Class RequireThisCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public class RequireThisCheck
    extends AbstractCheck

    Checks that references to instance variables and methods of the present object are explicitly of the form "this.varName" or "this.methodName(args)" and that those references don't rely on the default behavior when "this." is absent.

    Warning: the Check is very controversial if 'validateOnlyOverlapping' option is set to 'false' and not that actual nowadays.

    Rationale:

    1. The same notation/habit for C++ and Java (C++ have global methods, so having "this." do make sense in it to distinguish call of method of class instead of global).
    2. Non-IDE development (ease of refactoring, some clearness to distinguish static and non-static methods).

    Limitations: Nothing is currently done about static variables or catch-blocks. Static methods invoked on a class name seem to be OK; both the class name and the method name have a DOT parent. Non-static methods invoked on either this or a variable name seem to be OK, likewise.

    • Property checkFields - Control whether to check references to fields. Type is boolean. Default value is true.
    • Property checkMethods - Control whether to check references to methods. Type is boolean. Default value is true.
    • Property validateOnlyOverlapping - Control whether to check only overlapping by variables or arguments. Type is boolean. Default value is true.

    To configure the default check:

     <module name="RequireThis"/>
     

    Example:

     public class Test {
       private int a;
       private int b;
       private int c;
    
       public Test(int a) {
         // overlapping by constructor argument
         this.a = a;       // OK, this keyword used
         b = 0;            // OK, no overlap
         foo(5);           // OK
       }
    
       public void foo(int c) {
         // overlapping by method argument
         c = c;            // violation, reference to instance variable "c" requires "this"
       }
     }
     

    To configure the check for fields only:

     <module name="RequireThis">
       <property name="checkMethods" value="false"/>
     </module>
     

    Example:

     public class Test {
       private int a;
       private int b;
       private int c;
    
       public Test(int a) {
         // overlapping by constructor argument
         this.a = a;       // OK, this keyword used
         b = 0;            // OK, no overlap
         foo(5);           // OK, no validation for methods
       }
    
       public void foo(int c) {
         // overlapping by method argument
         c = c;            // violation, reference to instance variable "c" requires "this"
       }
     }
     

    To configure the check for methods only:

     <module name="RequireThis">
       <property name="checkFields" value="false"/>
     </module>
     

    Example:

     public class Test {
       private int a;
       private int b;
       private int c;
    
       public Test(int a) {
         // overlapping by constructor argument
         this.a = a;       // OK, no validation for fields
         b = 0;            // OK, no validation for fields
         foo(5);           // OK, no overlap
       }
    
       public void foo(int c) {
         // overlapping by method argument
         c = c;            // OK, no validation for fields
       }
     }
     

    Note that method call foo(5) does not raise a violation because methods cannot be overlapped in java.

    To configure the check to validate for non-overlapping fields and methods:

     <module name="RequireThis">
       <property name="validateOnlyOverlapping" value="false"/>
     </module>
     

    Example:

     public class Test {
       private int a;
       private int b;
       private int c;
    
       public Test(int a) {
         // overlapping by constructor argument
         this.a = a;       // OK, no validation for fields
         b = 0;            // violation, reference to instance variable "b" requires "this"
         foo(5);           // violation, method call "foo(5)" requires "this"
       }
    
       public void foo(int c) {
         // overlapping by method argument
         c = c;            // violation, reference to instance variable "c" requires "this"
       }
     }
     

    Please, be aware of the following logic, which is implemented in the check:

    1) If you arrange 'this' in your code on your own, the check will not raise violation for variables which use 'this' to reference a class field, for example:

     public class C {
       private int scale;
       private int x;
    
       public void foo(int scale) {
         scale = this.scale;      // no violation
    
         if (scale > 0) {
           scale = -scale;        // no violation
         }
         x *= scale;
       }
     }
     

    2) If method parameter is returned from the method, the check will not raise violation for returned variable/parameter, for example:

     public class D {
       private String prefix;
    
       public String modifyPrefix(String prefix) {
         prefix = "^" + prefix + "$";  // no violation, because method parameter is returned
         return prefix;
       }
     }
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • require.this.method
    • require.this.variable
    Since:
    3.4
    • Method Detail

