[cli] fail when local config is missing (#7516)

Currently, when the path is not found in a `vc deploy -A SOME_PATH` command, the fallback config is used, which is unexpected behavior. This PR changes that to throw an error that says the path was not found.

---

Card: https://linear.app/vercel/issue/BUI-32/vc-deploy-a-should-fail-when-path-not-found

packages/cli/src/util/get-config.ts

@@ -42,11 +42,14 @@ export default async function getConfig(
     if (localConfig instanceof CantParseJSONFile) {
       return localConfig;
     }
-    if (localConfig !== null) {
-      config = localConfig;
-      config[fileNameSymbol] = configFile;
-      return config;
+
+    if (localConfig === null) {
+      return new CantFindConfig([humanizePath(localFilePath)]);
     }
+
+    config = localConfig;
+    config[fileNameSymbol] = configFile;
+    return config;
   }
 
   // Then try with `vercel.json` or `now.json` in the same directory

packages/cli/test/integration.js

@@ -436,6 +436,30 @@ test('deploy using --local-config flag v2', async t => {
   t.is(anotherMainRes.status, 404, 'Should not deploy/build main now.json');
 });
 
+test('deploy fails using --local-config flag with non-existent path', async t => {
+  const target = fixture('local-config-v2');
+
+  const { exitCode, stderr, stdout } = await execa(
+    binaryPath,
+    [
+      'deploy',
+      target,
+      '--local-config',
+      'does-not-exist.json',
+      ...defaultArgs,
+      '--confirm',
+    ],
+    {
+      reject: false,
+    }
+  );
+
+  t.is(exitCode, 1, formatOutput({ stderr, stdout }));
+
+  t.regex(stderr, /Error! Couldn't find a project configuration file at/);
+  t.regex(stderr, /does-not-exist\.json/);
+});
+
 test('deploy using --local-config flag above target', async t => {
   const root = fixture('local-config-above-target');
   const target = path.join(root, 'dir');