Add test for $unwind and a complex $group stage

[OskarStark]

I am using it this way in my pipeline and when I use the assertSamePipeline method from this repository (copy/pasted), I receive the following error:

With this test in your CI I want to achieve, that it is not a problem of the assertSamePipeline method.

cc @alcaeus @GromNaN

[OskarStark]

I rewrote all my pipelines, and my integration tests are all passing, except the ones, where I compare the pipeline itself. That means, the pipeline is correct, the fetched data is correct, but the assertion method seems not to be able to handle $unwind and my complex $group stage

[GromNaN]

Thanks for your feedbacks.
MongoDB and the PHP driver are fairly permissive about the types they accept. We need to choose the most reliable for the encoder to cover all use cases.

[GromNaN]

This is the short syntax of $unwind. In order to cover all use cases while keeping the code as simple as possible, I've chosen not to detect when only the field path is provided. So it's always an object with at least one property "path" that's returned.

Suggested change

	['$unwind' => '$foo'],
	['$unwind' => ['path' => '$foo']],

[OskarStark]

Ok it would be helpful if the diff would show this when failing

[GromNaN]

Using JSON comparison, the error of looks like this:

1) MongoDB\Tests\Builder\BuilderEncoderTest::testUnwind
'{ "root" : [ { "$unwind" : { "path" : "$foo" } }, { "$unwind" : { "path" : "$foo.bar" } }, { "$unwind" : { "path" : "$foo.bar.baz" } } ] }'
Failed asserting that '{ "root" : [ { "$unwind" : { "path" : "$foo" } }, { "$unwind" : { "path" : "$foo.bar" } }, { "$unwind" : { "path" : "$foo.bar.baz" } } ] }' matches JSON string "{ "root" : [ { "$unwind" : "$foo" }, { "$unwind" : "$foo.bar" }, { "$unwind" : "$foo.bar.baz" } ] }".
--- Expected
+++ Actual
@@ @@
 {
     "root": [
         {
-            "$unwind": "$foo"
+            "$unwind": {
+                "path": "$foo"
+            }
         },
         {
-            "$unwind": "$foo.bar"
+            "$unwind": {
+                "path": "$foo.bar"
+            }
         },
         {
-            "$unwind": "$foo.bar.baz"
+            "$unwind": {
+                "path": "$foo.bar.baz"
+            }
         }
     ]
 }

[GromNaN]

It's strictly equivalent. But in order to match the expected pipeline, it have to be an object. Maybe assertSamePipeline need to be improved to accept array or object equally.

Suggested change

	Expression::arrayToObject([[
	'k' => Expression::toString(Expression::fieldPath('key')),
	'v' => Expression::fieldPath('value'),
	]]),
	Expression::arrayToObject([
	object(
	k: Expression::toString(Expression::fieldPath('key')),
	v: Expression::fieldPath('value'),
	),
	]),

[OskarStark]

Yes it should not be necessary to change the pipeline itself to make the assert method happy 👌🏻

[GromNaN]

This is solved by using a BSON round-trip. See #13

[OskarStark]

I changed my pipelines accordingly and my tests pass 👍 Thanks for the help

[GromNaN]

I'm closing your PR for now. The requested changes are tracked in PHPLIB-1291.