define docker baseimage and tag

src/Microsoft.Tye.Core/ApplicationFactory.cs

@@ -96,12 +96,12 @@ public static async Task<ApplicationBuilder> CreateAsync(OutputContext output, F
                         }
                         project.Replicas = configService.Replicas ?? 1;
 
-                        await ProjectReader.ReadProjectDetailsAsync(output, project);
-
                         // We don't apply more container defaults here because we might need
                         // to prompt for the registry name.
                         project.ContainerInfo = new ContainerInfo() { UseMultiphaseDockerfile = false, };
 
+                        await ProjectReader.ReadProjectDetailsAsync(output, project);
+
                         // Do k8s by default.
                         project.ManifestInfo = new KubernetesManifestInfo();
                     }

src/Microsoft.Tye.Core/ProjectReader.cs

@@ -268,6 +268,15 @@ private static void EvaluateProject(OutputContext output, ProjectServiceBuilder
             project.Frameworks.AddRange(sharedFrameworks.Select(s => new Framework(s)));
             output.WriteDebugLine($"Found shared frameworks: {string.Join(", ", sharedFrameworks)}");
 
+            // determine container base image
+            if (project.ContainerInfo == null)
+            {
+                project.ContainerInfo = new ContainerInfo() { UseMultiphaseDockerfile = false, };
+            }
+
+            project.ContainerInfo!.BaseImageName = projectInstance.GetPropertyValue("ContainerBaseImage");
+            project.ContainerInfo!.BaseImageTag = projectInstance.GetPropertyValue("ContainerBaseTag");
+
             bool PropertyIsTrue(string property)
             {
                 return projectInstance.GetPropertyValue(property) is string s && !string.IsNullOrEmpty(s) && bool.Parse(s);

src/Microsoft.Tye.Hosting/Model/ProjectRunInfo.cs

@@ -24,6 +24,8 @@ public ProjectRunInfo(ProjectServiceBuilder project)
             RunCommand = project.RunCommand;
             RunArguments = project.RunArguments;
             PublishOutputPath = project.PublishDir;
+            ContainerBaseImage = project.ContainerInfo?.BaseImageName;
+            ContainerBaseTag = project.ContainerInfo?.BaseImageTag;
             IsAspNet = project.IsAspNet;
         }
 
@@ -47,6 +49,9 @@ public ProjectRunInfo(ProjectServiceBuilder project)
         public string RunCommand { get; }
         public string RunArguments { get; }
 
+        public string? ContainerBaseTag { get; }
+        public string? ContainerBaseImage { get; }
+
         // This exists for running projects as containers
         public List<DockerVolume> VolumeMappings { get; } = new List<DockerVolume>();
     }

src/Microsoft.Tye.Hosting/TransformProjectsIntoContainers.cs

@@ -127,7 +127,14 @@ private static string DetermineContainerImage(ProjectRunInfo project)
         {
             var baseImage = project.IsAspNet ? "mcr.microsoft.com/dotnet/core/aspnet" : "mcr.microsoft.com/dotnet/core/runtime";
 
-            return $"{baseImage}:{project.TargetFrameworkVersion}";
+            if (!string.IsNullOrEmpty(project.ContainerBaseImage))
+            {
+                baseImage = project.ContainerBaseImage;
+            }
+
+            var imageTag = string.IsNullOrEmpty(project.ContainerBaseTag) ? project.TargetFrameworkVersion : project.ContainerBaseTag;
+
+            return $"{baseImage}:{imageTag}";
         }
 
         public Task StopAsync(Application application)

test/E2ETest/TyeRunTests.cs

@@ -246,6 +246,30 @@ public async Task FrontendDockerBackendProject()
             });
         }
 
+        [ConditionalFact]
+        public async Task DockerBaseImageAndTagTest()
+        {
+            using var projectDirectory = CopyTestProjectDirectory(Path.Combine("frontend-backend", "backend"));
+
+            var projectFile = new FileInfo(Path.Combine(projectDirectory.DirectoryPath, "backend-baseimage.csproj"));
+
+            var outputContext = new OutputContext(_sink, Verbosity.Debug);
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile);
+
+            // Transform the backend into a docker image for testing
+            var project = (ProjectServiceBuilder)application.Services.First(s => s.Name == "backend-baseimage");
+
+            // check ContainerInfo values
+            Assert.True(string.Equals(project.ContainerInfo!.BaseImageName, "mcr.microsoft.com/dotnet/core/sdk"));
+            Assert.True(string.Equals(project.ContainerInfo!.BaseImageTag, "3.1-buster"));
+
+            // check projectInfo values
+            var projectRunInfo = new ProjectRunInfo(project);
+
+            Assert.True(string.Equals(projectRunInfo!.ContainerBaseImage, project.ContainerInfo.BaseImageName));
+            Assert.True(string.Equals(projectRunInfo!.ContainerBaseTag, project.ContainerInfo.BaseImageTag));
+        }
+
         [ConditionalFact]
         [SkipIfDockerNotRunning]
         public async Task DockerNamedVolumeTest()

test/E2ETest/testassets/projects/frontend-backend/backend/backend-baseimage.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <RootNamespace>Backend</RootNamespace>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <ContainerBaseImage>mcr.microsoft.com/dotnet/core/sdk</ContainerBaseImage>
+    <ContainerBaseTag>3.1-buster</ContainerBaseTag>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="$(TyeLibrariesPath)\Microsoft.Tye.Extensions.Configuration\Microsoft.Tye.Extensions.Configuration.csproj" />
+  </ItemGroup>
+
+</Project>