Add input caching for glob change detection

TestAssets/TestProjects/TestSimpleIncrementalApp/Program2.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace ConsoleApplication
+{
+    public class Program2
+    {
+        public static void Foo(string[] args)
+        {
+            Console.WriteLine("Hello World!");
+        }
+    }
+}

src/Microsoft.DotNet.Cli.Utils/DotnetFiles.cs

@@ -1,8 +1,10 @@
 // Copyright (c) .NET Foundation and contributors. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
+using System;
 using System.IO;
 using System.Reflection;
+using Microsoft.Extensions.PlatformAbstractions;
 
 namespace Microsoft.DotNet.Cli.Utils
 {
@@ -12,5 +14,16 @@ namespace Microsoft.DotNet.Cli.Utils
         /// The CLI ships with a .version file that stores the commit information and CLI version
         /// </summary>
         public static string VersionFile => Path.GetFullPath(Path.Combine(typeof(DotnetFiles).GetTypeInfo().Assembly.Location, "..", ".version"));
+
+        /// <summary>
+        /// Reads the version file and adds runtime specific information
+        /// </summary>
+        public static string ReadAndInterpretVersionFile()
+        {
+            var content = File.ReadAllText(DotnetFiles.VersionFile);
+            content += Environment.NewLine;
+            content += PlatformServices.Default.Runtime.GetRuntimeIdentifier();
+            return content;
+        }
     }
 }

src/Microsoft.DotNet.Cli.Utils/Reporter.cs

@@ -37,12 +37,14 @@ namespace Microsoft.DotNet.Cli.Utils
             {
                 Output = new Reporter(AnsiConsole.GetOutput());
                 Error = new Reporter(AnsiConsole.GetError());
-                Verbose = CommandContext.IsVerbose() ?
+                Verbose = IsVerbose ?
                     new Reporter(AnsiConsole.GetOutput()) :
                     NullReporter;
             }
         }
 
+        public static bool IsVerbose => CommandContext.IsVerbose();
+
         public void WriteLine(string message)
         {
             lock (_lock)

src/Microsoft.DotNet.Compiler.Common/ProjectContextExtensions.cs

@@ -37,6 +37,12 @@ namespace Microsoft.DotNet.Cli.Compiler.Common
             return Path.Combine(intermediatePath, ".SDKVersion");
         }
 
+        public static string IncrementalCacheFile(this ProjectContext context, string configuration, string buildBasePath, string outputPath)
+        {
+            var intermediatePath = context.GetOutputPaths(configuration, buildBasePath, outputPath).IntermediateOutputDirectoryPath;
+            return Path.Combine(intermediatePath, ".IncrementalCache");
+        }
+
         // used in incremental compilation for the key file
         public static CommonCompilerOptions ResolveCompilationOptions(this ProjectContext context, string configuration)
         {

src/Microsoft.DotNet.TestFramework/Microsoft.DotNet.TestFramework.TestInstance.cs

@@ -11,6 +11,9 @@ namespace Microsoft.DotNet.TestFramework
 {
     public class TestInstance
     {
+        // made tolower because the rest of the class works with normalized tolower strings
+        private static readonly IEnumerable<string> BuildArtifactBlackList = new List<string>() {".IncrementalCache", ".SDKVersion"}.Select(s => s.ToLower()).ToArray();
+
         private string _testDestination;
         private string _testAssetRoot;
 
@@ -105,8 +108,13 @@ namespace Microsoft.DotNet.TestFramework
                                  .Where(file =>
                                  {
                                      file = file.ToLower();
-                                     return file.Contains($"{Path.DirectorySeparatorChar}bin{Path.DirectorySeparatorChar}") 
+
+                                     var isArtifact = file.Contains($"{Path.DirectorySeparatorChar}bin{Path.DirectorySeparatorChar}") 
                                             || file.Contains($"{Path.DirectorySeparatorChar}obj{Path.DirectorySeparatorChar}");
+
+                                     var isBlackListed = BuildArtifactBlackList.Any(b => file.Contains(b));
+
+                                     return isArtifact && !isBlackListed;
                                  });
 
             foreach (string binFile in binFiles)

src/dotnet/commands/dotnet-build/CompilerIO.cs

@@ -2,18 +2,43 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Microsoft.DotNet.Tools.Build
 {
-    internal struct CompilerIO
+    internal class CompilerIO
     {
-        public readonly List<string> Inputs;
+        public readonly IEnumerable<string> Inputs;
-        public readonly List<string> Outputs;
+        public readonly IEnumerable<string> Outputs;
 
