PY-1194 Provide completion and navigation for url tag in django template

PY-3591  Support {% url %} tag arguments completion

Params to be supported

python/psi-api/src/com/jetbrains/python/FunctionParameter.java

@@ -0,0 +1,21 @@
+package com.jetbrains.python;
+
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * This class (possibly enum) represents function parameter
+ *
+ * @author Ilya.Kazakevich
+ */
+public interface FunctionParameter {
+  /**
+   * @return parameter position
+   */
+  int getPosition();
+
+  /**
+   * @return parameter name (if known)
+   */
+  @Nullable
+  String getName();
+}

python/psi-api/src/com/jetbrains/python/psi/PyArgumentList.java

@@ -16,6 +16,7 @@
 package com.jetbrains.python.psi;
 
 import com.intellij.lang.ASTNode;
+import com.jetbrains.python.FunctionParameter;
 import com.jetbrains.python.psi.resolve.PyResolveContext;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -78,4 +79,13 @@ public interface PyArgumentList extends PyElement {
 
   @Nullable
   ASTNode getClosingParen();
+
+  /**
+   * Searches parameter value and returns it if exists.
+   *
+   * @param parameter param to search
+   * @return function parameter value expression or null if does not exist
+   */
+  @Nullable
+  PyExpression getValueExpressionForParam(@NotNull FunctionParameter parameter);
 }

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

@@ -27,6 +27,7 @@ import com.jetbrains.NotNullPredicate;
 import com.jetbrains.python.PyElementTypes;
 import com.jetbrains.python.PyTokenTypes;
 import com.jetbrains.python.PythonDialectsTokenSetProvider;
+import com.jetbrains.python.FunctionParameter;
 import com.jetbrains.python.psi.*;
 import com.jetbrains.python.psi.resolve.PyResolveContext;
 import org.jetbrains.annotations.NotNull;
@@ -203,7 +204,6 @@ public class PyArgumentListImpl extends PyElementImpl implements PyArgumentList
       catch (IncorrectOperationException e1) {
         throw new IllegalStateException(e1);
       }
-
     }
     else {
       getNode().addChild(arg.getNode(), par);
@@ -214,7 +214,7 @@ public class PyArgumentListImpl extends PyElementImpl implements PyArgumentList
   public ASTNode getClosingParen() {
     ASTNode node = getNode();
     final ASTNode[] children = node.getChildren(TokenSet.create(PyTokenTypes.RPAR));
-    return children.length == 0 ? null : children[children.length-1];
+    return children.length == 0 ? null : children[children.length - 1];
   }
 
   private void addArgumentNode(PyExpression arg, ASTNode beforeThis, boolean commaFirst) {
@@ -256,14 +256,12 @@ public class PyArgumentListImpl extends PyElementImpl implements PyArgumentList
         // 1: Nothing, just add
         addArgumentNode(argument, node, true);
         break;
-
       }
       else if (PythonDialectsTokenSetProvider.INSTANCE.getExpressionTokens().contains(type)) {
         // 2: After some argument followed by comma: after comma, add element, add comma
         // 3: After some argument not followed by comma: add comma, add element
         addArgumentNode(argument, node, true);
         break;
-
       }
       else if (type == PyTokenTypes.COMMA) {
         ASTNode next = PyUtil.getNextNonWhitespace(node);
@@ -333,4 +331,23 @@ public class PyArgumentListImpl extends PyElementImpl implements PyArgumentList
       return (PsiTreeUtil.getParentOfType(input, PyKeywordArgument.class) == null) && !(input instanceof PyKeywordArgument);
     }
   }
+
+  @Nullable
+  @Override
+  public PyExpression getValueExpressionForParam(@NotNull final FunctionParameter parameter) {
+    final String parameterName = parameter.getName();
+    if (parameterName != null) {
+      final PyKeywordArgument kwarg = getKeywordArgument(parameterName);
+      if (kwarg != null) {
+        return kwarg.getValueExpression();
+      }
+    }
+
+    final PyExpression[] arguments = getArguments();
+    if (arguments.length > parameter.getPosition()) {
+      return arguments[parameter.getPosition()];
+    }
+
+    return null;
+  }
 }