      • setCheckFields

        public void setCheckFields​(boolean checkFields)
        Setter to control whether to check references to fields.
        Parameters:
        checkFields - should we check fields usage or not
      • setCheckMethods

        public void setCheckMethods​(boolean checkMethods)
        Setter to control whether to check references to methods.
        Parameters:
        checkMethods - should we check methods usage or not
      • setValidateOnlyOverlapping

        public void setValidateOnlyOverlapping​(boolean validateOnlyOverlapping)
        Setter to control whether to check only overlapping by variables or arguments.
        Parameters:
        validateOnlyOverlapping - should we check only overlapping by variables or arguments
      • getAcceptableTokens

        public int[] getAcceptableTokens()
        Description copied from class: AbstractCheck
        The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.
        Specified by:
        getAcceptableTokens in class AbstractCheck
        Returns:
        the token set this check is designed for.
        See Also:
        TokenTypes
      • beginTree

        public void beginTree​(DetailAST rootAST)
        Description copied from class: AbstractCheck
        Called before the starting to process a tree. Ideal place to initialize information that is to be collected whilst processing a tree.
        Overrides:
        beginTree in class AbstractCheck
        Parameters:
        rootAST - the root of the tree
      • processIdent

        private void processIdent​(DetailAST ast)
        Checks if a given IDENT is method call or field name which requires explicit this qualifier.
        Parameters:
        ast - IDENT to check.
      • logViolation

        private void logViolation​(String msgKey,
                                  DetailAST ast,
                                  RequireThisCheck.AbstractFrame frame)
        Helper method to log a Violation.
        Parameters:
        msgKey - key to locale message format.
        ast - a node to get line id column numbers associated with the message.
        frame - the class frame where the violation is found.
      • getFieldWithoutThis

        private RequireThisCheck.AbstractFrame getFieldWithoutThis​(DetailAST ast,
                                                                   int parentType)
        Returns the frame where the field is declared, if the given field is used without 'this', and null otherwise.
        Parameters:
        ast - field definition ast token.
        parentType - type of the parent.
        Returns:
        the frame where the field is declared, if the given field is used without 'this' and null otherwise.
      • isInCompactConstructor

        private static boolean isInCompactConstructor​(DetailAST ast)
        Return whether ast is in a COMPACT_CTOR_DEF.
        Parameters:
        ast - The token to check
        Returns:
        true if ast is in a COMPACT_CTOR_DEF, false otherwise
      • isAnonymousClassDef

        private static boolean isAnonymousClassDef​(DetailAST ast)
        Whether the AST is a definition of an anonymous class.
        Parameters:
        ast - the AST to process.
        Returns:
        true if the AST is a definition of an anonymous class.
      • isInExpression

        private static boolean isInExpression​(DetailAST ast)
        Checks ast parent is in expression.
        Parameters:
        ast - token to check
        Returns:
        true if token is part of expression, false otherwise
      • isUserDefinedArrangementOfThis

        private static boolean isUserDefinedArrangementOfThis​(RequireThisCheck.AbstractFrame currentFrame,
                                                              DetailAST ident)
        Checks whether user arranges 'this' for variable in method, constructor, or block on his own.
        Parameters:
        currentFrame - current frame.
        ident - ident token.
        Returns:
        true if user arranges 'this' for variable in method, constructor, or block on his own.
      • getBlockEndToken

        private static DetailAST getBlockEndToken​(DetailAST blockNameIdent,
                                                  DetailAST blockStartToken)
        Returns the token which ends the code block.
        Parameters:
        blockNameIdent - block name identifier.
        blockStartToken - token which starts the block.
        Returns:
        the token which ends the code block.
      • isReturnedVariable

        private static boolean isReturnedVariable​(RequireThisCheck.AbstractFrame currentFrame,
                                                  DetailAST ident)
        Checks whether the current variable is returned from the method.
        Parameters:
        currentFrame - current frame.
        ident - variable ident token.
        Returns:
        true if the current variable is returned from the method.
      • isAstInside

        private static boolean isAstInside​(DetailAST tree,
                                           DetailAST ast)
        Checks if the given ast is equal to the tree or a child of it.
        Parameters:
        tree - The tree to search.
        ast - The AST to look for.
        Returns:
        true if the ast was found.
      • canBeReferencedFromStaticContext

        private boolean canBeReferencedFromStaticContext​(DetailAST ident)
        Checks whether a field can be referenced from a static context.
        Parameters:
        ident - ident token.
        Returns:
        true if field can be referenced from a static context.
      • getCodeBlockDefinitionToken

        private static DetailAST getCodeBlockDefinitionToken​(DetailAST ident)
        Returns code block definition token for current identifier.
        Parameters:
        ident - ident token.
        Returns:
        code block definition token for current identifier or null if code block definition was not found.
      • canAssignValueToClassField

        private boolean canAssignValueToClassField​(DetailAST ast)
        Checks whether a value can be assigned to a field. A value can be assigned to a final field only in constructor block. If there is a method block, value assignment can be performed only to non final field.
        Parameters:
        ast - an identifier token.
        Returns:
        true if a value can be assigned to a field.
      • isInsideConstructorFrame

        private static boolean isInsideConstructorFrame​(RequireThisCheck.AbstractFrame frame)
        Checks whether a field usage frame is inside constructor frame.
        Parameters:
        frame - frame, where field is used.
        Returns:
        true if the field usage frame is inside constructor frame.
      • isOverlappingByArgument

