[Blazor WASM] - Investigate 6% size regression in System.Collections.dll.br

[SamMonoRT]

Size increase in System.Collections.dll.br as observed in https://msit.powerbi.com/groups/me/apps/54e0e83f-07bc-45bf-87b7-a7677ff3af2a/dashboards/fa051820-ff60-4d40-8a08-bdcc1b47b1d0

cc @CoffeeFlux - is this worth investigating ?

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[GrabYourPitchforks]

Likely related to #51571. Seeing lots of infrastructure to support SortedDictionary and SortedSet coming back into the assembly. Will track down the callers.

[GrabYourPitchforks]

I believe the code path below is responsible for this regression.

runtime/src/libraries/System.Text.Json/src/System/Text/Json/Node/JsonObject.IDictionary.cs

Lines 108 to 124 in ccc25a9

	public bool Remove(string propertyName)
	{
	if (propertyName == null)
	{
	throw new ArgumentNullException(nameof(propertyName));
	}
	if (!Dictionary.TryGetValue(propertyName, out JsonNode? item))
	{
	return false;
	}
	bool success = Dictionary.Remove(propertyName);
	Debug.Assert(success);
	DetachParent(item);
	return true;
	}

In particular, on line 120, there's a call to Dictionary.Remove(string). However, the Dictionary property getter is typed as IDictionary<,>, backed by an IDictionary<,> field. This means that the linker needs to keep every possible implementation of IDictionary<,>.Remove around, and in the case of SortedDictionary<,> that means also keeping much of the SortedSet<> infrastructure around as well.

If the Dictionary property getter is changed to be a strongly-typed Dictionary<,> rather than an interface IDictionary<,> I believe this might resolve the issue, since the target method will now be statically known rather than a virtual dispatch.

Tagging subscribers to this area: @eiriktsarpalis, @layomia
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Issue Details

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Size increase in System.Collections.dll.br as observed in https://msit.powerbi.com/groups/me/apps/54e0e83f-07bc-45bf-87b7-a7677ff3af2a/dashboards/fa051820-ff60-4d40-8a08-bdcc1b47b1d0

cc @CoffeeFlux - is this worth investigating ?

Author:	SamMonoRT
Assignees:	-
Labels:	area-System.Text.Json, untriaged
Milestone:	-

[layomia]

cc @steveharter. This overlaps with the effort to use a strongly-typed sorted dictionary to store JsonObject values (to preserve insertion order when enumerating over the object).

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That aside, this is related to #51311 and my comment here #51571 (comment).