implemented pylint W0601

Inspection is used when a variable is defined through the "global" statement but the variable is not defined in the module scope.

python/src/META-INF/python-plugin-common.xml

@@ -319,6 +319,7 @@
     <localInspection language="Python" shortName="PyAttributeOutsideInitInspection" displayName="Instance attribute defined outside _init_" groupKey="INSP.GROUP.python" enabledByDefault="true" level="WEAK WARNING" implementationClass="com.jetbrains.python.inspections.PyAttributeOutsideInitInspection"/>
     <localInspection language="Python" shortName="PyClassHasNoInitInspection" displayName="Class has no __init__ method" groupKey="INSP.GROUP.python" enabledByDefault="true" level="WEAK WARNING" implementationClass="com.jetbrains.python.inspections.PyClassHasNoInitInspection"/>
     <localInspection language="Python" shortName="PyNoneFunctionAssignmentInspection" displayName="Assigning function call that doesn't return anything" groupKey="INSP.GROUP.python" enabledByDefault="true" level="WEAK WARNING" implementationClass="com.jetbrains.python.inspections.PyNoneFunctionAssignmentInspection"/>
+    <localInspection language="Python" shortName="PyGlobalUndefinedInspection" displayName="Global variable is undefined at the module level" groupKey="INSP.GROUP.python" enabledByDefault="true" level="WEAK WARNING" implementationClass="com.jetbrains.python.inspections.PyGlobalUndefinedInspection"/>
     <localInspection language="Python" shortName="PyProtectedMemberInspection" displayName="Access to a protected member of a class" groupKey="INSP.GROUP.python" enabledByDefault="true" level="WEAK WARNING" implementationClass="com.jetbrains.python.inspections.PyProtectedMemberInspection"/>
     <localInspection language="Python" shortName="PyDocstringTypesInspection" bundle="com.jetbrains.python.PyBundle" key="INSP.NAME.docstring.types" groupKey="INSP.GROUP.python" enabledByDefault="true"  level="WEAK WARNING" implementationClass="com.jetbrains.python.inspections.PyDocstringTypesInspection"/>
     <localInspection language="Python" shortName="PyShadowingBuiltinsInspection" displayName="Shadowing built-ins" groupKey="INSP.GROUP.python" enabledByDefault="true"  level="WARNING" implementationClass="com.jetbrains.python.inspections.PyShadowingBuiltinsInspection"/>

python/src/com/jetbrains/python/PyBundle.properties

@@ -474,11 +474,15 @@ INSP.NAME.requirements=Package requirements
 # PyClassHasNoInitInspection
 INSP.NAME.class.has.no.init=Class has no __init__ method
 INSP.class.has.no.init=Class has no __init__ method
-INSP.parent.$0.has.no.init=Parent {0} has no __init__ method
+INSP.parent.$0.has.no.init=Parent ''{0}'' has no __init__ method
 
 #PyNoneFunctionAssignmentInspection
 INSP.NAME.none.function.assignment=Assigning function call that doesn't return anything (None)
-INSP.none.function.assignment=Function {0} doesn''t return anything
+INSP.none.function.assignment=Function ''{0}'' doesn''t return anything
+
+#PyGlobalUndefinedInspection
+INSP.NAME.global.undefined=Global variable is undefined at the module level
+INSP.NAME.global.$0.undefined=Global variable ''{0}'' is undefined at the module level
 
