Implement smart cobertura class path correction

As we parse the cobertura XML, based on the given project full path and
pipeline worktree paths, we will make some assumptions on how to
determine the correct path of filenames that are not relative to the
project root.

app/models/ci/build.rb

@@ -916,8 +916,20 @@ module Ci
     end
 
     def collect_coverage_reports!(coverage_report)
+      project_path, worktree_paths = if Feature.enabled?(:smart_cobertura_parser, project)
+                                       # If the flag is disabled, we intentionally pass nil
+                                       # for both project_path and worktree_paths to fallback
+                                       # to the non-smart behavior of the parser
+                                       [project.full_path, pipeline.all_worktree_paths]
+                                     end
+
       each_report(Ci::JobArtifact::COVERAGE_REPORT_FILE_TYPES) do |file_type, blob|
-        Gitlab::Ci::Parsers.fabricate!(file_type).parse!(blob, coverage_report)
+        Gitlab::Ci::Parsers.fabricate!(file_type).parse!(
+          blob,
+          coverage_report,
+          project_path: project_path,
+          worktree_paths: worktree_paths
+        )
       end
 
       coverage_report

app/models/ci/pipeline.rb

@@ -975,7 +975,7 @@ module Ci
 
     def coverage_reports
       Gitlab::Ci::Reports::CoverageReports.new.tap do |coverage_reports|
-        latest_report_builds(Ci::JobArtifact.coverage_reports).each do |build|
+        latest_report_builds(Ci::JobArtifact.coverage_reports).includes(:project).find_each do |build|
           build.collect_coverage_reports!(coverage_reports)
         end
       end

changelogs/unreleased/eb-cobertura-background-fix.yml

+---
+title: Implement smart cobertura class path correction
+merge_request: 48048
+author:
+type: changed

config/feature_flags/development/smart_cobertura_parser.yml

+---
+name: smart_cobertura_parser
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/48048
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/284822
+milestone: '13.7'
+type: development
+group: group::testing
+default_enabled: false

lib/gitlab/ci/parsers/coverage/cobertura.rb

@@ -5,50 +5,113 @@ module Gitlab
     module Parsers
       module Coverage
         class Cobertura
-          CoberturaParserError = Class.new(Gitlab::Ci::Parsers::ParserError)
+          InvalidXMLError = Class.new(Gitlab::Ci::Parsers::ParserError)
+          InvalidLineInformationError = Class.new(Gitlab::Ci::Parsers::ParserError)
 
-          def parse!(xml_data, coverage_report)
+          GO_SOURCE_PATTERN = '/usr/local/go/src'
+          MAX_SOURCES = 100
+
+          def parse!(xml_data, coverage_report, project_path: nil, worktree_paths: nil)
             root = Hash.from_xml(xml_data)
 
-            parse_all(root, coverage_report)
+            context = {
+              project_path: project_path,
+              paths: worktree_paths&.to_set,
+              sources: []
+            }
+
+            parse_all(root, coverage_report, context)
           rescue Nokogiri::XML::SyntaxError
-            raise CoberturaParserError, "XML parsing failed"
-          rescue
-            raise CoberturaParserError, "Cobertura parsing failed"
+            raise InvalidXMLError, "XML parsing failed"
           end
 
           private
 
-          def parse_all(root, coverage_report)
+          def parse_all(root, coverage_report, context)
             return unless root.present?
 
             root.each do |key, value|
-              parse_node(key, value, coverage_report)
+              parse_node(key, value, coverage_report, context)
             end
           end
 