-        public CompilerIO(List<string> inputs, List<string> outputs)
+        public CompilerIO(IEnumerable<string> inputs, IEnumerable<string> outputs)
         {
             Inputs = inputs;
             Outputs = outputs;
         }
+
+        public DiffResult DiffInputs(CompilerIO other)
+        {
+            var myInputSet = new HashSet<string>(Inputs);
+            var otherInputSet = new HashSet<string>(other.Inputs);
+
+            var additions = myInputSet.Except(otherInputSet);
+            var deletions = otherInputSet.Except(myInputSet);
+
+            return new DiffResult(additions, deletions);
+        }
+
+        internal class DiffResult
+        {
+            public IEnumerable<string> Additions { get; private set; }
+            public IEnumerable<string> Deletions { get; private set; }
+
+            public DiffResult(IEnumerable<string> additions, IEnumerable<string> deletions)
+            {
+                Additions = additions;
+                Deletions = deletions;
+            }
+        }
+
     }
 }

src/dotnet/commands/dotnet-build/CompilerIOManager.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -19,6 +20,7 @@ namespace Microsoft.DotNet.Tools.Build
         private readonly string _buildBasePath;
         private readonly IList<string> _runtimes;
         private readonly WorkspaceContext _workspace;
+		private readonly ConcurrentDictionary<ProjectContextIdentity, CompilerIO> _cache;
 
         public CompilerIOManager(string configuration,
             string outputPath,
@@ -31,49 +33,36 @@ namespace Microsoft.DotNet.Tools.Build
             _buildBasePath = buildBasePath;
             _runtimes = runtimes.ToList();
             _workspace = workspace;
+            
+            _cache = new ConcurrentDictionary<ProjectContextIdentity, CompilerIO>();
         }
 
-        public bool AnyMissingIO(ProjectContext project, IEnumerable<string> items, string itemsType)
-        {
-            var missingItems = items.Where(i => !File.Exists(i)).ToList();
-
-            if (!missingItems.Any())
-            {
-                return false;
-            }
-
-            Reporter.Verbose.WriteLine($"Project {project.GetDisplayName()} will be compiled because expected {itemsType} are missing.");
-
-            foreach (var missing in missingItems)
-            {
-                Reporter.Verbose.WriteLine($" {missing}");
-            }
-
-            Reporter.Verbose.WriteLine(); ;
-
-            return true;
-        }
 
         // computes all the inputs and outputs that would be used in the compilation of a project
-        // ensures that all paths are files
-        // ensures no missing inputs
         public CompilerIO GetCompileIO(ProjectGraphNode graphNode)
         {
+            return _cache.GetOrAdd(graphNode.ProjectContext.Identity, i => ComputeIO(graphNode));
+        }
+
+        private CompilerIO ComputeIO(ProjectGraphNode graphNode)
+        {
+            var inputs = new List<string>();
+            var outputs = new List<string>();
+
             var isRootProject = graphNode.IsRoot;
             var project = graphNode.ProjectContext;
 
-            var compilerIO = new CompilerIO(new List<string>(), new List<string>());
             var calculator = project.GetOutputPaths(_configuration, _buildBasePath, _outputPath);
             var binariesOutputPath = calculator.CompilationOutputPath;
 
             // input: project.json
-            compilerIO.Inputs.Add(project.ProjectFile.ProjectFilePath);
+            inputs.Add(project.ProjectFile.ProjectFilePath);
 
             // input: lock file; find when dependencies change
-            AddLockFile(project, compilerIO);
+            AddLockFile(project, inputs);
 
             // input: source files
-            compilerIO.Inputs.AddRange(CompilerUtil.GetCompilationSources(project));
+            inputs.AddRange(CompilerUtil.GetCompilationSources(project));
 
             var allOutputPath = new HashSet<string>(calculator.CompilationFiles.All());
             if (isRootProject && project.ProjectFile.HasRuntimeOutput(_configuration))
@@ -88,23 +77,22 @@ namespace Microsoft.DotNet.Tools.Build
             // output: compiler outputs
             foreach (var path in allOutputPath)
             {
-                compilerIO.Outputs.Add(path);
+                outputs.Add(path);
             }
 
             // input compilation options files
-            AddCompilationOptions(project, _configuration, compilerIO);
+            AddCompilationOptions(project, _configuration, inputs);
 
             // input / output: resources with culture
-            AddNonCultureResources(project, calculator.IntermediateOutputDirectoryPath, compilerIO);
+            AddNonCultureResources(project, calculator.IntermediateOutputDirectoryPath, inputs, outputs);
 
