Remove reflections: Misc and Summary

[karakasa]

try to fix #957

I found some upstream dependencies don't support AOT therefore NPOI cannot be completed AOTed. The library will get some performance improvement from removing reflections though.

@tonyqus What are your thoughts on this? These are the issues I've witnessed.

1. Following features relies on reflection.

Feature	Description	Mitigation
XWPFTableRow.CloneRow	Relies on deepcopying CT_* objects, hence NPOI.Util.ObjectExtensions.Copy<T>().	Needs testing. Probably keep metadata by rd.xml or source generators for deepcopy. Perhaps it will just work.
XML (de)serialization, as well as NPOI.OpenXml4Net.Util.XmlHelper	XMLSerializer and enum names relies on reflections obviously.	It looks like AOT compiler handles well. Thorough tests are needed.

2. Following methods are converted from dynamic dispatch to static lookup. These may prevent some later-injected custom encryptor, record types, etc. I think it's fine. Maybe it's better to use source generators. They will lead to a slight increase of binary size.

Class	Method
NPOI.DDF.DefaultEscherRecordFactory	Entire Class	#1159
NPOI.HSSF.Record.RecordFactory	Entire Class	#1159
NPOI.POIFS.Crypt.EncryptionInfo	GetBuilder	#1160
NPOI.XSSF.UserModel.XSSFFactory	CreateDocumentPart	#1157
NPOI.XSSF.UserModel.XWPFFactory	CreateDocumentPart	#1157

3. The following classes / methods, using reflection, are useless.

Target	Reason
NPOI.HSSF.UserModel.OperationEvaluatorFactory	Wrong use of reflection. Maybe incorrectly ported from Java.	#1161
NPOI.POIFS.NIO.FileBackedDataSource.unmap	Entire method contains no code. Seems Java-specific.	#1161
NPOI.SS.Formula.Eval.Forked.ForkedEvaluator.CreateEvaluationWorkbook	Don't work at all because of typo. 'NPOI.XSSF.UserMode', forgetting the last 'l'	#1161
NPOI.OpenXml4Net.Util.ZipSecureFile.AddThreshold	The code is used to deal with ZIP bombs but Java-specific. We should come up with ways in CLR.	#1161
NPOI.Util.POILogFactory.GetLogger	I doubt if the following line would work, because _loggerClassName is Name of the type but Type.GetType requires FullName. It all ends up using the null logger.	#1162

5. Others

Feature	Description
NPOI.SS.Formula.OperationEvaluatorFactory.Add	Reflection is used to ensure singleton-pattern. Can be removed if we're sure.	this
Ptg, OperandPtg	IClonable is removed from Ptg because not used and requires deepcopy, except for OperandPtg. After inspection, all derived classes of OperandPtg contain only value-type members so MemberwiseClone is enough. (besides, Ptg.IClonable.Clone() throws NotImplementedException so I doubt anyone is using it.)	this
HSSFColor	Slightly refactored	#1158
(T[])ArrayList.ToArray(typeof(T))	Rewritten as extension method	this

6. Dependencies AOT compiler complains about. Not necessarily non-AOTable. It's possible to remove some of them.

Library	State	Comments
System.Configuration.ConfigurationManager		Produce trim warnings. Solely used in NPOI.Util.SystemOutLogger & NPOI.Util.POILogFactory	Not dealt with
Enums.NET	Removed	Relies on Reflection. Converted into static dispatch & built-in methods	#1156

7. Probably need to add net8.0 as another target since .NET 6 doesn't fully support AOT and AOT analyzers. But the Github CI/action don't support .NET 8.

8. Generally there's no breaking change, except Remove reflections in POI Logger #1162

[karakasa]

btw comparsion of loading XSSF file. The performance is better for smaller files. And it looks like no obvious performance gains from removing Reflections alone.

File	Version	Time (s)
Large (30M)	PR w/ AOT	35.687
Large (30M)	PR	36.676
Large (30M)	Nuget	36.086
Small (600K)	PR w/ AOT	0.332
Small (600K)	PR	0.747
Small (600K)	Nuget	0.765

Nuget: the nuget version.

[karakasa]

Although new T() uses Activator.CreateInstance internally, this semantic is slightly different for AOT analyzers I believe.

[karakasa]

All derived classes of OperandPtg holds only value types (some unused members are not, but that's fine).

[karakasa]

This is not used elsewhere. And IClonable.Clone throws NotImplementedException, see below.

[tonyqus]

I created a new branch called AOT. AOT branch will become a RC version for NPOI vNext. I'd like to compare the performance between AOT and non-AOT release.

[josephmoresena]

I created a new branch called AOT. AOT branch will become a RC version for NPOI vNext. I'd like to compare the performance between AOT and non-AOT release.

Thanks, I'm here if you want some help.