-          def parse_node(key, value, coverage_report)
-            return if key == 'sources'
-
-            if key == 'class'
+          def parse_node(key, value, coverage_report, context)
+            if key == 'sources' && value['source'].present?
+              parse_sources(value['source'], context)
+            elsif key == 'package'
               Array.wrap(value).each do |item|
-                parse_class(item, coverage_report)
+                parse_package(item, coverage_report, context)
+              end
+            elsif key == 'class'
+              # This means the cobertura XML does not have classes within package nodes.
+              # This is possible in some cases like in simple JS project structures
+              # running Jest.
+              Array.wrap(value).each do |item|
+                parse_class(item, coverage_report, context)
               end
             elsif value.is_a?(Hash)
-              parse_all(value, coverage_report)
+              parse_all(value, coverage_report, context)
             elsif value.is_a?(Array)
               value.each do |item|
-                parse_all(item, coverage_report)
+                parse_all(item, coverage_report, context)
+              end
             end
           end
+
+          def parse_sources(sources, context)
+            return unless context[:project_path] && context[:paths]
+
+            sources = Array.wrap(sources)
+
+            # TODO: Go cobertura has a different format with how their packages
+            # are included in the filename. So we can't rely on the sources.
+            # We'll deal with this later.
+            return if sources.include?(GO_SOURCE_PATTERN)
+
+            sources.each do |source|
+              source = build_source_path(source, context)
+              context[:sources] << source if source.present?
+            end
+          end
+
+          def build_source_path(source, context)
+            # | raw source                  | extracted  |
+            # |-----------------------------|------------|
+            # | /builds/foo/test/SampleLib/ | SampleLib/ |
+            # | /builds/foo/test/something  | something  |
+            # | /builds/foo/test/           | nil        |
+            # | /builds/foo/test            | nil        |
+            source.split("#{context[:project_path]}/", 2)[1]
+          end
+
+          def parse_package(package, coverage_report, context)
+            classes = package.dig('classes', 'class')
+            return unless classes.present?
+
+            matched_filenames = Array.wrap(classes).map do |item|
+              parse_class(item, coverage_report, context)
             end
 
-          def parse_class(file, coverage_report)
+            # Remove these filenames from the paths to avoid conflict
+            # with other packages that may contain the same class filenames
+            remove_matched_filenames(matched_filenames, context)
+          end
+
+          def remove_matched_filenames(filenames, context)
+            return unless context[:paths]
+
+            filenames.each { |f| context[:paths].delete(f) }
+          end
+
+          def parse_class(file, coverage_report, context)
             return unless file["filename"].present? && file["lines"].present?
 
             parsed_lines = parse_lines(file["lines"])
+            filename = determine_filename(file["filename"], context)
+
+            coverage_report.add_file(filename, Hash[parsed_lines]) if filename
 
-            coverage_report.add_file(file["filename"], Hash[parsed_lines])
+            filename
           end
 
           def parse_lines(lines)
@@ -58,6 +121,27 @@ module Gitlab
               # Using `Integer()` here to raise exception on invalid values
               [Integer(line["number"]), Integer(line["hits"])]
             end
+          rescue
+            raise InvalidLineInformationError, "Line information had invalid values"
+          end
+
+          def determine_filename(filename, context)
+            return filename unless context[:sources].any?
+
+            full_filename = nil
+
+            context[:sources].each_with_index do |source, index|
+              break if index >= MAX_SOURCES
+              break if full_filename = check_source(source, filename, context)
+            end
+
+            full_filename
+          end
+
+          def check_source(source, filename, context)
+            full_path = File.join(source, filename)
+
+            return full_path if context[:paths].include?(full_path)
           end
         end
       end

spec/factories/ci/job_artifacts.rb

@@ -229,6 +229,16 @@ FactoryBot.define do
       end
     end
 
+    trait :coverage_with_paths_not_relative_to_project_root do
+      file_type { :cobertura }
+      file_format { :gzip }
+
+      after(:build) do |artifact, evaluator|
+        artifact.file = fixture_file_upload(
+          Rails.root.join('spec/fixtures/cobertura/coverage_with_paths_not_relative_to_project_root.xml.gz'), 'application/x-gzip')
+      end
+    end
+
     trait :coverage_with_corrupted_data do
       file_type { :cobertura }
       file_format { :gzip }

spec/lib/gitlab/ci/parsers/coverage/cobertura_spec.rb

@@ -4,114 +4,132 @@ require 'fast_spec_helper'
 
