add support for merging coverage results

src/coverlet.core/Coverage.cs

@@ -6,6 +6,8 @@ using System.Linq;
 using Coverlet.Core.Helpers;
 using Coverlet.Core.Instrumentation;
 
+using Newtonsoft.Json;
+
 namespace Coverlet.Core
 {
     public class Coverage
@@ -15,6 +17,7 @@ namespace Coverlet.Core
         private string[] _excludeFilters;
         private string[] _includeFilters;
         private string[] _excludedSourceFiles;
+        private string _mergeWith;
         private List<InstrumenterResult> _results;
 
         public string Identifier
@@ -22,12 +25,14 @@ namespace Coverlet.Core
             get { return _identifier; }
         }
 
-        public Coverage(string module, string[] excludeFilters, string[] includeFilters, string[] excludedSourceFiles)
+        public Coverage(string module, string[] excludeFilters, string[] includeFilters, string[] excludedSourceFiles, string mergeWith)
         {
             _module = module;
             _excludeFilters = excludeFilters;
             _includeFilters = includeFilters;
             _excludedSourceFiles = excludedSourceFiles;
+            _mergeWith = mergeWith;
+
             _identifier = Guid.NewGuid().ToString();
             _results = new List<InstrumenterResult>();
         }
@@ -144,11 +149,14 @@ namespace Coverlet.Core
                 InstrumentationHelper.RestoreOriginalModule(result.ModulePath, _identifier);
             }
 
-            return new CoverageResult
+            var coverageResult = new CoverageResult { Identifier = _identifier, Modules = modules };
+            if (!string.IsNullOrEmpty(_mergeWith) && !string.IsNullOrWhiteSpace(_mergeWith))
             {
-                Identifier = _identifier,
-                Modules = modules
-            };
+                string json = File.ReadAllText(_mergeWith);
+                coverageResult.Merge(JsonConvert.DeserializeObject<Modules>(json));
+            }
+
+            return coverageResult;
         }
 
         private void CalculateCoverage()

src/coverlet.core/CoverageResult.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 
 namespace Coverlet.Core
 {
@@ -38,5 +39,70 @@ namespace Coverlet.Core
         public Modules Modules;
 
         internal CoverageResult() { }
+
+        internal void Merge(Modules modules)
+        {
+            foreach (var module in modules)
+            {
+                if (!this.Modules.ContainsKey(module.Key))
+                {
+                    this.Modules.Add(module.Key, module.Value);
+                }
+                else
+                {
+                    foreach (var document in module.Value)
+                    {
+                        if (!this.Modules[module.Key].ContainsKey(document.Key))
+                        {
+                            this.Modules[module.Key].Add(document.Key, document.Value);
+                        }
+                        else
+                        {
+                            foreach (var @class in document.Value)
+                            {
+                                if (!this.Modules[module.Key][document.Key].ContainsKey(@class.Key))
+                                {
+                                    this.Modules[module.Key][document.Key].Add(@class.Key, @class.Value);
+                                }
+                                else
+                                {
+                                    foreach (var method in @class.Value)
+                                    {
+                                        if (!this.Modules[module.Key][document.Key][@class.Key].ContainsKey(method.Key))
+                                        {
+                                            this.Modules[module.Key][document.Key][@class.Key].Add(method.Key, method.Value);
+                                        }
+                                        else
+                                        {
+                                            foreach (var line in method.Value.Lines)
+                                            {
+                                                if (!this.Modules[module.Key][document.Key][@class.Key][method.Key].Lines.ContainsKey(line.Key))
+                                                {
+                                                    this.Modules[module.Key][document.Key][@class.Key][method.Key].Lines.Add(line.Key, line.Value);
+                                                }
+                                                else
+                                                {
+                                                    this.Modules[module.Key][document.Key][@class.Key][method.Key].Lines[line.Key] += line.Value;
+                                                }
+                                            }
+
+                                            foreach (var branch in method.Value.Branches)
+                                            {
+                                                var branches = this.Modules[module.Key][document.Key][@class.Key][method.Key].Branches;
+                                                var branchInfo = branches.FirstOrDefault(b => b.EndOffset == branch.EndOffset && b.Line == branch.Line && b.Offset == branch.Offset && b.Ordinal == branch.Ordinal && b.Path == branch.Path);
+                                                if (branchInfo == null)
+                                                    branches.Add(branch);
+                                                else
+                                                    branchInfo.Hits += branch.Hits;
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
     }
 }

src/coverlet.msbuild.tasks/InstrumentationTask.cs

@@ -12,6 +12,7 @@ namespace Coverlet.MSbuild.Tasks
         private string _exclude;
         private string _include;
         private string _excludeByFile;
+        private string _mergeWith;
 
         internal static Coverage Coverage
         {
@@ -43,6 +44,12 @@ namespace Coverlet.MSbuild.Tasks
             set { _excludeByFile = value; }
         }
 
+        public string MergeWith
+        {
+            get { return _mergeWith; }
+            set { _mergeWith = value; }
+        }
+
         public override bool Execute()
         {
             try
@@ -51,7 +58,7 @@ namespace Coverlet.MSbuild.Tasks
                 var excludeFilters = _exclude?.Split(',');
                 var includeFilters = _include?.Split(',');
 
-                _coverage = new Coverage(_path, excludeFilters, includeFilters, excludedSourceFiles);
+                _coverage = new Coverage(_path, excludeFilters, includeFilters, excludedSourceFiles, _mergeWith);
                 _coverage.PrepareModules();
             }
             catch (Exception ex)

src/coverlet.msbuild/coverlet.msbuild.props

@@ -5,6 +5,7 @@
     <CoverletOutput Condition="$(CoverletOutput) == ''">$([MSBuild]::EnsureTrailingSlash('$(MSBuildProjectDirectory)'))</CoverletOutput>
     <Exclude Condition="$(Exclude) == ''"></Exclude>
     <ExcludeByFile Condition="$(ExcludeByFile) == ''"></ExcludeByFile>
+    <MergeWith Condition="$(MergeWith) == ''"></MergeWith>
     <Threshold Condition="$(Threshold) == ''">0</Threshold>
     <ThresholdType Condition="$(ThresholdType) == ''">line,branch,method</ThresholdType>
   </PropertyGroup>

src/coverlet.msbuild/coverlet.msbuild.targets

@@ -8,6 +8,7 @@
       Condition="'$(VSTestNoBuild)' == 'true' and $(CollectCoverage) == 'true'"
       Exclude="$(Exclude)"
       ExcludeByFile="$(ExcludeByFile)"
+      MergeWith="$(MergeWith)"
       Path="$(TargetPath)" />
   </Target>
 
@@ -16,6 +17,7 @@
       Condition="'$(VSTestNoBuild)' != 'true' and $(CollectCoverage) == 'true'"
       Exclude="$(Exclude)"
       ExcludeByFile="$(ExcludeByFile)"
+      MergeWith="$(MergeWith)"
       Path="$(TargetPath)" />
   </Target>
 

test/coverlet.core.tests/CoverageTests.cs

@@ -27,7 +27,7 @@ namespace Coverlet.Core.Tests
             // Since Coverage only instruments dependancies, we need a fake module here
             var testModule = Path.Combine(directory.FullName, "test.module.dll");
 
-            var coverage = new Coverage(testModule, Array.Empty<string>(), Array.Empty<string>(), Array.Empty<string>());
+            var coverage = new Coverage(testModule, Array.Empty<string>(), Array.Empty<string>(), Array.Empty<string>(), string.Empty);
             coverage.PrepareModules();
 
             var result = coverage.GetCoverageResult();