pegjs/test/unit/compiler/passes/report-incorrect-plucking.spec.js

"use strict";

const { expect, use } = require( "chai" );
const helpers = require( "./helpers" );
const pass = require( "pegjs" ).compiler.passes.check.reportIncorrectPlucking;

use( helpers );

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

    function reports( error, edgecases ) {

        it( error.slice( 0, -1 ), () => {

            edgecases.forEach( grammar => expect( pass ).to.reportError( grammar, error ) );

        } );

    }

    reports( `"@" cannot be used with an action block.`, [

        `start1 = 'a' @'b' 'c' { /* empty action block */ }`,
        `start2 = 'a' @('b' @'c' { /* empty action block */ })`,

    ] );

    reports( `"@" cannot be used on a semantic predicate.`, [

        `start1 = 'a' @&{ /* semantic_and */ } 'c'`,
        `start2 = 'a' @!{ /* semantic_not */ } 'c'`,

    ] );

    it( "allows valid plucking", function () {

        expect( pass ).not.to.reportError( `

            start1 =  @'1'               // return '1'
            start2 =  @'1' / @'2'        // return '1' or '2'
            start2 =   '1'   @'2' '3'    // return '2'
            start3 =   '1' @b:'2' '3'    // return '2', label "b" can be used in semantic predicates
            start4 = a:'1' @b:'2' '3'    // return '2', labels "a" and "b" can be used in semantic predicates
            start5 =  @'1'   @'2' '3'    // return ['1', '2']
            start6 =  @'1' @b:'2' '3'    // return ['1', '2'], label "b" can be used in semantic predicates
            start7 = a:'1'   @'2' &{}    // return '2' if the semantic predicate doesnt fail

        ` );

    } );

} );