prompt to configure external documentation location if none is configured

java/java-impl/src/com/intellij/lang/java/JavaDocumentationProvider.java

@@ -681,6 +681,15 @@ public class JavaDocumentationProvider implements CodeDocumentationProvider, Ext
     return CompositeDocumentationProvider.hasUrlsFor(this, element, originalElement);
   }
 
+  @Override
+  public boolean canPromptToConfigureDocumentation(PsiElement element) {
+    return false;
+  }
+
+  @Override
+  public void promptToConfigureDocumentation(PsiElement element) {
+  }
+
   public static String fetchExternalJavadoc(PsiElement element, final Project project, final List<String> docURLs) {
     final JavaDocExternalFilter docFilter = new JavaDocExternalFilter(project);
 

platform/lang-api/src/com/intellij/lang/documentation/CompositeDocumentationProvider.java

@@ -148,6 +148,28 @@ public class CompositeDocumentationProvider implements DocumentationProvider, Ex
     return false;
   }
 
+  @Override
+  public boolean canPromptToConfigureDocumentation(PsiElement element) {
+    for (DocumentationProvider provider : myProviders) {
+      if (provider instanceof ExternalDocumentationProvider &&
+          ((ExternalDocumentationProvider)provider).canPromptToConfigureDocumentation(element)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  @Override
+  public void promptToConfigureDocumentation(PsiElement element) {
+    for (DocumentationProvider provider : myProviders) {
+      if (provider instanceof ExternalDocumentationProvider &&
+          ((ExternalDocumentationProvider)provider).canPromptToConfigureDocumentation(element)) {
+        ((ExternalDocumentationProvider)provider).promptToConfigureDocumentation(element);
+        break;
+      }
+    }
+  }
+
   public static boolean hasUrlsFor(DocumentationProvider provider, PsiElement element, PsiElement originalElement) {
     final List<String> urls = provider.getUrlFor(element, originalElement);
     if (urls != null && !urls.isEmpty()) return true;

platform/lang-api/src/com/intellij/lang/documentation/ExternalDocumentationProvider.java

@@ -39,4 +39,19 @@ public interface ExternalDocumentationProvider {
    * @return true if the external documentation action should be enabled, false otherwise.
    */
   boolean hasDocumentationFor(PsiElement element, PsiElement originalElement);
+
+  /**
+   * Checks if the provider is capable of asking the user to configure external documentation for an element.
+   *
+   * @param element the element for which no documentation was found
+   * @return true if the element is applicable to this provider and the provider has a UI to configure the documentation location, false otherwise
+   */
+  boolean canPromptToConfigureDocumentation(PsiElement element);
+
+  /**
+   * Prompts the user to configure the external documentation for an element if none was found.
+   *
+   * @param element the element for which no documentation was found
+   */
+  void promptToConfigureDocumentation(PsiElement element);
 }

platform/lang-impl/src/com/intellij/ide/actions/ExternalJavaDocAction.java

@@ -68,9 +68,15 @@ public class ExternalJavaDocAction extends AnAction {
     DocumentationManager.storeOriginalElement(project, originalElement, element);
     final DocumentationProvider provider = DocumentationManager.getProviderFromElement(element);
     final List<String> urls = provider.getUrlFor(element, originalElement);
-    assert urls != null;
-    assert !urls.isEmpty();
-    showExternalJavadoc(urls);
+    if (urls != null && !urls.isEmpty()) {
+      showExternalJavadoc(urls);
+    }
+    else if (provider instanceof ExternalDocumentationProvider) {
+      final ExternalDocumentationProvider externalDocumentationProvider = (ExternalDocumentationProvider)provider;
+      if (externalDocumentationProvider.canPromptToConfigureDocumentation(element)) {
+        externalDocumentationProvider.promptToConfigureDocumentation(element);
+      }
+    }
   }
 
   public static void showExternalJavadoc(List<String> urls) {
@@ -103,7 +109,8 @@ public class ExternalJavaDocAction extends AnAction {
     final DocumentationProvider provider = DocumentationManager.getProviderFromElement(element);
     boolean enabled;
     if (provider instanceof ExternalDocumentationProvider) {
-      enabled = ((ExternalDocumentationProvider) provider).hasDocumentationFor(element, originalElement);
+      final ExternalDocumentationProvider edProvider = (ExternalDocumentationProvider)provider;
+      enabled = edProvider.hasDocumentationFor(element, originalElement) || edProvider.canPromptToConfigureDocumentation(element);
     }
     else {
       final List<String> urls = provider.getUrlFor(element, originalElement);

plugins/android/src/org/jetbrains/android/AndroidDocumentationProvider.java

@@ -18,7 +18,6 @@ package org.jetbrains.android;
 import com.android.sdklib.SdkConstants;
 import com.intellij.codeInsight.javadoc.JavaDocExternalFilter;
 import com.intellij.facet.ProjectFacetManager;
-import com.intellij.lang.documentation.CompositeDocumentationProvider;
 import com.intellij.lang.documentation.DocumentationProvider;
 import com.intellij.lang.documentation.ExternalDocumentationProvider;
 import com.intellij.lang.java.JavaDocumentationProvider;
@@ -85,6 +84,15 @@ public class AndroidDocumentationProvider implements DocumentationProvider, Exte
     return false;
   }
 
+  @Override
+  public boolean canPromptToConfigureDocumentation(PsiElement element) {
+    return false;
+  }
+
+  @Override
+  public void promptToConfigureDocumentation(PsiElement element) {
+  }
+
   private static boolean isMyContext(@NotNull final PsiElement element, @NotNull final Project project) {
     if (element instanceof PsiClass) {
       return ApplicationManager.getApplication().runReadAction(new Computable<Boolean>() {

plugins/groovy/src/org/jetbrains/plugins/groovy/lang/documentation/GroovyDocumentationProvider.java

@@ -298,6 +298,15 @@ public class GroovyDocumentationProvider implements CodeDocumentationProvider, E
     return CompositeDocumentationProvider.hasUrlsFor(this, element, originalElement);
   }
 
+  @Override
+  public boolean canPromptToConfigureDocumentation(PsiElement element) {
+    return false;
+  }
+
+  @Override
+  public void promptToConfigureDocumentation(PsiElement element) {
+  }
+
   private static String getMethodCandidateInfo(GrReferenceExpression expr) {
     final GroovyResolveResult[] candidates = expr.multiResolve(false);
     final String text = expr.getText();