From c4bdd9b9c362357ad49a7a1400cf1ffc8b17a949 Mon Sep 17 00:00:00 2001
From: Hadley Wickham <h.wickham@gmail.com>
Date: Tue, 12 Aug 2025 08:11:35 -0500
Subject: [PATCH 1/5] Display diffs when snapshotting text files

I haven't yet figured out how to test snapshots with snapshots, so you can run this to test interactively

```R
test_that("expect_snapshot_file() show differences for text files", {
  path1 <- withr::local_tempfile(lines = sample(letters[1:10]))
  expect_snapshot_file(path1, "text-diff.txt")
})
```

Fixes #1593
---
 NEWS.md                                |  2 ++
 R/snapshot-file.R                      | 47 ++++++++++++++++++++------
 tests/testthat/_snaps/snapshot-file.md |  2 +-
 3 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index c3f30caab..e0e225f08 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,7 @@
 # testthat (development version)
 
+* `expect_snapshot_file()` now considers `.json` to be a text file (#1593).
+* `expect_snapshot_file()` now shows differences for text files (#1593).
 * `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)
 * `test_dir()`, `test_file()`, `test_package()`, `test_check()`, `test_local()`, `source_file()` gain a `shuffle` argument uses `sample()` to randomly reorder the top-level expressions in each test file (#1942). This random reordering surfaces dependencies between tests and code outside of any test, as well as dependencies between tests. This helps you find and eliminate unintentional dependencies.
 * `snapshot_accept(test)` now works when the test file name contains `.` (#1669).
diff --git a/R/snapshot-file.R b/R/snapshot-file.R
index ece60bd66..b7cd55d88 100644
--- a/R/snapshot-file.R
+++ b/R/snapshot-file.R
@@ -94,6 +94,8 @@ expect_snapshot_file <- function(
   transform = NULL,
   variant = NULL
 ) {
+  lab <- quo_label(enquo(path))
+
   check_string(path)
   check_string(name)
   check_bool(cran)
@@ -111,6 +113,7 @@ expect_snapshot_file <- function(
     return(invisible())
   }
 
+  is_text <- is_text_file(name)
   if (!is_missing(binary)) {
     lifecycle::deprecate_soft(
       "3.0.3",
@@ -120,8 +123,6 @@ expect_snapshot_file <- function(
     compare <- if (binary) compare_file_binary else compare_file_text
   }
   if (is.null(compare)) {
-    ext <- tools::file_ext(name)
-    is_text <- ext %in% c("r", "R", "txt", "md", "Rmd")
     compare <- if (is_text) compare_file_text else compare_file_binary
   }
 
@@ -131,7 +132,6 @@ expect_snapshot_file <- function(
     brio::write_lines(lines, path)
   }
 
-  lab <- quo_label(enquo(path))
   equal <- snapshotter$take_file_snapshot(
     name,
     path,
@@ -142,13 +142,30 @@ expect_snapshot_file <- function(
     return(equal)
   }
 
-  hint <- snapshot_review_hint(snapshotter$file, name)
+  file <- snapshotter$file
+  hint <- snapshot_review_hint(file, name, is_text = is_text)
 
   if (!equal) {
-    msg <- sprintf(
-      "Snapshot of %s to '%s' has changed\n%s",
-      lab,
-      paste0(snapshotter$file, "/", name),
+    if (is_text) {
+      base <- paste0(c(snapshotter$snap_dir, file, variant), collapse = "/")
+      old_path <- paste0(c(base, name), collapse = "/")
+      new_path <- paste0(c(base, new_name(name)), collapse = "/")
+
+      comp <- waldo_compare(
+        x = brio::read_lines(old_path),
+        x_arg = "old",
+        y = brio::read_lines(new_path),
+        y_arg = "new",
+        quote_strings = FALSE
+      )
+      comp <- c("Differences:", comp)
+    } else {
+      comp <- NULL
+    }
+
+    msg <- c(
+      sprintf("Snapshot of %s has changed.", lab),
+      comp,
       hint
     )
     return(fail(msg))
@@ -156,6 +173,11 @@ expect_snapshot_file <- function(
   pass(NULL)
 }
 
