mongodb/jstests/mr_errorhandling.js

t = db.mr_errorhandling;
t.drop();

t.save( { a : [ 1 , 2 , 3 ] } )
t.save( { a : [ 2 , 3 , 4 ] } )

m_good = function(){
    for ( var i=0; i<this.a.length; i++ ){
        emit( this.a[i] , 1 );
    }
}

m_bad = function(){
    for ( var i=0; i<this.a.length; i++ ){
        emit( this.a[i] );
    }
}

r = function( k , v ){
    var total = 0;
    for ( var i=0; i<v.length; i++ )
        total += v[i];
    return total;
}

res = t.mapReduce( m_good , r , "mr_errorhandling_out" );
assert.eq( { 1 : 1 , 2 : 2 , 3 : 2 , 4 : 1 } , res.convertToSingleObject() , "A" );
res.drop()

res = null;

theerror = null;
try {
    res = t.mapReduce( m_bad , r , "mr_errorhandling_out" );
}
catch ( e ){
    theerror = e.toString();
}
assert.isnull( res , "B1" );
assert( theerror , "B2" );
assert( theerror.indexOf( "emit" ) >= 0 , "B3" );

// test things are still in an ok state
res = t.mapReduce( m_good , r , "mr_errorhandling_out" );
assert.eq( { 1 : 1 , 2 : 2 , 3 : 2 , 4 : 1 } , res.convertToSingleObject() , "A" );
res.drop()

assert.throws( function(){ t.mapReduce( m_good , r , { out : "xxx" , query : "foo" } ); } )