cargo/lints/rules/
blanket_hint_mostly_unused.rs

1use std::path::Path;
2
3use annotate_snippets::AnnotationKind;
4use annotate_snippets::Group;
5use annotate_snippets::Level;
6use annotate_snippets::Origin;
7use annotate_snippets::Patch;
8use annotate_snippets::Snippet;
9use cargo_util_schemas::manifest::ProfilePackageSpec;
10use cargo_util_schemas::manifest::TomlToolLints;
11
12use crate::CargoResult;
13use crate::GlobalContext;
14use crate::core::MaybePackage;
15use crate::core::Workspace;
16use crate::lints::Lint;
17use crate::lints::LintLevel;
18use crate::lints::SUSPICIOUS;
19use crate::lints::get_key_value_span;
20use crate::lints::rel_cwd_manifest_path;
21
22pub static LINT: &Lint = &Lint {
23    name: "blanket_hint_mostly_unused",
24    desc: "blanket_hint_mostly_unused lint",
25    primary_group: &SUSPICIOUS,
26    msrv: Some(super::CARGO_LINTS_MSRV),
27    feature_gate: None,
28    docs: Some(
29        r#"
30### What it does
31Checks if `hint-mostly-unused` being applied to all dependencies.
32
33### Why it is bad
34`hint-mostly-unused` indicates that most of a crate's API surface will go
35unused by anything depending on it; this hint can speed up the build by
36attempting to minimize compilation time for items that aren't used at all.
37Misapplication to crates that don't fit that criteria will slow down the build
38rather than speeding it up. It should be selectively applied to dependencies
39that meet these criteria. Applying it globally is always a misapplication and
40will likely slow down the build.
41
42### Example
43```toml
44[profile.dev.package."*"]
45hint-mostly-unused = true
46```
47
48Should instead be:
49```toml
50[profile.dev.package.huge-mostly-unused-dependency]
51hint-mostly-unused = true
52```
53"#,
54    ),
55};
56
57pub fn blanket_hint_mostly_unused(
58    ws: &Workspace<'_>,
59    maybe_pkg: &MaybePackage,
60    path: &Path,
61    pkg_lints: &TomlToolLints,
62    error_count: &mut usize,
63    gctx: &GlobalContext,
64) -> CargoResult<()> {
65    let (lint_level, reason) = LINT.level(
66        pkg_lints,
67        ws.lowest_rust_version(),
68        maybe_pkg.unstable_features(),
69    );
70
71    if lint_level == LintLevel::Allow {
72        return Ok(());
73    }
74
75    let level = lint_level.to_diagnostic_level();
76    let manifest_path = rel_cwd_manifest_path(path, gctx);
77    let mut paths = Vec::new();
78
79    if let Some(profiles) = maybe_pkg.profiles() {
80        for (profile_name, top_level_profile) in &profiles.0 {
81            if let Some(true) = top_level_profile.hint_mostly_unused {
82                paths.push((
83                    vec!["profile", profile_name.as_str(), "hint-mostly-unused"],
84                    true,
85                ));
86            }
87
88            if let Some(build_override) = &top_level_profile.build_override
89                && let Some(true) = build_override.hint_mostly_unused
90            {
91                paths.push((
92                    vec![
93                        "profile",
94                        profile_name.as_str(),
95                        "build-override",
96                        "hint-mostly-unused",
97                    ],
98                    false,
99                ));
100            }
101
102            if let Some(packages) = &top_level_profile.package
103                && let Some(profile) = packages.get(&ProfilePackageSpec::All)
104                && let Some(true) = profile.hint_mostly_unused
105            {
106                paths.push((
107                    vec![
108                        "profile",
109                        profile_name.as_str(),
110                        "package",
111                        "*",
112                        "hint-mostly-unused",
113                    ],
114                    false,
115                ));
116            }
117        }
118    }
119
120    for (i, (path, show_per_pkg_suggestion)) in paths.iter().enumerate() {
121        if lint_level.is_error() {
122            *error_count += 1;
123        }
124        let title = "`hint-mostly-unused` is being blanket applied to all dependencies";
125        let help_txt =
126            "scope `hint-mostly-unused` to specific packages with a lot of unused object code";
127
128        let mut report = Vec::new();
129        let mut primary_group = Group::with_title(level.clone().primary_title(title));
130
131        if let Some(contents) = maybe_pkg.contents()
132            && let Some(document) = maybe_pkg.document()
133            && let Some(span) = get_key_value_span(document, &path)
134            && let Some(table_span) = get_key_value_span(document, &path[..path.len() - 1])
135        {
136            primary_group = primary_group.element(
137                Snippet::source(contents)
138                    .path(&manifest_path)
139                    .annotation(
140                        AnnotationKind::Primary.span(table_span.key.start..table_span.key.end),
141                    )
142                    .annotation(AnnotationKind::Context.span(span.key.start..span.value.end)),
143            );
144        } else {
145            primary_group = primary_group.element(Origin::path(&manifest_path))
146        }
147
148        if *show_per_pkg_suggestion {
149            let help_group = Group::with_title(Level::HELP.secondary_title(help_txt));
150
151            report.push(
152                if let Some(contents) = maybe_pkg.contents()
153                    && let Some(document) = maybe_pkg.document()
154                    && let Some(table_span) = get_key_value_span(document, &path[..path.len() - 1])
155                {
156                    help_group.element(Snippet::source(contents).path(&manifest_path).patch(
157                        Patch::new(
158                            table_span.key.end..table_span.key.end,
159                            ".package.<pkg_name>",
160                        ),
161                    ))
162                } else {
163                    help_group.element(Origin::path(&manifest_path))
164                },
165            );
166        } else {
167            primary_group = primary_group.element(Level::HELP.message(help_txt));
168        }
169
170        if i == 0 {
171            primary_group =
172                primary_group.element(Level::NOTE.message(LINT.emitted_source(lint_level, reason)));
173        }
174
175        // The primary group should always be first
176        report.insert(0, primary_group);
177
178        gctx.shell().print_report(&report, lint_level.force())?;
179    }
180
181    Ok(())
182}
cargo/lints/rules/blanket_hint_mostly_unused.rs

cargo/lints/rules/
blanket_hint_mostly_unused.rs
