Handle empty lists as well as undefined ones

src/init.test.ts

@@ -0,0 +1,32 @@
+import test from "ava";
+
+import { Config } from "./config-utils";
+import { printPathFiltersWarning } from "./init";
+import { Language } from "./languages";
+import { LoggedMessage, getRecordingLogger, setupTests } from "./testing-utils";
+
+setupTests(test);
+
+test("printPathFiltersWarning does not trigger when 'paths' and 'paths-ignore' are undefined", async (t) => {
+  const messages: LoggedMessage[] = [];
+  printPathFiltersWarning(
+    {
+      languages: [Language.cpp],
+      originalUserInput: {},
+    } as Partial<Config> as Config,
+    getRecordingLogger(messages),
+  );
+  t.is(messages.length, 0);
+});
+
+test("printPathFiltersWarning does not trigger when 'paths' and 'paths-ignore' are empty", async (t) => {
+  const messages: LoggedMessage[] = [];
+  printPathFiltersWarning(
+    {
+      languages: [Language.cpp],
+      originalUserInput: { paths: [], "paths-ignore": [] },
+    } as Partial<Config> as Config,
+    getRecordingLogger(messages),
+  );
+  t.is(messages.length, 0);
+});

src/init.ts

@@ -127,12 +127,15 @@ export async function runInit(
   return await getCombinedTracerConfig(config);
 }
 
-function printPathFiltersWarning(config: configUtils.Config, logger: Logger) {
+export function printPathFiltersWarning(
+  config: configUtils.Config,
+  logger: Logger,
+) {
   // Index include/exclude/filters only work in javascript/python/ruby.
   // If any other languages are detected/configured then show a warning.
   if (
-    (config.originalUserInput.paths ||
-      config.originalUserInput["paths-ignore"]) &&
+    (config.originalUserInput.paths?.length ||
+      config.originalUserInput["paths-ignore"]?.length) &&
     !config.languages.every(isScannedLanguage)
   ) {
     logger.warning(