Fix handling of zero length reads.

Author: samuel-williams-shopify

lib/protocol/http/body/stream.rb

@@ -52,7 +52,7 @@ module Reader
 					# @parameter buffer [String] the buffer which will receive the data
 					# @returns [String] a buffer containing the data
 					def read(length = nil, buffer = nil)
-						return "" if length == 0
+						return (buffer ? buffer.clear : String.new) if length == 0
 
 						buffer ||= String.new.force_encoding(Encoding::BINARY)
 

releases.md

@@ -1,5 +1,9 @@
 # Releases
 
+## Unreleased
+
+  - Fix handling of `Stream#read(0)`, it must return a mutable string (or clear the given buffer).
+
 ## v0.61.0
 
   - Introduce `Protocol::HTTP::RefusedError` for indicating a stream or request was refused before processing and can be safely retried. `RequestRefusedError` is provided as an alias for backwards compatibility.

test/protocol/http/body/stream.rb

@@ -38,6 +38,18 @@
 			expect(stream.read(0)).to be == ""
 		end
 
+		it "returns a mutable string for zero-length read" do
+			result = stream.read(0)
+			expect(result).not.to be(:frozen?)
+		end
+		
+		it "populates the buffer on zero-length read" do
+			buffer = String.new
+			result = stream.read(0, buffer)
+			expect(result).to be == ""
+			expect(result).to be_equal(buffer)
+		end
+		
 		it "can read the entire input" do
 			expect(stream.read).to be == "HelloWorld"
 		end