 RSpec.describe Gitlab::Ci::Parsers::Coverage::Cobertura do
   describe '#parse!' do
-    subject { described_class.new.parse!(cobertura, coverage_report) }
+    subject(:parse_report) { described_class.new.parse!(cobertura, coverage_report, project_path: project_path, worktree_paths: paths) }
 
     let(:coverage_report) { Gitlab::Ci::Reports::CoverageReports.new }
+    let(:project_path) { 'foo/bar' }
+    let(:paths) { ['app/user.rb'] }
+
+    let(:cobertura) do
+      <<~EOF
+      <coverage>
+        #{sources_xml}
+        #{classes_xml}
+      </coverage>
+      EOF
+    end
 
     context 'when data is Cobertura style XML' do
+      shared_examples_for 'ignoring sources, project_path, and worktree_paths' do
         context 'when there is no <class>' do
-        let(:cobertura) { '' }
+          let(:classes_xml) { '' }
 
           it 'parses XML and returns empty coverage' do
-          expect { subject }.not_to raise_error
-
-          expect(coverage_report.files).to eq({})
-        end
-      end
-
-      context 'when there is a <sources>' do
-        shared_examples_for 'ignoring sources' do
-          it 'parses XML without errors' do
-            expect { subject }.not_to raise_error
+            expect { parse_report }.not_to raise_error
 
             expect(coverage_report.files).to eq({})
           end
         end
 
-        context 'and has a single source' do
-          let(:cobertura) do
-            <<-EOF.strip_heredoc
-            <sources>
-              <source>project/src</source>
-            </sources>
+        context 'when there is a single <class>' do
+          context 'with no lines' do
+            let(:classes_xml) do
+              <<~EOF
+              <packages><package name="app"><classes>
+                <class filename="app.rb"></class>
+              </classes></package></packages>
               EOF
             end
 
-          it_behaves_like 'ignoring sources'
-        end
-
-        context 'and has multiple sources' do
-          let(:cobertura) do
-            <<-EOF.strip_heredoc
-            <sources>
-              <source>project/src/foo</source>
-              <source>project/src/bar</source>
-            </sources>
-            EOF
-          end
+            it 'parses XML and returns empty coverage' do
+              expect { parse_report }.not_to raise_error
 
-          it_behaves_like 'ignoring sources'
+              expect(coverage_report.files).to eq({})
             end
           end
 
-      context 'when there is a single <class>' do
-        context 'with no lines' do
-          let(:cobertura) do
-            <<-EOF.strip_heredoc
-            <classes><class filename="app.rb"></class></classes>
+          context 'with a single line' do
+            let(:classes_xml) do
+              <<~EOF
+              <packages><package name="app"><classes>
+                <class filename="app.rb"><lines>
+                  <line number="1" hits="2"/>
+                </lines></class>
+              </classes></package></packages>
               EOF
             end
 
-          it 'parses XML and returns empty coverage' do
-            expect { subject }.not_to raise_error
+            it 'parses XML and returns a single file with coverage' do
+              expect { parse_report }.not_to raise_error
 
-            expect(coverage_report.files).to eq({})
+              expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 2 } })
             end
           end
 
-        context 'with a single line' do
-          let(:cobertura) do
-            <<-EOF.strip_heredoc
-            <classes>
+          context 'without a package parent' do
+            let(:classes_xml) do
+              <<~EOF
+              <packages>
                 <class filename="app.rb"><lines>
                   <line number="1" hits="2"/>
                 </lines></class>
-            </classes>
+              </packages>
               EOF
             end
 
             it 'parses XML and returns a single file with coverage' do
-            expect { subject }.not_to raise_error
+              expect { parse_report }.not_to raise_error
 
               expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 2 } })
             end
           end
 
-        context 'with multipe lines and methods info' do
-          let(:cobertura) do
-            <<-EOF.strip_heredoc
-            <classes>
+          context 'with multiple lines and methods info' do
+            let(:classes_xml) do
+              <<~EOF
+              <packages><package name="app"><classes>
                 <class filename="app.rb"><methods/><lines>
                   <line number="1" hits="2"/>
                   <line number="2" hits="0"/>
                 </lines></class>
-            </classes>
+              </classes></package></packages>
               EOF
             end
 
             it 'parses XML and returns a single file with coverage' do
-            expect { subject }.not_to raise_error
+              expect { parse_report }.not_to raise_error
 
               expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 2, 2 => 0 } })
             end
           end
         end
 
