[OE-core] [PATCH 1/2] commands: send stderr to a new pipe

[Patrick Ohly]

On Thu, 2017-06-22 at 10:37 -0500, Leonardo Sandoval wrote:
> On Thu, 2017-06-22 at 17:14 +0200, Patrick Ohly wrote:
> > On Thu, 2017-06-22 at 09:58 -0500, Leonardo Sandoval wrote:
> > > On Thu, 2017-06-22 at 16:17 +0200, Patrick Ohly wrote:
> > > > On Mon, 2017-06-19 at 07:39 -0700,
> > > > leonardo.sandoval.gonzalez at linux.intel.com wrote:
> > > > > From: Leonardo Sandoval <leonardo.sandoval.gonzalez at linux.intel.com>
> > > > > 
> > > > > Do not mix the stderr into stdout, allowing test cases to query
> > > > > the specific output.
> > > > 
> > > > This changes the behavior of functions that are also used outside of
> > > > OE-core in a way that won't be easy to notice. I also don't think that
> > > > it is the right default. For example, for bitbake it is easier to
> > > > understand where an error occurred when stderr goes to the same stream
> > > > as stdout.
> > > 
> > > how would that make it easier?
> > 
> > Because then output will be properly interleaved, as it would be on a
> > console.
> > 
> > Actually, the entire error reporting in runCmd() only prints
> > result.output, so with stderr going to result.error by default, you
> > won't get the actual errors reported anymore at all, will you? 
> > 
> 
> process stderr will go into result.error and process stdout into
> result.output. So when the process is executed ignoring the return
> status, then test must check result.error. I find the latter cleaner
> that checking errors into stdout.

It depends on how the result is used. That you prefer split output for
some tests does not mean that everyone wants the same in their tests. I
don't want it in my own usage of runCmd() or bitbake() because I don't
care about where a message was printed. I just want it in proper order.

If you change the default, then you will also have to enhance runCmd()'s
error handling to include results.error. That's currently missing in
your patch.

> > > > Can't you keep the current semantic and just override it explicitly in
> > > > those tests that need separate stdout/stderr?
> > > > 
> > > 
> > > My proposed patch was mainly based on a RP's comment [1], suggesting to
> > > split std[out|err].
> > 
> > He did not suggest to change the default behavior. I agree that using
> > split stdout/stderr in those specific tests which specifically want to
> > check for error messages makes sense, but only in those tests.
> 
> No tests require splitting the output (all tests pass with and without
> this series). The series is actually an enhancement and without it, we
> saw (specially when the python 2 to 3 was going on) past warnings going
> into stdout, so Chris and RP suggested the approach.

Richard, can you please comment on whether changing the default is
really what you meant?

-- 
Best Regards, Patrick Ohly

The content of this message is my personal opinion only and although
I am an employee of Intel, the statements I make here in no way
represent Intel's position on the issue, nor am I authorized to speak
on behalf of Intel on this matter.