Description

I have code that has a DeflateStream and uses a StreamReader on it - this code works fine in .NET Framework, .NET Core 3.1, and .NET 5 - but it breaks in .NET 6.

When trying to Peek() on the stream, internally StreamReader reads a block out that ends up being smaller than it requested, I'm pretty sure this is due to this breaking change. After that happens, it sets a flag called "_isBlocked" and starts returning -1 from Peek() which is not expected.

This seems like a bug in StreamReader?

Reproduction Steps

Construct a StreamReader over a DeflateStream
Read for a while, peeking as you go

Expected behavior

Peek() returns -1 only at the end of the stream, as it did before

Actual behavior

Peek() returns -1 early in the middle of the file.

Regression?

Yes, regressed in .NET 6

Known Workarounds

Can use StreamReader.EndOfStream instead of looking for -1 from Peek(), but this was still a difficult to hunt down bug on upgrading the .NET version of this library.

Configuration

No response

Other information

No response