From deae1328804813c4b10ed7c1135ef9fcb0737807 Mon Sep 17 00:00:00 2001
From: peter <peter@jetbrains.com>
Date: Wed, 19 Oct 2016 15:55:40 +0200
Subject: [PATCH] show lookup preview for empty prefix (IDEA-CR-14687)

---
 .../intellij/codeInsight/lookup/impl/LookupPreview.java    | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/platform/lang-impl/src/com/intellij/codeInsight/lookup/impl/LookupPreview.java b/platform/lang-impl/src/com/intellij/codeInsight/lookup/impl/LookupPreview.java
index 9f4134aa5bbc..a3908fa72984 100644
--- a/platform/lang-impl/src/com/intellij/codeInsight/lookup/impl/LookupPreview.java
+++ b/platform/lang-impl/src/com/intellij/codeInsight/lookup/impl/LookupPreview.java
@@ -70,7 +70,12 @@ class LookupPreview {
   private String getSuffixText(@Nullable LookupElement item) {
     if (item != null) {
       String itemText = StringUtil.notNullize(LookupElementPresentation.renderElement(item).getItemText());
-      FList<TextRange> fragments = LookupCellRenderer.getMatchingFragments(myLookup.itemPattern(item), itemText);
+      String prefix = myLookup.itemPattern(item);
+      if (prefix.isEmpty()) {
+        return itemText;
+      }
+
+      FList<TextRange> fragments = LookupCellRenderer.getMatchingFragments(prefix, itemText);
       if (fragments != null && !fragments.isEmpty()) {
         List<TextRange> list = ContainerUtil.newArrayList(fragments);
         return itemText.substring(list.get(list.size() - 1).getEndOffset(), itemText.length());