Test for piped config, and fix to make it work

Signed-off-by: Clinton Wolfe <clintoncwolfe@gmail.com>

lib/inspec/config.rb

@@ -143,6 +143,7 @@ module Inspec
     # Regardless of our situation, end up with a readable IO object
     def resolve_cfg_io(cli_opts, cfg_io)
       raise(ArgumentError, 'Inspec::Config must use an IO to read from') if cfg_io && !cfg_io.respond_to?(:read)
+      cfg_io ||= check_for_piped_config(cli_opts)
       return cfg_io if cfg_io
 
       path = determine_cfg_path(cli_opts)
@@ -151,13 +152,20 @@ module Inspec
       cfg_io || StringIO.new('{ "version": "1.1" }')
     end
 
+    def check_for_piped_config(cli_opts)
+      cli_opt = cli_opts[:config] || cli_opts[:json_config]
+      return nil unless cli_opt
+      return nil unless cli_opt == '-'
+      # This warning is here so that if a user invokes inspec with --config=-,
+      # they will have an explanation for why it appears to hang.
+      Inspec::Log.warn 'Reading JSON config from standard input' if STDIN.tty?
+      STDIN
+    end
+
     def determine_cfg_path(cli_opts)
       path = cli_opts[:config] || cli_opts[:json_config] # TODO: deprecate --json-config see #3661
 
-      if path == '-'
-        Inspec::Log.warn 'Reading JSON config from standard input' if STDIN.tty?
-        path = STDIN
-      elsif path.nil?
+      if path.nil?
         default_path = File.join(Inspec.config_dir, 'config.json')
         path = default_path if File.exist?(default_path)
       elsif !File.exist?(path)

test/functional/inspec_exec_test.rb

@@ -580,17 +580,24 @@ Test Summary: \e[38;5;41m2 successful\e[0m, 0 failures, 0 skipped\n"
       end
     end
 
-    # TODO - Use bash redirection to populate STDIN
-    # unless windows?
-    #   describe 'when using the --config option to read from STDIN' do
-    #     let(:cli_args) { '--config ' + File.join(config_dir_path, 'json-config', 'good.json') }
-    #     it 'should see the custom target ID value' do
-    #       stderr.must_be_empty
-    #       seen_target_id.must_equal 'from-config-file'
-    #       # TODO
-    #     end
-    #   end
-    # end
+    unless windows?
+      describe 'when using the --config option to read from STDIN' do
+        let(:json_path) { File.join(config_dir_path, 'json-config', 'good.json') }
+        let(:cli_args) { '--config -' }
+        let(:run_result) do
+          prefix = 'cat ' + json_path + ' | '
+          simple_profile = File.join(profile_path, 'simple-metadata')
+          run_inspec_process(
+            'exec ' + simple_profile + ' ' + cli_args + ' ',
+            { prefix: prefix, json: true, env: env }
+          )
+        end
+        it 'should see the custom target ID value' do
+          stderr.must_be_empty
+          seen_target_id.must_equal 'from-config-file'
+        end
+      end
+    end
 
     describe 'when reading from the default location' do
       # Should read from File.join(config_dir_path, 'fakehome-2', '.inspec', 'config.json')