Report error requiring references to have composite only if the program is not container only

src/compiler/program.ts

@@ -2806,7 +2806,11 @@ namespace ts {
                 }
                 const options = resolvedRef.commandLine.options;
                 if (!options.composite) {
-                    createDiagnosticForReference(parentFile, index, Diagnostics.Referenced_project_0_must_have_setting_composite_Colon_true, ref.path);
+                    // ok to not have composite if the current program is container only
+                    const inputs = parent ? parent.commandLine.fileNames : rootNames;
+                    if (inputs.length) {
+                        createDiagnosticForReference(parentFile, index, Diagnostics.Referenced_project_0_must_have_setting_composite_Colon_true, ref.path);
+                    }
                 }
                 if (ref.prepend) {
                     const out = options.outFile || options.out;

src/harness/virtualFileSystemWithWatch.ts

@@ -988,4 +988,16 @@ interface Array<T> {}`
             return this.environmentVariables && this.environmentVariables.get(name) || "";
         }
     }
+
+    export const tsbuildProjectsLocation = "/user/username/projects";
+    export function getTsBuildProjectFilePath(project: string, file: string) {
+        return `${tsbuildProjectsLocation}/${project}/${file}`;
+    }
+
+    export function getTsBuildProjectFile(project: string, file: string): File {
+        return {
+            path: getTsBuildProjectFilePath(project, file),
+            content: Harness.IO.readFile(`${Harness.IO.getWorkspaceRoot()}/tests/projects/${project}/${file}`)!
+        };
+    }
 }

src/testRunner/unittests/tsbuildWatchMode.ts

@@ -1,6 +1,9 @@
 namespace ts.tscWatch {
     export import libFile = TestFSWithWatch.libFile;
-    function createSolutionBuilder(system: WatchedSystem, rootNames: ReadonlyArray<string>, defaultOptions?: BuildOptions) {
+    import projectsLocation = TestFSWithWatch.tsbuildProjectsLocation;
+    import getFilePathInProject = TestFSWithWatch.getTsBuildProjectFilePath;
+    import getFileFromProject = TestFSWithWatch.getTsBuildProjectFile;
+    export function createSolutionBuilder(system: WatchedSystem, rootNames: ReadonlyArray<string>, defaultOptions?: BuildOptions) {
         const host = createSolutionBuilderWithWatchHost(system);
         return ts.createSolutionBuilder(host, rootNames, defaultOptions || { watch: true });
     }
@@ -13,7 +16,6 @@ namespace ts.tscWatch {
     }
 
     describe("tsbuild-watch program updates", () => {
-        const projectsLocation = "/user/username/projects";
         const project = "sample1";
         const enum SubProject {
             core = "core",
@@ -24,23 +26,10 @@ namespace ts.tscWatch {
         type ReadonlyFile = Readonly<File>;
         /** [tsconfig, index] | [tsconfig, index, anotherModule, someDecl] */
         type SubProjectFiles = [ReadonlyFile, ReadonlyFile] | [ReadonlyFile, ReadonlyFile, ReadonlyFile, ReadonlyFile];
-        const root = Harness.IO.getWorkspaceRoot();
-
         function getProjectPath(project: string) {
             return `${projectsLocation}/${project}`;
         }
 
-        function getFilePathInProject(project: string, file: string) {
-            return `${projectsLocation}/${project}/${file}`;
-        }
-
-        function getFileFromProject(project: string, file: string): File {
-            return {
-                path: getFilePathInProject(project, file),
-                content: Harness.IO.readFile(`${root}/tests/projects/${project}/${file}`)!
-            };
-        }
-
         function projectPath(subProject: SubProject) {
             return getFilePathInProject(project, subProject);
         }

src/testRunner/unittests/tsserverProjectSystem.ts

@@ -10427,6 +10427,55 @@ declare class TestLib {
         });
     });
 