-      context 'when there are multipe <class>' do
+        context 'when there are multiple <class>' do
+          context 'without a package parent' do
+            let(:classes_xml) do
+              <<~EOF
+              <packages>
+                <class filename="app.rb"><methods/><lines>
+                  <line number="1" hits="2"/>
+                </lines></class>
+                <class filename="foo.rb"><methods/><lines>
+                  <line number="6" hits="1"/>
+                </lines></class>
+              </packages>
+              EOF
+            end
+
+            it 'parses XML and returns coverage information per class' do
+              expect { parse_report }.not_to raise_error
+
+              expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 2 }, 'foo.rb' => { 6 => 1 } })
+            end
+          end
+
           context 'with the same filename and different lines' do
-          let(:cobertura) do
-            <<-EOF.strip_heredoc
-            <classes>
+            let(:classes_xml) do
+              <<~EOF
+              <packages><package name="app"><classes>
                 <class filename="app.rb"><methods/><lines>
                   <line number="1" hits="2"/>
                   <line number="2" hits="0"/>
@@ -120,21 +138,21 @@ RSpec.describe Gitlab::Ci::Parsers::Coverage::Cobertura do
                   <line number="6" hits="1"/>
                   <line number="7" hits="1"/>
                 </lines></class>
-            </classes>
+              </classes></package></packages>
               EOF
             end
 
             it 'parses XML and returns a single file with merged coverage' do
-            expect { subject }.not_to raise_error
+              expect { parse_report }.not_to raise_error
 
               expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 2, 2 => 0, 6 => 1, 7 => 1 } })
             end
           end
 
           context 'with the same filename and lines' do
-          let(:cobertura) do
-            <<-EOF.strip_heredoc
-            <packages><package><classes>
+            let(:classes_xml) do
+              <<~EOF
+              <packages><package name="app"><classes>
                 <class filename="app.rb"><methods/><lines>
                   <line number="1" hits="2"/>
                   <line number="2" hits="0"/>
@@ -148,16 +166,16 @@ RSpec.describe Gitlab::Ci::Parsers::Coverage::Cobertura do
             end
 
             it 'parses XML and returns a single file with summed-up coverage' do
-            expect { subject }.not_to raise_error
+              expect { parse_report }.not_to raise_error
 
               expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 3, 2 => 1 } })
             end
           end
 
           context 'with missing filename' do
-          let(:cobertura) do
-            <<-EOF.strip_heredoc
-            <classes>
+            let(:classes_xml) do
+              <<~EOF
+              <packages><package name="app"><classes>
                 <class filename="app.rb"><methods/><lines>
                   <line number="1" hits="2"/>
                   <line number="2" hits="0"/>
@@ -166,21 +184,21 @@ RSpec.describe Gitlab::Ci::Parsers::Coverage::Cobertura do
                   <line number="6" hits="1"/>
                   <line number="7" hits="1"/>
                 </lines></class>
-            </classes>
+              </classes></package></packages>
               EOF
             end
 
             it 'parses XML and ignores class with missing name' do
-            expect { subject }.not_to raise_error
+              expect { parse_report }.not_to raise_error
 
               expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 2, 2 => 0 } })
             end
           end
 
