#253 Object factories

[sanelli]

Summary

• Add [MappaObjectFactory] so mappings can construct targets via user factory methods (mapper-local, static type, or field/property) instead of new.
• Wire generator resolution/emission with signature tiers, MP00062–64 diagnostics, nested-target support, and projection incompatibility.
• Add samples, AOT runner, documentation, CI AOT output silencing, and coverage-oriented tests (version 10.2.0-alpha.28).

Test plan

• .\Scripts\RunTestsAndReportCoverage.ps1 (line/branch/method ≥ pre-change baseline)
• Review generated syntax for factory tiers (fully produced / empty-ctor-like / parameterized)
• Confirm MP00062 duplicate, MP00063 unresolved fallback, MP00064 projection diagnostics
• Spot-check AOT runner and sample runtime tests

[github-actions]

Code coverage

Compared against the latest published coverage history from the code coverage gist.

Metric	Baseline	PR	Δ	Trend
Line	98.4%	98.4%	0	=
Branch	90.6%	90.6%	0	=
Method	100%	100%	0	=

No coverage metric dropped by more than 1 percentage point(s) versus baseline.

Benchmarks

AutoMapper is the BenchmarkDotNet ratio baseline. Absolute values are mean time in nanoseconds and allocated bytes. Ratio columns are competitor / Mappa as a percentage (n/a when either side is missing or Mappa is zero).

Benchmark	Automapper Mean (ns)	Automapper Allocated (B)	Mapster Mean (ns)	Mapster Allocated (B)	Mapperly Mean (ns)	Mapperly Allocated (B)	Mappa Mean (ns)	Mappa Allocated (B)	Automapper/Mappa Time	Automapper/Mappa Alloc	Mapperly/Mappa Time	Mapperly/Mappa Alloc	Mapster/Mappa Time	Mapster/Mappa Alloc
ArrayToListBenchmark	71.57	32	71456.57	194456	6593.24	38456	6556.72	38456	1.1%	0.1%	100.6%	100%	1089.8%	505.7%
DictionaryBenchmark	135470	185221.12	82620	214364.16	10270	46018.56	12080	58316.8	1121.4%	317.6%	85%	78.9%	683.9%	367.6%
FastListToArrayBenchmark	n/a	n/a	71892	194426.88	6195	38420.48	6823	38420.48	n/a	n/a	90.8%	100%	1053.7%	506.1%
IQueryableProjectionBenchmark	611800	31784.96	583400	31016.96	596100	33105.92	596600	32983.04	102.5%	96.4%	99.9%	100.4%	97.8%	94%
ListToArrayBenchmark	n/a	n/a	72728	194426.88	6800	38420.48	6285	38420.48	n/a	n/a	108.2%	100%	1157.2%	506.1%
ListToHashSetBenchmark	307.9	5765.12	2133.7	5765.12	2378	5806.08	2329.9	5765.12	13.2%	100%	102.1%	100.7%	91.6%	100%
NestedDtoBenchmark	122145	225320.96	86691	227471.36	6672	38942.72	6825	38942.72	1789.7%	578.6%	97.8%	100%	1270.2%	584.1%

Benchmark trends (Mappa)

Lower is better. Compared against the latest published Mappa-only rows from MAPPA-BENCHMARK-HISTORY.md.

Benchmark	Measure	Baseline	PR	Δ	Trend
ArrayToListBenchmark	TIME_NS	6775.41	6556.72	-218.69	▲
ArrayToListBenchmark	ALLOC_B	38456	38456	0	=
DictionaryBenchmark	TIME_NS	12021	12080	+59	▼
DictionaryBenchmark	ALLOC_B	58316.8	58316.8	0	=
ListToArrayBenchmark	TIME_NS	6303	6285	-18	▲
ListToArrayBenchmark	ALLOC_B	38420.48	38420.48	0	=
FastListToArrayBenchmark	TIME_NS	6371	6823	+452	▼
FastListToArrayBenchmark	ALLOC_B	38420.48	38420.48	0	=
IQueryableProjectionBenchmark	TIME_NS	596000	596600	+600	▼
IQueryableProjectionBenchmark	ALLOC_B	33136.64	32983.04	-153.6	▲
NestedDtoBenchmark	TIME_NS	6616	6825	+209	▼
NestedDtoBenchmark	ALLOC_B	38942.72	38942.72	0	=
ListToHashSetBenchmark	TIME_NS	1936.9	2329.9	+393	▼
ListToHashSetBenchmark	ALLOC_B	5765.12	5765.12	0	=