un-deprecate stream-like objects

- this splits the purpose of "stream" and "file" inside_route methods.
- file will now always setup headers for streaming.
- stream is purely for stream-like objects. This allows you to have streaming responses of generated data

Author: urkle

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 #### Features
 
+* [#1520](https://github.com/ruby-grape/grape/pull/1520): Un-deprecate stream-like objects - [@urkle](https://github.com/urkle).
 * [#2060](https://github.com/ruby-grape/grape/pull/2060): Drop support for Ruby 2.4 - [@dblock](https://github.com/dblock).
 * [#2060](https://github.com/ruby-grape/grape/pull/2060): Upgraded Rubocop to 0.84.0 - [@dblock](https://github.com/dblock).
 * Your contribution here.

README.md

@@ -3168,7 +3168,7 @@ end
 
 Use `body false` to return `204 No Content` without any data or content-type.
 
-You can also set the response to a file with `file`.
+You can also set the response to a file with `file` and it will be streamed using Rack::Chunked.
 
 ```ruby
 class API < Grape::API
@@ -3178,12 +3178,22 @@ class API < Grape::API
 end
 ```
 
-If you want a file to be streamed using Rack::Chunked, use `stream`.
+If you want to stream non-file data you use the stream method and a Stream object.
+This is simply an object that responds to each and yields for each chunk to send to the client.
+Each chunk will be sent as it is yielded instead of waiting for all of the content to be available.
 
 ```ruby
+class MyStream
+  def each
+    yield 'part 1'
+    yield 'part 2'
+    yield 'part 3'
+  end
+end
+
 class API < Grape::API
   get '/' do
-    stream '/path/to/file'
+    stream MyStream.new
   end
 end
 ```

UPGRADING.md

@@ -1,6 +1,42 @@
 Upgrading Grape
 ===============
 
+### Upgrading to >= 1.3.4
+
+#### Reworking stream and file and un-deprecating stream like-objects
+
+Previously in 0.16 stream-like objects were deprecated. This release restores their functionality for use-cases other than file streaming.
+
+For streaming files, simply use file always.
+
+```ruby
+class API < Grape::API
+  get '/' do
+    file '/path/to/file'
+  end
+end
+```
+
+If you want to stream other kinds of content from a streamer object you may.
+An example would be a streamer class that fetches several pages of data from a database and streams the formatted responses back.
+
+```ruby
+class MyObject
+  def each
+    yield '['
+    # maybe do some paginated DB fetches and return each page
+    yield {}.to_json
+    yield ']'  
+  end
+end
+
+class API < Grape::API
+  get '/' do
+    stream MyObject.new
+  end
+end
+```
+
 ### Upgrading to >= 1.3.3
 
 #### Nil values for structures

lib/grape.rb

@@ -206,12 +206,12 @@ module Presenters
     end
   end
 
-  module ServeFile
+  module ServeStream
     extend ::ActiveSupport::Autoload
     eager_autoload do
-      autoload :FileResponse
       autoload :FileBody
       autoload :SendfileResponse
+      autoload :StreamResponse
     end
   end
 end

lib/grape/dsl/inside_route.rb

@@ -289,13 +289,13 @@ def return_no_content
       #   GET /file # => "contents of file"
       def file(value = nil)
         if value.is_a?(String)
-          file_body = Grape::ServeFile::FileBody.new(value)
-          @file = Grape::ServeFile::FileResponse.new(file_body)
+          file_body = Grape::ServeStream::FileBody.new(value)
+          stream(file_body)
         elsif !value.is_a?(NilClass)
-          warn '[DEPRECATION] Argument as FileStreamer-like object is deprecated. Use path to file instead.'
-          @file = Grape::ServeFile::FileResponse.new(value)
+          warn '[DEPRECATION] Argument as FileStreamer-like object is deprecated. Use path to file instead or stream to use a Stream object.'
+          stream(value)
         else
-          instance_variable_defined?(:@file) ? @file : nil
+          stream
         end
       end
 
