WooCommerce Reset Password only by email

It is possible to change form-lost-password in the way, that user can be reset password only by email (validate username like email and show error, when input not email), I don't find a hook for this.

You can use "lostpassword_errors" hook.

Please check line 2930 of wp-includes/user.php

$errors = apply_filters( 'lostpassword_errors', $errors, $user_data );

So, if you want to reset password only by email address, not by username, you can use following code.

add_filter( 'lostpassword_errors', 'reset_password_by_email_only', 20, 2 );

function reset_password_by_email_only( $errors, $user_data ) {
    $user_login = !empty($_POST['user_login'])?$_POST['user_login']:'';

    if ( empty( $user_login ) ) {
        $errors->add( 'empty_username', __( '<strong>Error</strong>: Please enter a username or email address.' ) );
    } elseif ( strpos( $user_login, '@' ) ) {
        $user_data = get_user_by( 'email', trim( wp_unslash( $user_login ) ) );
        if ( empty( $user_data ) ) {
            $errors->add( 'invalid_email', __( '<strong>Error</strong>: There is no account with that username or email address.' ) );
        }
    } else {
        $errors->add( 'invalid_input', __('<strong>Error</strong>: YOUR MESSAGE FOR INVALID INPUT HERE.' ) );
    }

    return $errors;
}

It will return error when user input is not email address.

Hope it would help you.

UPDATE:

If you are using woocommerce and you want to reset password by email address only on myaccount page(customer area), you need to use "lostpassword_post" hook.

    add_action( 'lostpassword_post', 'reset_password_by_email_only', 20, 2 );

function reset_password_by_email_only( $errors, $user_data ) {
    $user_login = !empty($_POST['user_login'])?$_POST['user_login']:'';

    if ( empty( $user_login ) ) {
        $errors->add( 'empty_username', __( '<strong>Error</strong>: Please enter a username or email address.' ) );
    } elseif ( strpos( $user_login, '@' ) ) {
        $user_data = get_user_by( 'email', trim( wp_unslash( $user_login ) ) );
        if ( empty( $user_data ) ) {
            $errors->add( 'invalid_email', __( '<strong>Error</strong>: There is no account with that username or email address.' ) );
        }
    } else {
        $errors->add( 'invalid_input', __('<strong>Error</strong>: YOUR MESSAGE FOR INVALID INPUT HERE.' ) );
    }
}