             // input / output: resources without culture
-            AddCultureResources(project, binariesOutputPath, compilerIO);
+            AddCultureResources(project, binariesOutputPath, inputs, outputs);
 
-            return compilerIO;
+            return new CompilerIO(inputs, outputs);
         }
 
-
+        private static void AddLockFile(ProjectContext project, List<string> inputs)
-        private static void AddLockFile(ProjectContext project, CompilerIO compilerIO)
         {
             if (project.LockFile == null)
             {
@@ -113,48 +101,48 @@ namespace Microsoft.DotNet.Tools.Build
                 throw new InvalidOperationException(errorMessage);
             }
 
-            compilerIO.Inputs.Add(project.LockFile.LockFilePath);
+            inputs.Add(project.LockFile.LockFilePath);
 
             if (project.LockFile.ExportFile != null)
             {
-                compilerIO.Inputs.Add(project.LockFile.ExportFile.ExportFilePath);
+                inputs.Add(project.LockFile.ExportFile.ExportFilePath);
             }
         }
 
 
-        private static void AddCompilationOptions(ProjectContext project, string config, CompilerIO compilerIO)
+        private static void AddCompilationOptions(ProjectContext project, string config, List<string> inputs)
         {
             var compilerOptions = project.ResolveCompilationOptions(config);
 
             // input: key file
             if (compilerOptions.KeyFile != null)
             {
-                compilerIO.Inputs.Add(compilerOptions.KeyFile);
+                inputs.Add(compilerOptions.KeyFile);
             }
         }
 
-        private static void AddNonCultureResources(ProjectContext project, string intermediaryOutputPath, CompilerIO compilerIO)
+        private static void AddNonCultureResources(ProjectContext project, string intermediaryOutputPath, List<string> inputs, IList<string> outputs)
         {
             foreach (var resourceIO in CompilerUtil.GetNonCultureResources(project.ProjectFile, intermediaryOutputPath))
             {
-                compilerIO.Inputs.Add(resourceIO.InputFile);
+                inputs.Add(resourceIO.InputFile);
 
                 if (resourceIO.OutputFile != null)
                 {
-                    compilerIO.Outputs.Add(resourceIO.OutputFile);
+                    outputs.Add(resourceIO.OutputFile);
                 }
             }
         }
 
-        private static void AddCultureResources(ProjectContext project, string outputPath, CompilerIO compilerIO)
+        private static void AddCultureResources(ProjectContext project, string outputPath, List<string> inputs, List<string> outputs)
         {
             foreach (var cultureResourceIO in CompilerUtil.GetCultureResources(project.ProjectFile, outputPath))
             {
-                compilerIO.Inputs.AddRange(cultureResourceIO.InputFileToMetadata.Keys);
+                inputs.AddRange(cultureResourceIO.InputFileToMetadata.Keys);
 
                 if (cultureResourceIO.OutputFile != null)
                 {
-                    compilerIO.Outputs.Add(cultureResourceIO.OutputFile);
+                    outputs.Add(cultureResourceIO.OutputFile);
                 }
             }
         }

src/dotnet/commands/dotnet-build/DotnetProjectBuilder.cs

@@ -21,14 +21,17 @@ namespace Microsoft.DotNet.Tools.Build
         private readonly CompilerIOManager _compilerIOManager;
         private readonly ScriptRunner _scriptRunner;
         private readonly DotNetCommandFactory _commandFactory;
+        private readonly IncrementalManager _incrementalManager;
 
         public DotNetProjectBuilder(BuildCommandApp args)
         {
             _args = args;
+
             _preconditionManager = new IncrementalPreconditionManager(
                 args.ShouldPrintIncrementalPreconditions,
                 args.ShouldNotUseIncrementality,
                 args.ShouldSkipDependencies);
+
             _compilerIOManager = new CompilerIOManager(
                 args.ConfigValue,
                 args.OutputValue,
@@ -36,7 +39,19 @@ namespace Microsoft.DotNet.Tools.Build
                 args.GetRuntimes(),
                 args.Workspace
                 );
+
+            _incrementalManager = new IncrementalManager(
+                this,
+                _compilerIOManager,
+                _preconditionManager,
+                _args.ShouldSkipDependencies,
+                _args.ConfigValue,
+                _args.BuildBasePathValue,
+                _args.OutputValue
+                );
+
             _scriptRunner = new ScriptRunner();
+
             _commandFactory = new DotNetCommandFactory();
         }
 
@@ -52,7 +67,7 @@ namespace Microsoft.DotNet.Tools.Build
                     Directory.CreateDirectory(parentDirectory);
                 }
 
