Re: separating regression test patches from fixes, was Re: [PATCH 3/3] cherry-pick --continue: remember options

Duy Nguyen [off-list ref] writes:

On Thu, Mar 14, 2019 at 9:10 PM Johannes Schindelin
[off-list ref] wrote:

quoted

In any case, before we get better tooling to work around these issues, I
still think it makes a ton of sense to encourage proper separation of
concerns: to keep patches that introduce regression tests demonstrating a
breakage separate from patches that fix the breakage. It would certainly
help me (e.g. when staring at a range diff).

Then perhaps improve the tools now because these separate patches
enter 'master' and stay in the history forever. One of the problems I
have with separating tests from the actual code change is the
description of the problem often stays on the test commit, which I
can't see in git-log if I'm searching for the code change. And no
sometimes I can't just look at the parent commit if I filter code by
path (and with --full-diff)

I do not think the phrase "separation of concerns" is applied
correctly here.

The concern of a simple single-patch is to fix a bug---the test that
shows what bug was fixed and protects the code by ensuring that a
reintroduction of the bug gets noticed is an integral part of it.
It does not make much sense to artificially split it into two.

It's like arguing for adding declarations for new functions and
global variables in *.h files in a step before a separate step adds
their implementations in *.c files, claiming that the first step
designs the interface (which is sufficient for writing the client
code) and the second one gives an implementation of the interface
(which can be replaced later), and they address two separate
concerns.

And then you would find that there are some compilers that warn
against unimplemented functions and undefined variables.  The
"solution" would be to enclose the whole thing that was added in the
first "*.h only patch" inside "#if 0/#endif" to hide it from the
compiler ;-) That in fact looks quite similar to how "test only
patch" marks the new tests as expecting failure in the beginning.
Neither is truly useful when applied to a context different from
where it is originally developed for.