yaml aliases/anchors not supported about rosmon HOT 8 CLOSED

Hi, thanks for the report! Could you share a full .launch file that shows how you include the YAML data?

I'm kind of surprised since rosmon uses yaml-cpp as the YAML parser, which should be pretty feature-complete. Well, you never know ;-)

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also I just noticed: Where is frequency coming from? I guess the YAML file you tried has more fields?

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param.launch.txt
robot_localization.yaml.txt

Here ya go. Sorry for the .txt extension, seemed most convenient to attach to issue.

I tried to create a minimal example.
These example files work with roslaunch but not with mon launch

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Thanks! I had a look and I think the syntax you are using is not supported by yaml-cpp. See here for a PR against yaml-cpp: jbeder/yaml-cpp#300

Furthermore, the syntax is not even in the YAML spec: https://stackoverflow.com/a/47203224

Maybe it is possible to work around this in rosmon, but I doubt it, so we will have to wait for the yaml-cpp developers to implement this.

But there is an alternative: You can do the same at launch file level. Example:

<node ...>
  <rosparam command="load" file=".../generic.yaml">
  <rosparam command="load" file=".../special_A.yaml">
</node>

<node ...>
  <rosparam command="load" file=".../generic.yaml">
  <rosparam command="load" file=".../special_B.yaml">
</node>

rosmon guarantees that <rosparam> tags are executed in order. Because the <rosparam> tags are scoped inside the node tag, the contents will be loaded inside the node namespace.

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That must be a discrepancy with the python yaml import then.
That's a bummer...

Thanks for the alternative though! I'll see if we want to convert the files (this will place some of the substitution in two places, param & launch) or switch back to roslaunch.

Implementing a workaround in rosmon sounds like the least neat solution. And since your referenced PR is open since 2015 I have little hopes there...

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Implementing a workaround in rosmon sounds like the least neat solution. And since your referenced PR is open since 2015 I have little hopes there...

That could actually be quite easy - just do a first pass over the YAML nodes to find all << nodes and work on these, then the rest (overwriting already set parameters). If you are interested in working on this, I'd be happy to consider a PR - otherwise I might have time to look at this next week.

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Hmm, might still be an option then to include this. Would be consistent with roslaunch 👍
Working towards a deadline I won't get to this again before the holidays :(
If your up to speed with the code, feel free to check next week. Otherwise I might pick it up later!

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Fixed by @Cartoonman in #117.

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