Announce snapshot file before evaluation (#109)

Closes r-lib/testthat#1393

Author: lionel-

DESCRIPTION

@@ -30,7 +30,7 @@ Imports:
     htmltools,
     lifecycle,
     rlang,
-    testthat (>= 3.0.0),
+    testthat (>= 3.0.2.9001),
     xml2 (>= 1.0.0)
 Suggests:
     covr,
@@ -39,6 +39,8 @@ Suggests:
     withr
 LinkingTo:
     cpp11
+Remotes:
+    r-lib/testthat
 RoxygenNote: 7.1.1.9001
 Roxygen: list(markdown = TRUE)
 URL: https://vdiffr.r-lib.org/, https://github.com/r-lib/vdiffr

NEWS.md

@@ -1,5 +1,10 @@
 # vdiffr (development version)
 
+* testthat no longer auto-deletes snapshot files that were not
+  generated because of an unexpected error or a `skip()`
+  (r-lib/testthat#1393).
+
+
 # vdiffr 1.0.0
 
 This release includes two major changes:

R/expect-doppelganger.R

@@ -91,7 +91,16 @@ expect_doppelganger <- function(title,
                                 ...,
                                 writer = write_svg,
                                 cran = FALSE) {
+  testthat::local_edition(3)
+
   fig_name <- str_standardise(title)
+  file <- paste0(fig_name, ".svg")
+
+  # Announce snapshot file before touching `fig` in case evaluation
+  # causes an error. This allows testthat to restore the files
+  # (see r-lib/testthat#1393).
+  testthat::announce_snapshot_file(name = file)
+
   testcase <- make_testcase_file(fig_name)
   writer(fig, testcase, title)
 
@@ -115,10 +124,6 @@ expect_doppelganger <- function(title,
     ))
   }
 
-  testthat::local_edition(3)
-
-  file <- paste0(fig_name, ".svg")
-
   withCallingHandlers(
     testthat::expect_snapshot_file(
       testcase,
@@ -134,7 +139,7 @@ expect_doppelganger <- function(title,
         ))
       }
 
-      if (!is.null(snapshotter <- get_snapshotter())) {
+      if (!is_null(snapshotter <- get_snapshotter())) {
         path_old <- snapshot_path(snapshotter, file)
         path_new <- snapshot_path(snapshotter, paste0(fig_name, ".new.svg"))
 

tests/testthat/test-expect-doppelganger.R

@@ -89,3 +89,21 @@ test_that("supports `grob` objects (#36)", {
   )
   expect_doppelganger("grob", circle)
 })
+
+test_that("skips and unexpected errors reset snapshots (r-lib/testthat#1393)", {
+  regenerate <- FALSE
+
+  if (regenerate) {
+    withr::local_envvar(c(VDIFFR_REGENERATE_SNAPS = "true"))
+  }
+
+  suppressMessages(
+    test_file(
+      test_path("test-snapshot", "test-snapshot.R"),
+      reporter = NULL
+    )
+  )
+
+  expect_true(file.exists("test-snapshot/_snaps/snapshot/error-resets-snapshots.svg"))
+  expect_true(file.exists("test-snapshot/_snaps/snapshot/skip-resets-snapshots.svg"))
+})

tests/testthat/test-snapshot/_snaps/snapshot/error-resets-snapshots.svg

@@ -0,0 +1,15 @@
+test_that("errors reset snapshots", {
+  if (nzchar(Sys.getenv("VDIFFR_REGENERATE_SNAPS"))) {
+    expect_doppelganger("error resets snapshots", function() plot(1:3))
+  } else {
+    expect_doppelganger("error resets snapshots", function() stop("failing"))
+  }
+})
+
+test_that("skips reset snapshots", {
+  if (nzchar(Sys.getenv("VDIFFR_REGENERATE_SNAPS"))) {
+    expect_doppelganger("skip resets snapshots", function() plot(1:3))
+  } else {
+    expect_doppelganger("skip resets snapshots", function() skip("skipping"))
+  }
+})