Preliminarily closes PY-12 and PY-8. Import resolution is still quite suboptimal, though.

PyFile and PyFileImpl: added getUrl() method.
PyResolveUtil and PyFile: more of (lame) means to squash SOEs on circular imports.
ResolveImportUtil: actual PY-12 resolve order fix.
PyMultiFileResolveTest and friends: a test case for name resolution inside subpackage.

python/src/com/jetbrains/python/psi/PyFile.java

@@ -5,6 +5,7 @@ package com.jetbrains.python.psi;
 
 import com.intellij.openapi.util.Key;
 import com.intellij.psi.PsiFile;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.List;
 
@@ -19,4 +20,10 @@ public interface PyFile extends PyElement, PsiFile {
   List<PyFunction> getTopLevelFunctions();
 
   List<PyTargetExpression> getTopLevelAttributes();
+  
+  /**
+  @return an URL of file, maybe bogus if virtual file is not present.
+  */
+  @NotNull
+  String getUrl(); 
 }

python/src/com/jetbrains/python/psi/PyResolveUtil.java

@@ -63,6 +63,10 @@ public class PyResolveUtil {
       if ((processor instanceof ResolveProcessor) && !(((ResolveProcessor)processor).approve(cur))) {
         return null;
       }
+      /* // resolution debug tracker
+      if (cur instanceof PsiFile) System.out.println(processor.toString() + ": " + cur.toString());
+      else System.out.println(processor.toString() + ": " + _fmt_node(cur)); 
+      */
       if (!cur.processDeclarations(processor, ResolveState.initial(), cur == elt ? lastParent : null, elt)) {
         if (processor instanceof ResolveProcessor) {
           return ((ResolveProcessor)processor).getResult();
@@ -140,7 +144,20 @@ public class PyResolveUtil {
     public PsiElement getResult() {
       return myResult;
     }
-
+    
+    static String _nvl(Object s) {
+      if (s != null) return "'" + s.toString() + "'";
+      else return "null";
+    }
+    
+    public Set<String> getSeen() {
+      return mySeen;
+    }
+    
+    public String toString() {
+      return _nvl(myName) + ", " + _nvl(myResult);
+    }
+    
     public boolean execute(PsiElement element, ResolveState substitutor) {
       if (element instanceof PyFile) {
         final VirtualFile file = ((PyFile)element).getVirtualFile();

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

@@ -18,10 +18,8 @@ package com.jetbrains.python.psi.impl;
 
 import com.intellij.extapi.psi.PsiFileBase;
 import com.intellij.openapi.fileTypes.FileType;
-import com.intellij.psi.FileViewProvider;
-import com.intellij.psi.PsiElement;
-import com.intellij.psi.PsiElementVisitor;
-import com.intellij.psi.ResolveState;
+import com.intellij.openapi.vfs.VirtualFile;
+import com.intellij.psi.*;
 import com.intellij.psi.scope.PsiScopeProcessor;
 import com.intellij.psi.stubs.StubElement;
 import com.intellij.psi.tree.IElementType;
@@ -35,7 +33,9 @@ import org.jetbrains.annotations.Nullable;
 
 import javax.swing.*;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
 public class PyFileImpl extends PsiFileBase implements PyFile {
   public PyFileImpl(FileViewProvider viewProvider) {
@@ -50,6 +50,15 @@ public class PyFileImpl extends PsiFileBase implements PyFile {
   public String toString() {
     return "PyFile:" + getName();
   }
+  
+  @NotNull
+  public String getUrl() {
+    String fname;
+    VirtualFile vfile = getVirtualFile();
+    if (vfile != null) fname = vfile.getUrl();
+    else fname = "(null)://" + ((Object)this).toString();
+    return fname;
+  }
 
   public Icon getIcon(int flags) {
     return PythonFileType.INSTANCE.getIcon();
@@ -87,7 +96,11 @@ public class PyFileImpl extends PsiFileBase implements PyFile {
       if (!processor.execute(e, substitutor)) return false;
     }
 
-    for(PyFromImportStatement e: getFromImports()) {
+    Set<String> procSeen = null;
+    if (processor instanceof PyResolveUtil.ResolveProcessor) {
+      procSeen = ((PyResolveUtil.ResolveProcessor)processor).getSeen();
+    }
+    for(PyFromImportStatement e: getFromImports(procSeen)) {
       if (e == lastParent) continue;
       if (!e.processDeclarations(processor, substitutor, null, this)) return false;
     }
@@ -153,10 +166,20 @@ public class PyFileImpl extends PsiFileBase implements PyFile {
     return ret;
   }
   
