PY-13140 Top-level module names starting with underscore are not imported via wildcard import

python/src/com/jetbrains/python/psi/impl/PyStarImportElementImpl.java

@@ -15,6 +15,8 @@
  */
 package com.jetbrains.python.psi.impl;
 
+import com.google.common.base.Predicate;
+import com.google.common.collect.Iterables;
 import com.intellij.lang.ASTNode;
 import com.intellij.navigation.ItemPresentation;
 import com.intellij.psi.PsiElement;
@@ -50,7 +52,13 @@ public class PyStarImportElementImpl extends PyElementImpl implements PyStarImpo
       for (PsiElement importedFile : new HashSet<PsiElement>(importedFiles)) { // resolver gives lots of duplicates
         final PsiElement source = PyUtil.turnDirIntoInit(importedFile);
         if (source instanceof PyFile) {
-          chain.add(((PyFile) source).iterateNames());
+          // PY-13140
+          Iterable<PyElement> declaredNames = ((PyFile)source).iterateNames();
+          // Filter out names starting with underscore only if __all__ attribute is not defined in the module
+          if (((PyFile)source).getDunderAll() == null) {
+            declaredNames = excludeUnderscoredNames(declaredNames);
+          }
+          chain.add(declaredNames);
         }
       }
       return chain;
@@ -58,6 +66,19 @@ public class PyStarImportElementImpl extends PyElementImpl implements PyStarImpo
     return Collections.emptyList();
   }
 
+  private static Iterable<PyElement> excludeUnderscoredNames(Iterable<PyElement> declaredNames) {
+    return Iterables.filter(declaredNames, new Predicate<PyElement>() {
+      @Override
+      public boolean apply(@Nullable PyElement input) {
+        String name = input != null ? input.getName() : null;
+        if (name != null && name.startsWith("_")) {
+          return false;
+        }
+        return true;
+      }
+    });
+  }
+
   @Nullable
   public PsiElement getElementNamed(final String name) {
     if (PyUtil.isClassPrivateName(name)) {
@@ -76,7 +97,8 @@ public class PyStarImportElementImpl extends PyElementImpl implements PyStarImpo
           final PsiElement result = results != null && !results.isEmpty() ? results.get(0).getElement() : null;
           if (result != null) {
             final List<String> all = sourceFile.getDunderAll();
-            if (all != null && !all.contains(name)) {
+            // PY-13140
+            if (all != null ? !all.contains(name) : name.startsWith("_")) {
               continue;
             }
             return result;

python/testData/inspections/PyUnresolvedReferencesInspection/PrivateModuleNames/a.py

@@ -0,0 +1,5 @@
+from lib import *
+
+normal_name
+<error descr="Unresolved reference '_private_name'">_private_name</error>
+<error descr="Unresolved reference '__magic_name__'">__magic_name__</error>

python/testData/inspections/PyUnresolvedReferencesInspection/PrivateModuleNames/lib.py

@@ -0,0 +1,3 @@
+normal_name = 'spam'
+private_name = 'ham'
+__magic_name__ = 'green eggs'

python/testData/resolve/multiFile/modulePrivateName/ImportedFile.py

@@ -0,0 +1 @@
+_private_name = "spam"

python/testData/resolve/multiFile/modulePrivateName/ModulePrivateName.py

@@ -0,0 +1,5 @@
+from ImportedFile import *
+
+_private_name
+# <ref>
+

python/testData/resolve/multiFile/modulePrivateNameInDunderAll/ImportedFile.py

@@ -0,0 +1,4 @@
+__all__ = [
+    "_private_name",
+]
+_private_name = "spam"

python/testData/resolve/multiFile/modulePrivateNameInDunderAll/ModulePrivateNameInDunderAll.py

@@ -0,0 +1,5 @@
+from ImportedFile import *
+
+_private_name
+# <ref>
+

python/testSrc/com/jetbrains/python/PyMultiFileResolveTest.java

@@ -363,4 +363,14 @@ public class PyMultiFileResolveTest extends PyMultiFileResolveTestCase {
   public void testFromPackageModuleImportStarElementNamedAsModule() {
     assertResolvesTo(PyFunction.class, "foo");
   }
+
+  // PY-13140
+  public void testModulePrivateName() {
+    assertNull(doResolve());
+  }
+
+  // PY-13140
+  public void testModulePrivateNameInDunderAll() {
+    assertResolvesTo(PyTargetExpression.class, "_private_name");
+  }
 }

python/testSrc/com/jetbrains/python/inspections/PyUnresolvedReferencesInspectionTest.java

@@ -366,6 +366,10 @@ public class PyUnresolvedReferencesInspectionTest extends PyInspectionTestCase {
     doMultiFileTest();
   }
 
+  public void testPrivateModuleNames() {
+    doMultiFileTest();
+  }
+
   @NotNull
   @Override
   protected Class<? extends PyInspection> getInspectionClass() {