           context 'with invalid line information' do
-          let(:cobertura) do
-            <<-EOF.strip_heredoc
-            <classes>
+            let(:classes_xml) do
+              <<~EOF
+              <packages><package name="app"><classes>
                 <class filename="app.rb"><methods/><lines>
                   <line number="1" hits="2"/>
                   <line number="2" hits="0"/>
@@ -189,22 +207,487 @@ RSpec.describe Gitlab::Ci::Parsers::Coverage::Cobertura do
                   <line null="test" hits="1"/>
                   <line number="7" hits="1"/>
                 </lines></class>
-            </classes>
+              </classes></package></packages>
+              EOF
+            end
+
+            it 'raises an error' do
+              expect { parse_report }.to raise_error(described_class::InvalidLineInformationError)
+            end
+          end
+        end
+      end
+
+      context 'when there is no <sources>' do
+        let(:sources_xml) { '' }
+
+        it_behaves_like 'ignoring sources, project_path, and worktree_paths'
+      end
+
+      context 'when there is a <sources>' do
+        context 'and has a single source with a pattern for Go projects' do
+          let(:project_path) { 'local/go' } # Make sure we're not making false positives
+          let(:sources_xml) do
+            <<~EOF
+            <sources>
+              <source>/usr/local/go/src</source>
+            </sources>
+            EOF
+          end
+
+          it_behaves_like 'ignoring sources, project_path, and worktree_paths'
+        end
+
+        context 'and has multiple sources with a pattern for Go projects' do
+          let(:project_path) { 'local/go' } # Make sure we're not making false positives
+          let(:sources_xml) do
+            <<~EOF
+            <sources>
+              <source>/usr/local/go/src</source>
+              <source>/go/src</source>
+            </sources>
+            EOF
+          end
+
+          it_behaves_like 'ignoring sources, project_path, and worktree_paths'
+        end
+
+        context 'and has a single source but already is at the project root path' do
+          let(:sources_xml) do
+            <<~EOF
+            <sources>
+              <source>builds/#{project_path}</source>
+            </sources>
+            EOF
+          end
+
+          it_behaves_like 'ignoring sources, project_path, and worktree_paths'
+        end
+
+        context 'and has multiple sources but already are at the project root path' do
+          let(:sources_xml) do
+            <<~EOF
+            <sources>
+              <source>builds/#{project_path}/</source>
+              <source>builds/somewhere/#{project_path}</source>
+            </sources>
+            EOF
+          end
+
+          it_behaves_like 'ignoring sources, project_path, and worktree_paths'
+        end
+
+        context 'and has a single source that is not at the project root path' do
+          let(:sources_xml) do
+            <<~EOF
+            <sources>
+              <source>builds/#{project_path}/app</source>
+            </sources>
+            EOF
+          end
+
+          context 'when there is no <class>' do
+            let(:classes_xml) { '' }
+
+            it 'parses XML and returns empty coverage' do
+              expect { parse_report }.not_to raise_error
+
+              expect(coverage_report.files).to eq({})
+            end
+          end
+
+          context 'when there is a single <class>' do
+            context 'with no lines' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages><package name="app"><classes>
+                  <class filename="user.rb"></class>
+                </classes></package></packages>
+                EOF
+              end
+
+              it 'parses XML and returns empty coverage' do
+                expect { parse_report }.not_to raise_error
+
+                expect(coverage_report.files).to eq({})
+              end
+            end
+
+            context 'with a single line but the filename cannot be determined based on extracted source and worktree paths' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages><package name="app"><classes>
+                  <class filename="member.rb"><lines>
+                    <line number="1" hits="2"/>
+                  </lines></class>
+                </classes></package></packages>
+                EOF
+              end
+
+              it 'parses XML and returns empty coverage' do
+                expect { parse_report }.not_to raise_error
+
+                expect(coverage_report.files).to eq({})
+              end
+            end
+
+            context 'with a single line' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages><package name="app"><classes>
+                  <class filename="user.rb"><lines>
+                    <line number="1" hits="2"/>
+                  </lines></class>
+                </classes></package></packages>
+                EOF
+              end
+
+              it 'parses XML and returns a single file with the filename relative to project root' do
+                expect { parse_report }.not_to raise_error
+
+                expect(coverage_report.files).to eq({ 'app/user.rb' => { 1 => 2 } })
+              end
+            end
+
+            context 'with multiple lines and methods info' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages><package name="app"><classes>
+                  <class filename="user.rb"><methods/><lines>
+                    <line number="1" hits="2"/>
+                    <line number="2" hits="0"/>
+                  </lines></class>
+                </classes></package></packages>
+                EOF
+              end
+
+              it 'parses XML and returns a single file with the filename relative to project root' do
+                expect { parse_report }.not_to raise_error
+
+                expect(coverage_report.files).to eq({ 'app/user.rb' => { 1 => 2, 2 => 0 } })
+              end
+            end
+          end
+
+          context 'when there are multiple <class>' do
