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

In writeAlizer: Generate Predicted Writing Quality Scores

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

Arguments

file	Character scalar; relative 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). NULL, NA, and an empty string mean no checksum. Local mock artifacts bypass checksums.
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.

Local file URLs work offline. Internet URLs require a connection unless a valid cached copy exists. Downloads are verified before replacing a cached file, and failed transfers leave the previous copy intact. Nested relative filenames are accepted; absolute names and parent-directory traversal are not. The filename is the cache key: changing only the URL does not refresh an existing file. Supply the expected checksum or clear the cache to refresh it.

Value

A character scalar: the absolute path to the cached file, or the local artifact path when writeAlizer.mock_dir is set.

Examples

local({
  cache <- tempfile("wa-cache-")
  old <- options(writeAlizer.cache_dir = cache,
                 writeAlizer.mock_dir = NULL, writeAlizer.offline = TRUE)
  on.exit(options(old))
  on.exit(unlink(cache, recursive = TRUE), add = TRUE)
  src <- tempfile(fileext = ".bin")
  writeBin(as.raw(1:10), src)
  on.exit(unlink(src), add = TRUE)
  path <- normalizePath(src, winslash = "/")
  url <- paste0(if (.Platform$OS.type == "windows") "file:///" else "file://",
                utils::URLencode(path))
  sha <- digest::digest(src, algo = "sha256", file = TRUE)
  dest <- wa_download("example.bin", url, sha256 = sha)
  file.exists(dest)
})

writeAlizer documentation built on Sept. 17, 2026, 1:08 a.m.