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Refresh flattened references when interpolating values #8

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Refresh flattened references when interpolating values #8

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Commits on Jul 25, 2022

  1. Refresh flattened references when interpolating values 

    Sometimes using nested references to lookup values for parameters based
on a parameter which is set differently in the hierarchy for different
nodes leads to a ResolveError.

The original issue was discovered in Project Syn component
[backup-k8up], which supports being compiled multiple times with
different configurations in multiple Kapitan targets. If the two
configurations use different values for the parameter
`backup_k8up.majorVersion`, the nested references which use this
parameter to look up values for the appropriate major version sometimes
use stale flattened refs when checking whether all nested references are
resolved causing a `ResolveError`.

From what I was able to determine this happens because nested references
are flattened in `RefItem.assembleRefs()` which can cause interpolation
to operate with stale flattened references if the same `RefItem` is part
of the parameters structure for multiple nodes.

We address the problem by calling `value.assembleRefs(self._base)` for
each value which is processed in `Parameters._interpolate_inner()`. This
fixes the issue both in the included minimal test case and our
real-world case when rendering the reclass inventory for Project Syn
clusters which include component [backup-k8up] as described in the
[component v2 to v3 migration how-to].

I haven't been able to determine exactly how a `RefItem` object can be
part of multiple nodes and therefore I'm not sure if it's expected that
the same `RefItem` object can be part of multiple nodes or not.
Unfortunately this means that I can't tell if my fix is just masking
another bug somewhere which wrongly adds the same `RefItem` to the
parameters of multiple nodes.

[backup-k8up]: https://github.com/projectsyn/component-backup-k8up.git
[component migration how-to]: https://hub.syn.tools/backup-k8up/how-tos/upgrade-v2-v3.html#_steps_to_run_two_instances_at_once
    @simu
    simu committed Jul 25, 2022
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