+is_text_file <- function(path) {
+  ext <- tools::file_ext(path)
+  ext %in% c("r", "R", "txt", "md", "Rmd", "qmd", "json")
+}
+
 #' @rdname expect_snapshot_file
 #' @export
 announce_snapshot_file <- function(path, name = basename(path)) {
@@ -172,6 +194,7 @@ snapshot_review_hint <- function(
   name,
   ci = on_ci(),
   check = in_rcmd_check(),
+  is_text = FALSE,
   reset_output = TRUE
 ) {
   if (reset_output) {
@@ -184,9 +207,13 @@ snapshot_review_hint <- function(
     if (check && ci) "* Download and unzip run artifact\n",
     if (check && !ci) "* Locate check directory\n",
     if (check) paste0("* Copy '", path, "' to local test directory\n"),
-    if (check) "* ",
+    if (is_text) {
+      cli::format_inline(
+        "* Run {.run testthat::snapshot_accept('{test}/')} to accept the change.\n"
+      )
+    },
     cli::format_inline(
-      "Run {.run testthat::snapshot_review('{test}/')} to review changes"
+      "* Run {.run testthat::snapshot_review('{test}/')} to review changes\n"
     )
   )
 }
diff --git a/tests/testthat/_snaps/snapshot-file.md b/tests/testthat/_snaps/snapshot-file.md
index 8d8e7b406..51272724a 100644
--- a/tests/testthat/_snaps/snapshot-file.md
+++ b/tests/testthat/_snaps/snapshot-file.md
@@ -27,7 +27,7 @@
     Code
       cat(snapshot_review_hint("lala", "foo.r", check = FALSE, ci = FALSE))
     Output
-      Run `testthat::snapshot_review('lala/')` to review changes
+      * Run `testthat::snapshot_review('lala/')` to review changes
 
 ---
 

From 1380480d1cc089e76434c2244edc8ee3e66c9884 Mon Sep 17 00:00:00 2001
From: Hadley Wickham <h.wickham@gmail.com>
Date: Wed, 27 Aug 2025 15:09:38 -0500
Subject: [PATCH 2/5] Elimiante no longer used argument

---
 R/snapshot-file.R                          |  7 +--
 tests/testthat/_snaps/snapshot-file.md     | 10 +++-
 tests/testthat/_snaps/snapshot-file.new.md | 57 ++++++++++++++++++++++
 tests/testthat/test-snapshot-file.R        |  9 +++-
 4 files changed, 75 insertions(+), 8 deletions(-)
 create mode 100644 tests/testthat/_snaps/snapshot-file.new.md

diff --git a/R/snapshot-file.R b/R/snapshot-file.R
index 0dd3be701..81af74d9d 100644
--- a/R/snapshot-file.R
+++ b/R/snapshot-file.R
@@ -160,7 +160,7 @@ expect_snapshot_file <- function(
   if (in_check_reporter()) {
     hint <- ""
   } else {
-    hint <- snapshot_review_hint(file, name, is_text = is_text)
+    hint <- snapshot_review_hint(file, is_text = is_text)
   }
 
   if (!equal) {
@@ -209,7 +209,6 @@ announce_snapshot_file <- function(path, name = basename(path)) {
 
 snapshot_review_hint <- function(
   test,
-  name,
   is_text = FALSE,
   reset_output = TRUE
 ) {
@@ -217,8 +216,6 @@ snapshot_review_hint <- function(
     local_reporter_output()
   }
 
-  path <- paste0("tests/testthat/_snaps/", test, "/", new_name(name))
-
   c(
     if (is_text) {
       cli::format_inline(
@@ -226,7 +223,7 @@ snapshot_review_hint <- function(
       )
     },
     cli::format_inline(
-      "* Run {.run testthat::snapshot_review('{test}/')} to review changes."
+      "* Run {.run testthat::snapshot_review('{test}/')} to review the change."
     )
   )
 }
diff --git a/tests/testthat/_snaps/snapshot-file.md b/tests/testthat/_snaps/snapshot-file.md
index 1f1d06cbe..13c89dbe5 100644
--- a/tests/testthat/_snaps/snapshot-file.md
+++ b/tests/testthat/_snaps/snapshot-file.md
@@ -25,10 +25,18 @@
 # generates informative hint
 
     Code
-      cat(snapshot_review_hint("lala", "foo.r", reset_output = FALSE))
+      base::writeLines(snapshot_review_hint("lala", reset_output = FALSE))
     Output
       * Run `testthat::snapshot_review('lala/')` to review changes.
 
