Skip truncate when offset == size. Fix static analysys.

lib/gitlab/ci/trace/chunked_io.rb

@@ -135,6 +135,7 @@ module Gitlab
 
         def truncate(offset)
           raise ArgumentError, 'Outside of file' if offset > size
+          return if offset == size # Skip the following process as it doesn't affect anything
 
           @tell = offset
           @size = offset

spec/models/ci/build_trace_chunk_spec.rb

@@ -345,7 +345,7 @@ describe Ci::BuildTraceChunk, :clean_gitlab_redis_shared_state do
     shared_examples_for 'deletes all build_trace_chunk and data in redis' do
       it do
         Gitlab::Redis::SharedState.with do |redis|
-          expect(redis.scan_each(match: "gitlab:ci:trace:?:chunks:?").to_a.count).to eq(3)
+          expect(redis.scan_each(match: "gitlab:ci:trace:?:chunks:?").to_a.size).to eq(3)
         end
 
         expect(described_class.count).to eq(3)
@@ -355,14 +355,16 @@ describe Ci::BuildTraceChunk, :clean_gitlab_redis_shared_state do
         expect(described_class.count).to eq(0)
 
         Gitlab::Redis::SharedState.with do |redis|
-          expect(redis.scan_each(match: "gitlab:ci:trace:?:chunks:?").to_a.count).to eq(0)
+          expect(redis.scan_each(match: "gitlab:ci:trace:?:chunks:?").to_a.size).to eq(0)
         end
       end
     end
 
-    context 'when build is destroyed' do
+    context 'when traces are archived' do
       let(:subject) do
-        project.builds.destroy_all
+        project.builds.each do |build|
+          build.success!
+        end
       end
 
       it_behaves_like 'deletes all build_trace_chunk and data in redis'