Allow passing file contents via standard input

Various third-party tools want the ability to lint a file passed via
standard input. A quirk of this feature is that there's no way to
specify a file name in this way, so we need to expose a flag that can be
specified in addition so that the appropriate linter configuration can
be applied based on the path.

CHANGELOG.md

@@ -10,6 +10,8 @@
   pseudo elements and single colons with pseudo classes
 * Add `disabled_properties` option to `PropertySpelling` allowing properties
   to be prohibited from use
+* Add support for linting files via STDIN by specifying `--stdin-file-path`
+  so the appropriate configuration can be applied based on the path
 
 ## 0.42.2
 

README.md

@@ -68,6 +68,13 @@ You can also specify a list of files explicitly:
 scss-lint app/assets/stylesheets/**/*.css.scss
 ```
 
+...or you can lint a file passed via standard input (**note** the
+`--stdin-file-path` flag is required when passing via standard input):
+
+```bash
+cat some-file | scss-lint --stdin-file-path=path/to/treat/stdin/as/having.scss
+```
+
 `scss-lint` will output any problems with your SCSS, including the offending
 filename and line number (if available).
 
@@ -80,6 +87,7 @@ Command Line Flag         | Description
 `-r`/`--require`          | Require file/library (mind `$LOAD_PATH`, uses `Kernel.require`)
 `-i`/`--include-linter`   | Specify which linters you specifically want to run
 `-x`/`--exclude-linter`   | Specify which linters you _don't_ want to run
+`--stdin-file-path`       | When linting a file passed via standard input, treat it as having the specified path to apply the appropriate configuration
 `-h`/`--help`             | Show command line flag documentation
 `--show-formatters`       | Show all available formatters
 `--show-linters`          | Show all available linters

lib/scss_lint/cli.rb

@@ -54,8 +54,16 @@ def act_on_options(options)
 
     def scan_for_lints(options, config)
       runner = Runner.new(config)
-      runner.run(FileFinder.new(config).find(options[:files]))
-      report_lints(options, runner.lints, runner.files)
+      files =
+        if options[:stdin_file_path]
+          [{ file: STDIN, path: options[:stdin_file_path] }]
+        else
+          FileFinder.new(config).find(options[:files]).map do |file_path|
+            { path: file_path }
+          end
+        end
+      runner.run(files)
+      report_lints(options, runner.lints, files)
 
       if runner.lints.any?(&:error?)
         halt :error

lib/scss_lint/engine.rb

@@ -17,8 +17,8 @@ class Engine
     # @option options [String] :file The file to load
     # @option options [String] :code The code to parse
     def initialize(options = {})
-      if options[:file]
-        build_from_file(options[:file])
+      if options[:path]
+        build_from_file(options)
       elsif options[:code]
         build_from_string(options[:code])
       end
@@ -41,11 +41,14 @@ def initialize(options = {})
 
   private
 
-    # @param path [String]
-    def build_from_file(path)
-      @filename = path
-      @engine = Sass::Engine.for_file(path, ENGINE_OPTIONS)
-      @contents = File.open(path, 'r').read
+    # @param options [Hash]
+    # @option file [IO] if provided, us this as the file object
+    # @option path [String] path of file, loading from this if `file` object not
+    #   given
+    def build_from_file(options)
+      @filename = options[:path]
+      @contents = options[:file] ? file.read : File.read(@filename)
+      @engine = Sass::Engine.new(@contents, ENGINE_OPTIONS.merge(filename: @filename))
     end
 
     # @param scss [String]

lib/scss_lint/options.rb

@@ -77,6 +77,11 @@ def add_file_options(parser)
         @options[:excluded_files] = files
       end
 
+      parser.on('--stdin-file-path file-path', String,
+                'Specify the path to assume for the file passed via STDIN') do |stdin_file_path|
+        @options[:stdin_file_path] = stdin_file_path
+      end
+
       parser.on('-o', '--out path', 'Write output to a file instead of STDOUT', String) do |path|
         define_output_path(path)
       end

lib/scss_lint/runner.rb

@@ -12,7 +12,7 @@ def initialize(config)
       @linters.map!(&:new)
     end
 
-    # @param files [Array]
+    # @param files [Array<Hash>] list of file object/path hashes
     def run(files)
       @files = files
       @files.each do |file|
@@ -22,16 +22,18 @@ def run(files)
 
   private
 
-    # @param file [String]
+    # @param file [Hash]
+    # @option file [String] File object
+    # @option path [String] path to File (determines which Linter config to apply)
     def find_lints(file)
-      engine = Engine.new(file: file)
+      engine = Engine.new(file)
 
       @linters.each do |linter|
         begin
-          run_linter(linter, engine, file)
+          run_linter(linter, engine, file[:path])
         rescue => error
           raise SCSSLint::Exceptions::LinterError,
-                "#{linter.class} raised unexpected error linting file #{file}: " \
+                "#{linter.class} raised unexpected error linting file #{file[:path]}: " \
                 "'#{error.message}'",
                 error.backtrace
         end
@@ -40,12 +42,12 @@ def find_lints(file)
       @lints << Lint.new(nil, ex.sass_filename, Location.new(ex.sass_line),
                          "Syntax Error: #{ex}", :error)
     rescue FileEncodingError => ex
-      @lints << Lint.new(nil, file, Location.new, ex.to_s, :error)
+      @lints << Lint.new(nil, file[:path], Location.new, ex.to_s, :error)
     end
 
     # For stubbing in tests.
-    def run_linter(linter, engine, file)
-      return if @config.excluded_file_for_linter?(file, linter)
+    def run_linter(linter, engine, file_path)
+      return if @config.excluded_file_for_linter?(file_path, linter)
       @lints += linter.run(engine, @config.linter_options(linter))
     end
   end

spec/scss_lint/cli_spec.rb

@@ -154,6 +154,20 @@ def safe_run
       end
     end
 
+    context 'when the --stdin-file-path argument is specified' do
+      let(:flags) { ['--stdin-file-path', 'some-fake-file-path.scss'] }
+
+      before do
+        STDIN.stub(:read).and_return('// Nothing interesting')
+      end
+
+      it 'passes STDIN and the file path as a file tuple to the runner' do
+        SCSSLint::Runner.any_instance.should_receive(:run)
+                        .with([file: STDIN, path: 'some-fake-file-path.scss'])
+        safe_run
+      end
+    end
+
     context 'when specified SCSS file globs match no files' do
       before do
         SCSSLint::FileFinder.any_instance.stub(:find)

spec/scss_lint/runner_spec.rb

@@ -23,7 +23,7 @@ class SCSSLint::Linter::FakeLinter1 < SCSSLint::Linter; end
   class SCSSLint::Linter::FakeLinter2 < SCSSLint::Linter; end
 
   describe '#run' do
-    let(:files) { ['dummy1.scss', 'dummy2.scss'] }
+    let(:files) { [{ path: 'dummy1.scss' }, { path: 'dummy2.scss' }] }
     subject     { runner.run(files) }
 
     before do
@@ -112,7 +112,7 @@ class SCSSLint::Linter::FakeLinter2 < SCSSLint::Linter; end
       end
 
       it 'has the name of the file the linter was checking' do
-        expect { subject }.to raise_error { |e| e.message.should include files.first }
+        expect { subject }.to raise_error { |e| e.message.should include files.first[:path] }
       end
 
       it 'has the same backtrace as the original error' do