Fix: prefer-some-in-iteration false positive iteration in fn args

This fixes one of the errors reported in #528

Signed-off-by: Anders Eknert <anders@styra.com>

bundle/regal/rules/style/prefer_some_in_iteration.rego

@@ -70,6 +70,24 @@ invalid_some_context(rule, path) if {
 	impossible_some(node)
 }
 
+# don't recommend `some .. in` if iteration occurs inside of a
+# function call args list, like `startswith(input.foo[_], "foo")`
+# this should honestly be a rule of its own, I think, but it's
+# not _directly_ replaceable by `some .. in`, so we'll leave it
+# be here
+invalid_some_context(rule, path) if {
+	some p in all_paths(path)
+
+	node := object.get(rule, p, [])
+
+	node.terms[0].type == "ref"
+	node.terms[0].value[0].type == "var"
+	node.terms[0].value[0].value in ast.all_function_names # regal ignore:external-reference
+}
+
+# if previous node is of type call, also don't recommend `some .. in`
+invalid_some_context(rule, path) if object.get(rule, array.slice(path, 0, count(path) - 2), {}).type == "call"
+
 impossible_some(node) if node.type in {"array", "object", "set"}
 
 impossible_some(node) if node.key

bundle/regal/rules/style/prefer_some_in_iteration_test.rego

@@ -3,6 +3,7 @@ package regal.rules.style["prefer-some-in-iteration_test"]
 import rego.v1
 
 import data.regal.ast
+import data.regal.capabilities
 import data.regal.config
 import data.regal.rules.style["prefer-some-in-iteration"] as rule
 
@@ -233,6 +234,32 @@ test_success_allow_if_contains_check_equal if {
 	r == set()
 }
 
+test_success_iteration_in_args if {
+	policy := ast.with_rego_v1(`no_violation if {
+		startswith(input.foo[_], "f")
+	}`)
+
+	r := rule.report with config.for_rule as {
+		"level": "error",
+		"ignore-nesting-level": 5,
+	}
+		with input as policy
+		with data.internal.combined_config as {"capabilities": capabilities.provided}
+	r == set()
+}
+
+test_success_iteration_in_args_call_in_comprehension_head if {
+	policy := ast.with_rego_v1(`r := [f(obj[k], v) | some k, v in p]`)
+
+	r := rule.report with config.for_rule as {
+		"level": "error",
+		"ignore-nesting-level": 5,
+	}
+		with input as policy
+		with data.internal.combined_config as {"capabilities": capabilities.provided}
+	r == set()
+}
+
 allow_nesting(i) := {
 	"level": "error",
 	"ignore-nesting-level": i,