j2gen

Tool to render Jinja2 templates with mutliple input YAML data sources.

Features

• Render files as Jinja2 templates (usually ending with .j2)
• Use YAML as data source for templating
• Multiple YAML data sources are allowed to overlay sources

Usage

Let's show some examples what j2gen is good for.

Simple rendering

A test.j2 template:

Hello {{ variable }} !

A test.yaml file containing the data:

---
variable: world

Will render to:

$ j2gen generate test.j2 test.yaml
Hello world !

By default, j2gen will write its output to stdout. Use the --output (or -o) flag to write to a file:

$ j2gen generate -o output test.j2 test.yaml
$ cat output
Hello world !

Rendering with multiple sources

There are cases where you want a common data source (eg. common.yaml) but need to overwrite parts of the common source (eg. with special.yaml):

common.yaml looks like:

container:
  base: openSUSE-Leap-15.1
  name: memcached container for openSUSE
  description:
    short: memcached container
    long: memcached container for openSUSE

special.yaml looks like:

container:
  base: SLES15SP1
  name: memcached container for SLES15SP1
  description:
    long: memcached container for SUSE Linux Enterprise Server 15 SP1

template.j2 looks like:

Base      : {{ container.base }}
Name      : {{ container.name }}
Desc short: {{ container.description.short }}
Desc long : {{ container.description.long }}

This results in:

$ j2gen generate template.j2 common.yaml special.yaml
Base      : SLES15SP1
Name      : memcached container for SLES15SP1
Desc short: memcached container
Desc long : memcached container for SUSE Linux Enterprise Server 15 SP1

Note here that container.description.short is taken from the common.yaml input while all the other variables are overwritten with the values from special.yaml. So dict/hash like structures in the YAML data sources are deep merged. Another important part is the order of the input files when calling j2gen generate. The last source wins (in this case special.yaml).

Contributing

I'm happy about every contribution like bugfixes, filling issues, improving documentation or whatever.

• For bugs: https://github.com/toabctl/j2gen/issues
• For changes: https://github.com/toabctl/j2gen/pulls

Running tests

The testsuite can be executed locally with:

$ tox