Prune outlet connections during gc and clean up graph node interface

js/packages/offline-renderer/__tests__/__snapshots__/mc.test.js.snap

@@ -136,3 +136,24 @@ Float32Array [
   27,
 ]
 `;
+
+exports[`mc table 4`] = `
+Float32Array [
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+  42,
+]
+`;

js/packages/offline-renderer/__tests__/mc.test.js

@@ -63,6 +63,28 @@ test("mc table", async function () {
   // Process another small block
   core.process(inps, outs);
   expect(outs[0]).toMatchSnapshot();
+
+  // Now here we expect that the first graph has been totally nudged out
+  // of relevance, except for the nodes that remain shared which are the table
+  // and the const 0. If we gc then, we should remove that add() and root() from
+  // the original graph.
+  expect(await core.gc()).toEqual([1611541315, 1811703364]);
+
+  // But now the act of removing that add node should have pruned the outlet connections
+  // list on the table node. We'll test that original graph again to ensure that after
+  // rebuilding that connection everything still looks good.
+  await core.render(
+    el.add(...el.mc.table({ path: "/v/stereo", channels: 2 }, 0)),
+  );
+
+  // Get past the fade-in
+  for (let i = 0; i < 100; ++i) {
+    core.process(inps, outs);
+  }
+
+  // Process another small block
+  core.process(inps, outs);
+  expect(outs[0]).toMatchSnapshot();
 });
 
 test("mc sampleseq", async function () {

runtime/elem/GraphNode.h

@@ -38,10 +38,6 @@ namespace elem
         double getSampleRate() { return sampleRate; }
         size_t getBlockSize() { return blockSize; }
 
-        //==============================================================================
-        // Returns the number of output channels this node will write to
-        virtual size_t getNumOutputChannels() { return 1; }
-
         //==============================================================================
         // Sets a property onto the graph node.
         //

runtime/elem/Runtime.h

@@ -234,9 +234,33 @@ namespace elem
         // active graph rendering sequence have multiple references, while those
         // that are unused are held only by the nodeTable. Those nodes we clean up here.
         for (auto it = nodeTable.begin(); it != nodeTable.end(); /* skip increment */) {
-            if (it->second.node.use_count() == 1) {
-                ELEM_DBG("[Native] gc " << nodeIdToHex(it->second.node->getId()));
-                pruned.insert(it->first);
+            auto& nodeId = it->first;
+            auto& entry = it->second;
+
+            if (entry.node.use_count() == 1) {
+                ELEM_DBG("[Native] gc " << nodeIdToHex(nodeId));
+                pruned.insert(nodeId);
+
+                // Update the adjacency list to remove the parent pointers from each
+                // of the removed node's children.
+                for (auto& inlet : entry.inlets) {
+                    auto& childId = inlet.source;
+
+                    // It's possible we already removed the child in this same gc pass
+                    if (nodeTable.count(childId) > 0) {
+                        auto& childEntry = nodeTable.at(childId);
+                        childEntry.outlets.erase(
+                            std::remove_if(
+                                childEntry.outlets.begin(),
+                                childEntry.outlets.end(),
+                                [&](auto const& outlet) {
+                                    return outlet.destination == nodeId;
+                                }
+                            )
+                        );
+                    }
+                }
+
                 it = nodeTable.erase(it);
             } else {
                 it++;

runtime/elem/builtins/mc/SampleSeq.h

@@ -101,11 +101,6 @@ namespace elem
             }
         }
 
-        size_t getNumOutputChannels() override
-        {
-            return 2;
-        }
-
         int setProperty(std::string const& key, js::Value const& val, SharedResourceMap& resources) override
         {
             if constexpr (WithStretch) {

runtime/elem/builtins/mc/Table.h

@@ -12,11 +12,6 @@ namespace elem
     struct StereoTableNode : public GraphNode<FloatType> {
         using GraphNode<FloatType>::GraphNode;
 
-        size_t getNumOutputChannels() override
-        {
-            return 2;
-        }
-
         int setProperty(std::string const& key, js::Value const& val, SharedResourceMap& resources) override
         {
             if (key == "path") {