alint_rules/
file_min_lines.rs

1//! `file_min_lines` — files in scope must have at least
2//! `min_lines` lines.
3//!
4//! Catches the "README is a title plus two sentences" case
5//! where the file exists, isn't empty, but is far too thin to
6//! actually document anything. Pairs well with `file_exists`
7//! on README / CHANGELOG / SECURITY.md in governance rulesets.
8//!
9//! A **line** is any run of bytes terminated by `\n`. The
10//! trailing segment after the last newline (or the whole file
11//! when there is no newline) counts as one additional line
12//! only when it is non-empty — so `"a\nb\n"` and `"a\nb"` both
13//! report 2 lines, while `"a\nb\n\n"` reports 3 (the empty
14//! line between the two newlines counts). This matches the
15//! usual `wc -l` semantics closely enough for policy use;
16//! pedantic counting differences aren't worth the surprise.
17
18use std::path::Path;
19
20use alint_core::{
21    Context, Error, Level, PerFileRule, Result, Rule, RuleSpec, Scope, Violation, eval_per_file,
22};
23use serde::Deserialize;
24
25#[derive(Debug, Deserialize)]
26#[serde(deny_unknown_fields)]
27struct Options {
28    min_lines: u64,
29}
30
31#[derive(Debug)]
32pub struct FileMinLinesRule {
33    id: String,
34    level: Level,
35    policy_url: Option<String>,
36    message: Option<String>,
37    scope: Scope,
38    min_lines: u64,
39}
40
41impl Rule for FileMinLinesRule {
42    alint_core::rule_common_impl!();
43
44    fn evaluate(&self, ctx: &Context<'_>) -> Result<Vec<Violation>> {
45        eval_per_file(self, ctx)
46    }
47
48    fn as_per_file(&self) -> Option<&dyn PerFileRule> {
49        Some(self)
50    }
51}
52
53impl PerFileRule for FileMinLinesRule {
54    fn path_scope(&self) -> &Scope {
55        &self.scope
56    }
57
58    fn evaluate_file(
59        &self,
60        _ctx: &Context<'_>,
61        path: &Path,
62        bytes: &[u8],
63    ) -> Result<Vec<Violation>> {
64        let lines = count_lines(bytes);
65        if lines >= self.min_lines {
66            return Ok(Vec::new());
67        }
68        let msg = self.message.clone().unwrap_or_else(|| {
69            format!(
70                "file has {} line(s); at least {} required",
71                lines, self.min_lines,
72            )
73        });
74        Ok(vec![
75            Violation::new(msg).with_path(std::sync::Arc::<Path>::from(path)),
76        ])
77    }
78}
79
80/// Count lines with `wc -l`-style semantics: every `\n` is a
81/// line terminator, plus one more line when the file doesn't
82/// end with `\n` but has content after the last `\n`. Empty
83/// file → 0 lines.
84fn count_lines(bytes: &[u8]) -> u64 {
85    if bytes.is_empty() {
86        return 0;
87    }
88    // `bytecount` would be faster, but line-count files are
89    // typically READMEs / CHANGELOGs (small). Not worth a
90    // dep for a hot loop that isn't.
91    #[allow(clippy::naive_bytecount)]
92    let newlines = bytes.iter().filter(|&&b| b == b'\n').count() as u64;
93    let trailing_unterminated = u64::from(!bytes.ends_with(b"\n"));
94    newlines + trailing_unterminated
95}
96
97pub fn build(spec: &RuleSpec) -> Result<Box<dyn Rule>> {
98    let Some(_paths) = &spec.paths else {
99        return Err(Error::rule_config(
100            &spec.id,
101            "file_min_lines requires a `paths` field",
102        ));
103    };
104    let opts: Options = spec
105        .deserialize_options()
106        .map_err(|e| Error::rule_config(&spec.id, format!("invalid options: {e}")))?;
107    Ok(Box::new(FileMinLinesRule {
108        id: spec.id.clone(),
109        level: spec.level,
110        policy_url: spec.policy_url.clone(),
111        message: spec.message.clone(),
112        scope: Scope::from_spec(spec)?,
113        min_lines: opts.min_lines,
114    }))
115}
116
117#[cfg(test)]
118mod tests {
119    use super::count_lines;
120
121    #[test]
122    fn empty_file_has_zero_lines() {
123        assert_eq!(count_lines(b""), 0);
124    }
125
126    #[test]
127    fn content_with_trailing_newline_counts_each_line() {
128        assert_eq!(count_lines(b"a\n"), 1);
129        assert_eq!(count_lines(b"a\nb\n"), 2);
130        assert_eq!(count_lines(b"a\nb\nc\n"), 3);
131    }
132
133    #[test]
134    fn content_without_trailing_newline_adds_one_for_tail() {
135        assert_eq!(count_lines(b"a"), 1);
136        assert_eq!(count_lines(b"a\nb"), 2);
137    }
138
139    #[test]
140    fn blank_lines_count() {
141        assert_eq!(count_lines(b"a\n\nb\n"), 3);
142        assert_eq!(count_lines(b"\n\n"), 2);
143    }
144}
alint_rules/file_min_lines.rs

alint_rules/
file_min_lines.rs
