Handle mutually recursive re-exports in dartdocgen

pkg/docgen/lib/src/models/model_helpers.dart

Index: pkg/docgen/lib/src/models/model_helpers.dart
diff --git a/pkg/docgen/lib/src/models/model_helpers.dart b/pkg/docgen/lib/src/models/model_helpers.dart
index 3c4c430464ed9539560eca995d7c22cd7efff68f..f962e757b46328f2ca0532c20a261678c8180e44 100644
--- a/pkg/docgen/lib/src/models/model_helpers.dart
+++ b/pkg/docgen/lib/src/models/model_helpers.dart
@@ -217,8 +217,9 @@ Map addAll(Map map, Iterable<DeclarationMirror> mirrors) {
 /// values of which point to a map of exported name identifiers with values
 /// corresponding to the actual DeclarationMirror.
 Map<String, Map<String, DeclarationMirror>> calcExportedItems(
-    LibrarySourceMirror library) {
+    LibrarySourceMirror library, Map visited) {

[tjblasi, 2015/02/19 00:52:55]

It seems a bit strange that this is a required param since non-recursive calls
don't really need to specify it.

I'd put in a weak vote for:
- Have calcExportedItems call _calcExportedItemsRecursive(...) which accepts the
visited map
- Make it an optional positional parameter & check if (visited == null) visited
= {};

Or do nothing, I don't feel strongly about it :)

[Alan Knight, 2015/02/19 01:07:04]

We can't know in advance if it's recursive or not. Or at least not without
re-doing much of the same work. And there are only two callers - the one just
below that passes it through, and the one that starts it all off with the empty
map. So it seemed simplest just to always pass it.

   var exports = {};
+  visited[library] = exports;
   exports['classes'] = new SplayTreeMap();
   exports['methods'] = new SplayTreeMap();
   exports['variables'] = new SplayTreeMap();
@@ -226,7 +227,8 @@ Map<String, Map<String, DeclarationMirror>> calcExportedItems(
   // Determine the classes, variables and methods that are exported for a
   // specific dependency.
   void _populateExports(LibraryDependencyMirror export, bool showExport) {
-    var transitiveExports = calcExportedItems(export.targetLibrary);
+    if (visited[export.targetLibrary] != null) return;
+    var transitiveExports = calcExportedItems(export.targetLibrary, visited);
     exports['classes'].addAll(transitiveExports['classes']);
     exports['methods'].addAll(transitiveExports['methods']);
     exports['variables'].addAll(transitiveExports['variables']);