// Tests expression object compilation with different placements of expression objects in the
// expression tree contained in the projection.

import {documentEq} from "jstests/aggregation/extras/utils.js";

const coll = db.expression_object;
coll.drop();
assert.commandWorked(coll.insert({"_id": "doc1", "field": "val1"}));

// All of the following tests filter nothing out and only compute the required projections.
// Each test contains Expression Object(s) at different positions within the expression tree.
// The fourth test projects the comparison result of two empty objects, which is true.
const emptyFilterDoc = {};
const testCases = [
    {projectionDoc: {label1: "$fieldRef1"}, resultDoc: {_id: "doc1"}},
    {
        projectionDoc: {label2: {"$eq": ["$_id", {label21: "$fieldRef21"}]}},
        resultDoc: {_id: "doc1", label2: false},
    },
    {
        projectionDoc: {label3: {"$eq": [{label31: "$fieldRef31"}, "$_id"]}},
        resultDoc: {_id: "doc1", label3: false},
    },
    {
        projectionDoc: {label4: {"$eq": [{label41: "$fieldRef41"}, {label42: "$fieldRef42"}]}},
        resultDoc: {_id: "doc1", label4: true},
    },
    {
        projectionDoc: {
            label5: {
                "$eq": [
                    {label51: {"$eq": ["$_id", {label511: "$fieldRef511"}]}},
                    {label52: {"$eq": [{label521: "$fieldRef521"}, "$_id"]}},
                ],
            },
        },
        resultDoc: {_id: "doc1", label5: false},
    },
    {
        projectionDoc: {label6: {"$eq": [{label61: {"$eq": [{label611: "$fieldRef611"}, "$_id"]}}, "$_id"]}},
        resultDoc: {_id: "doc1", label6: false},
    },
];

for (let testCase of testCases) {
    assert(documentEq(testCase.resultDoc, coll.findOne(emptyFilterDoc, testCase.projectionDoc)));
}