-                string content = ComputeCurrentVersionFileData();
+                string content = DotnetFiles.ReadAndInterpretVersionFile();
 
                 File.WriteAllText(projectVersionFile, content);
             }
@@ -62,14 +77,6 @@ namespace Microsoft.DotNet.Tools.Build
             }
         }
 
-        private static string ComputeCurrentVersionFileData()
-        {
-            var content = File.ReadAllText(DotnetFiles.VersionFile);
-            content += Environment.NewLine;
-            content += PlatformServices.Default.Runtime.GetRuntimeIdentifier();
-            return content;
-        }
-
         private void PrintSummary(ProjectGraphNode projectNode, bool success)
         {
             // todo: Ideally it's the builder's responsibility for adding the time elapsed. That way we avoid cross cutting display concerns between compile and build for printing time elapsed
@@ -83,17 +90,6 @@ namespace Microsoft.DotNet.Tools.Build
             Reporter.Output.WriteLine();
         }
 
-        private void CreateOutputDirectories()
-        {
-            if (!string.IsNullOrEmpty(_args.OutputValue))
-            {
-                Directory.CreateDirectory(_args.OutputValue);
-            }
-            if (!string.IsNullOrEmpty(_args.BuildBasePathValue))
-            {
-                Directory.CreateDirectory(_args.BuildBasePathValue);
-            }
-        }
 
         private void CopyCompilationOutput(OutputPaths outputPaths)
         {
@@ -151,118 +147,47 @@ namespace Microsoft.DotNet.Tools.Build
             finally
             {
                 StampProjectWithSDKVersion(projectNode.ProjectContext);
+                _incrementalManager.CacheIncrementalState(projectNode);
             }
         }
 
         protected override void ProjectSkiped(ProjectGraphNode projectNode)
         {
             StampProjectWithSDKVersion(projectNode.ProjectContext);
-        }
+            _incrementalManager.CacheIncrementalState(projectNode);
-
-        private bool CLIChangedSinceLastCompilation(ProjectContext project)
-        {
-            var currentVersionFile = DotnetFiles.VersionFile;
-            var versionFileFromLastCompile = project.GetSDKVersionFile(_args.ConfigValue, _args.BuildBasePathValue, _args.OutputValue);
-
-            if (!File.Exists(currentVersionFile))
-            {
-                // this CLI does not have a version file; cannot tell if CLI changed
-                return false;
-            }
-
-            if (!File.Exists(versionFileFromLastCompile))
-            {
-                // this is the first compilation; cannot tell if CLI changed
-                return false;
-            }
-
-            var currentContent = ComputeCurrentVersionFileData();
-
-            var versionsAreEqual = string.Equals(currentContent, File.ReadAllText(versionFileFromLastCompile), StringComparison.OrdinalIgnoreCase);
-
-            return !versionsAreEqual;
         }
 
         protected override bool NeedsRebuilding(ProjectGraphNode graphNode)
         {
-            var project = graphNode.ProjectContext;
+            var result = _incrementalManager.NeedsRebuilding(graphNode);
-            if (_args.ShouldNotUseIncrementality)
+
-            {
+            PrintIncrementalResult(graphNode.ProjectContext.GetDisplayName(), result);
-                return true;
+
-            }
+            return result.NeedsRebuilding;
-            if (!_args.ShouldSkipDependencies &&
-                graphNode.Dependencies.Any(d => GetCompilationResult(d) != CompilationResult.IncrementalSkip))
-            {
-                Reporter.Output.WriteLine($"Project {project.GetDisplayName()} will be compiled because some of it's dependencies changed");
-                return true;
-            }
-            var preconditions = _preconditionManager.GetIncrementalPreconditions(graphNode);
-            if (preconditions.PreconditionsDetected())
-            {
-                return true;
         }
 
-            if (CLIChangedSinceLastCompilation(project))
+        private void PrintIncrementalResult(string projectName, IncrementalResult result)
         {
-                Reporter.Output.WriteLine($"Project {project.GetDisplayName()} will be compiled because the version or bitness of the CLI changed since the last build");
+            if (result.NeedsRebuilding)
-                return true;
+            {
+                Reporter.Output.WriteLine($"Project {projectName} will be compiled because {result.Reason}");
+                PrintIncrementalItems(result);
+            }
+            else
+            {
+                Reporter.Output.WriteLine($"Project {projectName} was previously compiled. Skipping compilation.");
+            }
         }
 
