Re: [PATCH v3 16/21] iotests: Add VM.assert_block_path() - Vladimir Sementsov-Ogievskiy

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: Max Reitz <mreitz@redhat.com>, qemu-block@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [PATCH v3 16/21] iotests: Add VM.assert_block_path()
Date: Tue, 4 Feb 2020 17:09:45 +0300	[thread overview]
Message-ID: <978b5d21-ccd9-7cef-3d39-585c5764c788@virtuozzo.com> (raw)
In-Reply-To: <20200130214431.333510-17-mreitz@redhat.com>

31.01.2020 0:44, Max Reitz wrote:
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>   tests/qemu-iotests/iotests.py | 56 +++++++++++++++++++++++++++++++++++
>   1 file changed, 56 insertions(+)
> 
> diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
> index 01b58dcb50..69861cf05e 100644
> --- a/tests/qemu-iotests/iotests.py
> +++ b/tests/qemu-iotests/iotests.py
> @@ -713,6 +713,62 @@ class VM(qtest.QEMUQtestMachine):
>   
>           return fields.items() <= ret.items()
>   
> +    def assert_block_path(self, root, path, expected_node, graph=None):
> +        """
> +        Check whether the node under the given path in the block graph
> +        is @expected_node.
> +
> +        @root is the node name of the node where the @path is rooted.
> +
> +        @path is a string that consists of child names separated by
> +        slashes.  It must begin with a slash.
> +
> +        Examples for @root + @path:
> +          - root="qcow2-node", path="/backing/file"
> +          - root="quorum-node", path="/children.2/file"
> +
> +        Hypothetically, @path could be empty, in which case it would
> +        point to @root.  However, in practice this case is not useful
> +        and hence not allowed.
> +
> +        @expected_node may be None.  (All elements of the path but the
> +        leaf must still exist.)
> +
> +        @graph may be None or the result of an x-debug-query-block-graph
> +        call that has already been performed.
> +        """
> +        if graph is None:
> +            graph = self.qmp('x-debug-query-block-graph')['return']
> +
> +        iter_path = iter(path.split('/'))
> +
> +        # Must start with a /
> +        assert next(iter_path) == ''
> +
> +        node = next((node for node in graph['nodes'] if node['name'] == root),
> +                    None)
> +
> +        for child_name in iter_path:
> +            assert node is not None, 'Cannot follow path %s' % path

this error message will be a bit misleading if we failed to find root node. So,
may be add additional assert for root node, or at least
'Cannot follow path %s%s'.format(root, path)

It doesn't worth to resend only for this, apply it if you want and keep my r-b anyway.

> +
> +            try:
> +                node_id = next(edge['child'] for edge in graph['edges'] \
> +                                             if edge['parent'] == node['id'] and
> +                                                edge['name'] == child_name)
> +
> +                node = next(node for node in graph['nodes'] \
> +                                 if node['id'] == node_id)
> +            except StopIteration:
> +                node = None
> +
> +        if node is None:
> +            assert expected_node is None, \
> +                   'No node found under %s (but expected %s)' % \
> +                   (path, expected_node)
> +        else:
> +            assert node['name'] == expected_node, \
> +                   'Found node %s under %s (but expected %s)' % \
> +                   (node['name'], path, expected_node)
>   
>   index_re = re.compile(r'([^\[]+)\[([^\]]+)\]')
>   
> 

-- 
Best regards,
Vladimir