nu-lint 1.2.0

Linter for Nu shell scripts that helpfully suggests improvements
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128

use nu_protocol::ast::{Call, Expr, MatchPattern, Pattern};

use crate::{
    LintLevel,
    ast::{call::CallExt, expression::ExpressionExt},
    context::LintContext,
    rule::{DetectFix, Rule},
    violation::Detection,
};

fn extract_optional_string_param(call: &Call, context: &LintContext) -> Option<String> {
    let sig_text = call.get_positional_arg(1)?.span_text(context);

    (sig_text.contains("?: string") || sig_text.contains(": string = "))
        .then(|| {
            sig_text
                .split(&['[', ']', ':', '?'][..])
                .find(|s| !s.is_empty() && !s.starts_with(' '))
                .map(|s| s.trim().to_string())
        })
        .flatten()
}

fn is_string_literal_pattern(pattern: &MatchPattern) -> bool {
    matches!(
        &pattern.pattern,
        Pattern::Expression(expr) if matches!(&expr.expr, Expr::String(_))
    )
}

fn matches_dispatch_variable(call: &Call, var_name: &str, context: &LintContext) -> bool {
    call.get_first_positional_arg()
        .and_then(|cond| cond.extract_variable_name(context))
        .is_some_and(|v| v.trim_start_matches('$').trim_end_matches('?') == var_name)
}

fn has_string_patterns(call: &Call) -> bool {
    call.get_positional_arg(1)
        .and_then(|arg| match &arg.expr {
            Expr::MatchBlock(patterns) => Some(patterns),
            _ => None,
        })
        .is_some_and(|patterns| patterns.iter().any(|(p, _)| is_string_literal_pattern(p)))
}

fn find_match_dispatch<'a>(
    block_id: nu_protocol::BlockId,
    param_name: &str,
    context: &'a LintContext<'a>,
) -> Option<&'a Call> {
    context
        .working_set
        .get_block(block_id)
        .pipelines
        .iter()
        .flat_map(|p| &p.elements)
        .filter_map(|e| match &e.expr.expr {
            Expr::Call(call) => Some(call.as_ref()),
            _ => None,
        })
        .find(|call| {
            call.get_call_name(context) == "match"
                && matches_dispatch_variable(call, param_name, context)
                && has_string_patterns(call)
        })
}

fn build_violation(param_name: &str, match_call: &Call) -> Detection {
    Detection::from_global_span(
        format!(
            "Main function uses match dispatch on '{param_name}' - use native subcommands instead"
        ),
        match_call.span(),
    )
    .with_primary_label("match-based dispatch")
}

struct DispatchWithSubcommands;

impl DetectFix for DispatchWithSubcommands {
    type FixInput<'a> = ();

    fn id(&self) -> &'static str {
        "dispatch_with_subcommands"
    }

    fn short_description(&self) -> &'static str {
        "Match dispatch replaceable with subcommands"
    }

    fn source_link(&self) -> Option<&'static str> {
        Some("https://www.nushell.sh/book/custom_commands.html#subcommands")
    }

    fn level(&self) -> LintLevel {
        LintLevel::Warning
    }

    fn detect<'a>(&self, context: &'a LintContext) -> Vec<(Detection, Self::FixInput<'a>)> {
        Self::no_fix(context.detect(|expr, ctx| {
            let Expr::Call(def_call) = &expr.expr else {
                return vec![];
            };

            let Some(def) = def_call.custom_command_def(ctx) else {
                return vec![];
            };

            if !def.is_main() {
                return vec![];
            }

            extract_optional_string_param(def_call, ctx)
                .and_then(|param| {
                    find_match_dispatch(def.body, &param, ctx).map(|call| (param, call))
                })
                .map(|(param, call)| vec![build_violation(&param, call)])
                .unwrap_or_default()
        }))
    }
}

pub static RULE: &dyn Rule = &DispatchWithSubcommands;

#[cfg(test)]
mod detect_bad;
#[cfg(test)]
mod ignore_good;