Can YAML anchors/references occur across files/documents?

Question

Just getting up to speed with YAML and want to confirm whether it's possible to utilise its anchor (&) and reference (*) functionality across separate files or separate documents within one file. For example, for the latter:

--- # Document A
Lunch: &lunch01     # Already thinking of lunch ;-)
    - BBQ Chicken
    - Sirloin Steak
    - Roast Beef
    - Salmon
...

--- # Document B
Monday:    *lunch01
Tuesday:   closed
Wednesday: *lunch01
Thursday:  closed
Friday:    *lunch01
...

(Apologies if my syntax is incorrect, still trying to convert across from thinking in terms of arrays and dictionaries.)

Does this work? Or would I go about this by merging the data within my programming language of choice at run time?

score 8 · Accepted Answer · answered Jun 14 '12 at 08:27

8

I am not an expert on YAML, but from my experience, this doesn't work. I am using PyYAML, and the parser throws an error when reaching the reference, complaining about an "undefined alias".

So you will have to merge the data at runtime.

answered Jun 14 '12 at 08:27

Bastien Gorissen

96
1

2

It appears that you're right, reading into [this post](http://code.google.com/p/snakeyaml/issues/detail?id=32) backs it up somewhat. – Jun 18 '12 at 11:17

score 1 · Answer 2 · answered Jul 13 '23 at 08:43

Per YAML's spec, there's no way to do that. but...

This is possible with yq's explode operator if you're using a single file with multiple documents:

cat <<EOF | yq 'explode(.)' 
---
Lunch: &lunch01
    - BBQ Chicken
    - Sirloin Steak
    - Roast Beef
    - Salmon

---
Monday:    *lunch01
Tuesday:   closed
Wednesday: *lunch01
Thursday:  closed
Friday:    *lunch01
EOF

I've came across a problem like that when creating a Kubernetes manifest with a lot of repeating fields, and yq integrated beautifully on my workflow!

Can YAML anchors/references occur across files/documents?

2 Answers2

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