r + shiny + ggplot2 + flexdashboard object of type 'closure' is not subsettable

Question

I am currently making a dashboard to produce a dynamic plot depending on user input. I collect 3 parameters from the user: the starting date, ending date to set the time window in my plot and the specific physical site he wants to see information about. The dataset I am using is a simple csv file with dates and numeric physical data.

I'm getting the following error related to my ds() function called in the renderPlot:

object of type 'closure' is not subsettable I thought the parenthesis would solve this but they did not, I think my ds() function does return a dataframe which should be the correct data type for the data argument in the ggplot function call but it is not. Maybe there is a problem when I wrap the ggplot call in the renderPlot function but I was not able to debug this. I'm a bit confused If somebody can help me I'd appreciate that. Thanks

Here is the code

# préparation des tables (préliminaire)
dataset_stockage <- read.csv2('stock-quotidien-stockages-gaz.csv')
dataset_stockage[,2] <- as.numeric(dataset_stockage[,2])
dataset_stockage$date <- as.Date(dataset_stockage$date,format="%d/%m/%Y")
dataset_stockage <- arrange(dataset_stockage,date)

dataset_debit <- read.csv2('debit-quotidien-stockages-gaz.csv')
dataset_debit[,2] <- as.numeric(dataset_debit[,2])

dataset_impexp <- read.csv2('imports-exports-commerciaux.csv')
dataset_impexp <- dataset_impexp %>% mutate(date = str_replace_all(date, "-", "/"))
dataset_impexp$date <- as.Date(dataset_impexp$date,format="%Y/%m/%d")
dataset_impexp <- arrange(dataset_impexp,date)
```

# Stockage de gaz naturel 

Column {.sidebar}
-----------------------------------------------------------------------

Selectionnez le PITS que vous souhaitez visualiser ainsi que la plage temporelle qui vous intéresse

```{r}
dataset_stockage$date <- format(dataset_stockage$date, "%Y-%m-%d")

selectInput("pit", label = "PITS à visualiser:",
            choices = c(unique(dataset_stockage$pits)))

dateInput(
  "startdate",
  "Date de début: ",
  value = min(dataset_stockage$date, na.rm = TRUE),
  min = min(dataset_stockage$date, na.rm = TRUE),
  max = max(dataset_stockage$date, na.rm = TRUE),
  language = "fr"
)

dateInput(
  "enddate",
  "Date de fin: ",
  value = max(dataset_stockage$date, na.rm = TRUE),
  min = min(dataset_stockage$date, na.rm = TRUE),
  max = max(dataset_stockage$date, na.rm = TRUE),
  language = "fr"
)
```

Column
-----------------------------------------------------------------------

### Plot du niveau de stockage dans le site demandé

```{r}
ds <- reactive({dataset_stockage[dataset_stockage$pits==input$pit,] %>% ds[ds$stock_fin_de_journee<6*1000000000,] %>%
subset(ds,(date<as.Date(input$enddate)&date>as.Date(input$tartdate)))
})

renderPlot({ggplot(data=ds(),aes(x=date)) + geom_point(mapping=aes(y=stock_fin_de_journee)) + 
          labs(title = "Niveau de stockage (GWh PCS 0C)",
               x = "Date",
               y = "Stock de gaz (GWh PCS 0C)")
})

```