Separate the browser-facing origin from the dev server's bind address

CHANGELOG.md

@@ -8,6 +8,10 @@ main
 * Require `ember-cli-rails-assets >= 0.9.0`, which serves the
   `include_ember_script_tags` startup tags from Vite's development server
   when the application is served from it
+* Add an `origin` option to `dev_server`, separating the origin the browser
+  loads assets from, from the address the development server binds to — for
+  containers, where the server must bind to `0.0.0.0` but browsers refuse
+  that address as an origin
 
 0.13.0.beta1
 ------

README.md

@@ -218,6 +218,26 @@ If something is already listening on the configured `host` and `port`,
 possible to run `npm start` yourself, on a port the initializer names, and have
 Rails serve the application from it.
 
+`host` is both the address the development server binds to and — together with
+`port` — the origin the browser loads the application's modules from. When the
+two differ, configure the browser-facing origin separately with `origin`. The
+typical case is Rails running in a container: the development server must bind
+to `0.0.0.0` to be reachable through the container's published port, but
+browsers refuse to connect to `http://0.0.0.0`:
+
+```rb
+EmberCli.configure do |c|
+  c.app :frontend, dev_server: {
+    host: "0.0.0.0",
+    port: 4200,
+    origin: "http://localhost:4200",
+  }
+end
+```
+
+With `host: "0.0.0.0"`, Rails itself reaches the development server through the
+loopback interface.
+
 The development server's output is written to
 `log/ember-<app>.<environment>.log`.
 

UPGRADING.md

@@ -36,6 +36,11 @@ following differences in how `ember-cli-rails` treats it:
   end
   ```
 
+  When Rails runs in a container and the browser outside of it, bind the
+  development server to every interface and name the browser-facing origin
+  separately: `dev_server: { host: "0.0.0.0", port: 4200, origin:
+  "http://localhost:4200" }`.
+
   To opt out of the development server, disable it:
 
   ```rb

lib/ember_cli/dev_server.rb

@@ -37,8 +37,13 @@ def timeout
       @timeout ||= option(:timeout) { DEFAULT_TIMEOUT }.to_f
     end
 
+    # The origin the browser loads the application's assets from. It defaults
+    # to the address the development server binds to, but can be configured
+    # separately for setups where the two differ — a development server bound
+    # to `0.0.0.0` inside a container, reached by the browser through a
+    # published port, for instance.
     def origin
-      "http://#{host}:#{port}"
+      @origin ||= option(:origin) { "http://#{host}:#{port}" }.to_s.chomp("/")
     end
 
     # Boots the development server unless something is already listening on
@@ -96,7 +101,7 @@ def option(key)
     def request(request_class, path, headers)
       start
 
-      uri = URI.join(origin, path)
+      uri = URI.join("http://#{connect_host}:#{port}", path)
       # Pass `nil` as the proxy address so that a `http_proxy` environment
       # variable never routes requests for the local server through a proxy.
       Net::HTTP.start(uri.hostname, uri.port, nil, read_timeout: timeout) do |http|
@@ -112,8 +117,19 @@ def request(request_class, path, headers)
       MSG
     end
 
+    # The address Rails connects to the development server on. `0.0.0.0` asks
+    # the server to listen on every interface, but is not an address to
+    # connect to, so requests go to the loopback interface instead.
+    def connect_host
+      if host == "0.0.0.0"
+        "127.0.0.1"
+      else
+        host
+      end
+    end
+
     def listening?
-      Socket.tcp(host, port, connect_timeout: CONNECT_TIMEOUT, &:close)
+      Socket.tcp(connect_host, port, connect_timeout: CONNECT_TIMEOUT, &:close)
 
       true
     rescue SystemCallError, IOError

spec/lib/ember_cli/dev_server_spec.rb

@@ -27,6 +27,24 @@
 
       expect(origin).to eq("http://0.0.0.0:1234")
     end
+
+    it "honors a configured origin" do
+      dev_server = build_dev_server(
+        options: { host: "0.0.0.0", port: 4200, origin: "http://localhost:4200" },
+      )
+
+      origin = dev_server.origin
+
+      expect(origin).to eq("http://localhost:4200")
+    end
+
+    it "strips a trailing slash from a configured origin" do
+      dev_server = build_dev_server(options: { origin: "http://localhost:4200/" })
+
+      origin = dev_server.origin
+
+      expect(origin).to eq("http://localhost:4200")
+    end
   end
 
   describe "#port" do
@@ -64,6 +82,21 @@
       expect(shell.started_with).to be_nil
     end
 
+    it "connects through the loopback interface when bound to every interface" do
+      server = null_server
+      server.listen("127.0.0.1", 0)
+      shell = FakeShell.new
+      dev_server = build_dev_server(
+        shell: shell,
+        options: { host: "0.0.0.0", port: server.port },
+      )
+
+      started = dev_server.start
+
+      expect(started).to be true
+      expect(shell.started_with).to be_nil
+    end
+
     it "raises when the development server exits before it listens" do
       shell = FakeShell.new(running: false)
       dev_server = build_dev_server(shell: shell)
@@ -120,6 +153,22 @@
       expect(server.requested_paths).to eq(["/assets/logo.png?v=1"])
     end
 
+    it "requests the development server itself, not the configured origin" do
+      server = null_server
+      server.listen("127.0.0.1", 0, body: "ok")
+      dev_server = build_dev_server(
+        options: {
+          host: "0.0.0.0",
+          port: server.port,
+          origin: "http://origin.invalid:9999",
+        },
+      )
+
+      response = dev_server.get("/")
+
+      expect(response.body).to eq("ok")
+    end
+
     it "ignores a configured HTTP proxy" do
       server = null_server
       server.listen("127.0.0.1", 0, body: "ok")