Ensure that JSON properties can be skipped without buffering their entire contents. #96856
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Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis Issue DetailsMakes the following changes:
Fix #96559.
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| @@ -21,6 +21,59 @@ public static ReadOnlySpan<byte> GetSpan(this scoped ref Utf8JsonReader reader) | |||
| return reader.HasValueSequence ? reader.ValueSequence.ToArray() : reader.ValueSpan; | |||
| } | |||
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| /// <summary> | |||
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Logic moved essentially unchanged from JsonConverter.ReadAhead.cs
| /// </summary> | ||
| /// <param name="targetDepth">The target depth we want to eventually skip to.</param> | ||
| /// <returns>True if the entire JSON value has been skipped.</returns> | ||
| internal bool TrySkipPartial(int targetDepth) |
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The existing TrySkipHelper has been retrofitted to the resumable TrySkipPartial method, minus the checkpointing semantics.
| { | ||
| // For a continuation, read ahead here to avoid having to build and then tear | ||
| // down the call stack if there is more than one buffer fetch necessary. | ||
| if (!SingleValueReadWithReadAhead(requiresReadAhead: true, ref reader, ref state)) |
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Here's the crux of the second change made by this PR: re-entrant serialization operations no longer perform read-ahead of the next value (the converter doesn't require it in this case). We let the JsonSerializerOptions.DefaultBufferSize be the only guide of how much data we add to the buffer before re-entering deserialization.
| if (!isContinuation) | ||
| { | ||
| #if DEBUG | ||
| // For performance, only perform token type validation of converters on debug builds. | ||
| Debug.Assert(state.Current.OriginalTokenType == JsonTokenType.None); | ||
| state.Current.OriginalTokenType = reader.TokenType; |
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We now need to store this value in all builds to track resumable skip operations.
| [Fact] | ||
| [SkipOnCoreClr("https://github.com/dotnet/runtime/issues/45464", ~RuntimeConfiguration.Release)] | ||
| public async Task ReadSimpleObjectAsync() | ||
| [Theory] |
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Converted this test suite to use theories because it was causing me grief while debugging.
| // Read the key name. | ||
| if (!reader.Read()) | ||
| { | ||
| value = default; | ||
| return false; | ||
| } | ||
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Changing the order of state update operations since we no longer rely on the root method to advance the reader for us on resumed operations.
Makes the following changes:
Fix #96559.