-            var compilerIO = _compilerIOManager.GetCompileIO(graphNode);
+        private static void PrintIncrementalItems(IncrementalResult result)
-
-            // rebuild if empty inputs / outputs
-            if (!(compilerIO.Outputs.Any() && compilerIO.Inputs.Any()))
         {
-                Reporter.Output.WriteLine($"Project {project.GetDisplayName()} will be compiled because it either has empty inputs or outputs");
+            if (Reporter.IsVerbose)
-                return true;
-            }
-
-            //rebuild if missing inputs / outputs
-            if (_compilerIOManager.AnyMissingIO(project, compilerIO.Outputs, "outputs") || _compilerIOManager.AnyMissingIO(project, compilerIO.Inputs, "inputs"))
             {
-                return true;
+                foreach (var item in result.Items)
-            }
-
-            // find the output with the earliest write time
-            var minOutputPath = compilerIO.Outputs.First();
-            var minDateUtc = File.GetLastWriteTimeUtc(minOutputPath);
-
-            foreach (var outputPath in compilerIO.Outputs)
                 {
-                if (File.GetLastWriteTimeUtc(outputPath) >= minDateUtc)
+                    Reporter.Verbose.WriteLine($"\t{item}");
-                {
-                    continue;
                 }
-
-                minDateUtc = File.GetLastWriteTimeUtc(outputPath);
-                minOutputPath = outputPath;
             }
-
-            // find inputs that are older than the earliest output
-            var newInputs = compilerIO.Inputs.FindAll(p => File.GetLastWriteTimeUtc(p) >= minDateUtc);
-
-            if (!newInputs.Any())
-            {
-                Reporter.Output.WriteLine($"Project {project.GetDisplayName()} was previously compiled. Skipping compilation.");
-                return false;
-            }
-
-            Reporter.Output.WriteLine($"Project {project.GetDisplayName()} will be compiled because some of its inputs were newer than its oldest output.");
-            Reporter.Verbose.WriteLine();
-            Reporter.Verbose.WriteLine($" Oldest output item:");
-            Reporter.Verbose.WriteLine($"  {minDateUtc.ToLocalTime()}: {minOutputPath}");
-            Reporter.Verbose.WriteLine();
-
-            Reporter.Verbose.WriteLine($" Inputs newer than the oldest output item:");
-
-            foreach (var newInput in newInputs)
-            {
-                Reporter.Verbose.WriteLine($"  {File.GetLastWriteTime(newInput)}: {newInput}");
-            }
-
-            Reporter.Verbose.WriteLine();
-
-            return true;
         }
     }
 }

src/dotnet/commands/dotnet-build/IncrementalCache.cs

@@ -0,0 +1,92 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace Microsoft.DotNet.Tools.Build
+{
+    internal class IncrementalCache
+    {
+        private const string InputsKeyName = "inputs";
+        private const string OutputsKeyNane = "outputs";
+
+        public CompilerIO CompilerIO { get; }
+
+        public IncrementalCache(CompilerIO compilerIO)
+        {
+            CompilerIO = compilerIO;
+        }
+
+        public void WriteToFile(string cacheFile)
+        {
+            try
+            {
+                CreatePathIfAbsent(cacheFile);
+
+                using (var streamWriter = new StreamWriter(new FileStream(cacheFile, FileMode.Create, FileAccess.Write, FileShare.None)))
+                {
+                    var rootObject = new JObject();
+                    rootObject[InputsKeyName] = new JArray(CompilerIO.Inputs);
+                    rootObject[OutputsKeyNane] = new JArray(CompilerIO.Outputs);
+
+                    JsonSerializer.Create().Serialize(streamWriter, rootObject);
+                }
+            }
+            catch (Exception e)
+            {
+                throw new InvalidDataException($"Could not write the incremental cache file: {cacheFile}", e);
+            }
+        }
+
+        private static void CreatePathIfAbsent(string filePath)
+        {
+            var parentDir = Path.GetDirectoryName(filePath);
+
+            if (!Directory.Exists(parentDir))
+            {
+                Directory.CreateDirectory(parentDir);
+            }
+        }
+
+        public static IncrementalCache ReadFromFile(string cacheFile)
+        {
+            try
+            {
+                using (var streamReader = new StreamReader(new FileStream(cacheFile, FileMode.Open, FileAccess.Read, FileShare.Read)))
+                {
+                    var jObject = JObject.Parse(streamReader.ReadToEnd());
+
+                    if (jObject == null)
+                    {
+                        throw new InvalidDataException();
+                    }
+
+                    var inputs = ReadArray<string>(jObject, InputsKeyName);
+                    var outputs = ReadArray<string>(jObject, OutputsKeyNane);
+
+                    return new IncrementalCache(new CompilerIO(inputs, outputs));
+                }
+            }
+            catch (Exception e)
+            {
+                throw new InvalidDataException($"Could not read the incremental cache file: {cacheFile}", e);
+            }
+        }
+
+        private static IEnumerable<T> ReadArray<T>(JObject jObject, string keyName)
+        {
+            var array = jObject.Value<JToken>(keyName)?.Values<T>();
+
+            if (array == null)
+            {
+                throw new InvalidDataException($"Could not read key {keyName}");
+            }
+
+            return array;
+        }
+    }
+}

