Tell the user when a scraper runs but outputs nothing

.rubocop_todo.yml

@@ -36,7 +36,7 @@ Metrics/MethodLength:
 # Offense count: 1
 # Configuration parameters: CountComments, CountAsOne.
 Metrics/ModuleLength:
-  Max: 114
+  Max: 124
 
 # Offense count: 1
 # Configuration parameters: ExpectMatchingDefinition, CheckDefinitionPathHierarchy, CheckDefinitionPathHierarchyRoots, Regex, IgnoreExecutableScripts, AllowedAcronyms.

lib/morph-cli.rb

@@ -31,13 +31,23 @@ def self.execute(directory, _development, env_config, skip_data: false)
 
     file = MorphCLI.create_tar(directory, all_paths)
 
+    scraper_output = run(file, env_config)
+
+    puts "Scraper didn't output anything, but it ran successfully." unless scraper_output
+  end
+
+  # Uploads the code to the server, streams the run output to the local
+  # stdout/stderr and returns whether the scraper itself wrote anything
+  # to stdout or stderr
+  def self.run(file, env_config)
     connection = Faraday.new(url: env_config[:base_url]) do |f|
       f.request :multipart
       f.response :raise_error
       f.adapter Faraday.default_adapter
     end
 
     buffer = +""
+    scraper_output = false
     connection.post("/run") do |req|
       req.body = {
         api_key: env_config[:api_key],
@@ -52,12 +62,18 @@ def self.execute(directory, _development, env_config, skip_data: false)
 
         before, match, after = chunk.rpartition("\n")
         buffer << before << match
-        buffer.split("\n").each { |l| log(l) }
+        buffer.split("\n").each do |l|
+          stream = log(l)
+          scraper_output = true if %w[stdout stderr].include?(stream)
+        end
         buffer = after
       end
     end
+    scraper_output
   end
 
+  # Writes the line to the local stdout/stderr and returns the name of the
+  # stream it came from
   def self.log(line)
     return if line.empty?
 
@@ -72,6 +88,7 @@ def self.log(line)
         end
 
     s.puts a["text"]
+    a["stream"]
   end
 
   def self.config_path

spec/morph_cli_spec.rb

@@ -1,5 +1,7 @@
 require "fileutils"
 require "tmpdir"
+require "stringio"
+require "zlib"
 
 require "spec_helper"
 
@@ -20,6 +22,23 @@ def with_scraper_directory
       end
     end
 
+    # Extracts tar entry names from a multipart request body that contains
+    # a gzip-compressed tar as one of its parts.
+    def tar_entry_names(body)
+      binary = body.b
+      gzip_start = binary.index("\x1f\x8b".b)
+      return [] unless gzip_start
+
+      gzip_io = StringIO.new(binary[gzip_start..])
+      names = []
+      Zlib::GzipReader.wrap(gzip_io) do |gz|
+        Minitar::Input.open(gz) { |tar| tar.each { |entry| names << entry.full_name } }
+      end
+      names
+    rescue StandardError
+      []
+    end
+
     it "uploads the scraper and streams the run output to stdout" do
       stub_request(:post, "https://morph.io/run")
         .to_return(status: 200, body: %({"stream":"stdout","text":"hello from morph"}\n))
@@ -30,6 +49,38 @@ def with_scraper_directory
       end
     end
 
+    it "tells the user the run succeeded when the scraper produces no output" do
+      stub_request(:post, "https://morph.io/run")
+        .to_return(status: 200, body: %({"stream":"internalout","text":"Injecting configuration"}\n))
+
+      with_scraper_directory do |dir|
+        expect { described_class.execute(dir, false, env_config) }
+          .to output(/Scraper didn't output anything, but it ran successfully\./).to_stdout
+      end
+    end
+
+    it "doesn't add a message when the scraper writes to stdout" do
+      stub_request(:post, "https://morph.io/run")
+        .to_return(status: 200, body: %({"stream":"stdout","text":"hello from morph"}\n))
+
+      with_scraper_directory do |dir|
+        expect { described_class.execute(dir, false, env_config) }
+          .not_to output(/ran successfully/).to_stdout
+      end
+    end
+
+    it "doesn't add a message when the scraper writes to stderr" do
+      stub_request(:post, "https://morph.io/run")
+        .to_return(status: 200, body: %({"stream":"stderr","text":"oops"}\n))
+
+      with_scraper_directory do |dir|
+        expect do
+          expect { described_class.execute(dir, false, env_config) }
+            .not_to output(/ran successfully/).to_stdout
+        end.to output("oops\n").to_stderr
+      end
+    end
+
     it "posts the API key and the gzipped code as multipart form data" do
       stub_request(:post, "https://morph.io/run").to_return(status: 200, body: "")
 
@@ -52,11 +103,11 @@ def with_scraper_directory
         File.write(File.join(dir, "data.sqlite"), "sqlite data")
 
         expect { described_class.execute(dir, false, env_config) }
-          .to output(/\AUploading 21\.00 B \(including data\.sqlite\)\.\.\.\n\z/).to_stdout
+          .to output(/\AUploading 21\.00 B \(including data\.sqlite\)\.\.\.\n/).to_stdout
       end
 
       expect(WebMock).to(have_requested(:post, "https://morph.io/run").with do |req|
-        req.body.include?("data.sqlite")
+        tar_entry_names(req.body).include?("data.sqlite")
       end)
     end
 
@@ -67,11 +118,11 @@ def with_scraper_directory
         File.write(File.join(dir, "data.sqlite"), "sqlite data")
 
         expect { described_class.execute(dir, false, env_config, skip_data: true) }
-          .to output(/\AUploading 10\.00 B\.\.\.\n\z/).to_stdout
+          .to output(/\AUploading 10\.00 B\.\.\.\n/).to_stdout
       end
 
       expect(WebMock).to(have_requested(:post, "https://morph.io/run").with do |req|
-        !req.body.include?("data.sqlite")
+        !tar_entry_names(req.body).include?("data.sqlite")
       end)
     end