MySQL Connection Error Handling with tryCatch - mysql

Question

I have a R Shiny Application which uses MySQL as a datasource. When the application loads and the user logs into the app with their username and password, a database connection interface opens up where the user inputs their MySQL credentials. In order to prevent the app from crashing when the user enters the wrong MySQL connection credential, I am trying to use the following error handling.
# run when Load Data button is clicked
datapms <- eventReactive(input$pull_data, {
req(input$db_user,input$db_user,input$db_password,input$db_name,input$db_host,input$db_port)
progress <- Progress$new(session, min=1, max=15)
on.exit(progress$close())
progress$set(message = 'Pulling data from database',
detail = 'This message will disappear once completed.')
# establish a database connection
tryCatch({
con <- RMySQL::dbConnect(
RMySQL::MySQL(),
user = input$db_user,
password = input$db_password,
dbname = input$db_name,
host = input$db_host
)
}, error = function(e) {
debug_msg(e$message)
})
# construct the SQL statement
sql <- "SELECT * FROM pmsanalytics;"
# Fetch data
pmsanalytics <- tryCatch({
pmsanalytics <- dbGetQuery(conn = con, sql)
}, error = function(e) {
debug_msg(e$message)
})
### display debugging message in R (if local)
### and in the console log (if running in shiny)
debug_msg <- function(...) {
is_local <- Sys.getenv('SHINY_PORT') == ""
in_shiny <- !is.null(shiny::getDefaultReactiveDomain())
txt <- toString(list(...))
if (is_local) message(txt)
if (in_shiny) shinyjs::runjs(sprintf("console.debug(\"%s\")", text))
}
Initially this code was working, and the app was not crashing. However, now, when for example one enters the wrong connection credentials, i am getting the following error message:
Warning: Error in as.character: cannot coerce type 'closure' to vector of type 'character'
138: sprintf
136: debug_msg [C:\PMSAnalytics/app.R#107]
135: value[[3L]] [C:\PMSAnalytics/app.R#211]
134: tryCatchOne
133: tryCatchList
132: tryCatch
131: eventReactiveValueFunc [C:\PMSAnalytics/app.R#202]
Basically, the app crashes because there is no data which it is expecting to get, in other words the reactive datapms() data source it is expecting to get is empty.
Kind assist in reviewing my code to prevent app crashing.
Regards,
Chris