-  public List<PyFromImportStatement> getFromImports() {
+  public List<PyFromImportStatement> getFromImports(final Set<String> outerSeen) {
     final List<PyFromImportStatement> result = new ArrayList<PyFromImportStatement>();
     accept(new PyRecursiveElementVisitor() {
+      Set<String> alreadySeen;
+      {
+        alreadySeen = new HashSet<String>();
+        if (outerSeen != null) alreadySeen.addAll(outerSeen);
+      }
       public void visitPyElement(final PyElement node) {
+        if (node instanceof PyFile) { 
+          final String fname = ((PyFile)node).getUrl(); 
+          if (alreadySeen.contains(fname)) return; // don't descend into the same file again
+          else alreadySeen.add(fname);
+        }
         super.visitPyElement(node);
         if (PyFromImportStatement.class.isInstance(node)) {
           //noinspection unchecked

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

@@ -54,13 +54,14 @@ public class ResolveImportUtil {
     /*
     True resolve order is:
     - local modules,
-    - builtins (in fact),
+    - builtins? (check),
     - modules from sys.path (aka SdkOrderEntries).
     (http://docs.python.org/ref/import.html)
     */
     // TODO: assume some things like sys to be only from __builtins__
-    // FIXME: resolve sources relatively to file in hand, not project root
-    
+    // TODO: rewrite entirely imitating Python import process: global module table, under-initialisation, etc.
+
+    // qualified imports resolve their children    
     final PyExpression qualifier = importRef.getQualifier();
     if (qualifier instanceof PyReferenceExpression) {
       PsiElement qualifierElement = ((PyReferenceExpression) qualifier).resolve();
@@ -71,15 +72,29 @@ public class ResolveImportUtil {
     if (importFrom != null) {
       return resolveChild(importFrom, referencedName, importRef);
     }
-
+    
+    // unqualified import can be found:
+    // in the same dir
+    final PsiFile pfile = importRef.getContainingFile();
+    if (pfile != null) {
+      PsiDirectory pdir = pfile.getContainingDirectory();
+      if (pdir != null) {
+        PsiElement elt = resolveChild(pdir, referencedName, importRef);
+        if (elt != null) return elt;
+      }
+      
+    } 
+    
+    // .. or in SDK roots
     final Module module = ModuleUtil.findModuleForPsiElement(importRef);
     if (module != null) {
       RootPolicy<PsiElement> resolvePolicy = new RootPolicy<PsiElement>() {
+        /*         
         public PsiElement visitModuleSourceOrderEntry(final ModuleSourceOrderEntry moduleOrderEntry, final PsiElement value) {
           if (value != null) return value;
           return resolveInRoots(moduleOrderEntry.getRootModel().getContentRoots(), referencedName, importRef);
         }
-
+        */
         public PsiElement visitJdkOrderEntry(final JdkOrderEntry jdkOrderEntry, final PsiElement value) {
           if (value != null) return value;
           return resolveInRoots(jdkOrderEntry.getRootFiles(OrderRootType.SOURCES), referencedName, importRef);
@@ -197,6 +212,7 @@ public class ResolveImportUtil {
       if (subdir != null) return subdir;
       else { // not a subdir, not a file; could be a name in parent/__init__.py
         final PsiFile initPy = dir.findFile(INIT_PY);
+        if ((importRef != null) && (initPy == importRef.getContainingFile())) return ret; // don't dive into the file we're in
         if (initPy != null) {
           if (processor == null) processor = new PyResolveUtil.ResolveProcessor(referencedName); // should not normally happen 
           return PyResolveUtil.treeWalkUp(processor, initPy, null, importRef);

python/testData/resolve/multiFile/resolveInPkg/ResolveInPkg.py

@@ -0,0 +1,4 @@
+from pkg import token
+
+x = token
+#   <ref>

python/testData/resolve/multiFile/resolveInPkg/pkg/__init__.py

@@ -0,0 +1 @@
+from submodule import token # import and reexport

python/testData/resolve/multiFile/resolveInPkg/pkg/submodule.py

@@ -0,0 +1,2 @@
+def token():
+  pass

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

@@ -84,6 +84,11 @@ public class PyMultiFileResolveTest extends CodeInsightTestCase {
     assertTrue(element instanceof PyTargetExpression);
   }
 
+  public void testResolveInPkg() throws Exception {
+    PsiElement element = doResolve();
+    assertTrue(element instanceof PyFunction);
+  }
+
   private PsiElement doResolve() throws Exception {
     String testName = getTestName(true);
     String fileName = getTestName(false) + ".py";