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# A context object for tracking a cache that needs to be dirtied when a set of
# files changes on disk. Each time the cache is dirtied, the set of files is
# cleared. Therefore, the set of files needs to be re-built each time the cached
# code executes. This approach allows for dynamic dependency graphs.
CacheContext <- R6Class(
'CacheContext',
portable = FALSE,
class = FALSE,
public = list(
.dirty = TRUE,
# List of functions that return TRUE if dirty
.tests = list(),
addDependencyFile = function(file) {
if (.dirty)
return()
file <- normalizePath(file)
mtime <- file.info(file)$mtime
.tests <<- c(.tests, function() {
newMtime <- try(file.info(file)$mtime, silent=TRUE)
if (inherits(newMtime, 'try-error'))
return(TRUE)
return(!identical(mtime, newMtime))
})
invisible()
},
forceDirty = function() {
.dirty <<- TRUE
.tests <<- list()
invisible()
},
isDirty = function() {
if (.dirty)
return(TRUE)
for (test in .tests) {
if (test()) {
forceDirty()
return(TRUE)
}
}
return(FALSE)
},
reset = function() {
.dirty <<- FALSE
.tests <<- list()
},
with = function(func) {
oldCC <- .currentCacheContext$cc
.currentCacheContext$cc <- self
on.exit(.currentCacheContext$cc <- oldCC)
return(func())
}
)
)
.currentCacheContext <- new.env()
# Indicates to Shiny that the given file path is part of the dependency graph
# for whatever is currently executing (so far, only ui.R). By default, ui.R only
# gets re-executed when it is detected to have changed; this function allows the
# caller to indicate that it should also re-execute if the given file changes.
#
# If NULL or NA is given as the argument, then ui.R will re-execute next time.
dependsOnFile <- function(filepath) {
if (is.null(.currentCacheContext$cc))
return()
if (is.null(filepath) || is.na(filepath))
.currentCacheContext$cc$forceDirty()
else
.currentCacheContext$cc$addDependencyFile(filepath)
}
|
