tree 398dda9c2442a310b6be5adafaa895e6ee657986
parent e741e2fe0e51840b16bfc84d8daaba7670e7aac9
author Bryan C. Mills <bcmills@google.com> 1635366678 -0400
committer Bryan C. Mills <bcmills@google.com> 1635453819 +0000

cmd/go: disallow the -fuzz flag for tests outside the main module

Normally, when fuzzing identifies a failure it saves the failing input
to the package's testdata directory. However, the testdata directory
for packages outside the main module is normally not writable — and
when it is, writing to a testdata directory inside the module cache
would corrupt the checksum for that module (and permanently alter the
behavior of that version of the module globally).

In the future we could consider a flag to allow failures to be saved
to an alternate location, or perhaps in the build cache; or, we could
suppress writes entirely and rely on the user to identify and copy the
failing input from the test log. However, it's a bit late in the cycle
for that big a design decision right now. For Go 1.18, we will just
enforce that the package to be fuzzed resides in the main module,
which is typically a writable VCS checkout.

Fixes #48495

Change-Id: I8d3d56372394b1aaa94fa920399c659363fa17fa
Reviewed-on: https://go-review.googlesource.com/c/go/+/359414
Trust: Bryan C. Mills <bcmills@google.com>
Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>