Package io.github.treesitter.jtreesitter

Class LookaheadIterator

java.lang.Object

io.github.treesitter.jtreesitter.LookaheadIterator

All Implemented Interfaces:

AutoCloseable, Iterator<LookaheadIterator.Symbol>

@NullMarked
public final class LookaheadIterator
extends Object
implements AutoCloseable, Iterator<LookaheadIterator.Symbol>

A class that is used to look up valid symbols in a specific parse state.

Lookahead iterators can be useful to generate suggestions and improve syntax error diagnostics.
To get symbols valid in an ERROR node, use the lookahead iterator on its first leaf node state.
For MISSING nodes, a lookahead iterator created on the previous non-extra leaf node may be appropriate.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final record	LookaheadIterator.Symbol	A class that pairs a symbol ID with its name.

Method Summary

Modifier and Type	Method	Description
void	close()
short	getCurrentSymbol()	Get the current symbol ID.
String	getCurrentSymbolName()	The current symbol name.
Language	getLanguage()	Get the current language of the lookahead iterator.
boolean	hasNext()	Check if the lookahead iterator has more symbols.
Stream<String>	names()	Iterate over the symbol names.
LookaheadIterator.Symbol	next()	Advance the lookahead iterator to the next symbol.
boolean	reset(short state)	Reset the lookahead iterator to the given state.
boolean	reset(short state, Language language)	Reset the lookahead iterator to the given state and another language.
Stream<Short>	symbols()	Iterate over the symbol IDs.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Iterator

forEachRemaining

Method Details

getLanguage

public Language getLanguage()

Get the current language of the lookahead iterator.

getCurrentSymbol

@Unsigned
public short getCurrentSymbol()

Get the current symbol ID.

API Note:

The ID of the ERROR symbol is equal to -1.

getCurrentSymbolName

public String getCurrentSymbolName()

The current symbol name.

API Note:

Newly created lookahead iterators will contain the ERROR symbol.

reset

public boolean reset(@Unsigned
 short state)

Reset the lookahead iterator to the given state.

Returns:

true if the iterator was reset successfully or false if it failed.

reset

public boolean reset(@Unsigned
 short state,
 Language language)

Reset the lookahead iterator to the given state and another language.

Returns:

true if the iterator was reset successfully or false if it failed.

hasNext

public boolean hasNext()

Check if the lookahead iterator has more symbols.

Specified by:

hasNext in interface Iterator<LookaheadIterator.Symbol>

next

public LookaheadIterator.Symbol next()
                              throws NoSuchElementException

Advance the lookahead iterator to the next symbol.

Specified by:

next in interface Iterator<LookaheadIterator.Symbol>

Throws:

NoSuchElementException - If there are no more symbols.

symbols

@Unsigned
public Stream<Short> symbols()

Iterate over the symbol IDs.

Implementation Note:

Calling this method will reset the iterator to its original state.

names

public Stream<String> names()

Iterate over the symbol names.

Implementation Note:

Calling this method will reset the iterator to its original state.

close

public void close()
           throws RuntimeException

Specified by:

close in interface AutoCloseable

Throws:

RuntimeException