From 4c9be9e4d8045436626e7a1e44385116a75d7164 Mon Sep 17 00:00:00 2001
From: Jamis Buck <jamis.buck@mongodb.com>
Date: Wed, 14 Oct 2026 13:30:11 -0600
Subject: [PATCH] RUBY-3982 Enable Lint/UnreachableCode cop

Remove the cop's exclusion from .rubocop_todo.yml and fix the two
offenses it reported.

Sections::PayloadOne.deserialize is a deliberate NotImplementedError
stub; delete the abandoned implementation below the raise and widen
the signature to match its call site.

In the unified test runner, drop a stray raise that made the intended
Error::ErrorMismatch raise unreachable in the isTimeoutError branch.
---
 .rubocop_todo.yml                 |  6 ------
 lib/mongo/protocol/serializers.rb | 10 +---------
 spec/runners/unified/test.rb      |  1 -
 3 files changed, 1 insertion(+), 16 deletions(-)

diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 11bb45a214..74c97f2ec8 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -55,12 +55,6 @@ Lint/UnderscorePrefixedVariableName:
     - 'spec/mongo/server/monitor_spec.rb'
     - 'spec/support/local_resource_registry.rb'
 
-# Offense count: 2
-Lint/UnreachableCode:
-  Exclude:
-    - 'lib/mongo/protocol/serializers.rb'
-    - 'spec/runners/unified/test.rb'
-
 # Offense count: 2
 # Configuration parameters: AllowedPatterns.
 # AllowedPatterns: (?-mix:(exactly|at_least|at_most)\(\d+\)\.times)
diff --git a/lib/mongo/protocol/serializers.rb b/lib/mongo/protocol/serializers.rb
index 0902fc6fe5..804081569c 100644
--- a/lib/mongo/protocol/serializers.rb
+++ b/lib/mongo/protocol/serializers.rb
@@ -319,16 +319,8 @@ def self.serialize(buffer, value, max_bson_size = nil, _validating_keys = nil)
           # @return [ Array<BSON::Document> ] Deserialized section.
           #
           # @since 2.5.0
-          def self.deserialize(buffer)
+          def self.deserialize(buffer, _options = {})
             raise NotImplementedError
-
-            start_size = buffer.length
-            section_size = buffer.get_int32 # get the size
-            end_size = start_size - section_size
-            buffer.get_cstring # get the identifier
-            documents = []
-            documents << BSON::Document.from_bson(buffer) until buffer.length == end_size
-            documents
           end
         end
       end
diff --git a/spec/runners/unified/test.rb b/spec/runners/unified/test.rb
index ecbde6fef5..6e123c281e 100644
--- a/spec/runners/unified/test.rb
+++ b/spec/runners/unified/test.rb
@@ -527,7 +527,6 @@ def execute_operation(op, propagate_errors: false)
             public_send(method_name, op)
           rescue Mongo::Error, bson_error, Mongo::Auth::Unauthorized, ArgumentError => e
             if expected_error.use('isTimeoutError') && !e.is_a?(Mongo::Error::TimeoutError)
-              raise e
               raise Error::ErrorMismatch, %,Expected TimeoutError ("isTimeoutError") but got #{e},
             end
             # isClientError doesn't actually mean a client error.