Windows symlinks

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: hfhub
 Title: Hugging Face Hub Interface
-Version: 0.1.1.9000
+Version: 0.1.1.9001
 Authors@R: c(
     person("Daniel", "Falbel", , "daniel@posit.co", role = c("aut", "cre")),
     person("Regouby", "Christophe", , "christophe.regouby@free.fr", c("ctb")),

NEWS.md

@@ -1,6 +1,7 @@
 # hfhub (development version)
 
 * Added FR translation of the R messages. (#8 @cregouby)
+* Fixed symlink issues on Windows that caused model snapshots to be empty. (#9)
 
 # hfhub 0.1.1
 

R/hub_download.R

@@ -129,10 +129,12 @@ hub_download <- function(repo_id, filename, ..., revision = "main", repo_type =
   }
 
   if (fs::file_exists(blob_path) && !force_download) {
-    fs::link_create(blob_path, pointer_path)
+    # Blob already exists, we'll link/copy it
+    link_or_copy(blob_path, pointer_path, FALSE, storage_folder)
     return(pointer_path)
   }
 
+  # Download the blob
   withr::with_tempfile("tmp", {
     lock <- filelock::lock(paste0(blob_path, ".lock"))
     on.exit({filelock::unlock(lock)})
@@ -156,12 +158,11 @@ hub_download <- function(repo_id, filename, ..., revision = "main", repo_type =
       cli::cli_abort(gettext("Error downloading from {.url {url}}"), parent = err)
     })
     fs::file_move(tmp, blob_path)
-
-    # fs::link_create doesn't work for linking files on windows.
-    try(fs::file_delete(pointer_path), silent = TRUE) # delete the link to avoid warnings
-    file.symlink(blob_path, pointer_path)
   })
 
+  # Create pointer file (symlink, move, or copy depending on symlink support)
+  link_or_copy(blob_path, pointer_path, TRUE, storage_folder)
+
   pointer_path
 }
 
@@ -288,5 +289,84 @@ reqst <- function(method, url, ..., follow_relative_redirects = FALSE) {
   method(url, ...)
 }
 
+# Cache for symlink support detection (per storage folder)
+symlink_support_cache <- new.env(parent = emptyenv())
+
+#' Check if symlinks are supported in the given directory
+#'
+#' Tests whether file.symlink() works in the storage folder.
+#' Caches the result per folder to avoid repeated tests.
+#' Matches Python's huggingface_hub behavior.
+#'
+#' @param storage_folder Path to storage folder
+#' @return TRUE if symlinks work, FALSE otherwise
+#' @noRd
+supports_symlinks <- function(storage_folder) {
+  # Check cache first
+  cache_key <- as.character(storage_folder)
+  if (exists(cache_key, envir = symlink_support_cache)) {
+    return(get(cache_key, envir = symlink_support_cache))
+  }
+
+  # Test symlink support
+  test_dir <- fs::path(storage_folder, ".symlink_test")
+  fs::dir_create(test_dir)
+  on.exit(fs::dir_delete(test_dir), add = TRUE)
+
+  test_file <- fs::path(test_dir, "test.txt")
+  test_link <- fs::path(test_dir, "test_link.txt")
+
+  writeLines("test", test_file)
+  result <- suppressWarnings(file.symlink(test_file, test_link))
+
+  # Cache the result
+  assign(cache_key, result, envir = symlink_support_cache)
+
+  # Show warning if symlinks aren't supported (matches Python's behavior)
+  if (!result && !isTRUE(Sys.getenv("HF_HUB_DISABLE_SYMLINKS_WARNING") != "")) {
+    cli::cli_warn(c(
+      "{.pkg hfhub} cache-system uses symlinks by default to efficiently store ",
+      "duplicated files but your machine does not support them in {.path {storage_folder}}. ",
+      "Caching files will still work but in a degraded version that might require ",
+      "more space on your disk. This warning can be disabled by setting the ",
+      "{.envvar HF_HUB_DISABLE_SYMLINKS_WARNING} environment variable.",
+      "i" = "For more details, see {.url https://huggingface.co/docs/huggingface_hub/how-to-cache#limitations}",
+      "i" = "To support symlinks on Windows, you either need to activate Developer Mode or run R as administrator."
+    ))
+  }
+
+  result
+}
+
+#' Link, move, or copy blob to pointer path based on symlink support
+#'
+#' Helper function that handles creating the final pointer file.
+#' - If symlinks supported: creates symlink
+#' - If symlinks not supported and blob just downloaded: moves file
+#' - If symlinks not supported and blob already existed: copies file
+#'
+#' @param blob_path Path to the blob file (source)
+#' @param pointer_path Path to the pointer file (destination)
+#' @param owned Whether the blob is safe to delete if symlinks are not supported
+#' @param storage_folder Path to storage folder (for symlink check)
+#' @noRd
+link_or_copy <- function(blob_path, pointer_path, owned, storage_folder) {
+  use_symlinks <- supports_symlinks(storage_folder)
+
+  if (use_symlinks) {
+    # Original behavior: create symlink
+    # fs::link_create doesn't work for linking files on windows.
+    try(fs::file_delete(pointer_path), silent = TRUE) # delete the link to avoid warnings
+    file.symlink(blob_path, pointer_path)
+  } else {
+    # Degraded mode: move if just downloaded, copy if already existed
+    if (owned) {
+      fs::file_move(blob_path, pointer_path)
+    } else {
+      fs::file_copy(blob_path, pointer_path, overwrite = TRUE)
+    }
+  }
+}
+
 utils::globalVariables("tmp")
 

tests/testthat/_snaps/hub_snapshot.md

@@ -3,7 +3,7 @@
     Code
       p <- hub_snapshot("dfalbel/cran-packages", repo_type = "dataset",
         allow_patterns = "\\.R")
-    Message <cliMessage>
+    Message
       i Snapshotting files 0/4
       v Snapshotting files 4/4 [0ms]
 

tests/testthat/test-hub_download.R

@@ -1,6 +1,8 @@
 skip_on_cran()
 
 test_that("hub_download", {
+  withr::local_envvar(list(HF_HUB_DISABLE_SYMLINKS_WARNING = "1"))
+
   file <- hub_download("gpt2", filename = "config.json")
 
   expect_equal(
@@ -26,6 +28,11 @@ test_that("hub_download", {
     file <- hub_download("gpt2", filename = "config.json")
   })
   expect_equal(list.files(tmp), "models--gpt2")
+  # Make sure the config.json exists (detect broken symlink support in Windows)
+  expect_length(
+    Sys.glob(file.path(tmp, "models--gpt2", "snapshots", "*", "config.json")),
+    1
+  )
 })
 
 test_that("can download from private repo", {