Allow specifying IndentCharacter and IndentSize when writing JSON

[manandre]

Closes #63882

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Issue Details

---

Closes #63882

Author:	manandre
Assignees:	-
Labels:	area-System.Text.Json, new-api-needs-documentation
Milestone:	-

[eiriktsarpalis]

This is adding logic to the JSON writer hot path, so we need to verify it doesn't introduce any unintentional performance regressions. Could you try running the benchmarks found in

https://github.com/dotnet/performance/tree/main/src/benchmarks/micro/libraries/System.Text.Json/Utf8JsonWriter

comparing the current main with your PR branch. Instructions on how to do this can be found here.

[eiriktsarpalis]

Thanks, this is getting really close. Would it be possible to share updated benchmark numbers with the newer implementation?

[manandre]

New benchmarks results

summary: better: 20, geomean: 1.090 worse: 31, geomean: 1.124 total diff: 51

Slower	diff/base	Base Median (ns)	Diff Median (ns)	Modality
System.Text.Json.Tests.Perf_Guids.WriteGuids(Formatted: False, SkipValidation: T	1.73	1084991.13	1881111.69
System.Text.Json.Tests.Perf_Ctor.Ctor(Formatted: False, SkipValidation: False)	1.60	14.68	23.47
System.Text.Json.Serialization.Tests.WriteJson.SerializeToUtf8Bytes(Mode:	1.20	85.67	103.17
System.Text.Json.Serialization.Tests.ReadJson.DeserializeFromString(Mode:	1.15	104.29	120.22
System.Text.Json.Tests.Perf_Reader.ReadSingleSpanSequenceEmptyLoop(IsDataCompact	1.15	1331.87	1527.20
System.Text.Json.Serialization.Tests.ReadJson.DeserializeFromString(Mode:	1.14	105.52	120.52
System.Text.Json.Serialization.Tests.WriteJson<Nullable>.Seriali	1.14	119.30	136.12
System.Text.Json.Document.Tests.Perf_EnumerateArray.EnumerateUsingIndexer(TestCa	1.14	1254.13	1425.34
System.Text.Json.Tests.Perf_Reader.ReadSingleSpanSequenceEmptyLoop(IsDataCompact	1.13	2750.80	3096.63
System.Text.Json.Tests.Perf_Ctor.Ctor(Formatted: False, SkipValidation: True)	1.11	14.46	16.10
System.Text.Json.Serialization.Tests.WriteJson.Serial	1.11	350.55	387.47
System.Text.Json.Tests.Perf_Reader.ReadMultiSpanSequenceEmptyLoop(IsDataCompact:	1.10	1721.12	1891.75
System.Text.Json.Tests.Perf_Basic.WriteBasicUtf8(Formatted: False, SkipValidatio	1.10	537.72	589.71
System.Text.Json.Serialization.Tests.WriteJson.SerializeToStream(Mo	1.09	301.87	328.84
System.Text.Json.Serialization.Tests.WriteJson<Nullable>.Seriali	1.08	193.20	209.51
System.Text.Json.Tests.Perf_Basic.WriteBasicUtf16(Formatted: False, SkipValidati	1.08	623.08	673.54
System.Text.Json.Document.Tests.Perf_ParseThenWrite.ParseThenWrite(IsDataIndente	1.08	4900.26	5291.65
System.Text.Json.Serialization.Tests.WriteJson.SerializeToStream(Mode: Re	1.08	186.65	200.94
System.Text.Json.Tests.Perf_Basic.WriteBasicUtf8(Formatted: True, SkipValidation	1.08	2205729.09	2374611.54
System.Text.Json.Serialization.Tests.WriteJson.SerializeToStream(Mode: So	1.08	190.44	204.97
System.Text.Json.Tests.Perf_Reader.ReadReturnBytes(IsDataCompact: True, TestCase	1.08	66.44	71.48
System.Text.Json.Tests.Perf_Reader.ReadReturnBytes(IsDataCompact: False, TestCas	1.07	10109.00	10861.52
System.Text.Json.Tests.Perf_Basic.WriteBasicUtf8(Formatted: True, SkipValidation	1.07	2216908.85	2369424.04
System.Text.Json.Serialization.Tests.WriteJson.SerializeToString(Mo	1.07	363.03	387.82
System.Text.Json.Tests.Perf_Basic.WriteBasicUtf16(Formatted: True, SkipValidatio	1.07	2218130.36	2367656.60
System.Text.Json.Reader.Tests.Perf_Base64.ReadBase64EncodedByteArray_NoEscaping(	1.06	76.25	81.05
System.Text.Json.Serialization.Tests.WriteJson<Nullable>.Seriali	1.06	188.73	200.20
System.Text.Json.Serialization.Tests.ReadJson<Nullable>.Deserial	1.06	320.92	340.19
System.Text.Json.Reader.Tests.Perf_Base64.ReadBase64EncodedByteArray_HeavyEscapi	1.06	76.27	80.72
System.Text.Json.Serialization.Tests.WriteJson.Seria	1.06	187.85	198.51
System.Text.Json.Serialization.Tests.WriteJson<HashSet>.SerializeObjectP	1.06	4630.13	4892.40