+            context 'with the same filename but the filename cannot be determined based on extracted source and worktree paths' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages><package name="app"><classes>
+                  <class filename="member.rb"><methods/><lines>
+                    <line number="1" hits="2"/>
+                    <line number="2" hits="0"/>
+                  </lines></class>
+                  <class filename="member.rb"><methods/><lines>
+                    <line number="6" hits="1"/>
+                    <line number="7" hits="1"/>
+                  </lines></class>
+                </classes></package></packages>
+                EOF
+              end
+
+              it 'parses XML and returns empty coverage' do
+                expect { parse_report }.not_to raise_error
+
+                expect(coverage_report.files).to eq({})
+              end
+            end
+
+            context 'without a parent package' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages>
+                  <class filename="user.rb"><methods/><lines>
+                    <line number="1" hits="2"/>
+                    <line number="2" hits="0"/>
+                  </lines></class>
+                  <class filename="user.rb"><methods/><lines>
+                    <line number="6" hits="1"/>
+                    <line number="7" hits="1"/>
+                  </lines></class>
+                </packages>
+                EOF
+              end
+
+              it 'parses XML and returns coverage information with the filename relative to project root' do
+                expect { parse_report }.not_to raise_error
+
+                expect(coverage_report.files).to eq({ 'app/user.rb' => { 1 => 2, 2 => 0, 6 => 1, 7 => 1 } })
+              end
+            end
+
+            context 'with the same filename and different lines' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages><package name="app"><classes>
+                  <class filename="user.rb"><methods/><lines>
+                    <line number="1" hits="2"/>
+                    <line number="2" hits="0"/>
+                  </lines></class>
+                  <class filename="user.rb"><methods/><lines>
+                    <line number="6" hits="1"/>
+                    <line number="7" hits="1"/>
+                  </lines></class>
+                </classes></package></packages>
+                EOF
+              end
+
+              it 'parses XML and returns a single file with merged coverage, and with the filename relative to project root' do
+                expect { parse_report }.not_to raise_error
+
+                expect(coverage_report.files).to eq({ 'app/user.rb' => { 1 => 2, 2 => 0, 6 => 1, 7 => 1 } })
+              end
+            end
+
+            context 'with the same filename and lines' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages><package name="app"><classes>
+                  <class filename="user.rb"><methods/><lines>
+                    <line number="1" hits="2"/>
+                    <line number="2" hits="0"/>
+                  </lines></class>
+                  <class filename="user.rb"><methods/><lines>
+                    <line number="1" hits="1"/>
+                    <line number="2" hits="1"/>
+                  </lines></class>
+                </classes></package></packages>
+                EOF
+              end
+
+              it 'parses XML and returns a single file with summed-up coverage, and with the filename relative to project root' do
+                expect { parse_report }.not_to raise_error
+
+                expect(coverage_report.files).to eq({ 'app/user.rb' => { 1 => 3, 2 => 1 } })
+              end
+            end
+
+            context 'with missing filename' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages><package name="app"><classes>
+                  <class filename="user.rb"><methods/><lines>
+                    <line number="1" hits="2"/>
+                    <line number="2" hits="0"/>
+                  </lines></class>
+                  <class><methods/><lines>
+                    <line number="6" hits="1"/>
+                    <line number="7" hits="1"/>
+                  </lines></class>
+                </classes></package></packages>
+                EOF
+              end
+
+              it 'parses XML and ignores class with missing name' do
+                expect { parse_report }.not_to raise_error
+
+                expect(coverage_report.files).to eq({ 'app/user.rb' => { 1 => 2, 2 => 0 } })
+              end
+            end
+
+            context 'with filename that cannot be determined based on extracted source and worktree paths' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages><package name="app"><classes>
+                  <class filename="user.rb"><methods/><lines>
+                    <line number="1" hits="2"/>
+                    <line number="2" hits="0"/>
+                  </lines></class>
+                  <class filename="member.rb"><methods/><lines>
+                    <line number="6" hits="1"/>
+                    <line number="7" hits="1"/>
+                  </lines></class>
+                </classes></package></packages>
+                EOF
+              end
+
+              it 'parses XML and ignores class with undetermined filename' do
+                expect { parse_report }.not_to raise_error
+
+                expect(coverage_report.files).to eq({ 'app/user.rb' => { 1 => 2, 2 => 0 } })
+              end
+            end
+
+            context 'with invalid line information' do
+              let(:classes_xml) do
+                <<~EOF
+                <packages><package name="app"><classes>
+                  <class filename="user.rb"><methods/><lines>
+                    <line number="1" hits="2"/>
+                    <line number="2" hits="0"/>
+                  </lines></class>
+                  <class filename="user.rb"><methods/><lines>
+                    <line null="test" hits="1"/>
+                    <line number="7" hits="1"/>
+                  </lines></class>
+                </classes></package></packages>
                 EOF
               end
 
