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

Class UnnecessaryPermitsClauseCheck

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.UnnecessaryPermitsClauseCheck

All Implemented Interfaces:

Configurable, Contextualizable

public class UnnecessaryPermitsClauseCheck
extends AbstractCheck

Checks that a permits clause of a sealed class or interface is not unnecessary, i.e. that it is not possible to omit the clause and have the compiler infer the exact same set of permitted subtypes.

See the Java Language Specification for more information about sealed classes.

This Check does not perform full type resolution. It determines whether a permitted type is local to the file by comparing simple names against every type declaration (class, interface, enum, or record) found anywhere in the compilation unit, including nested and sibling top-level types. As a result, a permitted type whose simple name coincidentally matches an unrelated local type declaration could, in theory, be misidentified as local. In practice this situation cannot occur in code that compiles, since the Java compiler would not be able to resolve such an ambiguous reference in the permits clause.

Since:

14.2.0

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 final Set<String>	localTypeNames	A set of simple names of every type declared in the current compilation unit, including nested types.
static final String	MSG_KEY	A key is pointing to the warning message text in "messages.properties" file.
private final List<DetailAST>	permitsClauseAstList	A list of TokenTypes.PERMITS_CLAUSE nodes found in the current compilation unit.

Constructor Summary

Constructors

Constructor	Description
UnnecessaryPermitsClauseCheck()	Creates a new UnnecessaryPermitsClauseCheck instance.

Method Summary

Modifier and Type	Method	Description
void	beginTree(DetailAST rootAST)	Called before the starting to process a tree.
void	finishTree(DetailAST rootAST)	Called after finished processing a tree.
int[]	getAcceptableTokens()	The configurable token set.
int[]	getDefaultTokens()	Returns the default token a check is interested in.
int[]	getRequiredTokens()	The tokens that this check must be registered for.
private static String	getSimpleName(DetailAST typeName)	Extracts the simple (unqualified) name from a type name node, which is either a single TokenTypes.IDENT or a TokenTypes.DOT chain representing a qualified name.
private static boolean	isTypeName(DetailAST ast)	Checks whether the given direct child of a permits clause represents a permitted type name, as opposed to a separating comma.
private boolean	isUnnecessary(DetailAST permitsClause)	Determines whether every type named in the given permits clause is declared somewhere within the same compilation unit, and is therefore redundant.
void	visitToken(DetailAST ast)	Called to process a token.

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

clearViolations, destroy, 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 text in "messages.properties" file.

See Also:

• Constant Field Values

localTypeNames

private final Set<String> localTypeNames

A set of simple names of every type declared in the current compilation unit, including nested types.

permitsClauseAstList

private final List<DetailAST> permitsClauseAstList

A list of TokenTypes.PERMITS_CLAUSE nodes found in the current compilation unit.

Constructor Details

UnnecessaryPermitsClauseCheck

public UnnecessaryPermitsClauseCheck()

Creates a new UnnecessaryPermitsClauseCheck instance.

Method Details

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

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

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

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

finishTree

public void finishTree(DetailAST rootAST)

Description copied from class: AbstractCheck

Called after finished processing a tree. Ideal place to report on information collected whilst processing a tree.

Overrides:

finishTree in class AbstractCheck

Parameters:

rootAST - the root of the tree

isUnnecessary

private boolean isUnnecessary(DetailAST permitsClause)

Determines whether every type named in the given permits clause is declared somewhere within the same compilation unit, and is therefore redundant.

Parameters:

permitsClause - the TokenTypes.PERMITS_CLAUSE node to inspect

Returns:

true if the clause is unnecessary

isTypeName

private static boolean isTypeName(DetailAST ast)

Checks whether the given direct child of a permits clause represents a permitted type name, as opposed to a separating comma.

Parameters:

ast - the node to check

Returns:

true if the node is a (possibly qualified) type name

getSimpleName

private static String getSimpleName(DetailAST typeName)

Extracts the simple (unqualified) name from a type name node, which is either a single TokenTypes.IDENT or a TokenTypes.DOT chain representing a qualified name.

Parameters:

typeName - the type name node

Returns:

the simple name of the type