Rust-clippy: clippy fails to check project but no error shown, due to doc comment

Created on 9 Sep 2020 · 14Comments · Source: rust-lang/rust-clippy

EDIT: reduced even further by @keiichiw
````rust

/// /// 'a()' ///
fn main() {}

````

git clone https://github.com/rust-lang/cargo cd cargo git checkout 875e0123259b0b6299903fe4aea0a12ecde9324f cargo check --all-features --all-targets find . | grep \.rs$ | xargs touch cargo clippy --all-features --all-targets
This throws an error on my machine but it does not say what the actual problem is, as if something was eating the error message:

```Checking cargo-test-support v0.1.0 (/home/matthias/vcs/github/cargo/crates/cargo-test-support) warning: callingpush_str()using a single-character string literal --> src/bin/cargo/cli.rs:121:5 | 121 | version_string.push_str("\n"); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider usingpushwith a character literal:version_string.push('\n')| = note:#[warn(clippy::single_char_push_str)]` on by default
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#single_char_push_str

warning: 1 warning emitted

warning: unneeded return statement
--> crates/cargo-test-support/src/cross_compile.rs:219:13
|
219 | return true;
| ^^^^^^^^^^^^ help: remove return: true
|
= note: #[warn(clippy::needless_return)] on by default
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_return

warning: unneeded return statement
--> crates/cargo-test-support/src/cross_compile.rs:222:13
|
222 | return false;
| ^^^^^^^^^^^^^ help: remove return: false
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_return

warning: unneeded return statement
--> crates/cargo-test-support/src/cross_compile.rs:226:9
|
226 | return true;
| ^^^^^^^^^^^^ help: remove return: true
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_return

warning: 3 warnings emitted

error: could not compile cargo-test-support.

````

I tried cargo check but that seems to work and does not throw any errors.

All 14 comments

I tried to poke around with some debug prints but I'm still not sure what causes this...

````diff
diff --git a/src/main.rs b/src/main.rs
index ea0674339..05b5abfeb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -53,7 +53,7 @@ pub fn main() {
return;
}

if let Err(code) = process(env::args().skip(2)) {
+if let Err(code) = dbg!(process(env::args().skip(2))) {
process::exit(code);
}
}
@@ -157,12 +157,12 @@ impl ClippyCmd {
.collect();
```
 cmd.env(self.path_env(), Self::path())
```
.envs(ClippyCmd::target_dir())
.env("CLIPPY_ARGS", clippy_args)
.arg(self.cargo_subcommand)
.envs(dbg!(ClippyCmd::target_dir()))
.env("CLIPPY_ARGS", dbg!(clippy_args))
.arg(dbg!(self.cargo_subcommand))
.args(&self.args);
cmd
dbg!(cmd)
}
}

@@ -172,7 +172,7 @@ where
{
let cmd = ClippyCmd::new(old_args);

let mut cmd = cmd.into_std_cmd();
let mut cmd = dbg!(cmd.into_std_cmd());

let exit_status = cmd
.spawn()
@@ -180,6 +180,8 @@ where
.wait()
.expect("failed to wait for cargo?");
dbg!(exit_status);
+
if exit_status.success() {
Ok(())
} else {
````

cargo-clippy --verbose -j 1 --all-targets
````
[src/main.rs:160] ClippyCmd::target_dir() = None
[src/main.rs:161] clippy_args = ""
[src/main.rs:162] self.cargo_subcommand = "check"
[src/main.rs:165] cmd = "cargo" "check" "-j" "1" "--all-targets"
[src/main.rs:175] cmd.into_std_cmd() = "cargo" "check" "-j" "1" "--all-targets"

clippy warnings *
[src/main.rs:183] exit_status = ExitStatus(
ExitStatus(
25856,
),
)
[src/main.rs:56] process(env::args().skip(2)) = Err(
101,
)
````

matthiaskrgr on 12 Dec 2020

Hmm, happens major release stable-x86_64-unknown-linux-gnu unchanged - rustc 1.48.0 (7eac88abb 2020-11-16)

matthiaskrgr on 12 Dec 2020

Someone encountered the same exit code in cargo here: https://github.com/rust-lang/cargo/issues/7147

Maybe this is caused by our cargo tests?

phansch on 12 Dec 2020

Maybe this is caused by our cargo tests?

I would be very surprised since clippy should not execute cargo tests. I also don't understand why cargo should lock the cargo_home for clippy, hm...