+---
+
+    Code
+      base::writeLines(snapshot_review_hint("lala", is_text = TRUE, reset_output = FALSE))
+    Output
+      * Run `testthat::snapshot_accept('lala/')` to accept the change.
+      * Run `testthat::snapshot_review('lala/')` to review changes.
+
 # expect_snapshot_file validates its inputs
 
     Code
diff --git a/tests/testthat/_snaps/snapshot-file.new.md b/tests/testthat/_snaps/snapshot-file.new.md
new file mode 100644
index 000000000..c3a5317bc
--- /dev/null
+++ b/tests/testthat/_snaps/snapshot-file.new.md
@@ -0,0 +1,57 @@
+# expect_snapshot_file finds duplicate snapshot files
+
+    Code
+      expect_snapshot_file(write_tmp_lines(r_version()), "version.txt", variant = r_version())
+    Condition
+      Error in `expect_snapshot_file()`:
+      ! Snapshot file names must be unique. `name` has already been used.
+
+# warns on first creation
+
+    Code
+      out <- snapshot_file_equal_(path)
+    Condition
+      Warning:
+      Adding new file snapshot: 'tests/testthat/_snaps/my-test/test.txt'
+
+---
+
+    Code
+      snapshot_file_equal_("doesnt-exist.txt")
+    Condition
+      Error in `snapshot_file_equal_()`:
+      ! 'doesnt-exist.txt' not found.
+
+# generates informative hint
+
+    Code
+      base::writeLines(snapshot_review_hint("lala", reset_output = FALSE))
+    Output
+      * Run `testthat::snapshot_review('lala/')` to review the change.
+
+---
+
+    Code
+      base::writeLines(snapshot_review_hint("lala", is_text = TRUE, reset_output = FALSE))
+    Output
+      * Run `testthat::snapshot_accept('lala/')` to accept the change.
+      * Run `testthat::snapshot_review('lala/')` to review the change.
+
+# expect_snapshot_file validates its inputs
+
+    Code
+      expect_snapshot_file(123, "test.txt")
+    Condition
+      Error in `expect_snapshot_file()`:
+      ! `path` must be a single string, not the number 123.
+    Code
+      expect_snapshot_file("test.txt", 123)
+    Condition
+      Error in `expect_snapshot_file()`:
+      ! `name` must be a single string, not the number 123.
+    Code
+      expect_snapshot_file("test.txt", "test.txt", cran = "yes")
+    Condition
+      Error in `expect_snapshot_file()`:
+      ! `cran` must be `TRUE` or `FALSE`, not the string "yes".
+
diff --git a/tests/testthat/test-snapshot-file.R b/tests/testthat/test-snapshot-file.R
index 493f9be39..139366e73 100644
--- a/tests/testthat/test-snapshot-file.R
+++ b/tests/testthat/test-snapshot-file.R
@@ -163,9 +163,14 @@ test_that("split_path handles edge cases", {
 })
 
 test_that("generates informative hint", {
-  expect_snapshot(cat(snapshot_review_hint(
+  expect_snapshot(base::writeLines(snapshot_review_hint(
     "lala",
-    "foo.r",
+    reset_output = FALSE
+  )))
+
+  expect_snapshot(base::writeLines(snapshot_review_hint(
+    "lala",
+    is_text = TRUE,
     reset_output = FALSE
   )))
 })

From 98158712855f73e2bb9af8d670fc6ab3ebe323ed Mon Sep 17 00:00:00 2001
From: Hadley Wickham <h.wickham@gmail.com>
Date: Wed, 27 Aug 2025 15:10:40 -0500
Subject: [PATCH 3/5] Update snapshot

---
 tests/testthat/_snaps/snapshot-file.md     |  4 +-
 tests/testthat/_snaps/snapshot-file.new.md | 57 ----------------------
 2 files changed, 2 insertions(+), 59 deletions(-)
 delete mode 100644 tests/testthat/_snaps/snapshot-file.new.md

diff --git a/tests/testthat/_snaps/snapshot-file.md b/tests/testthat/_snaps/snapshot-file.md
index 13c89dbe5..c3a5317bc 100644
--- a/tests/testthat/_snaps/snapshot-file.md
+++ b/tests/testthat/_snaps/snapshot-file.md
@@ -27,7 +27,7 @@
     Code
       base::writeLines(snapshot_review_hint("lala", reset_output = FALSE))
     Output
-      * Run `testthat::snapshot_review('lala/')` to review changes.
+      * Run `testthat::snapshot_review('lala/')` to review the change.
 
