Plan including cortex_rule with multi-line expressions always show changes

[janakerman-form3]

Observed

A cortex rule with the following content always shows changes:

name: watchdog
rules:
- alert: watchdog
  expr: >
      series_a or on (label)
          (
            series_b
          )

Details

The Cortex API returns the alert in the following format (note the additional new line) and usage of literal style | instead of folded style >:

name: watchdog
rules:
    - alert: watchdog
      expr: |
        series_a or on (label)

            (
              series_b
            )

The current DiffSurpressFunc for the cortex_rule resource detects a different due to the additional newlines in the expr field.

Suggested fix

#14 updates the DiffSurpressFunc to use cortex-tools packages to compare rule groups. This could 1) be extended to normalise alerting expressions using Prometheus' promql parsing packages.

[janakerman-form3]

After digging into this a bit more it seems to be an issue with go-yaml's handling of folded style yaml (i.e the > multi-line style) - go-yaml/yaml#804. Debugging the provider, the change in alert format can be seen before the alert is sent to the Cortex API.