Fix reading nested streams with stop_on_end=true set. (#191)

src/noop.jl

@@ -170,13 +170,18 @@ end
 # These methods are overloaded for the `Noop` codec because it has only one
 # buffer for efficiency.
 
-function fillbuffer(stream::NoopStream; eager::Bool = false)
+function fillbuffer(stream::NoopStream; eager::Bool = false)::Int
     changemode!(stream, :read)
     buffer = stream.buffer1
     @assert buffer === stream.buffer2
     if stream.stream isa TranscodingStream && buffer === stream.stream.buffer1
         # Delegate the operation when buffers are shared.
-        return fillbuffer(stream.stream, eager = eager)
+        underlying_mode::Symbol = stream.stream.state.mode
+        if underlying_mode === :idle || underlying_mode === :read
+            return fillbuffer(stream.stream, eager = eager)
+        else
+            return 0
+        end
     end
     nfilled::Int = 0
     while ((!eager && buffersize(buffer) == 0) || (eager && makemargin!(buffer, 0, eager = true) > 0)) && !eof(stream.stream)

src/stream.jl

@@ -706,10 +706,15 @@ end
 
 # Read as much data as possbile from `input` to the margin of `output`.
 # This function will not block if `input` has buffered data.
-function readdata!(input::IO, output::Buffer)
+function readdata!(input::IO, output::Buffer)::Int
     if input isa TranscodingStream && input.buffer1 === output
         # Delegate the operation to the underlying stream for shared buffers.
-        return fillbuffer(input)
+        mode::Symbol = input.state.mode
+        if mode === :idle || mode === :read
+            return fillbuffer(input)
+        else
+            return 0
+        end
     end
     nread::Int = 0
     navail = bytesavailable(input)

test/codecdoubleframe.jl

@@ -271,8 +271,8 @@ DoubleFrameDecoderStream(stream::IO; kwargs...) = TranscodingStream(DoubleFrameD
                 stop_on_end=true,
             )
         ))
-        @test_broken read(s1) == b""
-        @test_broken eof(s1)
+        @test read(s1) == b""
+        @test eof(s1)
 
         s2 = NoopStream(
             DoubleFrameDecoderStream(
@@ -281,7 +281,7 @@ DoubleFrameDecoderStream(stream::IO; kwargs...) = TranscodingStream(DoubleFrameD
             )
         )
         @test read(s2) == b""
-        @test_broken eof(s2)
+        @test eof(s2)
     end
 
     test_roundtrip_read(DoubleFrameEncoderStream, DoubleFrameDecoderStream)