HTTP::Client#exec causing some "400 Bad Request" response when using it with HTTP::Request object.

[newtonapple]

The following code triggers a 400 response from example.com:

require "http/client"

client = HTTP::Client.new "www.example.com"
req = HTTP::Request.new("GET", "/")
resp = client.exec HTTP::Request.new("GET", "/")
puts resp.status_code # 400

Note that HTTP::Client#exec seems to be generating an HTTP request without the Host header. Adding the missing header will trigger expected 200 response.

req2 = HTTP::Request.new("GET", "/", HTTP::Headers.new.tap{|h| h["Host"] = "example.com"})
resp2 = client.exec req2
puts resp2.status_code # 200

Class method is working as expected:

puts HTTP::Client.exec("GET", "http://www.example.com/").status_code # 200

I also noticed that this didn't seem to be a problem on google.com

client2 = HTTP::Client.new "www.google.com"
resp3 = client2.exec(req)
puts resp3.status_code # 200

The reason I ran into this problem was because I was trying to send the same Request object to multiple Hosts. I expect I should be able to reuse the same request object cross multiple client / hosts. Is this an acceptable usage pattern of the HTTP::Client API?

crystal -v
Crystal 0.25.1 (2018-06-30)

LLVM: 5.0.2
Default target: x86_64-apple-macosx