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feat: Add lint for global use of hint-mostly-unused
1 parent f400988 commit d820347

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4 files changed

+205
-7
lines changed

4 files changed

+205
-7
lines changed

src/cargo/core/workspace.rs

Lines changed: 21 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -25,7 +25,9 @@ use crate::util::context::FeatureUnification;
2525
use crate::util::edit_distance;
2626
use crate::util::errors::{CargoResult, ManifestError};
2727
use crate::util::interning::InternedString;
28-
use crate::util::lints::{analyze_cargo_lints_table, check_im_a_teapot};
28+
use crate::util::lints::{
29+
analyze_cargo_lints_table, blanket_hint_mostly_unused, check_im_a_teapot,
30+
};
2931
use crate::util::toml::{InheritableFields, read_manifest};
3032
use crate::util::{
3133
Filesystem, GlobalContext, IntoUrl, context::CargoResolverConfig, context::ConfigRelativePath,
@@ -1201,7 +1203,12 @@ impl<'gctx> Workspace<'gctx> {
12011203
pub fn emit_warnings(&self) -> CargoResult<()> {
12021204
let mut first_emitted_error = None;
12031205

1204-
if self.gctx.cli_unstable().cargo_lints {
1206+
if self.gctx.cli_unstable().cargo_lints
1207+
// This is a short term hack to allow `blanket_hint_mostly_unused`
1208+
// to run without requiring `-Zcargo-lints`, which should hopefully
1209+
// improve the testing expierience while we are collecting feedback
1210+
|| self.gctx.cli_unstable().profile_hint_mostly_unused
1211+
{
12051212
if let Err(e) = self.emit_ws_lints()
12061213
&& first_emitted_error.is_none()
12071214
{
@@ -1291,9 +1298,9 @@ impl<'gctx> Workspace<'gctx> {
12911298
}
12921299

12931300
pub fn emit_ws_lints(&self) -> CargoResult<()> {
1294-
let error_count = 0;
1301+
let mut error_count = 0;
12951302

1296-
let _cargo_lints = match self.root_maybe() {
1303+
let cargo_lints = match self.root_maybe() {
12971304
MaybePackage::Package(pkg) => {
12981305
let toml = pkg.manifest().normalized_toml();
12991306
if let Some(ws) = &toml.workspace {
@@ -1314,6 +1321,16 @@ impl<'gctx> Workspace<'gctx> {
13141321
.cloned()
13151322
.unwrap_or(manifest::TomlToolLints::default());
13161323

1324+
if self.gctx.cli_unstable().profile_hint_mostly_unused {
1325+
blanket_hint_mostly_unused(
1326+
self.root_maybe(),
1327+
self.root_manifest(),
1328+
&cargo_lints,
1329+
&mut error_count,
1330+
self.gctx,
1331+
)?;
1332+
}
1333+
13171334
if error_count > 0 {
13181335
Err(crate::util::errors::AlreadyPrintedError::new(anyhow!(
13191336
"encountered {error_count} errors(s) while running lints"

src/cargo/util/lints.rs

Lines changed: 123 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,14 +1,14 @@
1-
use crate::core::{Edition, Feature, Features, Manifest, Package};
1+
use crate::core::{Edition, Feature, Features, Manifest, MaybePackage, Package};
22
use crate::{CargoResult, GlobalContext};
33
use annotate_snippets::{AnnotationKind, Group, Level, Snippet};
4-
use cargo_util_schemas::manifest::{TomlLintLevel, TomlToolLints};
4+
use cargo_util_schemas::manifest::{ProfilePackageSpec, TomlLintLevel, TomlToolLints};
55
use pathdiff::diff_paths;
66
use std::fmt::Display;
77
use std::ops::Range;
88
use std::path::Path;
99

1010
const LINT_GROUPS: &[LintGroup] = &[TEST_DUMMY_UNSTABLE];
11-
pub const LINTS: &[Lint] = &[IM_A_TEAPOT, UNKNOWN_LINTS];
11+
pub const LINTS: &[Lint] = &[BLANKET_HINT_MOSTLY_UNUSED, IM_A_TEAPOT, UNKNOWN_LINTS];
1212

1313
pub fn analyze_cargo_lints_table(
1414
pkg: &Package,
@@ -473,6 +473,126 @@ pub fn check_im_a_teapot(
473473
Ok(())
474474
}
475475