 # Refactoring
 # introduce

python/src/com/jetbrains/python/inspections/PyGlobalUndefinedInspection.java

@@ -0,0 +1,51 @@
+package com.jetbrains.python.inspections;
+
+import com.intellij.codeInspection.LocalInspectionToolSession;
+import com.intellij.codeInspection.ProblemsHolder;
+import com.intellij.psi.PsiElementVisitor;
+import com.jetbrains.python.PyBundle;
+import com.jetbrains.python.psi.PyGlobalStatement;
+import com.jetbrains.python.psi.PyTargetExpression;
+import org.jetbrains.annotations.Nls;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * User: ktisha
+ *
+ * pylint W0601
+ */
+public class PyGlobalUndefinedInspection extends PyInspection {
+  @Nls
+  @NotNull
+  @Override
+  public String getDisplayName() {
+    return PyBundle.message("INSP.NAME.global.undefined");
+  }
+
+  @NotNull
+  @Override
+  public PsiElementVisitor buildVisitor(@NotNull ProblemsHolder holder,
+                                        boolean isOnTheFly,
+                                        @NotNull LocalInspectionToolSession session) {
+    return new Visitor(holder, session);
+  }
+
+
+  private static class Visitor extends PyInspectionVisitor {
+    public Visitor(@Nullable ProblemsHolder holder, @NotNull LocalInspectionToolSession session) {
+      super(holder, session);
+    }
+
+    @Override
+    public void visitPyGlobalStatement(PyGlobalStatement node) {
+      final PyTargetExpression[] globals = node.getGlobals();
+
+      for (PyTargetExpression global : globals) {
+        if (global.getReference().resolve() == global) {
+          registerProblem(global, PyBundle.message("INSP.NAME.global.$0.undefined", global.getName()));
+        }
+      }
+    }
+  }
+}

python/testData/inspections/PyClassHasNoInitInspection/parentClass.py

@@ -3,7 +3,7 @@ class <weak_warning descr="Class has no __init__ method">A</weak_warning>:
     def foo(self):
         self.b = 1
 
-class <weak_warning descr="Parent A has no __init__ method">B</weak_warning>(A):
+class <weak_warning descr="Parent 'A' has no __init__ method">B</weak_warning>(A):
     def __init__(self):
         self.b = 2
 

python/testData/inspections/PyGlobalUndefinedInspection/trueNegative.py

@@ -0,0 +1,8 @@
+__author__ = 'ktisha'
+bar = 1
+
+def foo():
+    global bar
+    print bar
+
+foo()

python/testData/inspections/PyGlobalUndefinedInspection/truePositive.py

@@ -0,0 +1,6 @@
+__author__ = 'ktisha'
+def foo():
+    global <weak_warning descr="Global variable 'bar' is undefined at the module level">bar</weak_warning>
+    print bar
+
+foo()

python/testData/inspections/PyNoneFunctionAssignmentInspection/noReturn.py

@@ -3,4 +3,4 @@ __author__ = 'ktisha'
 def foo():
     a = 1
 
-<weak_warning descr="Function foo doesn't return anything">b = foo()</weak_warning>
+<weak_warning descr="Function 'foo' doesn't return anything">b = foo()</weak_warning>

python/testData/inspections/PyNoneFunctionAssignmentInspection/pass.py

@@ -3,4 +3,4 @@ __author__ = 'ktisha'
 def foo():
     pass
 
-<weak_warning descr="Function foo doesn't return anything">b = foo()</weak_warning>
+<weak_warning descr="Function 'foo' doesn't return anything">b = foo()</weak_warning>

python/testData/inspections/PyNoneFunctionAssignmentInspection/returnNone.py

@@ -3,4 +3,4 @@ __author__ = 'ktisha'
 def foo():
     return None
 
-<weak_warning descr="Function foo doesn't return anything">b = foo()</weak_warning>
+<weak_warning descr="Function 'foo' doesn't return anything">b = foo()</weak_warning>

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

@@ -0,0 +1,23 @@
+package com.jetbrains.python.inspections;
+
+import com.jetbrains.python.fixtures.PyTestCase;
+
+/**
+ * User: ktisha
+ */
+public class PyGlobalUndefinedInspectionTest extends PyTestCase {
+
+  public void testTruePositive() {
+    doTest();
+  }
+
+  public void testTrueNegative() {
+    doTest();
+  }
+
+  private void doTest() {
+    myFixture.configureByFile("inspections/PyGlobalUndefinedInspection/" + getTestName(true) + ".py");
+    myFixture.enableInspections(PyGlobalUndefinedInspection.class);
+    myFixture.checkHighlighting(false, false, true);
+  }
+}