@@ -318,7 +318,16 @@ def stream(value = nil)
         header 'Content-Length', nil
         header 'Transfer-Encoding', nil
         header 'Cache-Control', 'no-cache' # Skips ETag generation (reading the response up front)
-        file(value)
+        if value.is_a?(String)
+          warn '[DEPRECATION] Use `file file_path` to stream a file instead.'
+          file(value)
+        elsif value.respond_to?(:each)
+          @stream = Grape::ServeStream::StreamResponse.new(value)
+        elsif !value.is_a?(NilClass)
+          raise ArgumentError, 'Stream object must respond to :each.'
+        else
+          instance_variable_defined?(:@stream) ? @stream : nil
+        end
       end
 
       # Allows you to make use of Grape Entities by setting

lib/grape/middleware/formatter.rb

@@ -36,9 +36,9 @@ def after
       def build_formatted_response(status, headers, bodies)
         headers = ensure_content_type(headers)
 
-        if bodies.is_a?(Grape::ServeFile::FileResponse)
-          Grape::ServeFile::SendfileResponse.new([], status, headers) do |resp|
-            resp.body = bodies.file
+        if bodies.is_a?(Grape::ServeStream::StreamResponse)
+          Grape::ServeStream::SendfileResponse.new([], status, headers) do |resp|
+            resp.body = bodies.stream
           end
         else
           # Allow content-type to be explicitly overwritten

lib/grape/serve_file/file_body.rb renamed to lib/grape/serve_stream/file_body.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module Grape
-  module ServeFile
+  module ServeStream
     CHUNK_SIZE = 16_384
 
     # Class helps send file through API

lib/grape/serve_file/sendfile_response.rb renamed to lib/grape/serve_stream/sendfile_response.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module Grape
-  module ServeFile
+  module ServeStream
     # Response should respond to to_path method
     # for using Rack::SendFile middleware
     class SendfileResponse < Rack::Response

lib/grape/serve_file/file_response.rb renamed to lib/grape/serve_stream/stream_response.rb

@@ -1,22 +1,22 @@
 # frozen_string_literal: true
 
 module Grape
-  module ServeFile
-    # A simple class used to identify responses which represent files and do not
+  module ServeStream
+    # A simple class used to identify responses which represent streams (or files) and do not
     # need to be formatted or pre-read by Rack::Response
-    class FileResponse
-      attr_reader :file
+    class StreamResponse
+      attr_reader :stream
 
-      # @param file [Object]
-      def initialize(file)
-        @file = file
+      # @param stream [Object]
+      def initialize(stream)
+        @stream = stream
       end
 
       # Equality provided mostly for tests.
       #
       # @return [Boolean]
       def ==(other)
-        file == other.file
+        stream == other.stream
       end
     end
   end

spec/grape/dsl/inside_route_spec.rb

@@ -208,31 +208,55 @@ def initialize
         let(:file_path) { '/some/file/path' }
 
         let(:file_response) do
-          file_body = Grape::ServeFile::FileBody.new(file_path)
-          Grape::ServeFile::FileResponse.new(file_body)
+          file_body = Grape::ServeStream::FileBody.new(file_path)
+          Grape::ServeStream::StreamResponse.new(file_body)
         end
 
         before do
+          subject.header 'Cache-Control', 'cache'
+          subject.header 'Content-Length', 123
+          subject.header 'Transfer-Encoding', 'base64'
+
           subject.file file_path
         end
 
