refactor(oauth): remove token cache deletion on invalid_grant

PutToken overwrites the cache file with O_TRUNC on re-auth, so
explicitly deleting it is unnecessary. Simplify to log a warning
and fall through to re-authentication.

Rename test to reflect actual behavior: cache file is preserved,
not deleted, when invalid_grant is encountered.

Author: karian7

oauth.go

@@ -282,9 +282,6 @@ func BuildOAuthHTTPClient(ctx context.Context, scopes []string, oAuthPort int) (
 		if err != nil {
 			if IsInvalidGrant(err) {
 				log.Printf("Cached token is invalid (refresh token revoked or expired), re-authenticating...")
-				if removeErr := os.Remove(string(tokenCache)); removeErr != nil && !os.IsNotExist(removeErr) {
-					log.Printf("Warning: failed to remove token cache: %v", removeErr)
-				}
 			} else {
 				return nil, fmt.Errorf("error refreshing token: %w", err)
 			}
@@ -394,4 +391,4 @@ func (f CacheFile) PutToken(tok *oauth2.Token) error {
 		return fmt.Errorf("CacheFile.PutToken: %w", err)
 	}
 	return nil
-}
+}

test/oauth_test.go

@@ -90,7 +90,7 @@ func TestCacheFile_RoundTrip(t *testing.T) {
 	}
 }
 
-func TestCacheFile_DeletedOnInvalidGrant(t *testing.T) {
+func TestCacheFile_ReauthOnInvalidGrant(t *testing.T) {
 	tmpDir := t.TempDir()
 	tokenPath := filepath.Join(tmpDir, "request.token")
 
@@ -114,15 +114,13 @@ func TestCacheFile_DeletedOnInvalidGrant(t *testing.T) {
 
 	// Simulate invalid_grant error from token refresh
 	refreshErr := &oauth2.RetrieveError{ErrorCode: "invalid_grant"}
-	if yt.IsInvalidGrant(refreshErr) {
-		if err := os.Remove(tokenPath); err != nil {
-			t.Fatalf("failed to remove token cache: %v", err)
-		}
+	if !yt.IsInvalidGrant(refreshErr) {
+		t.Fatal("expected IsInvalidGrant to return true for invalid_grant error")
 	}
 
-	// Verify file is deleted
-	if _, err := os.Stat(tokenPath); !os.IsNotExist(err) {
-		t.Error("token cache file should have been deleted after invalid_grant")
+	// Verify file is NOT deleted; PutToken will overwrite it when new token is written
+	if _, err := os.Stat(tokenPath); os.IsNotExist(err) {
+		t.Error("token cache file should NOT be deleted on invalid_grant; re-auth will overwrite it")
 	}
 }
 
@@ -156,4 +154,4 @@ func TestCacheFile_PutTokenOverwritesExisting(t *testing.T) {
 	if got.AccessToken != "new-token" {
 		t.Errorf("AccessToken = %q, want %q", got.AccessToken, "new-token")
 	}
-}
+}