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Set cache control headers to avoid caching UI #3810

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Set cache control headers to avoid caching UI #3810

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596165e
Set cache control headers to avoid caching UI
gadenbuie Apr 18, 2023
7909389
Only disable cache if a theme has been set
schloerke Apr 18, 2023
f8a91fb
Always disable UI cache (unless there's an existing `Cache-Control` h…
schloerke Apr 19, 2023
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29 changes: 25 additions & 4 deletions R/shinyui.R
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Original file line number Diff line number Diff line change
Expand Up @@ -231,11 +231,32 @@ uiHttpHandler <- function(ui, uiPattern = "^/$") {
if (is.null(uiValue))
return(NULL)

if (inherits(uiValue, "httpResponse")) {
return(uiValue)
} else {
# Avoid caching the UI response to ensure that UI is always re-evaluated.
# This is necessary for getCurrentTheme() to be known, required for BS4+.
no_cache_headers <- list(
"Cache-Control" = "no-cache, no-store, must-revalidate",
"Pragma" = "no-cache",
"Expires" = "0"
)

if (!inherits(uiValue, "httpResponse")) {
html <- renderPage(uiValue, showcaseMode, testMode)
return(httpResponse(200, content=html))
uiValue <- httpResponse(200, content=html)
}

# 2023-04-23 jcheng5: Example app in PR comment
# https://github.com/rstudio/shiny/pull/3810#issuecomment-1513828996
# > I think we should always add the cache-busting headers. Without it,
# Connect and ShinyApps.io configurations will have problems in that the
# workerId could be a stale value.
if (
# The user has not set a `Cache-Control` policy within their UI func
!"Cache-Control" %in% names(uiValue$headers)
) {
# Disable caching for the UI's response
uiValue$headers <- utils::modifyList(uiValue$headers, no_cache_headers)
}

uiValue
}
}