].
+
+[reference]: reference
+''';
+
+String md3Test = r'''
+This is a [link].
+''';
+
+String md3Pattern = r'''
+This is a [link].
+''';
+
+void referenceResolverTests() {
+  CommonMarkParser parser = new CommonMarkParser(new Options(linkResolver: linkResolver));
+  CommonMarkParser defaultParser = CommonMarkParser.DEFAULT;
+
+  t.group("Custom reference resolver test", () {
+    t.test("Should leave defined links as is", () {
+      Document d1 = parser.parse(md1Test);
+      Document d2 = defaultParser.parse(md1Pattern);
+      t.expect(d1, t.equals(d2));
+    });
+    t.test("May resolve undefined links", () {
+      Document d1 = parser.parse(md2Test);
+      Document d2 = defaultParser.parse(md2Pattern);
+      t.expect(d1, t.equals(d2));
+    });
+    t.test("May not resolve undefined links", () {
+      Document d1 = parser.parse(md3Test);
+      Document d2 = defaultParser.parse(md3Pattern);
+      t.expect(d1, t.equals(d2));
+    });
+  });
+}

tool/travis.sh

@@ -14,6 +14,7 @@ dartanalyzer --fatal-warnings \
   lib/src/options.dart \
   test/parser.dart \
   test/service.dart \
+  test/reference_resolver.dart \
   test/library_test.dart
 
 # Run the tests.