Don't ignore files and resolve modules in them (PY-28764)

python/src/com/jetbrains/python/psi/resolve/PyResolveImportUtil.kt

@@ -122,7 +122,7 @@ private fun resolveModuleFromRoots(name: QualifiedName, context: PyQualifiedName
   return nameNoHead.components.fold(resultsFromRoots(head, context)) { results, component ->
     findFirstResults(results, context.module)
       .asSequence()
-      .filterIsInstance<PsiDirectory>()
+      .filterIsInstance<PsiFileSystemItem>()
       .flatMap { resolveModuleAt(QualifiedName.fromComponents(component), it, context).asSequence() }
       .toList()
   }
@@ -143,15 +143,15 @@ fun resolveTopLevelMember(name: QualifiedName, context : PyQualifiedNameResolveC
 }
 
 /**
- * Resolves a [name] relative to the specified [directory].
+ * Resolves a [name] relative to the specified [item].
  */
-fun resolveModuleAt(name: QualifiedName, directory: PsiDirectory?, context: PyQualifiedNameResolveContext): List<PsiElement> {
+fun resolveModuleAt(name: QualifiedName, item: PsiFileSystemItem?, context: PyQualifiedNameResolveContext): List<PsiElement> {
   checkAccess()
   val empty = emptyList<PsiElement>()
-  if (directory == null || !directory.isValid) {
+  if (item == null || !item.isValid) {
     return empty
   }
-  return name.components.fold(listOf<PsiElement>(directory)) { seekers, component ->
+  return name.components.fold(listOf<PsiElement>(item)) { seekers, component ->
     if (component == null) empty
     else seekers.flatMap {
       val children = ResolveImportUtil.resolveChildren(it, component, context.footholdFile, !context.withMembers,

python/testData/resolve/multiFile/osAttributesFromPosixPathAndNTPath/a.py

@@ -0,0 +1,2 @@
+from os.path import join
+#         <ref>

python/testData/resolve/multiFile/osAttributesFromPosixPathAndNTPath/lib/os.py

@@ -0,0 +1,4 @@
+if a:
+    import posixpath as path
+elif b:
+    import ntpath as path

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

@@ -24,6 +24,7 @@ import com.jetbrains.python.sdk.PythonSdkType;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
@@ -559,4 +560,26 @@ public class PyMultiFileResolveTest extends PyMultiFileResolveTestCase {
     prepareTestDirectory();
     assertSameElements(doMultiResolveAndGetFileUrls("pkg1/pkg2/mod1.py"), "pkg1/pkg2/__init__.py");
   }
+
+  // PY-28764
+  public void testOsAttributesFromPosixPathAndNTPath() {
+    myFixture.copyDirectoryToProject(getTestName(true), "");
+
+    runWithSourceRoots(
+      Collections.singletonList(myFixture.findFileInTempDir("lib")),
+      () -> {
+        final PsiReference reference = PyResolveTestCase.findReferenceByMarker(myFixture.configureByFile("a.py"));
+        assertInstanceOf(reference, PsiPolyVariantReference.class);
+
+        final List<PsiElement> elements = PyUtil.multiResolveTopPriority((PsiPolyVariantReference)reference);
+        assertEquals(1, elements.size());
+
+        final PsiElement element = elements.get(0);
+        assertInstanceOf(element, PyFile.class);
+
+        final VirtualFile file = ((PyFile)element).getVirtualFile();
+        assertEquals("ntpath.py", file.getName());
+      }
+    );
+  }
 }