        private boolean isOverlappingByArgument​(DetailAST ast)
        Checks whether an overlapping by method or constructor argument takes place.
        Parameters:
        ast - an identifier.
        Returns:
        true if an overlapping by method or constructor argument takes place.
      • isOverlappingByLocalVariable

        private boolean isOverlappingByLocalVariable​(DetailAST ast)
        Checks whether an overlapping by local variable takes place.
        Parameters:
        ast - an identifier.
        Returns:
        true if an overlapping by local variable takes place.
      • getAllTokensOfType

        private static Set<DetailASTgetAllTokensOfType​(DetailAST ast,
                                                         int tokenType)
        Collects all tokens of specific type starting with the current ast node.
        Parameters:
        ast - ast node.
        tokenType - token type.
        Returns:
        a set of all tokens of specific type starting with the current ast node.
      • getAllTokensOfType

        private static Set<DetailASTgetAllTokensOfType​(DetailAST ast,
                                                         int tokenType,
                                                         int endLineNumber)
        Collects all tokens of specific type starting with the current ast node and which line number is lower or equal to the end line number.
        Parameters:
        ast - ast node.
        tokenType - token type.
        endLineNumber - end line number.
        Returns:
        a set of all tokens of specific type starting with the current ast node and which line number is lower or equal to the end line number.
      • getAllTokensWhichAreEqualToCurrent

        private static Set<DetailASTgetAllTokensWhichAreEqualToCurrent​(DetailAST ast,
                                                                         DetailAST token,
                                                                         int endLineNumber)
        Collects all tokens which are equal to current token starting with the current ast node and which line number is lower or equal to the end line number.
        Parameters:
        ast - ast node.
        token - token.
        endLineNumber - end line number.
        Returns:
        a set of tokens which are equal to current token starting with the current ast node and which line number is lower or equal to the end line number.
      • getMethodWithoutThis

        private RequireThisCheck.AbstractFrame getMethodWithoutThis​(DetailAST ast)
        Returns the frame where the method is declared, if the given method is used without 'this' and null otherwise.
        Parameters:
        ast - the IDENT ast of the name to check.
        Returns:
        the frame where the method is declared, if the given method is used without 'this' and null otherwise.
      • findClassFrame

        private RequireThisCheck.AbstractFrame findClassFrame​(DetailAST name,
                                                              boolean lookForMethod)
        Find the class frame containing declaration.
        Parameters:
        name - IDENT ast of the declaration to find.
        lookForMethod - whether we are looking for a method name.
        Returns:
        AbstractFrame containing declaration or null.
      • findFrame

        private RequireThisCheck.AbstractFrame findFrame​(DetailAST name,
                                                         boolean lookForMethod)
        Find frame containing declaration.
        Parameters:
        name - IDENT ast of the declaration to find.
        lookForMethod - whether we are looking for a method name.
        Returns:
        AbstractFrame containing declaration or null.
      • findFrame

        private static RequireThisCheck.AbstractFrame findFrame​(RequireThisCheck.AbstractFrame frame,
                                                                DetailAST name,
                                                                boolean lookForMethod)
        Find frame containing declaration.
        Parameters:
        frame - The parent frame to searching in.
        name - IDENT ast of the declaration to find.
        lookForMethod - whether we are looking for a method name.
        Returns:
        AbstractFrame containing declaration or null.
      • isDeclarationToken

        private static boolean isDeclarationToken​(int parentType)
        Check that token is related to Definition tokens.
        Parameters:
        parentType - token Type.
        Returns:
        true if token is related to Definition Tokens.
      • isAssignToken

        private static boolean isAssignToken​(int tokenType)
        Check that token is related to assign tokens.
        Parameters:
        tokenType - token type.
        Returns:
        true if token is related to assign tokens.
      • isCompoundAssignToken

        private static boolean isCompoundAssignToken​(int tokenType)
        Check that token is related to compound assign tokens.
        Parameters:
        tokenType - token type.
        Returns:
        true if token is related to compound assign tokens.
      • getNearestClassFrameName

        private String getNearestClassFrameName()
        Gets the name of the nearest parent ClassFrame.
        Returns:
        the name of the nearest parent ClassFrame.
      • isLambdaParameter

        private static boolean isLambdaParameter​(DetailAST ast)
        Checks if the token is a Lambda parameter.
        Parameters:
        ast - the DetailAST value of the token to be checked
        Returns:
        true if the token is a Lambda parameter
      • isAstSimilar

        private static boolean isAstSimilar​(DetailAST left,
                                            DetailAST right)
        Checks if 2 AST are similar by their type and text.
        Parameters:
        left - The first AST to check.
        right - The second AST to check.
        Returns:
        true if they are similar.