testing: fail if T.Setenv is called via T.Run in a parallel test

The existing implementation can call to T.Setenv in T.Run even after
calling to T.Parallel, so I changed it to cause a panic in that case.

Fixes #55128

Change-Id: Ib89d998ff56f00f96a5ca218af071bd35fdae53a
Reviewed-on: https://go-review.googlesource.com/c/go/+/431101
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/src/testing/testing_test.go b/src/testing/testing_test.go
index 08ae23991f..3616f04d5f 100644
--- a/src/testing/testing_test.go
+++ b/src/testing/testing_test.go
@@ -200,3 +200,35 @@ func TestSetenvWithParallelBeforeSetenv(t *testing.T) {
 
 	t.Setenv("GO_TEST_KEY_1", "value")
 }
+
+func TestSetenvWithParallelParentBeforeSetenv(t *testing.T) {
+	t.Parallel()
+
+	t.Run("child", func(t *testing.T) {
+		defer func() {
+			want := "testing: t.Setenv called after t.Parallel; cannot set environment variables in parallel tests"
+			if got := recover(); got != want {
+				t.Fatalf("expected panic; got %#v want %q", got, want)
+			}
+		}()
+
+		t.Setenv("GO_TEST_KEY_1", "value")
+	})
+}
+
+func TestSetenvWithParallelGrandParentBeforeSetenv(t *testing.T) {
+	t.Parallel()
+
+	t.Run("child", func(t *testing.T) {
+		t.Run("grand-child", func(t *testing.T) {
+			defer func() {
+				want := "testing: t.Setenv called after t.Parallel; cannot set environment variables in parallel tests"
+				if got := recover(); got != want {
+					t.Fatalf("expected panic; got %#v want %q", got, want)
+				}
+			}()
+
+			t.Setenv("GO_TEST_KEY_1", "value")
+		})
+	})
+}