               it 'raises an error' do
-            expect { subject }.to raise_error(described_class::CoberturaParserError)
+                expect { parse_report }.to raise_error(described_class::InvalidLineInformationError)
+              end
+            end
+          end
+        end
+
+        context 'and has multiple sources that are not at the project root path' do
+          let(:sources_xml) do
+            <<~EOF
+            <sources>
+              <source>builds/#{project_path}/app1/</source>
+              <source>builds/#{project_path}/app2/</source>
+            </sources>
+            EOF
+          end
+
+          context 'and a class filename is available under multiple extracted sources' do
+            let(:paths) { ['app1/user.rb', 'app2/user.rb'] }
+
+            let(:classes_xml) do
+              <<~EOF
+              <package name="app1">
+                <classes>
+                  <class filename="user.rb"><lines>
+                    <line number="1" hits="2"/>
+                  </lines></class>
+                </classes>
+              </package>
+              <package name="app2">
+                <classes>
+                  <class filename="user.rb"><lines>
+                    <line number="2" hits="3"/>
+                  </lines></class>
+                </classes>
+              </package>
+              EOF
+            end
+
+            it 'parses XML and returns the files with the filename relative to project root' do
+              expect { parse_report }.not_to raise_error
+
+              expect(coverage_report.files).to eq({
+                'app1/user.rb' => { 1 => 2 },
+                'app2/user.rb' => { 2 => 3 }
+              })
+            end
+          end
+
+          context 'and a class filename is available under one of the extracted sources' do
+            let(:paths) { ['app1/member.rb', 'app2/user.rb', 'app2/pet.rb'] }
+
+            let(:classes_xml) do
+              <<~EOF
+              <packages><package name="app"><classes>
+                <class filename="user.rb"><lines>
+                  <line number="1" hits="2"/>
+                </lines></class>
+              </classes></package></packages>
+              EOF
+            end
+
+            it 'parses XML and returns a single file with the filename relative to project root using the extracted source where it is first found under' do
+              expect { parse_report }.not_to raise_error
+
+              expect(coverage_report.files).to eq({ 'app2/user.rb' => { 1 => 2 } })
+            end
+          end
+
+          context 'and a class filename is not found under any of the extracted sources' do
+            let(:paths) { ['app1/member.rb', 'app2/pet.rb'] }
+
+            let(:classes_xml) do
+              <<~EOF
+              <packages><package name="app"><classes>
+                <class filename="user.rb"><lines>
+                  <line number="1" hits="2"/>
+                </lines></class>
+              </classes></package></packages>
+              EOF
+            end
+
+            it 'parses XML and returns empty coverage' do
+              expect { parse_report }.not_to raise_error
+
+              expect(coverage_report.files).to eq({})
+            end
+          end
+
+          context 'and a class filename is not found under any of the extracted sources within the iteratable limit' do
+            let(:paths) { ['app2/user.rb'] }
+
+            let(:classes_xml) do
+              <<~EOF
+              <packages><package name="app"><classes>
+                <class filename="record.rb"><lines>
+                  <line number="1" hits="2"/>
+                </lines></class>
+                <class filename="user.rb"><lines>
+                  <line number="1" hits="2"/>
+                </lines></class>
+              </classes></package></packages>
+              EOF
+            end
+
+            before do
+              stub_const("#{described_class}::MAX_SOURCES", 1)
+            end
+
+            it 'parses XML and returns empty coverage' do
+              expect { parse_report }.not_to raise_error
+
+              expect(coverage_report.files).to eq({})
             end
           end
         end
       end
 