+    describe("tsserverProjectSystem with tsbuild projects", () => {
+        function getProjectFiles(project: string): [File, File] {
+            return [
+                TestFSWithWatch.getTsBuildProjectFile(project, "tsconfig.json"),
+                TestFSWithWatch.getTsBuildProjectFile(project, "index.ts"),
+            ];
+        }
+        it("does not error on container only project", () => {
+            const project = "container";
+            const containerLib = getProjectFiles("container/lib");
+            const containerExec = getProjectFiles("container/exec");
+            const containerCompositeExec = getProjectFiles("container/compositeExec");
+            const containerConfig = TestFSWithWatch.getTsBuildProjectFile(project, "tsconfig.json");
+            const files = [libFile, ...containerLib, ...containerExec, ...containerCompositeExec, containerConfig];
+            const host = createServerHost(files);
+
+            // ts build should succeed
+            const solutionBuilder = tscWatch.createSolutionBuilder(host, [containerConfig.path], {});
+            solutionBuilder.buildAllProjects();
+            assert.equal(host.getOutput().length, 0);
+
+            // Open external project for the folder
+            const session = createSession(host);
+            const service = session.getProjectService();
+            service.openExternalProjects([{
+                projectFileName: TestFSWithWatch.getTsBuildProjectFilePath(project, project),
+                rootFiles: files.map(f => ({ fileName: f.path })),
+                options: {}
+            }]);
+            checkNumberOfProjects(service, { configuredProjects: 4 });
+            files.forEach(f => {
+                const args: protocol.FileRequestArgs = {
+                    file: f.path,
+                    projectFileName: endsWith(f.path, "tsconfig.json") ? f.path : undefined
+                };
+                const syntaxDiagnostics = session.executeCommandSeq<protocol.SyntacticDiagnosticsSyncRequest>({
+                    command: protocol.CommandTypes.SyntacticDiagnosticsSync,
+                    arguments: args
+                }).response;
+                assert.deepEqual(syntaxDiagnostics, []);
+                const semanticDiagnostics = session.executeCommandSeq<protocol.SemanticDiagnosticsSyncRequest>({
+                    command: protocol.CommandTypes.SemanticDiagnosticsSync,
+                    arguments: args
+                }).response;
+                assert.deepEqual(semanticDiagnostics, []);
+            });
+        });
+    });
+
     describe("tsserverProjectSystem duplicate packages", () => {
         // Tests that 'moduleSpecifiers.ts' will import from the redirecting file, and not from the file it redirects to, if that can provide a global module specifier.
         it("works with import fixes", () => {

tests/projects/container/compositeExec/index.ts

@@ -0,0 +1,5 @@
+namespace container {
+    export function getMyConst() {
+        return myConst;
+    }
+}

tests/projects/container/compositeExec/tsconfig.json

@@ -0,0 +1,12 @@
+{
+    "compilerOptions": {
+        "outFile": "../built/local/compositeExec.js",
+        "composite": true
+    },
+    "files": [
+        "index.ts"
+    ],
+    "references": [
+        { "path": "../lib", "prepend": true }
+    ]
+}

tests/projects/container/exec/index.ts

@@ -0,0 +1,5 @@
+namespace container {
+    export function getMyConst() {
+        return myConst;
+    }
+}

tests/projects/container/exec/tsconfig.json

@@ -0,0 +1,11 @@
+{
+    "compilerOptions": {
+        "outFile": "../built/local/exec.js"
+    },
+    "files": [
+        "index.ts"
+    ],
+    "references": [
+        { "path": "../lib", "prepend": true }
+    ]
+}

tests/projects/container/lib/index.ts

@@ -0,0 +1,3 @@
+namespace container {
+    export const myConst = 30;
+}

tests/projects/container/lib/tsconfig.json

@@ -0,0 +1,11 @@
+{
+    "compilerOptions": {
+        "outFile": "../built/local/lib.js",
+        "composite": true,
+        "declarationMap": true
+    },
+    "references": [],
+    "files": [
+        "index.ts"
+    ]
+}

tests/projects/container/tsconfig.json

@@ -0,0 +1,8 @@
+{
+    "files": [],
+    "include": [],
+    "references": [
+        { "path": "./exec" },
+        { "path": "./compositeExec" }
+    ]
+}