a registry option to show autopopup immediately

platform/lang-impl/src/com/intellij/codeInsight/completion/CompletionProgressIndicator.java

@@ -357,7 +357,7 @@ public class CompletionProgressIndicator extends ProgressIndicatorBase implement
   }
 
   private boolean shouldShowLookup() {
-    if (isAutopopupCompletion() && myLookup.isCalculating()) {
+    if (isAutopopupCompletion() && myLookup.isCalculating() && Registry.is("ide.completion.delay.autopopup.until.completed")) {
       return false;
     }
     return true;

platform/platform-resources-en/src/misc/registry.properties

@@ -217,6 +217,12 @@ documentation.component.editor.font=false
 find.usage.expand.all=false
 
 ide.completion.show.better.matching.classes=false
+# suppress inspection "UnusedProperty"
+ide.completion.show.better.matching.classes.description=Show non-imported but good matching classes in basic completion
+
+ide.completion.delay.autopopup.until.completed=true
+# suppress inspection "UnusedProperty"
+ide.completion.delay.autopopup.until.completed.description=Controls if completion autopopup is shown immediately and populated in background, or delayed until all suggestion are calculated
 
 ide.completion.middle.matching=true
 # suppress inspection "UnusedProperty"