Add pattern matching support to Net::HTTPExceptions

Implements deconstruct_keys for HTTP exception classes to enable
pattern matching on error handling.

Example:
  begin
    http.request(req)
  rescue => e
    case e
    in HTTPRetriableError[response: res] if res.code == '503'
      retry_with_backoff
    in HTTPClientException[message: /not found/]
      handle_not_found
    end
  end

Author: baweaver

lib/net/http/exceptions.rb

@@ -4,12 +4,37 @@ module Net
   # You cannot use Net::HTTPExceptions directly; instead, you must use
   # its subclasses.
   module HTTPExceptions
+    # Valid keys for pattern matching via #deconstruct_keys.
+    PATTERN_MATCHING_KEYS = %i[message response].freeze
+
     def initialize(msg, res)   #:nodoc:
       super msg
       @response = res
     end
     attr_reader :response
     alias data response    #:nodoc: obsolete
+
+    # Returns a hash of exception attributes for pattern matching.
+    #
+    # Valid keys are: +:message+, +:response+
+    #
+    # Example:
+    #
+    #   begin
+    #     http.request(req)
+    #   rescue => e
+    #     case e
+    #     in HTTPRetriableError[response: { code: '503' }]
+    #       retry_with_backoff
+    #     in HTTPClientException[response: { code: '404' }]
+    #       handle_not_found
+    #     end
+    #   end
+    #
+    def deconstruct_keys(keys)
+      valid_keys = keys ? PATTERN_MATCHING_KEYS & keys : PATTERN_MATCHING_KEYS
+      valid_keys.to_h { |key| [key, public_send(key)] }
+    end
   end
 
   class HTTPError < ProtocolError

test/net/http/test_httpexceptions.rb

@@ -0,0 +1,60 @@
+# frozen_string_literal: false
+require 'net/http'
+require 'test/unit'
+
+class HTTPExceptionsTest < Test::Unit::TestCase
+  def test_deconstruct_keys
+    response = Net::HTTPOK.new('1.1', '200', 'OK')
+    error = Net::HTTPError.new('test error', response)
+
+    keys = error.deconstruct_keys(nil)
+    assert_equal 'test error', keys[:message]
+    assert_equal response, keys[:response]
+  end
+
+  def test_deconstruct_keys_with_specific_keys
+    response = Net::HTTPNotFound.new('1.1', '404', 'Not Found')
+    error = Net::HTTPClientException.new('not found', response)
+
+    keys = error.deconstruct_keys([:message])
+    assert_equal({message: 'not found'}, keys)
+  end
+
+  def test_pattern_matching
+    response = Net::HTTPServiceUnavailable.new('1.1', '503', 'Service Unavailable')
+    error = Net::HTTPRetriableError.new('service unavailable', response)
+
+    begin
+      matched = instance_eval <<~RUBY, __FILE__, __LINE__ + 1
+        case error
+        in message: /unavailable/, response:
+          true
+        else
+          false
+        end
+      RUBY
+      assert_equal true, matched
+    rescue SyntaxError
+      omit "Pattern matching requires Ruby 2.7+"
+    end
+  end
+
+  def test_pattern_matching_with_response_attributes
+    response = Net::HTTPNotFound.new('1.1', '404', 'Not Found')
+    error = Net::HTTPClientException.new('not found', response)
+
+    begin
+      matched = instance_eval <<~RUBY, __FILE__, __LINE__ + 1
+        case error
+        in response: res if res.code == '404'
+          true
+        else
+          false
+        end
+      RUBY
+      assert_equal true, matched
+    rescue SyntaxError
+      omit "Pattern matching requires Ruby 2.7+"
+    end
+  end
+end