rule-length: add count-comments configuration option

This is set to `false` by default, as we don't want to "punish"
comments in rules.

Fixes #432

Signed-off-by: Anders Eknert <[email protected]>

bundle/regal/config/provided/data.yaml

@@ -93,6 +93,7 @@ rules:
       ignore-nesting-level: 2
       level: error
     rule-length:
+      count-comments: false
       except-empty-body: true
       level: error
       max-rule-length: 30

bundle/regal/rules/style/rule_length.rego

@@ -16,7 +16,7 @@ report contains violation if {
 	some rule in input.rules
 	lines := split(base64.decode(rule.location.text), "\n")
 
-	count(lines) > cfg["max-rule-length"]
+	line_count(cfg, rule, lines) > cfg["max-rule-length"]
 
 	not generated_body_exception(cfg, rule)
 
@@ -27,3 +27,25 @@ generated_body_exception(conf, rule) if {
 	conf["except-empty-body"] == true
 	ast.generated_body(rule)
 }
+
+line_count(cfg, _, lines) := count(lines) if cfg["count-comments"] == true
+
+line_count(cfg, rule, lines) := n if {
+	not cfg["count-comments"]
+
+	# Note that this assumes } on its own line
+	body_start := rule.location.row + 1
+	body_end := (body_start + count(lines)) - 3
+	body_total := (body_end - body_start) + 1
+
+	# This does not take into account comments that are
+	# on the same line as regular code
+	body_comments := sum([1 |
+		some comment in input.comments
+
+		comment.Location.row >= body_start
+		comment.Location.row <= body_end
+	])
+
+	n := body_total - body_comments
+}

bundle/regal/rules/style/rule_length_test.rego

@@ -21,6 +21,7 @@ test_fail_rule_longer_than_configured_max_length if {
 	r := rule.report with input as module with config.for_rule as {
 		"level": "error",
 		"max-rule-length": 3,
+		"count-comments": true,
 	}
 	r == {{
 		"category": "style",
@@ -49,6 +50,26 @@ test_success_rule_not_longer_than_configured_max_length if {
 	r := rule.report with input as module with config.for_rule as {
 		"level": "error",
 		"max-rule-length": 30,
+		"count-comments": true,
+	}
+	r == set()
+}
+
+test_success_rule_longer_than_configured_max_length_but_comments if {
+	module := regal.parse_module("policy.rego", `package p
+
+	my_short_rule {
+		# this rule is not longer than the configured max length
+		# which in this case is 30 lines
+		#
+		input.x
+	}
+	`)
+
+	r := rule.report with input as module with config.for_rule as {
+		"level": "error",
+		"max-rule-length": 2,
+		"count-comments": false,
 	}
 	r == set()
 }
@@ -62,6 +83,7 @@ test_success_rule_length_equals_max_length if {
 	r := rule.report with input as module with config.for_rule as {
 		"level": "error",
 		"max-rule-length": 1,
+		"count-comments": false,
 	}
 	r == set()
 }

docs/rules/style/rule-length.md

@@ -32,6 +32,9 @@ rules:
       level: error
       # default limit is 30 lines
       max-rule-length: 30
+      # whether to count comments as lines
+      # by default, this is set to false
+      count-comments: false
       # except rules with empty bodies from this rule, as they're
       # likely an assignment of long values rather than a "rule"
       # with conditions:

e2e/testdata/violations/most_violations.rego

@@ -154,6 +154,7 @@ rule_length {
 	input.x28
 	input.x29
 	input.x30
+	input.x31
 }
 
 default_over_else := 1 {