Enforce that snapshot files should be unique

NEWS.md

@@ -23,6 +23,8 @@
 
 * Test results show hyperlinks to failed expectation when supported (#1544). 
 
+* `expect_snapshot_file(name=)` must have a unique file path. If a snapshot file attempts to be
+  saved with a duplicate `name`, an error will be thrown. (#1592)
 
 # testthat 3.1.2
 

R/snapshot-reporter.R

@@ -7,6 +7,7 @@ SnapshotReporter <- R6::R6Class("SnapshotReporter",
     test = NULL,
     test_file_seen = character(),
     snap_file_seen = character(),
+    snap_file_saved = character(),
     variants_changed = FALSE,
     fail_on_new = FALSE,
 
@@ -22,6 +23,7 @@ SnapshotReporter <- R6::R6Class("SnapshotReporter",
     start_file = function(path, test = NULL) {
       self$file <- context_name(path)
       self$test_file_seen <- c(self$test_file_seen, self$file)
+      self$snap_file_saved <- character()
 
       self$variants_changed <- character()
 
@@ -98,6 +100,19 @@ SnapshotReporter <- R6::R6Class("SnapshotReporter",
       } else {
         snap_dir <- file.path(self$snap_dir, variant, self$file)
       }
+
+      save_path <- file.path(snap_dir, name)
+      if (save_path %in% self$snap_file_saved) {
+        fail(
+          paste0(
+            "Snapshot file '", name, "' has already been saved.",
+            " Please provide a unique snapshot file name"
+          ),
+          trace_env = trace_env
+        )
+      }
+      self$snap_file_saved <- c(self$snap_file_saved, save_path)
+
       snapshot_file_equal(
         snap_test_dir = snap_dir,
         snap_name = name,

tests/testthat/_snaps/R4.0/snapshot-file/nickname.txt

@@ -1 +1 @@
-Shake and Throw
+R4.0

tests/testthat/_snaps/R4.0/snapshot.md

@@ -1,7 +1,7 @@
 # can access nickname
 
     Code
-      version$nickname
+      r_version()
     Output
-      [1] "Shake and Throw"
+      [1] "R4.0"
 

tests/testthat/_snaps/R4.1/snapshot-file/nickname.txt

@@ -1 +1 @@
-Bird Hippie
+R4.1

tests/testthat/_snaps/R4.1/snapshot.md

@@ -1,7 +1,7 @@
 # can access nickname
 
     Code
-      version$nickname
+      r_version()
     Output
-      [1] "Bird Hippie"
+      [1] "R4.1"
 

tests/testthat/_snaps/snapshot-file/foo-binary.csv

@@ -0,0 +1,33 @@
+"","mpg","cyl","disp","hp","drat","wt","qsec","vs","am","gear","carb"
+"Mazda RX4",21,6,160,110,3.9,2.62,16.46,0,1,4,4
+"Mazda RX4 Wag",21,6,160,110,3.9,2.875,17.02,0,1,4,4
+"Datsun 710",22.8,4,108,93,3.85,2.32,18.61,1,1,4,1
+"Hornet 4 Drive",21.4,6,258,110,3.08,3.215,19.44,1,0,3,1
+"Hornet Sportabout",18.7,8,360,175,3.15,3.44,17.02,0,0,3,2
+"Valiant",18.1,6,225,105,2.76,3.46,20.22,1,0,3,1
+"Duster 360",14.3,8,360,245,3.21,3.57,15.84,0,0,3,4
+"Merc 240D",24.4,4,146.7,62,3.69,3.19,20,1,0,4,2
+"Merc 230",22.8,4,140.8,95,3.92,3.15,22.9,1,0,4,2
+"Merc 280",19.2,6,167.6,123,3.92,3.44,18.3,1,0,4,4
+"Merc 280C",17.8,6,167.6,123,3.92,3.44,18.9,1,0,4,4
+"Merc 450SE",16.4,8,275.8,180,3.07,4.07,17.4,0,0,3,3
+"Merc 450SL",17.3,8,275.8,180,3.07,3.73,17.6,0,0,3,3
+"Merc 450SLC",15.2,8,275.8,180,3.07,3.78,18,0,0,3,3
+"Cadillac Fleetwood",10.4,8,472,205,2.93,5.25,17.98,0,0,3,4
+"Lincoln Continental",10.4,8,460,215,3,5.424,17.82,0,0,3,4
+"Chrysler Imperial",14.7,8,440,230,3.23,5.345,17.42,0,0,3,4
+"Fiat 128",32.4,4,78.7,66,4.08,2.2,19.47,1,1,4,1
+"Honda Civic",30.4,4,75.7,52,4.93,1.615,18.52,1,1,4,2
+"Toyota Corolla",33.9,4,71.1,65,4.22,1.835,19.9,1,1,4,1
+"Toyota Corona",21.5,4,120.1,97,3.7,2.465,20.01,1,0,3,1
+"Dodge Challenger",15.5,8,318,150,2.76,3.52,16.87,0,0,3,2
+"AMC Javelin",15.2,8,304,150,3.15,3.435,17.3,0,0,3,2
+"Camaro Z28",13.3,8,350,245,3.73,3.84,15.41,0,0,3,4
+"Pontiac Firebird",19.2,8,400,175,3.08,3.845,17.05,0,0,3,2
+"Fiat X1-9",27.3,4,79,66,4.08,1.935,18.9,1,1,4,1
+"Porsche 914-2",26,4,120.3,91,4.43,2.14,16.7,0,1,5,2
+"Lotus Europa",30.4,4,95.1,113,3.77,1.513,16.9,1,1,5,2
+"Ford Pantera L",15.8,8,351,264,4.22,3.17,14.5,0,1,5,4
+"Ferrari Dino",19.7,6,145,175,3.62,2.77,15.5,0,1,5,6
+"Maserati Bora",15,8,301,335,3.54,3.57,14.6,0,1,5,8
+"Volvo 142E",21.4,4,121,109,4.11,2.78,18.6,1,1,4,2

tests/testthat/test-snapshot-file.R

@@ -26,7 +26,7 @@ test_that("expect_snapshot_file works", {
   withr::local_options(lifecycle_verbosity = "quiet")
   expect_snapshot_file(
     path,
-    "foo.csv",
+    "foo-binary.csv",
     binary = FALSE
   )
 })
@@ -48,13 +48,26 @@ test_that("expect_snapshot_file works in a different directory", {
 
 test_that("expect_snapshot_file works with variant", {
   expect_snapshot_file(
-    write_tmp_lines(version$nickname),
+    write_tmp_lines(r_version()),
     "nickname.txt",
     compare = compare_file_text,
     variant = r_version()
   )
 })
 
+test_that("expect_snapshot_file finds duplicate snapshot files", {
+  # Save to the same file as in previous test
+  expect_error(
+    expect_snapshot_file(
+      write_tmp_lines(r_version()),
+      "nickname.txt",
+      compare = compare_file_text,
+      variant = r_version()
+    ),
+    "provide a unique snapshot file name"
+  )
+})
+
 test_that("basic workflow", {
   snapper <- local_snapshotter()
 

tests/testthat/test-snapshot.R

@@ -1,5 +1,5 @@
 test_that("can access nickname", {
-  expect_snapshot(version$nickname, variant = r_version())
+  expect_snapshot(r_version(), variant = r_version())
 })
 
 test_that("can snapshot output", {