src/dotnet/commands/dotnet-build/IncrementalManager.cs

@@ -0,0 +1,207 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using Microsoft.DotNet.Cli.Compiler.Common;
+using Microsoft.DotNet.Cli.Utils;
+using Microsoft.DotNet.ProjectModel;
+using Microsoft.DotNet.ProjectModel.Utilities;
+using Microsoft.DotNet.Tools.Compiler;
+using Microsoft.Extensions.PlatformAbstractions;
+using Microsoft.DotNet.ProjectModel.Compilation;
+using NuGet.Protocol.Core.Types;
+
+namespace Microsoft.DotNet.Tools.Build
+{
+    internal class IncrementalManager
+    {
+        private readonly ProjectBuilder _projectBuilder;
+        private readonly CompilerIOManager _compilerIoManager;
+        private readonly IncrementalPreconditionManager _preconditionManager;
+        private readonly bool _shouldSkipDependencies;
+        private readonly string _configuration;
+        private readonly string _buildBasePath;
+        private readonly string _outputPath;
+
+        public IncrementalManager(
+            ProjectBuilder projectBuilder,
+            CompilerIOManager compilerIOManager,
+            IncrementalPreconditionManager incrementalPreconditionManager,
+            bool shouldSkipDependencies,
+            string configuration,
+            string buildBasePath,
+            string outputPath)
+        {
+            _projectBuilder = projectBuilder;
+            _compilerIoManager = compilerIOManager;
+            _preconditionManager = incrementalPreconditionManager;
+            _shouldSkipDependencies = shouldSkipDependencies;
+            _configuration = configuration;
+            _buildBasePath = buildBasePath;
+            _outputPath = outputPath;
+        }
+
+        public IncrementalResult NeedsRebuilding(ProjectGraphNode graphNode)
+        {
+            if (!_shouldSkipDependencies &&
+                graphNode.Dependencies.Any(d => _projectBuilder.GetCompilationResult(d) != CompilationResult.IncrementalSkip))
+            {
+                return new IncrementalResult("dependencies changed");
+            }
+
+            var preconditions = _preconditionManager.GetIncrementalPreconditions(graphNode);
+            if (preconditions.PreconditionsDetected())
+            {
+                return new IncrementalResult($"project is not safe for incremental compilation. Use {BuildCommandApp.BuildProfileFlag} flag for more information.");
+            }
+
+            var compilerIO = _compilerIoManager.GetCompileIO(graphNode);
+
+            var result = CLIChanged(graphNode);
+            if (result.NeedsRebuilding)
+            {
+                return result;
+            }
+
+            result = InputItemsChanged(graphNode, compilerIO);
+            if (result.NeedsRebuilding)
+            {
+                return result;
+            }
+
+            result = TimestampsChanged(compilerIO);
+            if (result.NeedsRebuilding)
+            {
+                return result;
+            }
+
+            return IncrementalResult.DoesNotNeedRebuild;
+        }
+
+        private IncrementalResult CLIChanged(ProjectGraphNode graphNode)
+        {
+            var currentVersionFile = DotnetFiles.VersionFile;
+            var versionFileFromLastCompile = graphNode.ProjectContext.GetSDKVersionFile(_configuration, _buildBasePath, _outputPath);
+
+            if (!File.Exists(currentVersionFile))
+            {
+                // this CLI does not have a version file; cannot tell if CLI changed
+                return IncrementalResult.DoesNotNeedRebuild;
+            }
+
+            if (!File.Exists(versionFileFromLastCompile))
+            {
+                // this is the first compilation; cannot tell if CLI changed
+                return IncrementalResult.DoesNotNeedRebuild;
+            }
+
+            var currentContent = DotnetFiles.ReadAndInterpretVersionFile();
+
+            var versionsAreEqual = string.Equals(currentContent, File.ReadAllText(versionFileFromLastCompile), StringComparison.OrdinalIgnoreCase);
+
