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987 B
987 B
tracer#trace()
Whether you are using the CLI or the API, as long as you pass the trace option, the generated parser can trace it's progress by calling tracer.trace( event ), which can then be overwritten by passing an alternative tracer in the options to the generated parser.
You can also optionally disable the default tracer by passing features: { DefaultTracer: false } to peg.generate or peg.compiler.compile, in which case a empty function will be called by default unless a tracer is passed to the parser.
The event passed to the trace method contains the following properties:
| property | description |
|---|---|
| type | name of the event |
| rule | rule that this event was emitted from |
| result | the result of the match |
| location | location in the grammar when the event was emitted |
The type property will only be 1 of 3 values:
rule.enterwhen entering a rulerule.matchwhen matching a rule was successfulrule.failwhen matching a rule failed