diagnostic: check if Xcode needs CLT installed.

Require the CLT on all but the latest version of macOS to avoid the
continuous workarounds for SDK weirdness.

2 files changed, 22 insertions, 4 deletions

diff --git a/Library/Homebrew/os/mac.rb b/Library/Homebrew/os/mac.rb
index 9215e3c96..ade801c42 100644
--- a/Library/Homebrew/os/mac.rb
+++ b/Library/Homebrew/os/mac.rb
@@ -31,16 +31,25 @@ module OS
       @version = nil
     end
 
-    def prerelease?
-      # TODO: bump version when new OS is released
-      version >= "10.14"
+    def latest_sdk_version
+      # TODO: bump version when new Xcode macOS SDK is released
+      Version.new "10.13"
+    end
+
+    def latest_stable_version
+      # TODO: bump version when new macOS is released
+      Version.new "10.13"
     end
 
     def outdated_release?
-      # TODO: bump version when new OS is released
+      # TODO: bump version when new macOS is released
       version < "10.11"
     end
 
+    def prerelease?
+      version > latest_stable_version
+    end
+
     def cat
       version.to_sym
     end
diff --git a/Library/Homebrew/os/mac/xcode.rb b/Library/Homebrew/os/mac/xcode.rb
index 96be56e3b..ae725d948 100644
--- a/Library/Homebrew/os/mac/xcode.rb
+++ b/Library/Homebrew/os/mac/xcode.rb
@@ -40,6 +40,15 @@ module OS
         version < minimum_version
       end
 
+      def latest_sdk_version?
+        OS::Mac.version == OS::Mac.latest_sdk_version
+      end
+
+      def needs_clt_installed?
+        return false if latest_sdk_version?
+        without_clt?
+      end
+
       def outdated?
         return false unless installed?
         version < latest_version