 ---
 
@@ -35,7 +35,7 @@
       base::writeLines(snapshot_review_hint("lala", is_text = TRUE, reset_output = FALSE))
     Output
       * Run `testthat::snapshot_accept('lala/')` to accept the change.
-      * Run `testthat::snapshot_review('lala/')` to review changes.
+      * Run `testthat::snapshot_review('lala/')` to review the change.
 
 # expect_snapshot_file validates its inputs
 
diff --git a/tests/testthat/_snaps/snapshot-file.new.md b/tests/testthat/_snaps/snapshot-file.new.md
deleted file mode 100644
index c3a5317bc..000000000
--- a/tests/testthat/_snaps/snapshot-file.new.md
+++ /dev/null
@@ -1,57 +0,0 @@
-# expect_snapshot_file finds duplicate snapshot files
-
-    Code
-      expect_snapshot_file(write_tmp_lines(r_version()), "version.txt", variant = r_version())
-    Condition
-      Error in `expect_snapshot_file()`:
-      ! Snapshot file names must be unique. `name` has already been used.
-
-# warns on first creation
-
-    Code
-      out <- snapshot_file_equal_(path)
-    Condition
-      Warning:
-      Adding new file snapshot: 'tests/testthat/_snaps/my-test/test.txt'
-
----
-
-    Code
-      snapshot_file_equal_("doesnt-exist.txt")
-    Condition
-      Error in `snapshot_file_equal_()`:
-      ! 'doesnt-exist.txt' not found.
-
-# generates informative hint
-
-    Code
-      base::writeLines(snapshot_review_hint("lala", reset_output = FALSE))
-    Output
-      * Run `testthat::snapshot_review('lala/')` to review the change.
-
----
-
-    Code
-      base::writeLines(snapshot_review_hint("lala", is_text = TRUE, reset_output = FALSE))
-    Output
-      * Run `testthat::snapshot_accept('lala/')` to accept the change.
-      * Run `testthat::snapshot_review('lala/')` to review the change.
-
-# expect_snapshot_file validates its inputs
-
-    Code
-      expect_snapshot_file(123, "test.txt")
-    Condition
-      Error in `expect_snapshot_file()`:
-      ! `path` must be a single string, not the number 123.
-    Code
-      expect_snapshot_file("test.txt", 123)
-    Condition
-      Error in `expect_snapshot_file()`:
-      ! `name` must be a single string, not the number 123.
-    Code
-      expect_snapshot_file("test.txt", "test.txt", cran = "yes")
-    Condition
-      Error in `expect_snapshot_file()`:
-      ! `cran` must be `TRUE` or `FALSE`, not the string "yes".
-

From 6006881c02490070e6cf779a08a8068f83a9deb1 Mon Sep 17 00:00:00 2001
From: Hadley Wickham <h.wickham@gmail.com>
Date: Wed, 27 Aug 2025 15:12:30 -0500
Subject: [PATCH 4/5] Fix snapshot failure difference upstream

---
 R/expect-self-test.R | 2 +-
 R/expect-that.R      | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/R/expect-self-test.R b/R/expect-self-test.R
index 56c7cde53..05da3bf9f 100644
--- a/R/expect-self-test.R
+++ b/R/expect-self-test.R
@@ -88,7 +88,7 @@ expect_failure <- function(expr, message = NULL, ...) {
 
   if (!is.null(message)) {
     act <- labelled_value(status$last_failure$message, "failure message")
-    return(expect_match_(act, message, ..., title = "message", all = FALSE))
+    return(expect_match_(act, message, ..., title = "message"))
   }
   pass(NULL)
 }
diff --git a/R/expect-that.R b/R/expect-that.R
index b32cd7098..9579d6f1c 100644
--- a/R/expect-that.R
+++ b/R/expect-that.R
@@ -48,6 +48,7 @@ fail <- function(
 
 snapshot_fail <- function(message, trace_env = caller_env()) {
   trace <- capture_trace(trace_env)
+  message <- paste(message, collapse = "\n")
   expectation("failure", message, trace = trace, snapshot = TRUE)
 }
 

