Display how many deferred expressions were run (#248)

NEWS.md

@@ -1,5 +1,8 @@
 # withr (development version)
 
+* `deferred_run()` now reports the number of executed expressions with
+  a message.
+
 ,* `local_tempfile()` now writes `lines` in UTF-8 (#210) and always uses 
   `\n` for newlines (#216).
 

R/defer.R

@@ -88,8 +88,21 @@ deferred_run <- function(envir = parent.frame()) {
   }
   deferred_clear(envir)
 
+  n <- length(handlers)
+  i <- 0L
+
+  if (!n) {
+    message("No deferred expressions to run")
+    return(invisible(NULL))
+  }
+
+  defer(message(
+    sprintf("Ran %s/%s deferred expressions", i, n)
+  ))
+
   for (expr in handlers) {
     eval(expr, envir)
+    i <- i + 1L
   }
 }
 

tests/testthat/_snaps/defer.md

@@ -0,0 +1,30 @@
+# deferred_run() displays how many expressions were run
+
+    Code
+      deferred_run()
+    Message
+      No deferred expressions to run
+
+---
+
+    Code
+      local({
+        local_tempfile()
+        local_tempfile()
+        deferred_run()
+      })
+    Message
+      Ran 2/2 deferred expressions
+
+---
+
+    Code
+      expect_error(local({
+        local_tempfile()
+        defer(stop("foo"))
+        local_tempfile()
+        deferred_run()
+      }))
+    Message
+      Ran 1/3 deferred expressions
+

tests/testthat/test-defer.R

@@ -11,3 +11,20 @@ test_that("`frame_exits()` and `frame_clear_exits()`", {
   frame_clear_exits()
   expect_equal(frame_exits(), list())
 })
+
+test_that("deferred_run() displays how many expressions were run", {
+  expect_snapshot(deferred_run())
+
+  expect_snapshot(local({
+    local_tempfile()
+    local_tempfile()
+    deferred_run()
+  }))
+
+  expect_snapshot(expect_error(local({
+    local_tempfile()
+    defer(stop("foo"))
+    local_tempfile()
+    deferred_run()
+  })))
+})

tests/testthat/test-standalone-defer.R

@@ -38,7 +38,9 @@ test_that("defer()'s global env facilities work", {
   expect_length(h, 2)
   expect_equal(Sys.getenv("abcdefg"), "tuvwxyz")
 
-  expect_output(deferred_run(globalenv()), "howdy")
+  suppressMessages(
+    expect_output(deferred_run(globalenv()), "howdy")
+  )
   expect_equal(Sys.getenv("abcdefg"), "abcdefg")
 
   expect_message(defer(print("never going to happen"), envir = globalenv()))