Use to_snapshot when cluster serializing LibraryPrefixes.

runtime/vm/object_service.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/debugger.h"
 #include "vm/disassembler.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
@@ skipping 508 matching lines @@
     while (class_iter.HasNext()) {
       klass = class_iter.GetNextClass();
       if (!klass.IsMixinApplication()) {
         jsarr.AddValue(klass);
       }
     }
   }
   {
     JSONArray jsarr(&jsobj, "dependencies");
 
     Array& ports = Array::Handle();

[siva, 2017/04/15 00:56:51]

Using the name ports for imports/exports is really confusing...

[rmacnak, 2017/04/17 16:02:58]

Renamed.

     Namespace& ns = Namespace::Handle();
     Library& target = Library::Handle();
 
     // Unprefixed imports.
     ports = imports();
     for (intptr_t i = 0; i < ports.Length(); i++) {
       ns ^= ports.At(i);
       if (ns.IsNull()) continue;
 
       JSONObject jsdep(&jsarr);
@@ skipping 21 matching lines @@
     // Prefixed imports.
     DictionaryIterator entries(*this);
     Object& entry = Object::Handle();
     LibraryPrefix& prefix = LibraryPrefix::Handle();
     String& prefixName = String::Handle();
     while (entries.HasNext()) {
       entry = entries.GetNext();
       if (entry.IsLibraryPrefix()) {
         prefix ^= entry.raw();
         ports = prefix.imports();
-        for (intptr_t i = 0; i < ports.Length(); i++) {
-          ns ^= ports.At(i);
-          if (ns.IsNull()) continue;
+        if (!ports.IsNull()) {
+          for (intptr_t i = 0; i < ports.Length(); i++) {
+            ns ^= ports.At(i);
+            if (ns.IsNull()) continue;
 
-          JSONObject jsdep(&jsarr);
-          jsdep.AddProperty("isDeferred", prefix.is_deferred_load());
-          jsdep.AddProperty("isExport", false);
-          jsdep.AddProperty("isImport", true);
-          prefixName = prefix.name();
-          ASSERT(!prefixName.IsNull());
-          jsdep.AddProperty("prefix", prefixName.ToCString());
-          target = ns.library();
-          jsdep.AddProperty("target", target);
+            JSONObject jsdep(&jsarr);
+            jsdep.AddProperty("isDeferred", prefix.is_deferred_load());
+            jsdep.AddProperty("isExport", false);
+            jsdep.AddProperty("isImport", true);
+            prefixName = prefix.name();
+            ASSERT(!prefixName.IsNull());
+            jsdep.AddProperty("prefix", prefixName.ToCString());
+            target = ns.library();
+            jsdep.AddProperty("target", target);
+          }
         }
       }
     }
   }
   {
     JSONArray jsarr(&jsobj, "variables");
     DictionaryIterator entries(*this);
     Object& entry = Object::Handle();
     while (entries.HasNext()) {
       entry = entries.GetNext();
@@ skipping 987 matching lines @@
   jsobj.AddProperty("mirrorReferent", referent_handle);
 }
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 #endif
 
 }  // namespace dart