From 50cf4198234b0e41e2e242a2ff6f6252ce6af519 Mon Sep 17 00:00:00 2001
From: Hadley Wickham <h.wickham@gmail.com>
Date: Wed, 27 Aug 2025 15:15:12 -0500
Subject: [PATCH 5/5] Oops it was used

---
 R/snapshot-file.R                      |  7 ++++---
 tests/testthat/_snaps/snapshot-file.md | 11 ++++++-----
 tests/testthat/test-snapshot-file.R    |  2 ++
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/R/snapshot-file.R b/R/snapshot-file.R
index 81af74d9d..4da38f96b 100644
--- a/R/snapshot-file.R
+++ b/R/snapshot-file.R
@@ -160,7 +160,7 @@ expect_snapshot_file <- function(
   if (in_check_reporter()) {
     hint <- ""
   } else {
-    hint <- snapshot_review_hint(file, is_text = is_text)
+    hint <- snapshot_review_hint(file, name, is_text = is_text)
   }
 
   if (!equal) {
@@ -209,6 +209,7 @@ announce_snapshot_file <- function(path, name = basename(path)) {
 
 snapshot_review_hint <- function(
   test,
+  name,
   is_text = FALSE,
   reset_output = TRUE
 ) {
@@ -219,11 +220,11 @@ snapshot_review_hint <- function(
   c(
     if (is_text) {
       cli::format_inline(
-        "* Run {.run testthat::snapshot_accept('{test}/')} to accept the change."
+        "* Run {.run testthat::snapshot_accept('{test}/{name}')} to accept the change."
       )
     },
     cli::format_inline(
-      "* Run {.run testthat::snapshot_review('{test}/')} to review the change."
+      "* Run {.run testthat::snapshot_review('{test}/{name}')} to review the change."
     )
   )
 }
diff --git a/tests/testthat/_snaps/snapshot-file.md b/tests/testthat/_snaps/snapshot-file.md
index c3a5317bc..522e28e44 100644
--- a/tests/testthat/_snaps/snapshot-file.md
+++ b/tests/testthat/_snaps/snapshot-file.md
@@ -25,17 +25,18 @@
 # generates informative hint
 
     Code
-      base::writeLines(snapshot_review_hint("lala", reset_output = FALSE))
+      base::writeLines(snapshot_review_hint("lala", "foo.R", reset_output = FALSE))
     Output
-      * Run `testthat::snapshot_review('lala/')` to review the change.
+      * Run `testthat::snapshot_review('lala/foo.R')` to review the change.
 
 ---
 
     Code
-      base::writeLines(snapshot_review_hint("lala", is_text = TRUE, reset_output = FALSE))
+      base::writeLines(snapshot_review_hint("lala", "foo.R", is_text = TRUE,
+        reset_output = FALSE))
     Output
-      * Run `testthat::snapshot_accept('lala/')` to accept the change.
-      * Run `testthat::snapshot_review('lala/')` to review the change.
+      * Run `testthat::snapshot_accept('lala/foo.R')` to accept the change.
+      * Run `testthat::snapshot_review('lala/foo.R')` to review the change.
 
 # expect_snapshot_file validates its inputs
 
diff --git a/tests/testthat/test-snapshot-file.R b/tests/testthat/test-snapshot-file.R
index 139366e73..f0e4d885a 100644
--- a/tests/testthat/test-snapshot-file.R
+++ b/tests/testthat/test-snapshot-file.R
@@ -165,11 +165,13 @@ test_that("split_path handles edge cases", {
 test_that("generates informative hint", {
   expect_snapshot(base::writeLines(snapshot_review_hint(
     "lala",
+    "foo.R",
     reset_output = FALSE
   )))
 
   expect_snapshot(base::writeLines(snapshot_review_hint(
     "lala",
+    "foo.R",
     is_text = TRUE,
     reset_output = FALSE
   )))