[tobias-tengler]

Batched array responses (variable batching) are the last source documents still parsed with Utf8JsonReader. Each element is parsed through a reader over a ReadOnlySequence of the filled chunks, which is slower than the tokenizer and allocates sequence segments when the chunks are not adjacent.

This PR reads the outer array in the source JSON tokenizer and parses each element into its own document over the shared chunks, through a second generic mode, so single document parses compile to the same code as before. The batched path accepts and rejects the same input as before and creates the same rows, which the tests added in the first commit pin down for every chunk boundary position of each chunk layout. The reader-based parser is removed.

Benchmarks against 7e8896336877

Method	Version	Mean	Ratio	Allocated	Alloc Ratio
Batch 1 × Small, adjacent	base	434.6 ns	1.00	360 B	1.00
Batch 1 × Small, adjacent	PR	356.5 ns	0.82	352 B	0.98
Batch 1 × Small, split	base	444.4 ns	1.00	360 B	1.00
Batch 1 × Small, split	PR	341.2 ns	0.77	352 B	0.98
Batch 1 × Entity, adjacent	base	2.66 μs	1.00	360 B	1.00
Batch 1 × Entity, adjacent	PR	1.70 μs	0.64	352 B	0.98
Batch 1 × Entity, split	base	2.74 μs	1.00	504 B	1.00
Batch 1 × Entity, split	PR	1.62 μs	0.59	352 B	0.70
Batch 10 × Small, adjacent	base	3.37 μs	1.00	1,392 B	1.00
Batch 10 × Small, adjacent	PR	2.51 μs	0.75	1,312 B	0.94
Batch 10 × Small, split	base	3.57 μs	1.00	1,488 B	1.00
Batch 10 × Small, split	PR	2.42 μs	0.68	1,312 B	0.88
Batch 10 × Entity, adjacent	base	25.30 μs	1.00	1,392 B	1.00
Batch 10 × Entity, adjacent	PR	16.73 μs	0.66	1,312 B	0.94
Batch 10 × Entity, split	base	26.44 μs	1.00	1,680 B	1.00
Batch 10 × Entity, split	PR	15.62 μs	0.59	1,312 B	0.78
Batch 100 × Small, adjacent	base	33.19 μs	1.00	13,528 B	1.00
Batch 100 × Small, adjacent	PR	23.25 μs	0.70	12,728 B	0.94
Batch 100 × Small, split	base	34.48 μs	1.00	13,720 B	1.00
Batch 100 × Small, split	PR	22.01 μs	0.64	12,728 B	0.93
Batch 100 × Entity, adjacent	base	264.78 μs	1.00	14,056 B	1.00
Batch 100 × Entity, adjacent	PR	150.10 μs	0.57	12,728 B	0.91
Batch 100 × Entity, split	base	264.24 μs	1.00	14,056 B	1.00
Batch 100 × Entity, split	PR	147.95 μs	0.56	12,728 B	0.91
Single Apollo, adjacent	base	28.91 μs	1.00	272 B	1.00
Single Apollo, adjacent	PR	16.70 μs	0.58	264 B	0.97
Single Apollo, split	base	29.75 μs	1.00	608 B	1.00
Single Apollo, split	PR	15.89 μs	0.53	264 B	0.43
Single Composite, adjacent	base	30.93 μs	1.00	1,152 B	1.00
Single Composite, adjacent	PR	17.44 μs	0.56	1,064 B	0.92
Single Composite, split	base	60.70 μs	1.00	2,784 B	1.00
Single Composite, split	PR	17.82 μs	0.29	1,064 B	0.38
Single Escaped, adjacent	base	72.57 μs	1.00	272 B	1.00
Single Escaped, adjacent	PR	45.37 μs	0.63	264 B	0.97
Single Escaped, split	base	76.17 μs	1.00	560 B	1.00
Single Escaped, split	PR	46.85 μs	0.62	264 B	0.47
Single Large, adjacent	base	97.89 μs	1.00	656 B	1.00
Single Large, adjacent	PR	51.33 μs	0.52	264 B	0.40
Single Large, split	base	97.48 μs	1.00	656 B	1.00
Single Large, split	PR	53.00 μs	0.54	264 B	0.40
Single LongStrings, adjacent	base	2.89 μs	1.00	272 B	1.00
Single LongStrings, adjacent	PR	2.37 μs	0.82	264 B	0.97
Single LongStrings, split	base	3.02 μs	1.00	560 B	1.00
Single LongStrings, split	PR	2.62 μs	0.87	264 B	0.47
Single Numbers, adjacent	base	170.22 μs	1.00	272 B	1.00
Single Numbers, adjacent	PR	92.78 μs	0.55	264 B	0.97
Single Numbers, split	base	186.67 μs	1.00	608 B	1.00
Single Numbers, split	PR	92.80 μs	0.50	264 B	0.43
Single Pretty, adjacent	base	50.15 μs	1.00	272 B	1.00
Single Pretty, adjacent	PR	27.59 μs	0.55	264 B	0.97
Single Pretty, split	base	50.01 μs	1.00	608 B	1.00
Single Pretty, split	PR	28.38 μs	0.57	264 B	0.43
Single Small, adjacent	base	365.3 ns	1.00	272 B	1.00
Single Small, adjacent	PR	275.7 ns	0.75	264 B	0.97
Single Small, split	base	365.3 ns	1.00	272 B	1.00
Single Small, split	PR	271.1 ns	0.74	264 B	0.97

[github-actions]

Patch coverage

94.3% of changed lines covered (132/140)

File	Covered	Changed	Patch %
…/Fusion.Execution/Text/Json/SourceResultDocument.Tokenizer.cs	101	109	92.7% 🟡
…/AspNetCore/src/Transport.Http/Json/JsonResultEnumerable.cs	1	1	100.0% 🟢
…/src/Fusion.Execution/Text/Json/SourceResultDocument.Parse.cs	30	30	100.0% 🟢

Uncovered changed lines (JSON)

{
  "sha": "bd12a1f944d89905597162c67e84ee5938c11321",
  "files": [
    { "path": "src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultDocument.Tokenizer.cs", "ranges": [[514, 515], [523, 524], [1154, 1155], [1158, 1159]] }
  ]
}

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Project coverage: 59.1% (312918/529175 lines)

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