Curly braces in a YAML file

Question

I've found the following .travis.yml template.

I've noticed this:

    repo: {GITHUB_USER}/{PROJECT_NAME}

Is this a special .yml variable syntax I'm not familiar with? Where can I set these values (GITHUB_USER, PROJECT_NAME)?

I know I can use environment variables, like so:

    repo: $GITHUB_USER/$PROJECT_NAME

but this syntax looks different.

practically every YAML parser I know complains about this. Curly braces in YAML stand for a flow style mapping and must be quoted if they are meant literal. I guess this YAML file is preprocessed, and those are template placeholders, so the final YAML file will be valid — tinita, Feb 11 '19 at 15:13
**See also:** https://stackoverflow.com/questions/30905103/yaml-reusable-variables-with-case-specific-values — dreftymac, Sep 30 '19 at 17:11

score 3 · Accepted Answer · answered Feb 11 '19 at 15:36

That is not a valid YAML file. After the first } the YAML parser will expect a block style continuation. This means either a key that aligns with repo or outdenting. Instead it finds a / and any YAML parser should throw an error on that.

This looks like a template for a YAML file, e.g. using something like the following in Python after loading the contents of the file in string templ:

templ.format(**dict(GITHUB_USER="Janez", PROJECT_NAME="test"))

On the other hand the recommended extension for YAML files has been .yaml for many more years than Travis exists, so maybe that is why they used the .yml extension.

Curly braces in a YAML file

1 Answers1