Add maximum file size for bundling wasm assets (#114)

* Add maximum file size for bundling wasm assets

* Tweak max_filesize arg use to match package_cache

* Apply suggestions from code review

Co-authored-by: Barret Schloerke <barret@posit.co>

* Handle empty SHINYLIVE_DEFAULT_MAX_FILESIZE envvar

* Print variable values in fs parse warning

---------

Co-authored-by: Barret Schloerke <barret@posit.co>

R/export.R

@@ -14,6 +14,10 @@
 #'   part of the output app's static assets. Defaults to `TRUE`.
 #' @param package_cache Cache downloaded binary WebAssembly packages. Defaults
 #'   to `TRUE`.
+#' @param max_filesize Maximum file size for bundling of WebAssembly package
+#'   assets. Parsed by [fs::fs_bytes()]. Defaults to `"100M"`. The default
+#'   value can be changed by setting the environment variable
+#'   `SHINYLIVE_DEFAULT_MAX_FILESIZE`. Set to `Inf`, `NA` or `-1` to disable.
 #' @param assets_version The version of the Shinylive assets to use in the
 #'   exported app. Defaults to [assets_version()]. Note, not all custom assets
 #'   versions may work with this release of \pkg{shinylive}. Please visit the
@@ -59,6 +63,7 @@ export <- function(
   quiet = getOption("shinylive.quiet", !is_interactive()),
   wasm_packages = TRUE,
   package_cache = TRUE,
+  max_filesize = NULL,
   assets_version = NULL,
   template_dir = NULL,
   template_params = list(),
@@ -194,7 +199,7 @@ export <- function(
   # Copy app package dependencies as Wasm binaries
   # =========================================================================
   if (wasm_packages) {
-    download_wasm_packages(appdir, destdir, package_cache)
+    download_wasm_packages(appdir, destdir, package_cache, max_filesize)
   }
 
   # =========================================================================

R/packages.R

@@ -1,3 +1,11 @@
+SHINYLIVE_DEFAULT_MAX_FILESIZE <- "100MB"
+
+# Sys env maximum filesize for asset bundling
+sys_env_max_filesize <- function() {
+  max_fs_env <- Sys.getenv("SHINYLIVE_DEFAULT_MAX_FILESIZE")
+  if (max_fs_env == "") NULL else max_fs_env
+}
+
 # Resolve package list hard dependencies
 resolve_dependencies <- function(pkgs, local = TRUE) {
   pkg_refs <- if (local) {
@@ -178,7 +186,22 @@ env_download_wasm_core_packages <- function() {
   strsplit(pkgs, "\\s*[ ,\n]\\s*")[[1]]
 }
 
-download_wasm_packages <- function(appdir, destdir, package_cache) {
+download_wasm_packages <- function(appdir, destdir, package_cache, max_filesize) {
+  max_filesize_missing <- is.null(sys_env_max_filesize()) && is.null(max_filesize)
+  max_filesize_cli_fn <- if (max_filesize_missing) cli::cli_warn else cli::cli_abort
+
+  max_filesize <- max_filesize %||% sys_env_max_filesize() %||% SHINYLIVE_DEFAULT_MAX_FILESIZE
+  max_filesize <- if (is.na(max_filesize) || (max_filesize < 0)) Inf else max_filesize
+  max_filesize_val <- max_filesize
+  max_filesize <- fs::fs_bytes(max_filesize)
+  if (is.na(max_filesize)) {
+    cli::cli_warn(c(
+      "!" = "Could not parse `max_filesize` value: {.code {max_filesize_val}}",
+      "i" = "Setting to {.code {SHINYLIVE_DEFAULT_MAX_FILESIZE}}"
+    ))
+    max_filesize <- fs::fs_bytes(SHINYLIVE_DEFAULT_MAX_FILESIZE)
+  }
+
   # Core packages in base webR image that we don't need to download
   shiny_pkgs <- c("shiny", "bslib", "renv")
   shiny_pkgs <- resolve_dependencies(shiny_pkgs, local = FALSE)
@@ -240,13 +263,31 @@ download_wasm_packages <- function(appdir, destdir, package_cache) {
     # Create package ref and lookup download URLs
     meta <- prepare_wasm_metadata(pkg, prev_meta)
 