476+
const BLANKET_HINT_MOSTLY_UNUSED: Lint = Lint {
477+
name: "blanket_hint_mostly_unused",
478+
desc: "blanket_hint_mostly_unused lint",
479+
groups: &[],
480+
default_level: LintLevel::Warn,
481+
edition_lint_opts: None,
482+
feature_gate: None,
483+
docs: Some(
484+
r#"
485+
### What it does
486+
Checks if `hint-mostly-unused` being applied to all dependencies.
487+
488+
### Why it is bad
489+
`hint-mostly-unused` indicates that most of a crate's API surface will go
490+
unused by anything depending on it; this hint can speed up the build by
491+
attempting to minimize compilation time for items that aren't used at all.
492+
Misapplication to crates that don't fit that criteria will slow down the build
493+
rather than speeding it up. It should be selectively applied to dependencies
494+
that meet these criteria. Applying it globally is always a misapplication and
495+
will likely slow down the build.
496+
497+
### Example
498+
```toml
499+
[profile.dev.package."*"]
500+
hint-mostly-unused = true
501+
```
502+
503+
Should instead be:
504+
```toml
505+
[profile.dev.package.huge-mostly-unused-dependency]
506+
hint-mostly-unused = true
507+
```
508+
"#,
509+
),
510+
};
511+
512+
pub fn blanket_hint_mostly_unused(
513+
maybe_pkg: &MaybePackage,
514+
path: &Path,
515+
pkg_lints: &TomlToolLints,
516+
error_count: &mut usize,
517+
gctx: &GlobalContext,
518+
) -> CargoResult<()> {
519+
let (lint_level, reason) = BLANKET_HINT_MOSTLY_UNUSED.level(
520+
pkg_lints,
521+
maybe_pkg.edition(),
522+
maybe_pkg.unstable_features(),
523+
);
524+
525+
if lint_level == LintLevel::Allow {
526+
return Ok(());
527+
}
528+
529+
let level = lint_level.to_diagnostic_level();
530+
let manifest_path = rel_cwd_manifest_path(path, gctx);
531+
let mut paths = Vec::new();
532+
533+
if let Some(profiles) = maybe_pkg.profiles() {
534+
for (profile_name, top_level_profile) in &profiles.0 {
535+
if let Some(true) = top_level_profile.hint_mostly_unused {
536+
paths.push(vec!["profile", profile_name.as_str(), "hint-mostly-unused"]);
537+
}
538+
539+
if let Some(build_override) = &top_level_profile.build_override
540+
&& let Some(true) = build_override.hint_mostly_unused
541+
{
542+
paths.push(vec![
543+
"profile",
544+
profile_name.as_str(),
545+
"build-override",
546+
"hint-mostly-unused",
547+
]);
548+
}
549+
550+
if let Some(packages) = &top_level_profile.package
551+
&& let Some(profile) = packages.get(&ProfilePackageSpec::All)
552+
&& let Some(true) = profile.hint_mostly_unused
553+
{
554+
paths.push(vec![
555+
"profile",
556+
profile_name.as_str(),
557+
"package",
558+
"*",
559+
"hint-mostly-unused",
560+
]);
561+
}
562+
}
563+
}
564+
565+
for (i, path) in paths.iter().enumerate() {
566+
if lint_level.is_error() {
567+
*error_count += 1;
568+
}
569+
let title = "`hint-mostly-unused` is being blanket applied to dependencies";
570+
if let (Some(span), Some(table_span)) = (
571+
get_key_value_span(maybe_pkg.document(), &path),
572+
get_key_value_span(maybe_pkg.document(), &path[..path.len() - 1]),
573+
) {
574+
let mut group = level.clone().primary_title(title).element(
575+
Snippet::source(maybe_pkg.contents())
576+
.path(&manifest_path)
577+
.annotation(AnnotationKind::Primary.span(span.key.start..span.value.end))
578+
.annotation(AnnotationKind::Visible.span(table_span.key)),
579+
);
580+
581+
if i == 0 {
582+
group =
583+
group
584+
.element(Level::NOTE.message(
585+
BLANKET_HINT_MOSTLY_UNUSED.emitted_source(lint_level, reason),
586+
));
587+
}
588+
589+
gctx.shell().print_report(&[group], lint_level.force())?;
590+
}
591+
}
592+
593+
Ok(())
594+
}
595+
476596
const UNKNOWN_LINTS: Lint = Lint {
477597
name: "unknown_lints",
478598
desc: "unknown lint",

src/doc/src/reference/lints.md

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -5,8 +5,37 @@ Note: [Cargo's linting system is unstable](unstable.md#lintscargo) and can only
55
## Warn-by-default
66

77
These lints are all set to the 'warn' level by default.
8+
- [`blanket_hint_mostly_unused`](#blanket_hint_mostly_unused)
89
- [`unknown_lints`](#unknown_lints)
910

