Fix crash in reporting unresolved project reference as part of compilerOptions verification (#39095)

* Fix crash in reporting unresolved project reference as part of compilerOptions verification
Fixes #38143

* Fix typo

src/compiler/program.ts

@@ -1530,7 +1530,7 @@ namespace ts {
         function getPrependNodes() {
             return createPrependNodes(
                 projectReferences,
-                (_ref, index) => resolvedProjectReferences![index]!.commandLine,
+                (_ref, index) => resolvedProjectReferences![index]?.commandLine,
                 fileName => {
                     const path = toPath(fileName);
                     const sourceFile = getSourceFileByPath(path);

src/testRunner/tsconfig.json

@@ -130,6 +130,7 @@
         "unittests/tsc/declarationEmit.ts",
         "unittests/tsc/incremental.ts",
         "unittests/tsc/listFilesOnly.ts",
+        "unittests/tsc/projectReferences.ts",
         "unittests/tsc/runWithoutArgs.ts",
         "unittests/tscWatch/consoleClearing.ts",
         "unittests/tscWatch/emit.ts",

src/testRunner/unittests/tsc/projectReferences.ts

@@ -0,0 +1,21 @@
+namespace ts {
+    describe("unittests:: tsc:: projectReferences::", () => {
+        verifyTsc({
+            scenario: "projectReferences",
+            subScenario: "when project contains invalid project reference",
+            fs: () => loadProjectFromFiles({
+                "/src/project/src/main.ts": "export const x = 10;",
+                "/src/project/tsconfig.json": JSON.stringify({
+                    compilerOptions: {
+                        module: "amd",
+                        outFile: "theApp.js"
+                    },
+                    references: [
+                        { path: "../Util/Dates" }
+                    ]
+                }),
+            }),
+            commandLineArgs: ["--p", "src/project"],
+        });
+    });
+}

tests/baselines/reference/tsc/projectReferences/initial-build/when-project-contains-invalid-project-reference.js

@@ -0,0 +1,46 @@
+Input::
+//// [/lib/lib.d.ts]
+/// <reference no-default-lib="true"/>
+interface Boolean {}
+interface Function {}
+interface CallableFunction {}
+interface NewableFunction {}
+interface IArguments {}
+interface Number { toExponential: any; }
+interface Object {}
+interface RegExp {}
+interface String { charAt: any; }
+interface Array<T> { length: number; [n: number]: T; }
+interface ReadonlyArray<T> {}
+declare const console: { log(msg: any): void; };
+
+//// [/src/project/src/main.ts]
+export const x = 10;
+
+//// [/src/project/tsconfig.json]
+{"compilerOptions":{"module":"amd","outFile":"theApp.js"},"references":[{"path":"../Util/Dates"}]}
+
+
+
+Output::
+/lib/tsc --p src/project
+src/project/tsconfig.json:1:73 - error TS6053: File '/src/Util/Dates' not found.
+
+1 {"compilerOptions":{"module":"amd","outFile":"theApp.js"},"references":[{"path":"../Util/Dates"}]}
+                                                                          ~~~~~~~~~~~~~~~~~~~~~~~~
+
+
+Found 1 error.
+
+exitCode:: ExitStatus.DiagnosticsPresent_OutputsGenerated
+
+
+//// [/src/project/theApp.js]
+define("main", ["require", "exports"], function (require, exports) {
+    "use strict";
+    exports.__esModule = true;
+    exports.x = void 0;
+    exports.x = 10;
+});
+
+