Personal Programming Notes

To err is human; to debug, divine.

Jsonnet Code Recipes

If you are sending/working with lots of JSON data in files such as AWS CloudFormation templates, Jsonnet tool can help reducing the hassle of maintaining. Using Jsonnet templates, it is easier to organize data and reduce repeated code present in such JSON data. This post goes over a few common Jsonnet code recipes for generating JSON data.

Automated tests

At least, make sure your jsonnet template files can compile. The following example bash script will find all the manifest files and try to compile that:

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# Provide a superset of required parameters
for i in `find Project1/manifests Project2/manifests   -name "*.jsonnet"`;
do
  jsonnet -V param1=1 -V param2=dummy -V param3=1 "${i}" >> /dev/null
done;
# This will lint-test the files, including libsonnet files.
for i in `find Project1 Project2 -name "*.*sonnet"`;
do
  jsonnet fmt -i -n 2 "${i}" --test
done;

Conditional add

Conditionally adding items to a list.

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  ports: [
           {
             port: $.httpPort,
             targetport: $.httpTargetPort,
           },
           {
             port: $.jnlpPort,
             targetport: 15372,
           },
         ] +
         (if $.sshEnabled then
            [{
              port: $.sshPort,
              targetport: 15373,
            }] else []),

Conditionally adding attributes to an object/map.

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  defaultContainerEnv:: {
    LOGGING_STDERR_LEVEL: "ALL",
    JENKINS_USER: "jenkins",
  } + (if $.sshEnabled then {
          SSH_PORT: 7012,
        } else {}
      )