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, RuleMetadata, 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    metadata: RuleMetadata,
89}
90
91impl FlawlessRule for RemoveNilDeclaration {
92    fn flawless_process(&self, block: &mut Block, _: &Context) {
93        let mut processor = Processor::default();
94        DefaultVisitor::visit_block(block, &mut processor);
95    }
96}
97
98impl RuleConfiguration for RemoveNilDeclaration {
99    fn configure(&mut self, properties: RuleProperties) -> Result<(), RuleConfigurationError> {
100        verify_no_rule_properties(&properties)?;
101
102        Ok(())
103    }
104
105    fn get_name(&self) -> &'static str {
106        REMOVE_NIL_DECLARATION_RULE_NAME
107    }
108
109    fn serialize_to_properties(&self) -> RuleProperties {
110        RuleProperties::new()
111    }
112
113    fn set_metadata(&mut self, metadata: RuleMetadata) {
114        self.metadata = metadata;
115    }
116
117    fn metadata(&self) -> &RuleMetadata {
118        &self.metadata
119    }
120}
121
122#[cfg(test)]
123mod test {
124    use super::*;
125    use crate::rules::Rule;
126
127    use insta::assert_json_snapshot;
128
129    fn new_rule() -> RemoveNilDeclaration {
130        RemoveNilDeclaration::default()
131    }
132
133    #[test]
134    fn serialize_default_rule() {
135        let rule: Box<dyn Rule> = Box::new(new_rule());
136
137        assert_json_snapshot!(rule, @r###""remove_nil_declaration""###);
138    }
139
140    #[test]
141    fn configure_with_extra_field_error() {
142        let result = json5::from_str::<Box<dyn Rule>>(
143            r#"{
144            rule: 'remove_nil_declaration',
145            prop: "something",
146        }"#,
147        );
148        insta::assert_snapshot!(result.unwrap_err().to_string(), @"unexpected field 'prop' at line 1 column 1");
149    }
150}
darklua_core/rules/remove_nil_declarations.rs

darklua_core/rules/
remove_nil_declarations.rs
