Remove Version#empty?.

Library/Homebrew/resource.rb

@@ -195,8 +195,10 @@ class Resource < Downloadable
     return super() if val.nil?
 
     @version = case val
-    when String  then Version.create(val)
+    when String
-    when Version then val
+      val.blank? ? Version::NULL : Version.new(val)
+    when Version
+      val
     else
       # TODO: This can probably go if/when typechecking is enforced in taps.
       raise TypeError, "version '#{val.inspect}' should be a string"

Library/Homebrew/test/os/os_spec.rb

@@ -1,9 +1,19 @@
 # frozen_string_literal: true
 
 describe OS do
-  describe ".kernel_version" do
+  describe "::kernel_version" do
-    it "is not empty" do
+    it "is not NULL" do
-      expect(described_class.kernel_version).not_to be_empty
+      expect(described_class.kernel_version).not_to be_null
+    end
+  end
+
+  describe "::kernel_name" do
+    it "returns Linux on Linux", :needs_linux do
+      expect(described_class.kernel_name).to eq "Linux"
+    end
+
+    it "returns Darwin on macOS", :needs_macos do
+      expect(described_class.kernel_name).to eq "Darwin"
     end
   end
 end

Library/Homebrew/test/version_spec.rb

@@ -240,16 +240,6 @@ describe Version do
     expect(versions.sort_by { |v| described_class.create(v) }).to eq(versions)
   end
 
-  describe "#empty?" do
-    it "returns true if version is empty" do
-      expect(described_class.create("").empty?).to be(true)
-    end
-
-    it "returns false if version is not empty" do
-      expect(described_class.create("1.2.3").empty?).to be(false)
-    end
-  end
-
   specify "hash equality" do
     v1 = described_class.create("0.1.0")
     v2 = described_class.create("0.1.0")

Library/Homebrew/version.rb

@@ -494,7 +494,10 @@ class Version
   def initialize(val, detected_from_url: false)
     raise TypeError, "Version value must be a string; got a #{val.class} (#{val})" unless val.respond_to?(:to_str)
 
-    @version = val.to_str
+    version = val.to_str
+    raise ArgumentError, "Version must not be empty" if version.blank?
+
+    @version = version
     @detected_from_url = detected_from_url
   end
 
@@ -679,11 +682,6 @@ class Version
     major_minor_patch.empty? ? NULL : self.class.new(major_minor_patch.join("."))
   end
 
-  sig { returns(T::Boolean) }
-  def empty?
-    version&.empty? || false
-  end
-
   sig { returns(Integer) }
   def hash
     version.hash