Add cli flag to read from STDIN

src/ameba/cli/cmd.cr

@@ -16,6 +16,7 @@ module Ameba::Cli
 
     config = Config.load opts.config, opts.colors?, opts.skip_reading_config?
     config.autocorrect = autocorrect
+    config.stdin_filename = opts.stdin_filename
 
     if globs = opts.globs
       config.globs = globs
@@ -59,6 +60,7 @@ module Ameba::Cli
     property describe_rule : String?
     property location_to_explain : NamedTuple(file: String, line: Int32, column: Int32)?
     property fail_level : Severity?
+    property stdin_filename : String? = nil
     property? skip_reading_config = false
     property? rules = false
     property? all = false
@@ -140,6 +142,10 @@ module Ameba::Cli
       parser.on("--no-color", "Disable colors") do
         opts.colors = false
       end
+
+      parser.on("--stdin-filename FILENAME", "Read source from STDIN") do |file|
+        opts.stdin_filename = file
+      end
     end
 
     opts

src/ameba/config.cr

@@ -86,6 +86,9 @@ class Ameba::Config
   # Returns `true` if correctable issues should be autocorrected.
   property? autocorrect = false
 
+  # Returns a filename if reading source file from STDIN.
+  property stdin_filename : String? = nil
+
   @rule_groups : Hash(String, Array(Rule::Base))
 
   # Creates a new instance of `Ameba::Config` based on YAML parameters.
@@ -156,8 +159,12 @@ class Ameba::Config
   # config.sources # => list of sources pointing to files found by the wildcards
   # ```
   def sources
-    (find_files_by_globs(globs) - find_files_by_globs(excluded))
-      .map { |path| Source.new File.read(path), path }
+    if file = stdin_filename
+      [Source.new(STDIN.gets_to_end, file)]
+    else
+      (find_files_by_globs(globs) - find_files_by_globs(excluded))
+        .map { |path| Source.new File.read(path), path }
+    end
   end
 
   # Returns a formatter to be used while inspecting files.