+      shared_examples_for 'non-smart parsing' do
+        let(:sources_xml) do
+          <<~EOF
+          <sources>
+            <source>builds/foo/bar/app</source>
+          </sources>
+          EOF
+        end
+
+        let(:classes_xml) do
+          <<~EOF
+          <packages><package name="app"><classes>
+            <class filename="user.rb"><lines>
+              <line number="1" hits="2"/>
+            </lines></class>
+          </classes></package></packages>
+          EOF
+        end
+
+        it 'parses XML and returns filenames unchanged just as how they are found in the class node' do
+          expect { parse_report }.not_to raise_error
+
+          expect(coverage_report.files).to eq({ 'user.rb' => { 1 => 2 } })
+        end
+      end
+
+      context 'when project_path is not present' do
+        let(:project_path) { nil }
+        let(:paths) { ['app/user.rb'] }
+
+        it_behaves_like 'non-smart parsing'
+      end
+
+      context 'when worktree_paths is not present' do
+        let(:project_path) { 'foo/bar' }
+        let(:paths) { nil }
+
+        it_behaves_like 'non-smart parsing'
+      end
+    end
+
     context 'when data is not Cobertura style XML' do
       let(:cobertura) { { coverage: '12%' }.to_json }
 
       it 'raises an error' do
-        expect { subject }.to raise_error(described_class::CoberturaParserError)
+        expect { parse_report }.to raise_error(described_class::InvalidXMLError)
       end
     end
   end

spec/models/ci/build_spec.rb

@@ -4059,13 +4059,40 @@ RSpec.describe Ci::Build do
         end
       end
 
+      context 'when there is a Cobertura coverage report with class filename paths not relative to project root' do
+        before do
+          allow(build.project).to receive(:full_path).and_return('root/javademo')
+          allow(build.pipeline).to receive(:all_worktree_paths).and_return(['src/main/java/com/example/javademo/User.java'])
+
+          create(:ci_job_artifact, :coverage_with_paths_not_relative_to_project_root, job: build, project: build.project)
+        end
+
+        it 'parses blobs and add the results to the coverage report with corrected paths' do
+          expect { subject }.not_to raise_error
+
+          expect(coverage_report.files.keys).to match_array(['src/main/java/com/example/javademo/User.java'])
+        end
+
+        context 'and smart_cobertura_parser feature flag is disabled' do
+          before do
+            stub_feature_flags(smart_cobertura_parser: false)
+          end
+
+          it 'parses blobs and add the results to the coverage report with unmodified paths' do
+            expect { subject }.not_to raise_error
+
+            expect(coverage_report.files.keys).to match_array(['com/example/javademo/User.java'])
+          end
+        end
+      end
+
       context 'when there is a corrupted Cobertura coverage report' do
         before do
           create(:ci_job_artifact, :coverage_with_corrupted_data, job: build, project: build.project)
         end
 
         it 'raises an error' do
-          expect { subject }.to raise_error(Gitlab::Ci::Parsers::Coverage::Cobertura::CoberturaParserError)
+          expect { subject }.to raise_error(Gitlab::Ci::Parsers::Coverage::Cobertura::InvalidLineInformationError)
         end
       end
     end

spec/models/ci/pipeline_spec.rb

@@ -3426,6 +3426,16 @@ RSpec.describe Ci::Pipeline, :mailer, factory_default: :keep do
         ])
       end
 
+      it 'does not execute N+1 queries' do
+        single_build_pipeline = create(:ci_empty_pipeline, status: :created, project: project)
+        single_rspec = create(:ci_build, :success, name: 'rspec', pipeline: single_build_pipeline, project: project)
+        create(:ci_job_artifact, :cobertura, job: single_rspec, project: project)
+
+        control = ActiveRecord::QueryRecorder.new { single_build_pipeline.coverage_reports }
+
+        expect { subject }.not_to exceed_query_limit(control)
+      end
+
       context 'when builds are retried' do
         let!(:build_rspec) { create(:ci_build, :retried, :success, name: 'rspec', pipeline: pipeline, project: project) }
         let!(:build_golang) { create(:ci_build, :retried, :success, name: 'golang', pipeline: pipeline, project: project) }

spec/services/ci/pipelines/create_artifact_service_spec.rb

@@ -7,7 +7,8 @@ RSpec.describe ::Ci::Pipelines::CreateArtifactService do
     subject { described_class.new.execute(pipeline) }
 
     context 'when pipeline has coverage reports' do
-      let(:pipeline) { create(:ci_pipeline, :with_coverage_reports) }
+      let(:project) { create(:project, :repository) }
+      let(:pipeline) { create(:ci_pipeline, :with_coverage_reports, project: project) }
 
       context 'when pipeline is finished' do
         it 'creates a pipeline artifact' do