+            return versionsAreEqual
+                ? IncrementalResult.DoesNotNeedRebuild
+                : new IncrementalResult("the version or bitness of the CLI changed since the last build");
+        }
+
+        private IncrementalResult InputItemsChanged(ProjectGraphNode graphNode, CompilerIO compilerIO)
+        {
+            // check empty inputs / outputs
+            if (!compilerIO.Inputs.Any())
+            {
+                return new IncrementalResult("the project has no inputs");
+            }
+
+            if (!compilerIO.Outputs.Any())
+            {
+                return new IncrementalResult("the project has no outputs");
+            }
+
+            // check non existent items
+            var result = CheckMissingIO(compilerIO.Inputs, "inputs");
+            if (result.NeedsRebuilding)
+            {
+                return result;
+            }
+
+            result = CheckMissingIO(compilerIO.Outputs, "outputs");
+            if (result.NeedsRebuilding)
+            {
+                return result;
+            }
+
+            return CheckInputGlobChanges(graphNode, compilerIO);
+        }
+
+        private IncrementalResult CheckInputGlobChanges(ProjectGraphNode graphNode, CompilerIO compilerIO)
+        {
+            // check cache against input glob pattern changes
+            var incrementalCacheFile = graphNode.ProjectContext.IncrementalCacheFile(_configuration, _buildBasePath, _outputPath);
+
+            if (!File.Exists(incrementalCacheFile))
+            {
+                // cache is not present (first compilation); can't determine if globs changed; cache will be generated after build processes project
+                return IncrementalResult.DoesNotNeedRebuild;
+            }
+
+            var incrementalCache = IncrementalCache.ReadFromFile(incrementalCacheFile);
+
+            var diffResult = compilerIO.DiffInputs(incrementalCache.CompilerIO);
+
+            if (diffResult.Deletions.Any())
+            {
+                return new IncrementalResult("Input items removed from last build", diffResult.Deletions);
+            }
+
+            if (diffResult.Additions.Any())
+            {
+                return new IncrementalResult("Input items added from last build", diffResult.Additions);
+            }
+
+            return IncrementalResult.DoesNotNeedRebuild;
+        }
+
+        private IncrementalResult CheckMissingIO(IEnumerable<string> items, string itemsType)
+        {
+            var missingItems = items.Where(i => !File.Exists(i)).ToList();
+
+            return missingItems.Any()
+                ? new IncrementalResult($"expected {itemsType} are missing", missingItems)
+                : IncrementalResult.DoesNotNeedRebuild;
+        }
+
+        private IncrementalResult TimestampsChanged(CompilerIO compilerIO)
+        {
+            // find the output with the earliest write time
+            var minDateUtc = DateTime.MaxValue;
+
+            foreach (var outputPath in compilerIO.Outputs)
+            {
+                var lastWriteTimeUtc = File.GetLastWriteTimeUtc(outputPath);
+
+                if (lastWriteTimeUtc < minDateUtc)
+                {
+                    minDateUtc = lastWriteTimeUtc;
+                }
+            }
+
+            // find inputs that are older than the earliest output
+            var newInputs = compilerIO.Inputs.Where(p => File.GetLastWriteTimeUtc(p) >= minDateUtc);
+
+            return newInputs.Any()
+                ? new IncrementalResult("inputs were modified", newInputs)
+                : IncrementalResult.DoesNotNeedRebuild;
+        }
+
+        public void CacheIncrementalState(ProjectGraphNode graphNode)
+        {
+            var incrementalCacheFile = graphNode.ProjectContext.IncrementalCacheFile(_configuration, _buildBasePath, _outputPath);
+
+            var incrementalCache = new IncrementalCache(_compilerIoManager.GetCompileIO(graphNode));
+            incrementalCache.WriteToFile(incrementalCacheFile);
+        }
+    }
+}

