Inconsistent JSON output on errors

[ievgenii-shepeliuk]

Hello

Let's say we have file test.rego with following content,

package test

default allow := true

Running regal with JSON format regal lint --format json test.rego - the successful output will be

{
  "violations": [],
  "summary": {
    "files_scanned": 1,
    "files_failed": 0,
    "rules_skipped": 0,
    "num_violations": 0
  }
}

Let's introduce a syntax error into test.rego, so it becomes

package test

def ault allow := true

Running regal with JSON format once again gives inconsistent output

error(s) encountered while linting: errors encountered when reading files to lint: 2 errors occurred:
test.rego:3: rego_parse_error: var cannot be used for rule name
test.rego:3: rego_parse_error: var cannot be used for rule name

The inconsistency is that error format is not JSON. It makes a difficulty when creating Editor/IDE plugin that tries to parse JSON for the list of error. Since in this case there's no JSON and error has no predefined format.