-    if (!meta$cached && length(meta$assets) > 0) {
+    if (!meta$cached) {
       # Download Wasm binaries and copy to static assets dir
       for (file in meta$assets) {
-        utils::download.file(file$url, fs::path(pkg_subdir, file$filename))
+        path <- fs::path(pkg_subdir, file$filename)
+        utils::download.file(file$url, path)
+
+        # Disallow this package if an asset is too large
+        if (fs::file_size(path) > max_filesize) {
+          fs::dir_delete(pkg_subdir)
+          meta$assets = list()
+          max_filesize_cli_fn(c(
+            "!" = "The file size of package {.pkg {pkg}} is larger than the maximum allowed file size of {.strong {max_filesize}}.",
+            "!" = "This package will not be included as part of the WebAssembly asset bundle.",
+            "i" = "Set the maximum allowed size to {.code -1}, {.code Inf}, or {.code NA} to disable this check.",
+            "i" = if (max_filesize_missing) "Explicitly set the maximum allowed size to treat this as an error." else NULL
+          ))
+          break
+        }
       }
+
       meta$cached <- TRUE
-      meta$path <- glue::glue("packages/{pkg}/{meta$assets[[1]]$filename}")
+      meta$path <- NULL
+      if (length(meta$assets) > 0) {
+        meta$path <- glue::glue("packages/{pkg}/{meta$assets[[1]]$filename}")
+      }
     }
     meta
   })

R/quarto_ext.R

@@ -256,7 +256,7 @@ build_app_resources <- function(app_json) {
   # Download wasm binaries ready to embed into Quarto deps
   withr::with_options(
     list(shinylive.quiet = TRUE),
-    download_wasm_packages(appdir, destdir, package_cache = TRUE)
+    download_wasm_packages(appdir, destdir, package_cache = TRUE, max_filesize = NULL)
   )
 
   # Enumerate R package Wasm binaries and prepare the VFS images as html deps

tests/testthat/apps/app-utf8/app.R

@@ -0,0 +1,7 @@
+library(shiny)
+library(utf8)
+
+ui <- fluidPage()
+server <- function(input, output) {}
+
+shinyApp(ui, server)

tests/testthat/test-export.R

@@ -134,4 +134,50 @@ test_that("export with template", {
     index_content,
     "<meta name=\"description\" content=\"My custom export template param test app\">"
   )
-})
+})
+
+test_that("export - include R package in wasm assets", {
+  maybe_skip_test()
+
+  assets_ensure()
+
+  # Ensure pkgcache metadata has been loaded
+  invisible(pkgcache::meta_cache_list())
+
+  # Create a temporary output directory
+  out_dir <- file.path(tempfile(), "out")
+  pkg_dir <- file.path(out_dir, "shinylive", "webr", "packages")
+
+  # A package with an external dependency
+  app_dir <- test_path("apps", "app-utf8")
+  asset_package <- c("utf8")
+
+  # Default filesize 100MB
+  expect_silent_unattended({
+    export(app_dir, out_dir)
+  })
+  expect_contains(dir(pkg_dir), c(asset_package))
+  unlink_path(out_dir)
+
+  # No maximum filesize
+  expect_silent_unattended({
+    export(app_dir, out_dir, max_filesize = Inf)
+  })
+  expect_contains(dir(pkg_dir), c(asset_package))
+  unlink_path(out_dir)
+
+  # Set a maximum filesize
+  expect_error({
+    export(app_dir, out_dir, max_filesize = "1K")
+  })
+  unlink_path(out_dir)
+
+  expect_error({
+    withr::with_envvar(
+      list("SHINYLIVE_DEFAULT_MAX_FILESIZE" = "1K"),
+      export(app_dir, out_dir)
+    )
+  })
+  unlink_path(out_dir)
+
+})