pegjs/test/spec/unit/compiler/passes/report-infinite-recursion.spec.js

"use strict";

const chai = require( "chai" );
const helpers = require( "./helpers" );
const pass = require( "pegjs-dev" ).compiler.passes.check.reportInfiniteRecursion;

chai.use( helpers );

const expect = chai.expect;

describe( "compiler pass |reportInfiniteRecursion|", function () {

    it( "reports direct left recursion", function () {

        expect( pass ).to.reportError( "start = start", {
            message: "Possible infinite loop when parsing (left recursion: start -> start).",
            location: {
                start: { offset: 8, line: 1, column: 9 },
                end: { offset: 13, line: 1, column: 14 }
            }
        } );

    } );

    it( "reports indirect left recursion", function () {

        expect( pass ).to.reportError( [
            "start = stop",
            "stop = start"
        ].join( "\n" ), {
            message: "Possible infinite loop when parsing (left recursion: start -> stop -> start).",
            location: {
                start: { offset: 20, line: 2, column: 8 },
                end: { offset: 25, line: 2, column: 13 }
            }
        } );

    } );

    describe( "in sequences", function () {

        it( "reports left recursion if all preceding elements match empty string", function () {

            expect( pass ).to.reportError( "start = '' '' '' start" );

        } );

        it( "doesn't report left recursion if some preceding element doesn't match empty string", function () {

            expect( pass ).to.not.reportError( "start = 'a' '' '' start" );
            expect( pass ).to.not.reportError( "start = '' 'a' '' start" );
            expect( pass ).to.not.reportError( "start = '' '' 'a' start" );

        } );

        // Regression test for #359.
        it( "reports left recursion when rule reference is wrapped in an expression", function () {

            expect( pass ).to.reportError( "start = '' start?" );

        } );

        it( "computes expressions that always consume input on success correctly", function () {

            expect( pass ).to.reportError( [
                "start = a start",
                "a 'a' = ''"
            ].join( "\n" ) );
            expect( pass ).to.not.reportError( [
                "start = a start",
                "a 'a' = 'a'"
            ].join( "\n" ) );

            expect( pass ).to.reportError( "start = ('' / 'a' / 'b') start" );
            expect( pass ).to.reportError( "start = ('a' / '' / 'b') start" );
            expect( pass ).to.reportError( "start = ('a' / 'b' / '') start" );
            expect( pass ).to.not.reportError( "start = ('a' / 'b' / 'c') start" );

            expect( pass ).to.reportError( "start = ('' { }) start" );
            expect( pass ).to.not.reportError( "start = ('a' { }) start" );

            expect( pass ).to.reportError( "start = ('' '' '') start" );
            expect( pass ).to.not.reportError( "start = ('a' '' '') start" );
            expect( pass ).to.not.reportError( "start = ('' 'a' '') start" );
            expect( pass ).to.not.reportError( "start = ('' '' 'a') start" );

            expect( pass ).to.reportError( "start = a:'' start" );
            expect( pass ).to.not.reportError( "start = a:'a' start" );

            expect( pass ).to.reportError( "start = $'' start" );
            expect( pass ).to.not.reportError( "start = $'a' start" );

            expect( pass ).to.reportError( "start = &'' start" );
            expect( pass ).to.reportError( "start = &'a' start" );

            expect( pass ).to.reportError( "start = !'' start" );
            expect( pass ).to.reportError( "start = !'a' start" );

            expect( pass ).to.reportError( "start = ''? start" );
            expect( pass ).to.reportError( "start = 'a'? start" );

            expect( pass ).to.reportError( "start = ''* start" );
            expect( pass ).to.reportError( "start = 'a'* start" );

            expect( pass ).to.reportError( "start = ''+ start" );
            expect( pass ).to.not.reportError( "start = 'a'+ start" );

            expect( pass ).to.reportError( "start = ('') start" );
            expect( pass ).to.not.reportError( "start = ('a') start" );

            expect( pass ).to.reportError( "start = &{ } start" );

            expect( pass ).to.reportError( "start = !{ } start" );

            expect( pass ).to.reportError( [
                "start = a start",
                "a = ''"
            ].join( "\n" ) );
            expect( pass ).to.not.reportError( [
                "start = a start",
                "a = 'a'"
            ].join( "\n" ) );

            expect( pass ).to.reportError( "start = '' start" );
            expect( pass ).to.not.reportError( "start = 'a' start" );

            expect( pass ).to.not.reportError( "start = [a-d] start" );

            expect( pass ).to.not.reportError( "start = . start" );

        } );

    } );

} );