-        it 'returns value wrapped in FileResponse' do
+        it 'returns value wrapped in StreamResponse' do
           expect(subject.file).to eq file_response
         end
+
+        it 'sets Cache-Control header to no-cache' do
+          expect(subject.header['Cache-Control']).to eq 'no-cache'
+        end
+
+        it 'sets Content-Length header to nil' do
+          expect(subject.header['Content-Length']).to eq nil
+        end
+
+        it 'sets Transfer-Encoding header to nil' do
+          expect(subject.header['Transfer-Encoding']).to eq nil
+        end
       end
 
       context 'as object (backward compatibility)' do
-        let(:file_object) { Class.new }
+        let(:file_object) { double('StreamerObject', each: nil) }
 
         let(:file_response) do
-          Grape::ServeFile::FileResponse.new(file_object)
+          Grape::ServeStream::StreamResponse.new(file_object)
         end
 
         before do
+          allow(subject).to receive(:warn)
+        end
+
+        it 'emits a warning that a stream object should be sent to the stream method' do
+          expect(subject).to receive(:warn).with(/Argument as FileStreamer-like/)
+
           subject.file file_object
         end
 
-        it 'returns value wrapped in FileResponse' do
+        it 'returns value wrapped in StreamResponse' do
+          subject.file file_object
+
           expect(subject.file).to eq file_response
         end
       end
@@ -245,38 +269,77 @@ def initialize
 
   describe '#stream' do
     describe 'set' do
-      let(:file_object) { Class.new }
+      context 'as a file path (backward compatibility)' do
+        let(:file_path) { '/some/file/path' }
 
-      before do
-        subject.header 'Cache-Control', 'cache'
-        subject.header 'Content-Length', 123
-        subject.header 'Transfer-Encoding', 'base64'
-        subject.stream file_object
-      end
+        let(:file_response) do
+          file_body = Grape::ServeStream::FileBody.new(file_path)
+          Grape::ServeStream::StreamResponse.new(file_body)
+        end
 
-      it 'returns value wrapped in FileResponse' do
-        expect(subject.stream).to eq Grape::ServeFile::FileResponse.new(file_object)
-      end
+        before do
+          allow(subject).to receive(:warn)
+        end
 
-      it 'also sets result of file to value wrapped in FileResponse' do
-        expect(subject.file).to eq Grape::ServeFile::FileResponse.new(file_object)
-      end
+        it 'emits a warning to use file method to stream a file' do
+          expect(subject).to receive(:warn).with(/file file_path/)
+
+          subject.stream file_path
+        end
+
+        it 'returns value wrapped in StreamResponse' do
+          subject.stream file_path
 
-      it 'sets Cache-Control header to no-cache' do
-        expect(subject.header['Cache-Control']).to eq 'no-cache'
+          expect(subject.file).to eq file_response
+        end
       end
 
-      it 'sets Content-Length header to nil' do
-        expect(subject.header['Content-Length']).to eq nil
+      context 'as a stream object' do
+        let(:stream_object) { double('StreamerObject', each: nil) }
+
+        let(:stream_response) do
+          Grape::ServeStream::StreamResponse.new(stream_object)
+        end
+
+        before do
+          subject.header 'Cache-Control', 'cache'
+          subject.header 'Content-Length', 123
+          subject.header 'Transfer-Encoding', 'base64'
+          subject.stream stream_object
+        end
+
+        it 'returns value wrapped in StreamResponse' do
+          expect(subject.stream).to eq stream_response
+        end
+
+        it 'also sets result of file to value wrapped in StreamResponse' do
+          expect(subject.file).to eq stream_response
+        end
+
+        it 'sets Cache-Control header to no-cache' do
+          expect(subject.header['Cache-Control']).to eq 'no-cache'
+        end
+
+        it 'sets Content-Length header to nil' do
+          expect(subject.header['Content-Length']).to eq nil
+        end
+
+        it 'sets Transfer-Encoding header to nil' do
+          expect(subject.header['Transfer-Encoding']).to eq nil
+        end
       end
 
-      it 'sets Transfer-Encoding header to nil' do
-        expect(subject.header['Transfer-Encoding']).to eq nil
+      context 'as a non-stream object' do
+        let(:non_stream_object) { double('NonStreamerObject') }
+
+        it 'raises an error that the object must implement :each' do
+          expect { subject.stream non_stream_object }.to raise_error(ArgumentError, /:each/)
+        end
       end
     end
 
     it 'returns default' do
-      expect(subject.file).to be nil
+      expect(subject.stream).to be nil
     end
   end