From ec0d5547a69b2d56d49001448dbb9d3a1837e3eb Mon Sep 17 00:00:00 2001
From: shafirov <max@jetbrains.com>
Date: Mon, 8 Jul 2019 19:22:00 +0300
Subject: [PATCH] Memory optimizations

Optimize for a) no errors case (most of them) b) no dependencies case (all of the library nodes). These two account for around 50mb of memory usage

GitOrigin-RevId: e92d6a1e5d50e7bfe94a41949905a576e80206d3
---
 .../view/ExternalSystemNode.java              | 28 ++++++++++++++-----
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/platform/external-system-impl/src/com/intellij/openapi/externalSystem/view/ExternalSystemNode.java b/platform/external-system-impl/src/com/intellij/openapi/externalSystem/view/ExternalSystemNode.java
index 98000ca21cff..08639e8767a5 100644
--- a/platform/external-system-impl/src/com/intellij/openapi/externalSystem/view/ExternalSystemNode.java
+++ b/platform/external-system-impl/src/com/intellij/openapi/externalSystem/view/ExternalSystemNode.java
@@ -58,14 +58,17 @@ public abstract class ExternalSystemNode<T> extends SimpleNode implements Compar
 
   protected static final ExternalSystemNode[] NO_CHILDREN = new ExternalSystemNode[0];
 
+  private static final List<ExternalSystemNode<?>> NO_CHILDREN_LIST = Collections.emptyList();
+  private static final List<String> NO_ERRORS_LIST = Collections.emptyList();
+
   private final ExternalProjectsView myExternalProjectsView;
-  private final List<ExternalSystemNode<?>> myChildrenList = new ArrayList<>();
+  private List<ExternalSystemNode<?>> myChildrenList = NO_CHILDREN_LIST;
   protected DataNode<T> myDataNode;
   @Nullable
   private ExternalSystemNode myParent;
   private ExternalSystemNode[] myChildren;
   private ExternalProjectsStructure.ErrorLevel myErrorLevel = ExternalProjectsStructure.ErrorLevel.NONE;
-  private final List<String> myErrors = new ArrayList<>();
+  private List<String> myErrors = NO_ERRORS_LIST;
   private ExternalProjectsStructure.ErrorLevel myTotalErrorLevel = null;
 
   public ExternalSystemNode(@NotNull ExternalProjectsView externalProjectsView,
@@ -209,7 +212,7 @@ public abstract class ExternalSystemNode<T> extends SimpleNode implements Compar
 
   public void cleanUpCache() {
     myChildren = null;
-    myChildrenList.clear();
+    myChildrenList = NO_CHILDREN_LIST;
     myTotalErrorLevel = null;
   }
 
@@ -219,7 +222,9 @@ public abstract class ExternalSystemNode<T> extends SimpleNode implements Compar
   }
 
   protected void sort(List<? extends ExternalSystemNode> list) {
-    Collections.sort(list, ORDER_AWARE_COMPARATOR);
+    if (!list.isEmpty()) {
+      Collections.sort(list, ORDER_AWARE_COMPARATOR);
+    }
   }
 
   public boolean addAll(Collection<? extends ExternalSystemNode> externalSystemNodes) {
@@ -229,6 +234,10 @@ public abstract class ExternalSystemNode<T> extends SimpleNode implements Compar
   private boolean addAll(Collection<? extends ExternalSystemNode> externalSystemNodes, boolean silently) {
     if (externalSystemNodes.isEmpty()) return false;
 
+    if (myChildrenList == NO_CHILDREN_LIST) {
+      myChildrenList = new ArrayList<>();
+    }
+
     for (ExternalSystemNode externalSystemNode : externalSystemNodes) {
       externalSystemNode.setParent(this);
       myChildrenList.add(externalSystemNode);
@@ -253,7 +262,7 @@ public abstract class ExternalSystemNode<T> extends SimpleNode implements Compar
 
     for (ExternalSystemNode externalSystemNode : externalSystemNodes) {
       externalSystemNode.setParent(null);
-      myChildrenList.remove(externalSystemNode);
+      if (myChildrenList != NO_CHILDREN_LIST) myChildrenList.remove(externalSystemNode);
     }
     if (!silently) {
       childrenChanged();
@@ -322,8 +331,13 @@ public abstract class ExternalSystemNode<T> extends SimpleNode implements Compar
   public void setErrorLevel(ExternalProjectsStructure.ErrorLevel level, String... errors) {
     if (myErrorLevel == level) return;
     myErrorLevel = level;
-    myErrors.clear();
-    Collections.addAll(myErrors, errors);
+
+    if (errors.length == 0) {
+      myErrors = NO_ERRORS_LIST;
+    }
+    else {
+      myErrors = Arrays.asList(errors);
+    }
     myExternalProjectsView.updateUpTo(this);
   }