Implement 'With crystal foo.cr --flag, when --flag isn't found, menti…

…on did you mean crystal foo.cr -- --flag' from PR crystal-lang#5291
benglewis · Jun 30, 2018 · cc52bb0 · cc52bb0
1 parent d6ba746
commit cc52bb0
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diff --git a/spec/std/option_parser_spec.cr b/spec/std/option_parser_spec.cr
@@ -215,7 +215,8 @@ describe "OptionParser" do
   end
 
   it "raises on invalid option" do
-    expect_raises OptionParser::InvalidOption, "Invalid option: -j" do
+    suggestion = "(did you mean 'crystal foo.cr -- -j'?)".colorize.yellow.bold.to_s
+    expect_raises OptionParser::InvalidOption, "Invalid option: -j #{suggestion}" do
       OptionParser.parse(["-f", "-j"]) do |opts|
         opts.on("-f", "some flag") { }
       end

diff --git a/src/option_parser.cr b/src/option_parser.cr
@@ -35,7 +35,11 @@ class OptionParser
 
   class InvalidOption < Exception
     def initialize(option)
-      super("Invalid option: #{option}")
+      super("Invalid option: #{option} #{
+        type.program.colorize(
+          "(did you mean 'crystal foo.cr -- #{option}')"
+        ).yellow.bold
+      }")
     end
   end