Package com.puppycrawl.tools.checkstyle.checks.coding

Class PatternVariableAssignmentCheck

java.lang.Object

com.puppycrawl.tools.checkstyle.AbstractAutomaticBean

com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

com.puppycrawl.tools.checkstyle.api.AbstractCheck

com.puppycrawl.tools.checkstyle.checks.coding.PatternVariableAssignmentCheck

All Implemented Interfaces:

Configurable, Contextualizable

public class PatternVariableAssignmentCheck
extends AbstractCheck

Checks for assignment of pattern variables.

Pattern variable assignment is considered bad programming practice. The pattern variable is meant to be a direct reference to the object being matched. Reassigning it can break this connection and mislead readers.

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

• pattern.variable.assignment

Since:

10.26.0

Nested Class Summary

Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.AbstractAutomaticBean

AbstractAutomaticBean.OutputStreamOptions

Field Summary

Fields

Modifier and Type	Field	Description
private static final Set<Integer>	ASSIGN_TOKEN_TYPES	The set of all valid types of ASSIGN token for this check.
static final String	MSG_KEY	A key is pointing to the warning message in "messages.properties" file.

Constructor Summary

Constructors

Constructor	Description
PatternVariableAssignmentCheck()

Method Summary

Modifier and Type	Method	Description
int[]	getAcceptableTokens()	The configurable token set.
private static DetailAST	getBranchLeadingToReassignedVars(DetailAST ast)	Gets the closest consistent AST branch that leads to reassigned variable's ident.
int[]	getDefaultTokens()	Returns the default token a check is interested in.
private static DetailAST	getMatchedAssignToken(DetailAST preAssignBranch)	Gets the type of ASSIGN tokens that particularly matches with what follows the preceding branch.
private static DetailAST	getNeededAssignIdent(DetailAST assignToken)	Gets the needed AST Ident of reassigned variable for check to compare.
private static List<DetailAST>	getPatternVariableIdents(DetailAST ast)	Gets the list of all pattern variable idents in instanceof expression.
private static List<DetailAST>	getReassignedVariableIdents(DetailAST ast)	Gets the array list made out of AST branches of reassigned variable idents.
int[]	getRequiredTokens()	The tokens that this check must be registered for.
private static DetailAST	shiftToNextTraversedBranch(DetailAST ast, DetailAST boundAst)	Shifts once to the next possible branch within traverse trajectory.
private static DetailAST	traverseUntilNeededBranchType(DetailAST startingBranch, DetailAST bound, int neededTokenType)	Traverses along the AST tree to locate the first branch of certain token type.
void	visitToken(DetailAST ast)	Called to process a token.

Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck

beginTree, clearViolations, destroy, finishTree, getFileContents, getFilePath, getLine, getLineCodePoints, getLines, getTabWidth, getTokenNames, getViolations, init, isCommentNodesRequired, leaveToken, log, log, log, setFileContents, setTabWidth, setTokens

Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

finishLocalSetup, getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, setId, setSeverity

Methods inherited from class com.puppycrawl.tools.checkstyle.AbstractAutomaticBean

configure, contextualize, getConfiguration, setupChild

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

MSG_KEY

public static final String MSG_KEY

A key is pointing to the warning message in "messages.properties" file.

See Also:

• Constant Field Values

ASSIGN_TOKEN_TYPES

private static final Set<Integer> ASSIGN_TOKEN_TYPES

The set of all valid types of ASSIGN token for this check.

Constructor Details

PatternVariableAssignmentCheck

public PatternVariableAssignmentCheck()

Method Details

getRequiredTokens

public int[] getRequiredTokens()

Description copied from class: AbstractCheck

The tokens that this check must be registered for.

Specified by:

getRequiredTokens in class AbstractCheck

Returns:

the token set this must be registered for.

See Also:

• TokenTypes

getDefaultTokens

public int[] getDefaultTokens()

Description copied from class: AbstractCheck

Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.

Specified by:

getDefaultTokens in class AbstractCheck

Returns:

the default tokens

See Also:

• TokenTypes

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

visitToken

public void visitToken(DetailAST ast)

Description copied from class: AbstractCheck

Called to process a token.

Overrides:

visitToken in class AbstractCheck

Parameters:

ast - the token to process

getPatternVariableIdents

private static List<DetailAST> getPatternVariableIdents(DetailAST ast)

Gets the list of all pattern variable idents in instanceof expression.

Parameters:

ast - ast tree of instanceof to get the list from.

Returns:

list of pattern variables.

getReassignedVariableIdents

private static List<DetailAST> getReassignedVariableIdents(DetailAST ast)

Gets the array list made out of AST branches of reassigned variable idents.

Parameters:

ast - ast tree of checked instanceof statement.

Returns:

the list of AST branches of reassigned variable idents.

getBranchLeadingToReassignedVars

@Nullable
private static DetailAST getBranchLeadingToReassignedVars(DetailAST ast)

Gets the closest consistent AST branch that leads to reassigned variable's ident.

Parameters:

ast - ast tree of checked instanceof statement.

Returns:

the closest consistent AST branch that leads to reassigned variable's ident.

traverseUntilNeededBranchType

@Nullable
private static DetailAST traverseUntilNeededBranchType(DetailAST startingBranch,
 DetailAST bound,
 int neededTokenType)

Traverses along the AST tree to locate the first branch of certain token type.

Parameters:

startingBranch - AST branch to start the traverse from, but not check.

bound - AST Branch that the traverse cannot further extend to.

neededTokenType - Token type whose first encountered branch is to look for.

Returns:

the AST tree of first encountered branch of needed token type.

shiftToNextTraversedBranch

@Nullable
private static DetailAST shiftToNextTraversedBranch(DetailAST ast,
 DetailAST boundAst)

Shifts once to the next possible branch within traverse trajectory.

Parameters:

ast - AST branch to shift from.

boundAst - AST Branch that the traverse cannot further extend to.

Returns:

the AST tree of next possible branch within traverse trajectory.

getMatchedAssignToken

@Nullable
private static DetailAST getMatchedAssignToken(DetailAST preAssignBranch)

Gets the type of ASSIGN tokens that particularly matches with what follows the preceding branch.

Parameters:

preAssignBranch - branch that precedes the branch of ASSIGN token types.

Returns:

type of ASSIGN token.

getNeededAssignIdent

private static DetailAST getNeededAssignIdent(DetailAST assignToken)

Gets the needed AST Ident of reassigned variable for check to compare.

Parameters:

assignToken - The AST branch of reassigned variable's ASSIGN token.

Returns:

needed AST Ident.