mudge · March 24, 2023 05:27 · Nov 22, 2022 · Nov 19, 2022 · Nov 19, 2022 · Nov 19, 2022
diff --git a/api_controller_spec.rb b/api_controller_spec.rb
@@ -4,14 +4,14 @@
   controller do
     def index
       respond_to do |format|
-        format.plain { render plain: "Plain text" }
+        format.text { render plain: "Plain text" }
         format.json { render json: "JSON" }
       end
     end
 
     def show
       respond_to do |format|
-        format.plain { render plain: "Plain text" }
+        format.text { render plain: "Plain text" }
         format.any { render plain: "Fallback" }
       end
     end

diff --git a/api_controller_spec.rb b/api_controller_spec.rb
@@ -72,12 +72,12 @@ def show
   it "raises an error when given an invalid MIME type" do
     request.headers["Accept"] = "not a valid MIME type"
 
-    expect { get :index }.to raise_error(ActionDispatch::Http::MimeNegotiation::InvalidType)
+    expect { get :index }.to raise_error(Mime::Type::InvalidMimeType)
   end
 
   it "raises an error when given an invalid MIME type even if an 'any' format is present" do
     request.headers["Accept"] = "not a valid MIME type"
 
-    expect { get :show, params: { id: 1 } }.to raise_error(ActionDispatch::Http::MimeNegotiation::InvalidType)
+    expect { get :show, params: { id: 1 } }.to raise_error(Mime::Type::InvalidMimeType)
   end
 end
diff --git a/api_controller_spec.rb b/api_controller_spec.rb
@@ -68,4 +68,16 @@ def show
 
     expect(response.body).to eq("Fallback")
   end
+
+  it "raises an error when given an invalid MIME type" do
+    request.headers["Accept"] = "not a valid MIME type"
+
+    expect { get :index }.to raise_error(ActionDispatch::Http::MimeNegotiation::InvalidType)
+  end
+
+  it "raises an error when given an invalid MIME type even if an 'any' format is present" do
+    request.headers["Accept"] = "not a valid MIME type"
+
+    expect { get :show, params: { id: 1 } }.to raise_error(ActionDispatch::Http::MimeNegotiation::InvalidType)
+  end
 end
diff --git a/api_controller_spec.rb b/api_controller_spec.rb
@@ -64,7 +64,7 @@ def show
   it "does not raise an error when given an unsupported MIME type if an 'any' format is present" do
     request.headers["Accept"] = "image/webp"
 
-    get :show, params: {id: 1}
+    get :show, params: { id: 1 }
 
     expect(response.body).to eq("Fallback")
   end

diff --git a/api_controller_spec.rb b/api_controller_spec.rb
@@ -8,6 +8,13 @@ def index
         format.json { render json: "JSON" }
       end
     end
+
+    def show
+      respond_to do |format|
+        format.plain { render plain: "Plain text" }
+        format.any { render plain: "Fallback" }
+      end
+    end
   end
 
   it "returns the first format when given no Accept header" do
@@ -53,4 +60,12 @@ def index
 
     expect { get :index }.to raise_error(ActionController::UnknownFormat)
   end
+
+  it "does not raise an error when given an unsupported MIME type if an 'any' format is present" do
+    request.headers["Accept"] = "image/webp"
+
+    get :show, params: {id: 1}
+
+    expect(response.body).to eq("Fallback")
+  end
 end
diff --git a/api_controller.rb b/api_controller.rb
@@ -1,8 +1,8 @@
 class ApiController < ApplicationController
   before_action :only_respect_accept_header
-  
+
   private
-  
+
   # By default, Rails will ignore the Accept header if it contains a wildcard
   # and assume the client wants HTML (or JS if using XMLHttpRequest). See
   # https://github.com/rails/rails/blob/a807a4f4f95798616a2a85856f77fdfc48da4832/actionpack/lib/action_dispatch/http/mime_negotiation.rb#L171-L173
@@ -11,8 +11,15 @@ class ApiController < ApplicationController
   # and only set the request formats from the Accept header, falling back to
   # the wildcard if it is not present (and therefore respecting our
   # priorities).
+  #
+  # Note we have to filter down the MIME types to ones Rails understands
+  # otherwise it will raise an error when attempting to set formats for the
+  # lookup context.
   def only_respect_accept_header
-    request.set_header("action_dispatch.request.formats", requested_mime_types)
+    request.set_header(
+      "action_dispatch.request.formats",
+      requested_mime_types.select { |type| type.symbol || type.ref == "*/*" }
+    )
   end
 
   def requested_mime_types

diff --git a/api_controller_spec.rb b/api_controller_spec.rb
@@ -0,0 +1,56 @@
+require "rails_helper"
+
+RSpec.describe ApiController do
+  controller do
+    def index
+      respond_to do |format|
+        format.plain { render plain: "Plain text" }
+        format.json { render json: "JSON" }
+      end
+    end
+  end
+
+  it "returns the first format when given no Accept header" do
+    get :index
+
+    expect(response.media_type).to eq("text/plain")
+  end
+
+  it "returns the first format when given a wildcard Accept header" do
+    request.headers["Accept"] = "*/*"
+
+    get :index
+
+    expect(response.media_type).to eq("text/plain")
+  end
+
+  it "returns the first format when given Safari and Chrome's default Accept header" do
+    request.headers["Accept"] = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8"
+
+    get :index
+
+    expect(response.media_type).to eq("text/plain")
+  end
+
+  it "returns a text/plain response when explicitly requested" do
+    request.headers["Accept"] = "text/plain"
+
+    get :index
+
+    expect(response.media_type).to eq("text/plain")
+  end
+
+  it "returns an application/json response when explicitly requested" do
+    request.headers["Accept"] = "application/json"
+
+    get :index
+
+    expect(response.media_type).to eq("application/json")
+  end
+
+  it "raises an error if given an unsupported MIME type" do
+    request.headers["Accept"] = "image/webp"
+
+    expect { get :index }.to raise_error(ActionController::UnknownFormat)
+  end
+end
diff --git a/api_controller.rb b/api_controller.rb
@@ -0,0 +1,21 @@
+class ApiController < ApplicationController
+  before_action :only_respect_accept_header
+
+  private
+
+  # By default, Rails will ignore the Accept header if it contains a wildcard
+  # and assume the client wants HTML (or JS if using XMLHttpRequest). See
+  # https://github.com/rails/rails/blob/a807a4f4f95798616a2a85856f77fdfc48da4832/actionpack/lib/action_dispatch/http/mime_negotiation.rb#L171-L173
+  #
+  # If you don't expect your clients to be browsers, we want to override this
+  # and only set the request formats from the Accept header, falling back to
+  # the wildcard if it is not present (and therefore respecting our
+  # priorities).
+  def only_respect_accept_header
+    request.set_header("action_dispatch.request.formats", requested_mime_types)
+  end
+
+  def requested_mime_types
+    Mime::Type.parse(request.get_header("HTTP_ACCEPT").to_s).presence || [Mime::ALL]
+  end
+end
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