darklua_core/rules/
remove_nil_declarations.rs

1use crate::nodes::{Block, Expression, LocalAssignStatement};
2use crate::process::{DefaultVisitor, Evaluator, NodeProcessor, NodeVisitor};
3use crate::rules::{
4    Context, FlawlessRule, RuleConfiguration, RuleConfigurationError, RuleProperties,
5};
6
7use super::verify_no_rule_properties;
8
9#[derive(Default)]
10struct Processor {
11    evaluator: Evaluator,
12}
13
14impl NodeProcessor for Processor {
15    fn process_local_assign_statement(&mut self, assignment: &mut LocalAssignStatement) {
16        {
17            let mut pop_extra_value_at = Vec::new();
18            for (index, extra_value) in assignment
19                .iter_values()
20                .enumerate()
21                .skip(assignment.variables_len())
22            {
23                if !self.evaluator.has_side_effects(extra_value) {
24                    pop_extra_value_at.push(index);
25                }
26            }
27
28            for index in pop_extra_value_at.into_iter().rev() {
29                assignment.remove_value(index);
30            }
31        }
32
33        if assignment.values_len() > assignment.variables_len() {
34            return;
35        }
36
37        let has_nil_value = assignment
38            .iter_values()
39            .any(|value| matches!(value, Expression::Nil(_)));
40
41        if !has_nil_value {
42            return;
43        }
44
45        if assignment.variables_len() > assignment.values_len()
46            && assignment
47                .last_value()
48                .filter(|last_value| self.evaluator.can_return_multiple_values(last_value))
49                .is_some()
50        {
51            return;
52        }
53
54        let mut remove_values_at = Vec::new();
55        for (index, value) in assignment.iter_values().enumerate() {
56            if matches!(value, Expression::Nil(_)) {
57                remove_values_at.push(index);
58            }
59        }
60
61        let insert_variables: Vec<_> = remove_values_at
62            .into_iter()
63            .rev()
64            .filter_map(|index| {
65                assignment.remove_value(index);
66                assignment.remove_variable(index)
67            })
68            .collect();
69
70        for variable in insert_variables.into_iter().rev() {
71            assignment.push_variable(variable);
72        }
73
74        if let Some(last_value) = assignment.last_value() {
75            if self.evaluator.can_return_multiple_values(last_value) {
76                let new_value = assignment.pop_value().unwrap().in_parentheses();
77                assignment.push_value(new_value);
78            }
79        }
80    }
81}
82
83pub const REMOVE_NIL_DECLARATION_RULE_NAME: &str = "remove_nil_declaration";
84
85/// A rule that removes trailing `nil` in local assignments.
86#[derive(Debug, Default, PartialEq, Eq)]
87pub struct RemoveNilDeclaration {}
88
89impl FlawlessRule for RemoveNilDeclaration {
90    fn flawless_process(&self, block: &mut Block, _: &Context) {
91        let mut processor = Processor::default();
92        DefaultVisitor::visit_block(block, &mut processor);
93    }
94}
95
96impl RuleConfiguration for RemoveNilDeclaration {
97    fn configure(&mut self, properties: RuleProperties) -> Result<(), RuleConfigurationError> {
98        verify_no_rule_properties(&properties)?;
99
100        Ok(())
101    }
102
103    fn get_name(&self) -> &'static str {
104        REMOVE_NIL_DECLARATION_RULE_NAME
105    }
106
107    fn serialize_to_properties(&self) -> RuleProperties {
108        RuleProperties::new()
109    }
110}
111
112#[cfg(test)]
113mod test {
114    use super::*;
115    use crate::rules::Rule;
116
117    use insta::assert_json_snapshot;
118
119    fn new_rule() -> RemoveNilDeclaration {
120        RemoveNilDeclaration::default()
121    }
122
123    #[test]
124    fn serialize_default_rule() {
125        let rule: Box<dyn Rule> = Box::new(new_rule());
126
127        assert_json_snapshot!("default_remove_nil_declaration", rule);
128    }
129
130    #[test]
131    fn configure_with_extra_field_error() {
132        let result = json5::from_str::<Box<dyn Rule>>(
133            r#"{
134            rule: 'remove_nil_declaration',
135            prop: "something",
136        }"#,
137        );
138        pretty_assertions::assert_eq!(result.unwrap_err().to_string(), "unexpected field 'prop'");
139    }
140}
darklua_core/rules/remove_nil_declarations.rs

darklua_core/rules/
remove_nil_declarations.rs