11+
## `blanket_hint_mostly_unused`
12+
Set to `warn` by default
13+
14+
### What it does
15+
Checks if `hint-mostly-unused` being applied to all dependencies.
16+
17+
### Why it is bad
18+
`hint-mostly-unused` indicates that most of a crate's API surface will go
19+
unused by anything depending on it; this hint can speed up the build by
20+
attempting to minimize compilation time for items that aren't used at all.
21+
Misapplication to crates that don't fit that criteria will slow down the build
22+
rather than speeding it up. It should be selectively applied to dependencies
23+
that meet these criteria. Applying it globally is always a misapplication and
24+
will likely slow down the build.
25+
26+
### Example
27+
```toml
28+
[profile.dev.package."*"]
29+
hint-mostly-unused = true
30+
```
31+
32+
Should instead be:
33+
```toml
34+
[profile.dev.package.huge-mostly-unused-dependency]
35+
hint-mostly-unused = true
36+
```
37+
38+
1039
## `unknown_lints`
1140
Set to `warn` by default
1241

tests/testsuite/lints/blanket_hint_mostly_unused.rs

Lines changed: 32 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -22,6 +22,14 @@ hint-mostly-unused = true
2222
p.cargo("check -Zprofile-hint-mostly-unused -v")
2323
.masquerade_as_nightly_cargo(&["profile-hint-mostly-unused", "cargo-lints"])
2424
.with_stderr_data(str![[r#"
25+
[WARNING] `hint-mostly-unused` is being blanket applied to dependencies
26+
--> Cargo.toml:8:1
27+
|
28+
7 | [profile.dev]
29+
8 | hint-mostly-unused = true
30+
| ^^^^^^^^^^^^^^^^^^^^^^^^^
31+
|
32+
= [NOTE] `cargo::blanket_hint_mostly_unused` is set to `warn` by default
2533
[CHECKING] foo v0.0.1 ([ROOT]/foo)
2634
[RUNNING] `rustc --crate-name foo [..]`
2735
[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
@@ -50,6 +58,14 @@ hint-mostly-unused = true
5058
p.cargo("check -Zprofile-hint-mostly-unused -v")
5159
.masquerade_as_nightly_cargo(&["profile-hint-mostly-unused", "cargo-lints"])
5260
.with_stderr_data(str![[r#"
61+
[WARNING] `hint-mostly-unused` is being blanket applied to dependencies
62+
--> Cargo.toml:8:1
63+
|
64+
7 | [profile.dev.package."*"]
65+
8 | hint-mostly-unused = true
66+
| ^^^^^^^^^^^^^^^^^^^^^^^^^
67+
|
68+
= [NOTE] `cargo::blanket_hint_mostly_unused` is set to `warn` by default
5369
[CHECKING] foo v0.0.1 ([ROOT]/foo)
5470
[RUNNING] `rustc --crate-name foo [..]`
5571
[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
@@ -78,6 +94,14 @@ hint-mostly-unused = true
7894
p.cargo("check -Zprofile-hint-mostly-unused -v")
7995
.masquerade_as_nightly_cargo(&["profile-hint-mostly-unused", "cargo-lints"])
8096
.with_stderr_data(str![[r#"
97+
[WARNING] `hint-mostly-unused` is being blanket applied to dependencies
98+
--> Cargo.toml:8:1
99+
|
100+
7 | [profile.dev.build-override]
101+
8 | hint-mostly-unused = true
102+
| ^^^^^^^^^^^^^^^^^^^^^^^^^
103+
|
104+
= [NOTE] `cargo::blanket_hint_mostly_unused` is set to `warn` by default
81105
[CHECKING] foo v0.0.1 ([ROOT]/foo)
82106
[RUNNING] `rustc --crate-name foo [..]`
83107
[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
@@ -115,6 +139,14 @@ authors = []
115139
p.cargo("check -Zprofile-hint-mostly-unused -v")
116140
.masquerade_as_nightly_cargo(&["profile-hint-mostly-unused", "cargo-lints"])
117141
.with_stderr_data(str![[r#"
142+
[WARNING] `hint-mostly-unused` is being blanket applied to dependencies
143+
--> Cargo.toml:6:1
144+
|
145+
5 | [profile.dev.package."*"]
146+
6 | hint-mostly-unused = true
147+
| ^^^^^^^^^^^^^^^^^^^^^^^^^
148+
|
149+
= [NOTE] `cargo::blanket_hint_mostly_unused` is set to `warn` by default
118150
[CHECKING] foo v0.0.1 ([ROOT]/foo/foo)
119151
[RUNNING] `rustc --crate-name foo [..]`
120152
[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s

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