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

Co-authored-by: RyanCavanaugh <[email protected]>

Author: Copilot

src/compiler/executeCommandLine.ts

@@ -638,19 +638,24 @@ function executeCommandLineWorker(
     if (configFileName) {
         const extendedConfigCache = new Map<string, ExtendedConfigCacheEntry>();
         const configParseResult = parseConfigFileWithSystem(configFileName, commandLineOptions, extendedConfigCache, commandLine.watchOptions, sys, reportDiagnostic)!; // TODO: GH#18217
-        if (commandLineOptions.showConfig) {
-            if (configParseResult.errors.length !== 0) {
-                reportDiagnostic = updateReportDiagnostic(
-                    sys,
-                    reportDiagnostic,
-                    configParseResult.options,
-                );
-                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);
+        if (commandLineOptions.showConfig) {
+            // For --showConfig, filter out "no inputs found" errors since the purpose is to show configuration, not compile
+            const errorsExcludingNoInputs = configParseResult.errors.filter(error => 
+                error.code !== Diagnostics.No_inputs_were_found_in_config_file_0_Specified_include_paths_were_1_and_exclude_paths_were_2.code
+            );
+            
+            if (errorsExcludingNoInputs.length !== 0) {
+                reportDiagnostic = updateReportDiagnostic(
+                    sys,
+                    reportDiagnostic,
+                    configParseResult.options,
+                );
+                errorsExcludingNoInputs.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(
             sys,

src/testRunner/unittests/config/showConfig.ts

@@ -129,9 +129,14 @@ describe("unittests:: config:: showConfig", () => {
         include: [
             "${configDir}/src/**/*", // eslint-disable-line no-template-curly-in-string
         ],
-        files: ["${configDir}/main.ts"], // eslint-disable-line no-template-curly-in-string
-    });
-
+        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);