// Providing the wrong number of fields in a pipeline stage specification triggers a parsing error.
// SERVER-6861
load('jstests/aggregation/extras/utils.js');

t = db.jstests_server6861;
t.drop();

t.save( { a:1 } );

function assertCode( code, expression ) {
    assertErrorCode(t, expression, code);
}

function assertResult( result, expression ) {
    assert.eq( result, t.aggregate( expression ).toArray() );
}

// Correct number of fields.
assertResult( [ { a:1 } ], { $project:{ _id:0, a:1 } } );

// Incorrect number of fields.
assertCode( 16435, {} );
assertCode( 16435, { $project:{ _id:0, a:1 }, $group:{ _id:0 } } );
assertCode( 16435, { $project:{ _id:0, a:1 }, $group:{ _id:0 }, $sort:{ a:1 } } );

// Invalid stage specification.
assertCode( 16436, { $noSuchStage:{ a:1 } } );