IDEA-60891 flex: (automatic) code completion should not suggest language keywords inside comments

WI-3734 PhpStorm tries show automplete window inside string in javascript file -> exception and editor became frozen for ~10 seconds

platform/lang-api/src/com/intellij/codeInsight/completion/CompletionConfidence.java

@@ -15,6 +15,8 @@
  */
 package com.intellij.codeInsight.completion;
 
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiFile;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -26,5 +28,8 @@ public abstract class CompletionConfidence {
   @Nullable
   public abstract Boolean shouldFocusLookup(@NotNull CompletionParameters parameters);
 
-
+  @Nullable
+  public Boolean shouldSkipAutopopup(@Nullable PsiElement contextElement, @NotNull PsiFile psiFile, int offset) {
+    return null;
+  }
 }

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

@@ -193,6 +193,23 @@ public class CodeCompletionHandlerBase implements CodeInsightActionHandler {
     };
     if (autopopup) {
       CommandProcessor.getInstance().runUndoTransparentAction(initCmd);
+
+      int offset = editor.getCaretModel().getOffset();
+
+      PsiElement elementAt = InjectedLanguageUtil.findInjectedElementNoCommit(psiFile, offset);
+      if (elementAt == null) {
+        elementAt = psiFile.findElementAt(offset);
+        if (elementAt == null && offset > 0) {
+          elementAt = psiFile.findElementAt(offset - 1);
+        }
+      }
+
+      Language language = elementAt != null ? PsiUtilBase.findLanguageFromElement(elementAt):psiFile.getLanguage();
+
+      for (CompletionConfidence confidence : CompletionConfidenceEP.forLanguage(language)) {
+        final Boolean result = confidence.shouldSkipAutopopup(elementAt, psiFile, offset); // TODO: Peter Lazy API
+        if (result == Boolean.TRUE) return;
+      }
     } else {
       CommandProcessor.getInstance().executeCommand(project, initCmd, null, null);
     }