The R script runs without problems, but the target pipeline gives error

I have started using targets (from package(targets)) in order to avoid re-runing my analyses several times and make them more reproducible. However, the same analysis that works fine when R in a normal R script gives me errors when I run the run.R file (using targets::tar_make()).I am using the data and script from this course: https://biostats-r.github.io/biostats/targets/

The data can be obtained using:

usethis::use_course("biostats-r/targets_workflow_svalbard")

My _targets.R file looks like this:

# Load packages required to define the pipeline:library(targets)# Set target options:tar_option_set(  packages = c("tibble", "tidyverse"))# Run the R scripts in the R/ folder with your custom functions:tar_source("R/functions2.R")# Replace the target list below with your own:list(  tar_target(    name = raw_traits,    command = "data/PFTC4_Svalbard_2018_Gradient_Traits.csv",    format = "file"  ),  tar_target(    name = traits,    command = clean_data(raw_traits)  ),  tar_target(    name = mod_area,    command = fit_model(data = traits,                        response = "Value",                        predictor = "Gradient")  ),  tar_target(    name = fig_area,    command = make_figure(traits)  ))

And myy functions2.R file is as follows:

# clean dataclean_data <- function(raw_traits){  traits <- raw_traits |>    filter(!is.na(Value)) |>    # order factor and rename variable gradient    mutate(Gradient = case_match(Gradient,"C" ~ "Control","B" ~ "Nutrients"),           Gradient = factor(Gradient, levels = c("Control", "Nutrients"))) |>    filter(Taxon == "alopecurus magellanicus",           Trait == "Leaf_Area_cm2")}# run a linear regressionfit_model <- function(data, response, predictor){  mod <- lm(as.formula(paste(response, "~", predictor)), data = data)  mod}# make figuremake_figure <- function(traits){  ggplot(traits, aes(x = Gradient, y = Value)) +    geom_boxplot(fill = c("grey80", "darkgreen")) +    labs(x = "", y = expression(Leaf~area~cm^2)) +    theme_bw()}

When I run targets:tar_make() I get the following error:

✔ skip target raw_traits▶ start target traits✖ error target traits▶ end pipeline [0.61 seconds]Error:! Error running targets::tar_make()  Error messages: targets::tar_meta(fields = error, complete_only = TRUE)  Debugging guide: https://books.ropensci.org/targets/debugging.html  How to ask for help: https://books.ropensci.org/targets/help.html  Last error: no applicable method for 'filter' applied to an object of class "character"

I have tried using only one function to make it simpler, but I always end up having a similar problem. Any suggestions on what the problem is, and how I could solve it? I find it strange that the script runs fine by itself, but then gives errors when using targets.