rigsql_rules/convention/
cv05.rs

1use rigsql_core::{Segment, SegmentType, TokenKind};
2
3use crate::rule::{CrawlType, Rule, RuleContext, RuleGroup};
4use crate::violation::{LintViolation, SourceEdit};
5
6/// CV05: Comparisons with NULL should use IS or IS NOT, not = or !=.
7///
8/// `WHERE col = NULL` is always false in SQL; use `WHERE col IS NULL` instead.
9#[derive(Debug, Default)]
10pub struct RuleCV05;
11
12impl Rule for RuleCV05 {
13    fn code(&self) -> &'static str {
14        "CV05"
15    }
16    fn name(&self) -> &'static str {
17        "convention.is_null"
18    }
19    fn description(&self) -> &'static str {
20        "Comparisons with NULL should use IS or IS NOT."
21    }
22    fn explanation(&self) -> &'static str {
23        "In SQL, NULL is not a value but the absence of one. Comparison operators \
24         (=, !=, <>) with NULL always return NULL (which is falsy). Use 'IS NULL' or \
25         'IS NOT NULL' instead of '= NULL' or '!= NULL'."
26    }
27    fn groups(&self) -> &[RuleGroup] {
28        &[RuleGroup::Convention]
29    }
30    fn is_fixable(&self) -> bool {
31        true
32    }
33
34    fn crawl_type(&self) -> CrawlType {
35        CrawlType::Segment(vec![SegmentType::BinaryExpression])
36    }
37
38    fn eval(&self, ctx: &RuleContext) -> Vec<LintViolation> {
39        let children = ctx.segment.children();
40
41        // Look for pattern: <expr> <comparison_op> NULL
42        // or: NULL <comparison_op> <expr>
43        let non_trivia: Vec<_> = children
44            .iter()
45            .filter(|c| !c.segment_type().is_trivia())
46            .collect();
47
48        if non_trivia.len() < 3 {
49            return vec![];
50        }
51
52        // Check if operator is comparison (=, !=, <>)
53        let op = non_trivia[1];
54        let is_comparison = matches!(op.segment_type(), SegmentType::ComparisonOperator);
55        if !is_comparison {
56            return vec![];
57        }
58
59        // Check if either side is NULL literal
60        let lhs_is_null = is_null_literal(non_trivia[0]);
61        let rhs_is_null = non_trivia.get(2).is_some_and(|s| is_null_literal(s));
62
63        if lhs_is_null || rhs_is_null {
64            // Determine the operator text to decide IS NULL vs IS NOT NULL
65            let op_text = op.tokens().first().map(|t| t.text.as_str()).unwrap_or("=");
66            let is_negated = op_text == "!=" || op_text == "<>";
67
68            // Build the fix: replace "op NULL" or "NULL op" portion
69            // For "expr = NULL" → "expr IS NULL"
70            // For "expr != NULL" → "expr IS NOT NULL"
71            let op_span = op.span();
72            let null_seg = if rhs_is_null {
73                non_trivia[2]
74            } else {
75                non_trivia[0]
76            };
77            let null_span = null_seg.span();
78
79            let fix = if rhs_is_null {
80                // "expr <op> <ws?> NULL" → replace from op start to NULL end
81                let replace_span = rigsql_core::Span::new(op_span.start, null_span.end);
82                let replacement = if is_negated { "IS NOT NULL" } else { "IS NULL" };
83                vec![SourceEdit::replace(replace_span, replacement)]
84            } else {
85                // "NULL <op> <ws?> expr" → rearrange to "expr IS [NOT] NULL"
86                let is_not = if is_negated { "IS NOT NULL" } else { "IS NULL" };
87                let expr = non_trivia[2];
88                let whole_span = ctx.segment.span();
89                let expr_text = ctx
90                    .source
91                    .get(expr.span().start as usize..expr.span().end as usize)
92                    .unwrap_or("?");
93                vec![SourceEdit::replace(
94                    whole_span,
95                    format!("{} {}", expr_text, is_not),
96                )]
97            };
98
99            return vec![LintViolation::with_fix_and_msg_key(
100                self.code(),
101                "Use IS NULL or IS NOT NULL instead of comparison operator with NULL.",
102                ctx.segment.span(),
103                fix,
104                "rules.CV05.msg",
105                vec![],
106            )];
107        }
108
109        vec![]
110    }
111}
112
113fn is_null_literal(seg: &Segment) -> bool {
114    match seg {
115        Segment::Token(t) => {
116            t.segment_type == SegmentType::NullLiteral
117                || (t.token.kind == TokenKind::Word && t.token.text.eq_ignore_ascii_case("NULL"))
118        }
119        Segment::Node(n) => n.segment_type == SegmentType::NullLiteral,
120    }
121}
122
123#[cfg(test)]
124mod tests {
125    use super::*;
126    use crate::test_utils::lint_sql;
127
128    #[test]
129    fn test_cv05_flags_equals_null() {
130        let violations = lint_sql("SELECT * FROM t WHERE a = NULL", RuleCV05);
131        assert_eq!(violations.len(), 1);
132        assert_eq!(violations[0].fixes.len(), 1);
133        assert_eq!(violations[0].fixes[0].new_text, "IS NULL");
134    }
135
136    #[test]
137    fn test_cv05_accepts_is_null() {
138        let violations = lint_sql("SELECT * FROM t WHERE a IS NULL", RuleCV05);
139        assert_eq!(violations.len(), 0);
140    }
141}
rigsql_rules/convention/cv05.rs

rigsql_rules/convention/
cv05.rs