src/dotnet/commands/dotnet-build/IncrementalResult.cs

@@ -0,0 +1,34 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Microsoft.DotNet.Tools.Build
+{
+    internal class IncrementalResult
+    {
+        public static readonly IncrementalResult DoesNotNeedRebuild = new IncrementalResult(false, "", Enumerable.Empty<string>());
+
+        public bool NeedsRebuilding { get; }
+        public string Reason { get; }
+        public IEnumerable<string> Items { get; }
+
+        private IncrementalResult(bool needsRebuilding, string reason, IEnumerable<string> items)
+        {
+            NeedsRebuilding = needsRebuilding;
+            Reason = reason;
+            Items = items;
+        }
+
+        public IncrementalResult(string reason)
+            : this(true, reason, Enumerable.Empty<string>())
+        {
+        }
+
+        public IncrementalResult(string reason, IEnumerable<string> items)
+            : this(true, reason, items)
+        {
+        }
+    }
+}

src/dotnet/commands/dotnet-build/ProjectBuilder.cs

@@ -21,7 +21,7 @@ namespace Microsoft.DotNet.Tools.Build
             }
         }
 
-        protected CompilationResult? GetCompilationResult(ProjectGraphNode projectNode)
+        public CompilationResult? GetCompilationResult(ProjectGraphNode projectNode)
         {
             CompilationResult result;
             if (_compilationResults.TryGetValue(projectNode.ProjectContext.Identity, out result))

test/dotnet-build.Tests/IncrementalTests.cs

@@ -38,6 +38,7 @@ namespace Microsoft.DotNet.Tools.Builder.Tests
             buildResult.Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
 
             buildResult = BuildProject(noIncremental: true);
+            buildResult.Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
             Assert.Contains("[Forced Unsafe]", buildResult.StdOut);
         }
 
@@ -85,12 +86,12 @@ namespace Microsoft.DotNet.Tools.Builder.Tests
             CreateTestInstance();
             BuildProject().Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
 
-            //change version file
+            // change version file
             var versionFile = Path.Combine(GetIntermediaryOutputPath(), ".SDKVersion");
             File.Exists(versionFile).Should().BeTrue();
             File.AppendAllText(versionFile, "text");
 
-            //assert rebuilt
+            // assert rebuilt
             BuildProject().Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
         }
 
@@ -100,19 +101,80 @@ namespace Microsoft.DotNet.Tools.Builder.Tests
             CreateTestInstance();
             BuildProject().Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
 
-            //delete version file
+            // delete version file
             var versionFile = Path.Combine(GetIntermediaryOutputPath(), ".SDKVersion");
             File.Exists(versionFile).Should().BeTrue();
             File.Delete(versionFile);
             File.Exists(versionFile).Should().BeFalse();
 
-            //assert build skipped due to no version file
+            // assert build skipped due to no version file
             BuildProject().Should().HaveSkippedProjectCompilation(MainProject, _appFrameworkFullName);
 
-            //the version file should have been regenerated during the build, even if compilation got skipped
+            // the version file should have been regenerated during the build, even if compilation got skipped
             File.Exists(versionFile).Should().BeTrue();
         }
 
+        [Fact]
+        public void TestRebuildDeletedSource()
+        {
+            CreateTestInstance();
+            BuildProject().Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
+
+            var sourceFile = Path.Combine(GetProjectDirectory(MainProject), "Program2.cs");
+            File.Delete(sourceFile);
+            Assert.False(File.Exists(sourceFile));
+
+            // second build; should get rebuilt since we deleted a source file
+            BuildProject().Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
+
+            // third build; incremental cache should have been regenerated and project skipped
+            BuildProject().Should().HaveSkippedProjectCompilation(MainProject, _appFrameworkFullName);
+        }
+
+        [Fact]
+        public void TestRebuildRenamedSource()
+        {
+            CreateTestInstance();
+            var buildResult = BuildProject();
+            buildResult.Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
+
+            var sourceFile = Path.Combine(GetProjectDirectory(MainProject), "Program2.cs");
+            var destinationFile = Path.Combine(Path.GetDirectoryName(sourceFile), "ProgramNew.cs");
+            File.Move(sourceFile, destinationFile);
+            Assert.False(File.Exists(sourceFile));
+            Assert.True(File.Exists(destinationFile));
+
+            // second build; should get rebuilt since we renamed a source file
+            buildResult = BuildProject();
+            buildResult.Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
+
+            // third build; incremental cache should have been regenerated and project skipped
+            BuildProject().Should().HaveSkippedProjectCompilation(MainProject, _appFrameworkFullName);
+        }
+
+        [Fact]
+        public void TestRebuildDeletedSourceAfterCliChanged()
+        {
+            CreateTestInstance();
+            BuildProject().Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
+
+            // change version file
+            var versionFile = Path.Combine(GetIntermediaryOutputPath(), ".SDKVersion");
+            File.Exists(versionFile).Should().BeTrue();
+            File.AppendAllText(versionFile, "text");
+
+            // delete a source file
+            var sourceFile = Path.Combine(GetProjectDirectory(MainProject), "Program2.cs");
+            File.Delete(sourceFile);
+            Assert.False(File.Exists(sourceFile));
+
+            // should get rebuilt since we changed version file and deleted source file
+            BuildProject().Should().HaveCompiledProject(MainProject, _appFrameworkFullName);
+
+            // third build; incremental cache should have been regenerated and project skipped
+            BuildProject().Should().HaveSkippedProjectCompilation(MainProject, _appFrameworkFullName);
+        }
+
         [Fact]
         public void TestRebuildChangedLockFile()
         {