Fix --showConfig to work when no input files are found

src/compiler/executeCommandLine.ts

@@ -639,6 +639,8 @@ function executeCommandLineWorker(
         const extendedConfigCache = new Map<string, ExtendedConfigCacheEntry>();
         const configParseResult = parseConfigFileWithSystem(configFileName, commandLineOptions, extendedConfigCache, commandLine.watchOptions, sys, reportDiagnostic)!; // TODO: GH#18217
         if (commandLineOptions.showConfig) {
+            // eslint-disable-next-line no-restricted-syntax
+            sys.write(JSON.stringify(convertToTSConfig(configParseResult, configFileName, sys), null, 4) + sys.newLine);
             if (configParseResult.errors.length !== 0) {
                 reportDiagnostic = updateReportDiagnostic(
                     sys,
@@ -648,8 +650,6 @@ function executeCommandLineWorker(
                 configParseResult.errors.forEach(reportDiagnostic);
                 return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
             }
-            // eslint-disable-next-line no-restricted-syntax
-            sys.write(JSON.stringify(convertToTSConfig(configParseResult, configFileName, sys), null, 4) + sys.newLine);
             return sys.exit(ExitStatus.Success);
         }
         reportDiagnostic = updateReportDiagnostic(

src/testRunner/unittests/config/showConfig.ts

@@ -132,6 +132,11 @@ describe("unittests:: config:: showConfig", () => {
         files: ["${configDir}/main.ts"], // eslint-disable-line no-template-curly-in-string
     });
 
+    // Test that --showConfig works even when no input files are found
+    showTSConfigCorrectly("Show TSConfig with no input files", ["-p", "tsconfig.json"], {
+        include: ["./*"],
+    });
+
     // Bulk validation of all option declarations
     for (const option of ts.optionDeclarations) {
         baselineOption(option, /*isCompilerOptions*/ true);

tests/baselines/reference/config/showConfig/Show TSConfig with no input files/tsconfig.json

@@ -0,0 +1,6 @@
+{
+    "compilerOptions": {},
+    "include": [
+        "./*"
+    ]
+}