#10421 fix: keep YAML anchors and aliases when writing meltano.yml Pull request opened by nanjeshramesh Description

meltano config set

(and anything else that writes

meltano.yml

back) expanded YAML anchors and aliases, so a value defined once with

&anchor

and reused with

*anchor

was written out in full at every use. The cause is in

Canonical.as_canonical

, which rebuilt every mapping and sequence as a new object. An alias is the same Python object appearing twice in the loaded tree. Rebuilding gave each occurrence its own copy, so the dumper had nothing left to turn back into an alias, and it also dropped the anchor. This keeps one canonical copy per anchored node while converting, so every alias still points at the same object and the anchor is written back. Nodes without an anchor are copied as before, so nothing that merely shares an object gets anchors it never had. Merge keys (

<<: *anchor

) are not covered by this change and behave as before. They go through separate handling in ruamel and I'd rather do them on their own. Tests: •

test_preserve_anchors_and_aliases

and

test_canonical_without_anchors_has_independent_copies

in

tests/meltano/core/behavior/test_canonical.py

•

test_config_set_preserves_yaml_anchors

in

tests/meltano/cli/test_config.py

, which runs

meltano config set

on a project with mapping and sequence anchors The anchor tests fail without the change and pass with it. Checklist • I have read the contribution guide Was generative AI tooling used to co-author this PR? • Yes (please specify the tool below) Generated-by: Claude Code following the agentic coding guidelines Related Issues • Closes #7206 Summary by Sourcery Preserve YAML anchors and aliases when writing canonicalized Meltano configuration files. Bug Fixes: • Preserve YAML anchors and aliases when canonicalized configuration is written back, preventing anchored mappings and sequences from being expanded. Enhancements: • Maintain independent copies for ordinary shared objects while reusing canonical copies only for explicitly anchored YAML nodes. Tests: • Add unit and CLI coverage for preserving mapping and sequence anchors through canonicalization and

meltano config set

. meltano/meltano