Faster	base/diff	Base Median (ns)	Diff Median (ns)	Modality
System.Text.Json.Serialization.Tests.ReadJson.Deseri	1.23	547.64	446.59
System.Text.Json.Tests.Perf_Reader.ReadMultiSpanSequenceEmptyLoop(IsDataCompact:	1.12	2704.65	2416.30
System.Text.Json.Serialization.Tests.ReadJson.DeserializeFromStrin	1.11	660.34	592.57
System.Text.Json.Tests.Perf_Reader.ReadMultiSpanSequenceEmptyLoop(IsDataCompact:	1.10	3486.84	3173.37
System.Text.Json.Serialization.Tests.ReadJson<Nullable>.Deserial	1.10	177.76	162.07
System.Text.Json.Serialization.Tests.ReadJson.DeserializeFromUtf8Byte	1.09	16925.82	15491.40
System.Text.Json.Serialization.Tests.WriteJson<Nullable>.Seriali	1.09	74.74	68.44
System.Text.Json.Serialization.Tests.WriteJson.SerializeToWriter(Mode: Re	1.09	28.75	26.36
System.Text.Json.Tests.Perf_Guids.WriteGuids(Formatted: False, SkipValidation: F	1.09	1202539.56	1103092.92
System.Text.Json.Serialization.Tests.WriteJson.SerializeToStream(Mode:	1.09	603.37	555.91
System.Text.Json.Serialization.Tests.ReadJson.DeserializeFromUtf8B	1.08	547.94	506.66
System.Text.Json.Serialization.Tests.WriteJson<Nullable>.Seriali	1.08	74.51	68.94
System.Text.Json.Tests.Perf_Reader.ReadReturnBytes(IsDataCompact: False, TestCas	1.08	79.61	73.78	bimodal
System.Text.Json.Serialization.Tests.ReadMissingAndCaseInsensitive.Cas	1.08	1026.32	951.98
System.Text.Json.Tests.Perf_Depth.ReadSpanEmptyLoop(Depth: 64)	1.07	1756.64	1639.75
System.Text.Json.Document.Tests.Perf_ParseThenWrite.ParseThenWrite(IsDataIndente	1.07	300.72	281.33
System.Text.Json.Serialization.Tests.WriteJson.SerializeToUtf8Bytes	1.07	312.57	292.93
System.Text.Json.Serialization.Tests.WriteJson<ImmutableSortedDictionary<String,	1.07	8509.42	7989.29
System.Text.Json.Tests.Perf_Get.GetInt32	1.06	782.77	738.39
System.Text.Json.Serialization.Tests.WriteJson<ImmutableSortedDictionary<String,	1.06	7665.66	7261.13

I do not know how to interpret these results, as even Read-based and deserialization tests are impacted !?!

[manandre]

