Merge pull request #9062 from baweaver/baweaver/platform-pattern-matching

Add pattern matching support to Gem::Platform

Author: hsbt

lib/rubygems/platform.rb

@@ -146,6 +146,37 @@ def to_s
     to_a.compact.join(@cpu.nil? ? "" : "-")
   end
 
+  ##
+  # Deconstructs the platform into an array for pattern matching.
+  # Returns [cpu, os, version].
+  #
+  #   Gem::Platform.new("x86_64-linux").deconstruct  #=> ["x86_64", "linux", nil]
+  #
+  # This enables array pattern matching:
+  #
+  #   case Gem::Platform.new("arm64-darwin-21")
+  #   in ["arm64", "darwin", version]
+  #     # version => "21"
+  #   end
+  alias_method :deconstruct, :to_a
+
+  ##
+  # Deconstructs the platform into a hash for pattern matching.
+  # Returns a hash with keys +:cpu+, +:os+, and +:version+.
+  #
+  #   Gem::Platform.new("x86_64-darwin-20").deconstruct_keys(nil)
+  #   #=> { cpu: "x86_64", os: "darwin", version: "20" }
+  #
+  # This enables hash pattern matching:
+  #
+  #   case Gem::Platform.new("x86_64-linux")
+  #   in cpu: "x86_64", os: "linux"
+  #     # Matches Linux on x86_64
+  #   end
+  def deconstruct_keys(keys)
+    { cpu: @cpu, os: @os, version: @version }
+  end
+
   ##
   # Is +other+ equal to this platform?  Two platforms are equal if they have
   # the same CPU, OS and version.

test/rubygems/test_gem_platform.rb

@@ -683,4 +683,38 @@ def assert_local_match(name)
   def refute_local_match(name)
     refute_match Gem::Platform.local, name
   end
+
+  def test_deconstruct
+    platform = Gem::Platform.new("x86_64-linux")
+    assert_equal ["x86_64", "linux", nil], platform.deconstruct
+  end
+
+  def test_deconstruct_keys
+    platform = Gem::Platform.new("x86_64-darwin-20")
+    assert_equal({ cpu: "x86_64", os: "darwin", version: "20" }, platform.deconstruct_keys(nil))
+  end
+
+  def test_pattern_matching_array
+    platform = Gem::Platform.new("arm64-darwin-21")
+    result =
+      case platform
+      in ["arm64", "darwin", version]
+        version
+      else
+        "no match"
+      end
+    assert_equal "21", result
+  end
+
+  def test_pattern_matching_hash
+    platform = Gem::Platform.new("x86_64-linux")
+    result =
+      case platform
+      in cpu: "x86_64", os: "linux"
+        "matched"
+      else
+        "no match"
+      end
+    assert_equal "matched", result
+  end
 end