Fix URI#host= to wrap IPv6 address in brackets (#16164)

The square brackets around IPv6 addresses are only required for URIs.

This also ensures a URI initialized with otherwise valid data is a valid URI.

Author: stakach

spec/std/uri_spec.cr

@@ -172,6 +172,42 @@ describe "URI" do
     it { URI.new(path: "/foo").hostname.should be_nil }
   end
 
+  describe "#host" do
+    it "works with IPv6 address literals" do
+      uri = URI.new("http", "[::1]", path: "foo")
+      uri.hostname.should eq("::1")
+      uri.host.should eq("[::1]")
+      uri.to_s.should eq "http://[::1]/foo"
+      uri.host = "[::1]"
+      uri.to_s.should eq "http://[::1]/foo"
+
+      uri = URI.new("http", "::1", path: "foo")
+      uri.hostname.should eq("::1")
+      uri.host.should eq("[::1]")
+      uri.to_s.should eq "http://[::1]/foo"
+      uri.host = "::1"
+      uri.to_s.should eq "http://[::1]/foo"
+    end
+
+    it "works with IPv4 addresses" do
+      uri = URI.new("http", "192.168.0.2", path: "foo")
+      uri.hostname.should eq("192.168.0.2")
+      uri.host.should eq("192.168.0.2")
+      uri.to_s.should eq "http://192.168.0.2/foo"
+      uri.host = "192.168.0.2"
+      uri.to_s.should eq "http://192.168.0.2/foo"
+    end
+
+    it "works with domain names" do
+      uri = URI.new("http", "test.domain", path: "foo")
+      uri.hostname.should eq("test.domain")
+      uri.host.should eq("test.domain")
+      uri.to_s.should eq "http://test.domain/foo"
+      uri.host = "test.domain"
+      uri.to_s.should eq "http://test.domain/foo"
+    end
+  end
+
   describe "#authority" do
     it { URI.new.authority.should be_nil }
     it { URI.new(scheme: "scheme").authority.should be_nil }

src/uri.cr

@@ -99,7 +99,9 @@ class URI
   getter host : String?
 
   # Sets the host component of the URI.
-  setter host : String?
+  def host=(host : String?)
+    @host = host && !host.starts_with?('[') && host.includes?(':') ? "[#{host}]" : host
+  end
 
   # Returns the port component of the URI.
   #
@@ -175,7 +177,9 @@ class URI
 
   def_equals_and_hash scheme, host, port, path, query, user, password, fragment
 
-  def initialize(@scheme = nil, @host = nil, @port = nil, @path = "", query : String | Params | Nil = nil, @user = nil, @password = nil, @fragment = nil)
+  def initialize(@scheme = nil, host = nil, @port = nil, @path = "", query : String | Params | Nil = nil, @user = nil, @password = nil, @fragment = nil)
+    # wrap IPv6 addresses
+    self.host = host
     @query = query.try(&.to_s)
   end