Benchmarks results

summary: better: 17, geomean: 1.111 worse: 21, geomean: 1.089 total diff: 38

Slower	diff/base	Base Median (ns)	Diff Median (ns)	Modality
System.Text.Json.Tests.Perf_Reader.ReadMultiSpanSequenceEmptyLoop(IsDataCompact:	1.20	2704.65	3259.01
System.Text.Json.Serialization.Tests.WriteJson.Seria	1.17	187.85	220.11
System.Text.Json.Tests.Perf_Reader.ReadSpanEmptyLoop(IsDataCompact: True, TestCa	1.12	32493.49	36383.36
System.Text.Json.Serialization.Tests.ReadJson.DeserializeFromString(Mode:	1.11	104.29	115.53
System.Text.Json.Tests.Perf_Basic.WriteBasicUtf16(Formatted: False, SkipValidati	1.10	623.08	685.92
System.Text.Json.Serialization.Tests.WriteJson.SerializeToUtf8Bytes(Mode:	1.10	85.67	94.01
System.Text.Json.Serialization.Tests.WriteJson.SerializeToStream(Mo	1.09	301.87	328.22
System.Text.Json.Tests.Perf_Basic.WriteBasicUtf8(Formatted: True, SkipValidation	1.08	2216908.85	2396831.73
System.Text.Json.Tests.Perf_Basic.WriteBasicUtf8(Formatted: False, SkipValidatio	1.08	537.72	580.41
System.Text.Json.Serialization.Tests.WriteJson<Nullable>.Seriali	1.08	188.73	203.58
System.Text.Json.Reader.Tests.Perf_Base64.ReadBase64EncodedByteArray_NoEscaping(	1.08	76.25	82.17
System.Text.Json.Serialization.Tests.WriteJson<Nullable>.Seriali	1.08	119.30	128.26
System.Text.Json.Tests.Perf_Basic.WriteBasicUtf16(Formatted: True, SkipValidatio	1.07	2218130.36	2381707.62
System.Text.Json.Serialization.Tests.WriteJson.SerializeToWriter(Mode: Re	1.07	28.75	30.81
System.Text.Json.Document.Tests.Perf_ParseThenWrite.ParseThenWrite(IsDataIndente	1.07	4900.26	5242.63
System.Text.Json.Serialization.Tests.WriteJson.SerializeToString(Mo	1.07	280.26	299.54
System.Text.Json.Serialization.Tests.WriteJson<ImmutableSortedDictionary<String,	1.07	8194.94	8755.16
System.Text.Json.Tests.Perf_Basic.WriteBasicUtf8(Formatted: True, SkipValidation	1.07	2205729.09	2355302.83
System.Text.Json.Document.Tests.Perf_ParseThenWrite.ParseThenWrite(IsDataIndente	1.07	17376.31	18536.19
System.Text.Json.Tests.Perf_Reader.ReadSpanEmptyLoop(IsDataCompact: True, TestCa	1.06	60.02	63.71
System.Text.Json.Node.Tests.Perf_ParseThenWrite.ParseThenWrite(IsDataIndented: F	1.06	8732.17	9248.11

Faster	base/diff	Base Median (ns)	Diff Median (ns)	Modality
System.Text.Json.Tests.Perf_Base64.WriteByteArrayAsBase64_NoEscaping(NumberOfByt	1.59	107.09	67.49
System.Text.Json.Serialization.Tests.ReadJson.Deseri	1.18	547.64	465.08
System.Text.Json.Serialization.Tests.WriteJson.Seria	1.13	155.31	137.54
System.Text.Json.Serialization.Tests.ReadJson.DeserializeFromStrin	1.12	660.34	587.55
System.Text.Json.Tests.Perf_Reader.ReadMultiSpanSequenceEmptyLoop(IsDataCompact:	1.09	3486.84	3188.09
System.Text.Json.Serialization.Tests.WriteJson.SerializeToStream(Mode:	1.09	603.37	552.69
System.Text.Json.Serialization.Tests.WriteJson<Nullable>.Seriali	1.09	74.74	68.62
System.Text.Json.Tests.Perf_Guids.WriteGuids(Formatted: False, SkipValidation: F	1.08	1202539.56	1108971.24
System.Text.Json.Serialization.Tests.WriteJson<Nullable>.Seriali	1.08	74.51	69.14
System.Text.Json.Serialization.Tests.ReadJson.DeserializeFromUtf8B	1.07	547.94	510.00
System.Text.Json.Serialization.Tests.WriteJson.SerializeToString(Mod	1.07	587.49	547.54
System.Text.Json.Serialization.Tests.WriteJson.SerializeToString(Mode: So	1.07	111.16	103.63
System.Text.Json.Serialization.Tests.ReadJson<Nullable>.Deserial	1.07	177.76	166.24
System.Text.Json.Serialization.Tests.ReadJson.Deseria	1.06	885.20	832.84
System.Text.Json.Tests.Perf_Get.GetInt32	1.06	782.77	737.68
System.Text.Json.Serialization.Tests.WriteJson.SerializeToUtf8By	1.06	313.90	297.13
System.Text.Json.Tests.Perf_Reader.ReadMultiSpanSequenceEmptyLoop(IsDataCompact:	1.06	10122.40	9586.38

Still no clue how to interpret these results...

[eiriktsarpalis]

Thank you so much for your work @manandre!