writeAlizer (version 1.7.3)

wa_download: Download and cache an artifact (graceful offline behavior)

Description

Public helper to fetch an artifact into the user cache. This function delegates to the internal downloader used by the package at runtime, so it benefits from the same behavior:

Usage

wa_download(file, url, sha256 = NULL, quiet = TRUE)
download(file, url) # deprecated

Value

A character scalar: the absolute path to the cached file.

Arguments

file

Character scalar; filename to use in the cache (e.g., `"rb_mod1a.rda"`).

url

Character scalar; source URL. May be a `file://` URL for local testing.

sha256

Optional 64-hex SHA-256 checksum for verification. If provided, the cached file must match it (or a re-download is attempted).

quiet

Logical; if `TRUE`, suppresses download progress messages.

Details

- Respects options(writeAlizer.mock_dir) to load local mock copies (useful for tests/examples and offline runs). - Fails gracefully with a clear, informative message when Internet resources are unavailable or have changed (per CRAN policy). - Verifies an optional SHA-256 checksum and re-downloads or errors if it does not match.

Examples

# Offline-friendly example using a local source (no network) — CRAN-safe
if (requireNamespace("withr", quietly = TRUE)) {
  withr::local_options(writeAlizer.mock_dir = NULL, writeAlizer.offline = FALSE)
}

src <- tempfile(fileext = ".bin")
writeBin(as.raw(1:10), src)
url <- paste0("file:///", normalizePath(src, winslash = "/"))

# Deterministic and quiet: checksum + cache reuse
sha <- digest::digest(src, algo = "sha256", file = TRUE)
dest <- wa_download("example.bin", url = url, sha256 = sha, quiet = TRUE)
file.exists(dest)

# Using a mock directory to avoid network access:
# options(writeAlizer.mock_dir = "/path/to/local/artifacts")
# dest <- wa_download("rb_mod1a.rda", url = "https://example.com/rb_mod1a.rda")