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Warn on empty lines after outer attributes #2340

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merged 4 commits into from Jan 30, 2018
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@@ -5,7 +5,7 @@ use rustc::lint::*;
use rustc::hir::*;
use rustc::ty::{self, TyCtxt};
use semver::Version;
use syntax::ast::{Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem, NestedMetaItemKind};
use syntax::ast::{Attribute, AttrStyle, Lit, LitKind, MetaItemKind, NestedMetaItem, NestedMetaItemKind};
use syntax::codemap::Span;
use utils::{in_macro, match_def_path, opt_def_id, paths, snippet_opt, span_lint, span_lint_and_then};
@@ -78,12 +78,44 @@ declare_lint! {
"use of `#[deprecated(since = \"x\")]` where x is not semver"
}
/// **What it does:** Checks for empty lines after outer attributes
///
/// **Why is this bad?**
/// Most likely the attribute was meant to be an inner attribute using a '!'.
/// If it was meant to be an outer attribute, then the following item
/// should not be separated by empty lines.
///
/// **Known problems:** None
///
/// **Example:**
/// ```rust
/// // Bad
/// #[inline(always)]
///
/// fn not_quite_good_code(..) { ... }
///
/// // Good (as inner attribute)
/// #![inline(always)]
///
/// fn this_is_fine_too(..) { ... }
///
/// // Good (as outer attribute)
/// #[inline(always)]
/// fn this_is_fine(..) { ... }
///
/// ```
declare_lint! {
pub EMPTY_LINE_AFTER_OUTER_ATTR,
Warn,
"empty line after outer attribute"
}
#[derive(Copy, Clone)]
pub struct AttrPass;
impl LintPass for AttrPass {
fn get_lints(&self) -> LintArray {
lint_array!(INLINE_ALWAYS, DEPRECATED_SEMVER, USELESS_ATTRIBUTE)
lint_array!(INLINE_ALWAYS, DEPRECATED_SEMVER, USELESS_ATTRIBUTE, EMPTY_LINE_AFTER_OUTER_ATTR)
}
}
@@ -171,7 +203,7 @@ fn is_relevant_item(tcx: TyCtxt, item: &Item) -> bool {
if let ItemFn(_, _, _, _, _, eid) = item.node {
is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir.body(eid).value)
} else {
false
true
}
}
@@ -230,6 +262,27 @@ fn check_attrs(cx: &LateContext, span: Span, name: &Name, attrs: &[Attribute]) {
}
for attr in attrs {
if attr.style == AttrStyle::Outer {
if !is_present_in_source(cx, attr.span) {
return;
}
let attr_to_item_span = Span::new(attr.span.lo(), span.lo(), span.ctxt());
if let Some(snippet) = snippet_opt(cx, attr_to_item_span) {
let lines = snippet.split('\n').collect::<Vec<_>>();
if lines.iter().filter(|l| l.trim().is_empty()).count() > 1 {
span_lint(
cx,
EMPTY_LINE_AFTER_OUTER_ATTR,
attr_to_item_span,
&format!("Found an empty line after an outer attribute. Perhaps you forgot to add a '!' to make it an inner attribute?")
);
}
}
}
if let Some(ref values) = attr.meta_item_list() {
if values.len() != 1 || attr.name().map_or(true, |n| n != "inline") {
continue;
@@ -270,3 +323,17 @@ fn is_word(nmi: &NestedMetaItem, expected: &str) -> bool {
false
}
}
// If the snippet is empty, it's an attribute that was inserted during macro
// expansion and we want to ignore those, because they could come from external
// sources that the user has no control over.
// For some reason these attributes don't have any expansion info on them, so
// we have to check it this way until there is a better way.
fn is_present_in_source(cx: &LateContext, span: Span) -> bool {
if let Some(snippet) = snippet_opt(cx, span) {
if snippet.is_empty() {
return false;
}
}
true
}
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@@ -438,6 +438,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
attrs::DEPRECATED_SEMVER,
attrs::INLINE_ALWAYS,
attrs::USELESS_ATTRIBUTE,
attrs::EMPTY_LINE_AFTER_OUTER_ATTR,
bit_mask::BAD_BIT_MASK,
bit_mask::INEFFECTIVE_BIT_MASK,
bit_mask::VERBOSE_BIT_MASK,
@@ -0,0 +1,56 @@
#![warn(empty_line_after_outer_attr)]
// This should produce a warning
#[crate_type = "lib"]
/// some comment
fn with_one_newline_and_comment() { assert!(true) }
// This should not produce a warning
#[crate_type = "lib"]
/// some comment
fn with_no_newline_and_comment() { assert!(true) }
// This should produce a warning
#[crate_type = "lib"]
fn with_one_newline() { assert!(true) }
// This should produce a warning, too
#[crate_type = "lib"]
fn with_two_newlines() { assert!(true) }
// This should produce a warning
#[crate_type = "lib"]
enum Baz {
One,
Two
}
// This should produce a warning
#[crate_type = "lib"]
struct Foo {
one: isize,
two: isize
}
// This should produce a warning
#[crate_type = "lib"]
mod foo {
}
// This should not produce a warning
#[allow(non_camel_case_types)]
#[allow(missing_docs)]
#[allow(missing_docs)]
fn three_attributes() { assert!(true) }
fn main() { }
@@ -0,0 +1,54 @@
error: Found an empty line after an outer attribute. Perhaps you forgot to add a '!' to make it an inner attribute?
--> $DIR/empty_line_after_outer_attribute.rs:5:1
|
5 | / #[crate_type = "lib"]
6 | |
7 | | /// some comment
8 | | fn with_one_newline_and_comment() { assert!(true) }
| |_
|
= note: `-D empty-line-after-outer-attr` implied by `-D warnings`
error: Found an empty line after an outer attribute. Perhaps you forgot to add a '!' to make it an inner attribute?
--> $DIR/empty_line_after_outer_attribute.rs:17:1
|
17 | / #[crate_type = "lib"]
18 | |
19 | | fn with_one_newline() { assert!(true) }
| |_
error: Found an empty line after an outer attribute. Perhaps you forgot to add a '!' to make it an inner attribute?
--> $DIR/empty_line_after_outer_attribute.rs:22:1
|
22 | / #[crate_type = "lib"]
23 | |
24 | |
25 | | fn with_two_newlines() { assert!(true) }
| |_
error: Found an empty line after an outer attribute. Perhaps you forgot to add a '!' to make it an inner attribute?
--> $DIR/empty_line_after_outer_attribute.rs:29:1
|
29 | / #[crate_type = "lib"]
30 | |
31 | | enum Baz {
| |_
error: Found an empty line after an outer attribute. Perhaps you forgot to add a '!' to make it an inner attribute?
--> $DIR/empty_line_after_outer_attribute.rs:37:1
|
37 | / #[crate_type = "lib"]
38 | |
39 | | struct Foo {
| |_
error: Found an empty line after an outer attribute. Perhaps you forgot to add a '!' to make it an inner attribute?
--> $DIR/empty_line_after_outer_attribute.rs:45:1
|
45 | / #[crate_type = "lib"]
46 | |
47 | | mod foo {
| |_
error: aborting due to 6 previous errors
@@ -11,7 +11,6 @@ trait Foo {
#[inline(always)]fn always_inline();
#[inline(never)]
fn never_inline();
#[inline]
@@ -19,8 +19,7 @@ error: use of `#[inline]` on trait method `never_inline` which has no body
|
13 | #[inline(never)]
| _____-^^^^^^^^^^^^^^^
14 | |
15 | | fn never_inline();
14 | | fn never_inline();
| |____- help: remove
error: aborting due to 3 previous errors
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