Thoughts on folded text block?

[drewgingerich]

This is cross-posted at google/go-jsonnet.

YAML has folded-style multi-line strings, which means that new-lines are replaced with spaces to end up with a single-line string. I find this convenient for splitting long shell commands over multiple lines for readability. Does this seem like something potentially good to implement?

I know that jsonnet has the ||| text block but this does not replace newlines, behaving like a "literal" instead of "folded" YAML multi-line string. Syntax for a "folded" text block in jsonnet could be an extension of the text block syntax: e.g. |||>.

For example and context, I'm looking at using jsonnet to produce YAML Gitlab CI config files. By hand a simplified version looks like this:

build:
  stage: build
  only:
    - main
  image: my.kaniko.image
  script:
    - init-kaniko
    - >-
      /kaniko/executor
      --context .
      --dockerfile Dockerfile
      --destination $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
      --destination $CI_REGISTRY_IMAGE:latest

To reproduce this in jsonnet I need to use a function to replace the newlines:

local folded_text_block(text_block) = std.strReplace(text_block, '\n', ' ');

{
  build: {
    stage: 'build',
    only: ['main'],
    image: 'my.kaniko.image',
    script: [
      'init-kaniko',
      folded_text_block(
        |||
          /kaniko/executor
          --context .
          --dockerfile Dockerfile
          --destination $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
          --destination $CI_REGISTRY_IMAGE:latest
        |||
      ),
    ],
  },
}

Whereas with a builtin folded text block (using my made-up syntax from above) I could do:

{
  build: {
    stage: 'build',
    only: ['main'],
    image: 'my.kaniko.image',
    script: [
      'init-kaniko',
      |||>
        /kaniko/executor
        --context .
        --dockerfile Dockerfile
        --destination $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
        --destination $CI_REGISTRY_IMAGE:latest
      |||,
    ],
  },
}

The "long line" in the above example is also pretty tame and could be squished into a single line. Some commands are far longer and simply must be split over multiple lines for readability, and I think a "folded" text block could make these easy handle.

This is a small deal in the scheme of things. I get a lot of joy from the flexibility of YAML's multi-line strings and would love to see some of it in jsonnet.

[sbarzowski]

Are you aware of ||| text blocks? See the tutorial: https://jsonnet.org/learning/tutorial.html.

[drewgingerich]

Hi @sbarzowski I did see the ||| text block, but I did not see a way to replace the newlines with it. I've done this with a small function, but I like the terseness and flow of the YAML folded-style multi-line string for long shell commands.

I've updated the question to better describe what I'm talking about related to the current ||| text block.

[sbarzowski]

Ah, so you want the newlines replaced with spaces. I see how it can be quite useful sometimes.