Re: [PATCH 1/2] commands: send stderr to a new pipe

[Patrick Ohly <patrick.ohly@intel.com>]

On Thu, 2017-06-22 at 11:18 -0500, Leonardo Sandoval wrote:
> On Thu, 2017-06-22 at 17:59 +0200, Patrick Ohly wrote:
> > 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@linux.intel.com wrote:
> > > > > > > From: Leonardo Sandoval <leonardo.sandoval.gonzalez@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.
> 
> it is not missing, it is on 2/2

I'm talking about this code:

def runCmd(command, ignore_status=False, timeout=None, assert_error=True,
          native_sysroot=None, limit_exc_output=0, **options):
...
    if result.status and not ignore_status:
        exc_output = result.output
        if limit_exc_output > 0:
            split = result.output.splitlines()
            if len(split) > limit_exc_output:
                exc_output = "\n... (last %d lines of output)\n" % limit_exc_output + \
                             '\n'.join(split[-limit_exc_output:])
        if assert_error:
            raise AssertionError("Command '%s' returned non-zero exit status %d:\n%s" % (command, result.status, exc_output))
        else:
            raise CommandError(result.status, command, exc_output)

You are not extending that in either 2/2, are you? At the moment, when a
command fails, one gets stdout+stderr. With your path, one only gets
stdout, which typically won't have the error message that caused the
non-zero status.

Here's my proposal:
     1. drop the "commands: send stderr to a new pipe" path, because
        that has much wider implications for everyone else
     2. in "selftest/cases: use stderr data when querying for errors",
        explicitly change the bitbake() calls so that they have
        stderr=subprocess.PIPE

Example:

     @OETestID(105)
     def test_bitbake_invalid_recipe(self):
-        result = bitbake('-b asdf', ignore_status=True)
-        self.assertTrue("ERROR: Unable to find any recipe file matching 'asdf'" in result.output, msg = "Though asdf recipe doesn't exist, bitbake didn't output any err. message. bitbake output: %s" % result.output)
+        invalid = 'asdf'
+        result = bitbake('-b %s' % invalid, ignore_status=True, stderr=subprocess.PIPE)
+        self.assertTrue("ERROR: Unable to find any recipe file matching '%s'" % invalid in result.error, msg = "Though %s recipe doesn't exist, bitbake didn't output any err. message. bitbake output: %s" % (invalid, result.error))



-- 
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.