Merge pull request #2637 from rolandwalker/version_caveats

add os_version_only to caveats DSL

CONTRIBUTING.md

@@ -320,6 +320,7 @@ The following methods may be called to generate standard warning messages:
 | `reboot`                          | The user should reboot to complete installation
 | `files_in_usr_local`              | The Cask installs files to `/usr/local`, which may confuse Homebrew
 | `arch_only(list)`                 | The Cask only supports certain architectures.  Currently valid elements of `list` are `intel-32` and `intel-64`
+| `os_version_only(list)`           | The Cask only supports certain OS X Versions.  Currently valid elements of `list` are `10.5`, `10.6`, `10.7`, `10.8`, and `10.9`
 
 Example:
 

lib/cask/caveats.rb

@@ -104,6 +104,32 @@ class Cask::CaveatsDSL
     end
   end
 
+  # minor bug: because output from os_version_only is conditional, the
+  # existence of this directive causes the "===> Caveats" header to
+  # appear even if no warning is output.  One workaround would
+  # be to spin out os-version-detection from caveats into a separate
+  # Cask stanza, and that is probably a sensible design.
+  def os_versions_only(*supported_versions)
+    known_versions = %w{10.0 10.1 10.2 10.3 10.3 10.5 10.6 10.7 10.8 10.9}
+    supported_versions.each do |version|
+      unless known_versions.include?(version)
+        # There ought to be some standard exceptions for Cask validation errors
+        raise "The only valid arguments to caveats os_version_only in #{@cask} are: #{known_versions.join(', ')}"
+      end
+    end
+    unless supported_versions.include?(MACOS_VERSION)
+      puts <<-EOS.undent
+      Cask #{@cask} provides binaries for these OS versions: #{supported_versions.join(', ')}.
+      But you appear to be running on an unsupported version
+
+        #{MACOS_VERSION}
+
+      Therefore #{@cask} is not expected to work on your system.
+
+      EOS
+    end
+  end
+
   def method_missing(method, *args)
     poo = <<-EOPOO.undent
       Unexpected method #{method} called on caveats in Cask #{@cask}.

test/support/Casks/with-caveats.rb

@@ -16,6 +16,9 @@ class WithCaveats < TestCask
   caveats do
     puts 'Custom text via puts followed by DSL-generated text:'
     manual_installer('Installer.app')
+    # since all known OS versions are specified, no output should be
+    # generated here during the test
+    os_versions_only('10.0', '10.1', '10.2', '10.3', '10.3', '10.5', '10.6', '10.7', '10.8', '10.9')
   end
   caveats do
     # since both valid arches are specified, no output should be