Fix error raised by Net::HTTPResponse#inflater if the block raises

* See https://bugs.ruby-lang.org/issues/13882#note-6

lib/net/http/response.rb

@@ -268,12 +268,13 @@ class Net::HTTPResponse
 
       begin
         yield inflate_body_io
+        success = true
       ensure
-        orig_err = $!
         begin
           inflate_body_io.finish
         rescue => err
-          raise orig_err || err
+          # Ignore #finish's error if there is an exception from yield
+          raise err if success
         end
       end
     when 'none', 'identity' then

spec/ruby/library/net/http/http/get_spec.rb

@@ -24,3 +24,70 @@ describe "Net::HTTP.get" do
     end
   end
 end
+
+describe "Net::HTTP.get" do
+  describe "when reading gzipped contents" do
+    def start_threads
+      require 'zlib'
+
+      server = nil
+      server_thread = Thread.new do
+        server = TCPServer.new("127.0.0.1", 0)
+        begin
+          c = server.accept
+        ensure
+          server.close
+        end
+        c.print "HTTP/1.1 200\r\n"
+        c.print "Content-Type: text/plain\r\n"
+        c.print "Content-Encoding: gzip\r\n"
+        s = StringIO.new
+        z = Zlib::GzipWriter.new(s)
+        begin
+          z.write 'Hello World!'
+        ensure
+          z.close
+        end
+        c.print "Content-Length: #{s.length}\r\n\r\n"
+        # Write partial gzip content
+        c.write s.string.byteslice(0..-2)
+        c.flush
+        c
+      end
+      Thread.pass until server && server_thread.stop?
+
+      client_thread = Thread.new do
+        Thread.current.report_on_exception = false
+        Net::HTTP.get("127.0.0.1", '/', server.connect_address.ip_port)
+      end
+      Thread.pass until client_thread.stop?
+
+      [server_thread, client_thread]
+    end
+
+    it "propagates exceptions interrupting the thread and does not replace it with Zlib::BufError" do
+      my_exception = Class.new(RuntimeError)
+      server_thread, client_thread = start_threads
+      socket = server_thread.value
+      begin
+        client_thread.raise my_exception, "my exception"
+        -> { client_thread.value }.should raise_error(my_exception)
+      ensure
+        socket.close
+      end
+    end
+
+    ruby_version_is "2.8" do # https://bugs.ruby-lang.org/issues/13882#note-6
+      it "lets the kill Thread exception goes through and does not replace it with Zlib::BufError" do
+        server_thread, client_thread = start_threads
+        socket = server_thread.value
+        begin
+          client_thread.kill
+          client_thread.value.should == nil
+        ensure
+          socket.close
+        end
+      end
+    end
+  end
+end