Document ways to make expect_snapshot_file() work on CI

[hughjonesd]

It's hard to make expect_snapshot_file() work on CI:

• Files like graphics typically have subtle differences between platforms
• Github actions don't persist files between runs

I don't know if there's any good solution to this, but whether there is or not, documenting that would be helpful. Perhaps it is worth mentioning in the vignette. I can add a PR if that would be useful.

[hadley]

I think these are two separate problems:

1. See vdiffr and all the hoops it jumps through to make graphics more reproducible (particularly around font metrics)
2. We need a tool that uses the gh package to download snapshot files from a PR and put them in the right place locally.

[hadley]

Basic idea:

url <- "https://github.com/r-lib/testthat/actions/runs/16852257664/job/47740252866"

path <- httr2::url_parse(url)$path
pattern <- "/(?<repo_owner>[^/]+)/(?<repo_name>[^/]+)/actions/runs/(?<run_id>[^/]+)/job/(?<job_id>[^/]+)"
match <- rematch2::re_match(path, pattern)

repo_owner <- match$repo_owner
repo_name <- match$repo_name
run_id <- match$run_id
job_id <- match$job_id

job_logs <- gh::gh(
  "GET /repos/{owner}/{repo}/actions/jobs/{job_id}/logs",
  owner = repo_owner,
  repo = repo_name,
  job_id = job_id,
  .send_headers = c("Accept" = "application/vnd.github.v3+json")
)
log_lines <- strsplit(job_logs$message, "\n")[[1]]
# todo: rewrite with rematch2
artifact <- log_lines[grepl("Artifact download URL: ", log_lines)]
# last match
artifact <- artifact[length(artifact)]
url <- strsplit(artifact, "download URL: ")[[1]][2]
artifact_id <- basename(url)

path <- withr::local_tempfile(pattern = "testthat-", fileext = ".zip")
gh::gh(
  "/repos/{owner}/{repo}/actions/artifacts/{artifact_id}/{archive_format}",
  owner = repo_owner,
  repo = repo_name,
  artifact_id = basename(url),
  archive_format = "zip",
  .destfile = path
)

files <- unzip(path, list = TRUE)
unzip_dir <- withr::local_tempdir(pattern = "unzip-")
unzip(path, exdir = unzip_dir)

src_dir <- file.path(dir(unzip_dir, full.names = TRUE)[1], "tests", "testthat", "_snaps")
dst_dir <- "tests/testthat/_snaps"

files <- dir(src_dir, recursive = TRUE)
dirs <- list.dirs(src_dir, recursive = TRUE, full.names = FALSE)

dir_create <- function(paths) {
  for (path in paths) {
    dir.create(path, recursive = TRUE, showWarnings = FALSE)
  }
}
dir_create(file.path(dst_dir, dirs))
file.copy(file.path(src_dir, files), file.path(dst_dir, files))

[hadley]

Also need to improve advice in snapshot_review_hint