Fix for KT-13699 Quick documentation doesn't show supertype docs for overridden Java

idea/src/org/jetbrains/kotlin/idea/KotlinQuickDocumentationProvider.kt

@@ -18,12 +18,18 @@ package org.jetbrains.kotlin.idea
 
 import com.google.common.html.HtmlEscapers
 import com.intellij.codeInsight.documentation.DocumentationManagerUtil
+import com.intellij.codeInsight.javadoc.JavaDocInfoGenerator
+import com.intellij.codeInsight.javadoc.JavaDocInfoGeneratorFactory
 import com.intellij.lang.documentation.AbstractDocumentationProvider
 import com.intellij.lang.java.JavaDocumentationProvider
+import com.intellij.lang.java.JavaLanguage
 import com.intellij.openapi.diagnostic.Logger
 import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiManager
+import com.intellij.psi.PsiMethod
+import org.jetbrains.kotlin.asJava.LightClassUtil
 import org.jetbrains.kotlin.asJava.elements.KtLightDeclaration
+import org.jetbrains.kotlin.descriptors.CallableDescriptor
 import org.jetbrains.kotlin.descriptors.ClassifierDescriptor
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
@@ -36,6 +42,7 @@ import org.jetbrains.kotlin.idea.kdoc.findKDoc
 import org.jetbrains.kotlin.idea.kdoc.isBoringBuiltinClass
 import org.jetbrains.kotlin.idea.kdoc.resolveKDocLink
 import org.jetbrains.kotlin.idea.references.mainReference
+import org.jetbrains.kotlin.js.resolve.diagnostics.findPsi
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getElementTextWithContext
 import org.jetbrains.kotlin.psi.psiUtil.getNonStrictParentOfType
@@ -169,6 +176,18 @@ class KotlinQuickDocumentationProvider : AbstractDocumentationProvider() {
                     renderedDecl = "$renderedDecl<br/>$renderedComment"
                 }
             }
+            else {
+                if (declarationDescriptor is CallableDescriptor) { // If we couldn't find KDoc, try to find javadoc in one of super's
+                    val psi = declarationDescriptor.findPsi() as? KtFunction
+                    if (psi != null) {
+                        val lightElement = LightClassUtil.getLightClassMethod(psi) // Light method for super's scan in javadoc info gen
+                        val javaDocInfoGenerator = JavaDocInfoGeneratorFactory.create(psi.project, lightElement)
+                        val builder = StringBuilder()
+                        if (javaDocInfoGenerator.generateDocInfoCore(builder, false))
+                            renderedDecl += builder.toString().substringAfter("</PRE>") // Cut off light method signature
+                    }
+                }
+            }
 
             return renderedDecl
         }

idea/testData/editor/quickDoc/JavaDocFromOverridenClass.kt

@@ -0,0 +1,9 @@
+class A : OverrideMe() {
+    override fun <caret>overrideMe() {
+    }
+}
+
+
+//INFO: <b>protected</b> <b>open</b> <b>fun</b> overrideMe(): Unit <i>defined in</i> A<DD><DL><DT><b>Description copied from class:</b>&nbsp;<a href="psi_element://OverrideMe"><code>OverrideMe</code></a><br>
+//INFO:        Some comment
+//INFO:      </DD></DL></DD><DD><DL><DT><b>Overrides:</b><DD><a href="psi_element://OverrideMe#overrideMe()"><code>overrideMe</code></a> in class <a href="psi_element://OverrideMe"><code>OverrideMe</code></a></DD></DL></DD>

idea/testData/editor/quickDoc/JavaDocFromOverridenClass_Data.java

@@ -0,0 +1,6 @@
+public class OverrideMe {
+    /**
+     * Some comment
+     */
+    void overrideMe();
+}

idea/testData/editor/quickDoc/JavaDocFromOverridenInterface.kt

@@ -0,0 +1,9 @@
+class A : OverrideMe {
+    override fun <caret>overrideMe() {
+    }
+}
+
+
+//INFO: <b>public</b> <b>open</b> <b>fun</b> overrideMe(): Unit <i>defined in</i> A<DD><DL><DT><b>Description copied from interface:</b>&nbsp;<a href="psi_element://OverrideMe"><code>OverrideMe</code></a><br>
+//INFO:        Some comment
+//INFO:      </DD></DL></DD><DD><DL><DT><b>Specified by:</b><DD><a href="psi_element://OverrideMe#overrideMe()"><code>overrideMe</code></a> in interface <a href="psi_element://OverrideMe"><code>OverrideMe</code></a></DD></DL></DD>

idea/testData/editor/quickDoc/JavaDocFromOverridenInterface_Data.java

@@ -0,0 +1,6 @@
+interface OverrideMe {
+    /**
+     * Some comment
+     */
+    void overrideMe();
+}

idea/tests/org/jetbrains/kotlin/idea/editor/quickDoc/QuickDocProviderTestGenerated.java

@@ -96,6 +96,18 @@ public class QuickDocProviderTestGenerated extends AbstractQuickDocProviderTest
         doTest(fileName);
     }
 
+    @TestMetadata("JavaDocFromOverridenClass.kt")
+    public void testJavaDocFromOverridenClass() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/editor/quickDoc/JavaDocFromOverridenClass.kt");
+        doTest(fileName);
+    }
+
+    @TestMetadata("JavaDocFromOverridenInterface.kt")
+    public void testJavaDocFromOverridenInterface() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/editor/quickDoc/JavaDocFromOverridenInterface.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("JavaMethodUsedInKotlin.kt")
     public void testJavaMethodUsedInKotlin() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("idea/testData/editor/quickDoc/JavaMethodUsedInKotlin.kt");