For the record I wondered if cargo clippy -Zunstable-options could be a culprint but it was added in cargo 1.44 and not in cargo 1.48.

matthiaskrgr on 12 Dec 2020

Oh wait, I meant cargo _lints_ not tests :sweat_smile:

phansch on 13 Dec 2020

👀1

cargo_common_metadata fires on the crate if it is enabled (it's allow by default) but I could not find any other culprints :/

matthiaskrgr on 14 Dec 2020

Isn't this because cargo has a feature to deny warnings? You were running with --all-features.

mikerite on 14 Dec 2020

I don't think this is the cause.
The mysterious error also happens when I check the cargo-test-support crate directly and it does not have any features and does not seem to deny warnings.

matthiaskrgr on 14 Dec 2020

So, I spent a some time reducing the issue and came down to this (as main.rs):
rust /// Adds a platform-specific dependency. Example: /// ``` /// [target.'cfg(windows)'.dependencies] /// foo = {version = "1.0"} /// ``` fn main() { println!("Hello, world!"); }

The problem seems to be the doc comment.

matthiaskrgr on 14 Dec 2020

👀1

I made it a bit smaller.

/// ```
/// 'a()'
/// ```
fn main() {}

keiichiw on 15 Dec 2020

❤1

I tested this a bit more, and it seems, that something with the string parsing/lexing in doc comments goes wrong. This happens when a string is not properly enclosed, like

r#"hi"
"a
"
'

All of this produces an error without a message when put in the doc comment.

The example by @keiichiw is kind of an outlier. IIUC it parses 'a as a lifetime, () as the unit type (?), and then trips over the trailing '. The error goes away if only [a-zA-Z0-9_] are used between the single quotes (aka chars allowed in an ident).

Maybe a bug in pulldown_cmark?

flip1995 on 15 Dec 2020

👀2

We're interpreting the fenced code block as rust code (there's no label), and the parser chokes, so there's a panic.

I'll see what would be the best way to recover from this later.

Backtrace

0  std::panicking::rust_panic () at library/std/src/panicking.rs:640
1  0x00007ffff32b9ae2 in std::panicking::rust_panic_without_hook () at library/std/src/panicking.rs:630
2  0x00007ffff32ae136 in std::panic::resume_unwind () at library/std/src/panic.rs:426
3  0x00007ffff6e79673 in rustc_span::fatal_error::FatalError::raise ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
4  0x00007ffff5e32dc0 in rustc_parse::lexer::StringReader::report_unterminated_raw_string ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
5  0x00007ffff5e31e4f in rustc_parse::lexer::StringReader::next_token ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
6  0x00007ffff5de6712 in rustc_parse::lexer::tokentrees::TokenTreesReader::parse_all_token_trees ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
7  0x00007ffff5e2fe9a in rustc_parse::lexer::parse_token_trees () from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
8  0x00007ffff5e2bec9 in rustc_parse::maybe_file_to_stream () from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
9  0x00007ffff5e2bb18 in rustc_parse::maybe_source_file_to_parser () from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
10 0x00007ffff5e2b6e7 in rustc_parse::maybe_new_parser_from_source_str ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
11 0x00005555559b327f in clippy_lints::doc::check_code::has_needless_main (code=...) at clippy_lints/src/doc.rs:462
12 0x00005555559b2f12 in clippy_lints::doc::check_code (cx=0x7fffee43d9f0, text=..., span=...) at clippy_lints/src/doc.rs:513
13 0x0000555555b682be in clippy_lints::doc::check_doc (cx=0x7fffee43d9f0, valid_idents=0x7fffe82ce160, events=..., spans=...) at clippy_lints/src/doc.rs:439
14 0x00005555559b2d93 in clippy_lints::doc::check_attrs (cx=0x7fffee43d9f0, valid_idents=0x7fffe82ce160, attrs=...) at clippy_lints/src/doc.rs:377
15 0x00005555559b158d in <clippy_lints::doc::DocMarkdown as rustc_lint::passes::LateLintPass>::check_item (self=0x7fffe82ce160, cx=0x7fffee43d9f0, item=0x7fffe8211698)
    at clippy_lints/src/doc.rs:175
16 0x00007ffff5f3d5b0 in <rustc_lint::late::LateLintPassObjects as rustc_lint::passes::LateLintPass>::check_item ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
17 0x00007ffff3da215c in rustc_hir::intravisit::Visitor::visit_nested_item ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
18 0x00007ffff3d1e4de in rustc_hir::intravisit::walk_crate () from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
19 0x00007ffff3d88bbc in rustc_lint::late::late_lint_pass_crate () from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
20 0x00007ffff3d8f9e1 in rustc_session::utils::<impl rustc_session::session::Session>::time ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
21 0x00007ffff3db56c8 in <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
22 0x00007ffff3d91758 in rustc_session::utils::<impl rustc_session::session::Session>::time ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
23 0x00007ffff3dd3920 in rustc_interface::passes::analysis () from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
24 0x00007ffff3bde27b in rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute () from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
25 0x00007ffff3bbc396 in rustc_query_system::dep_graph::graph::DepGraph<K>::with_eval_always_task ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
26 0x00007ffff3bcf8f6 in rustc_data_structures::stack::ensure_sufficient_stack ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
27 0x00007ffff3b5f685 in rustc_query_system::query::plumbing::get_query_impl ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
28 0x00007ffff3be118f in rustc_interface::passes::QueryContext::enter ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
29 0x00007ffff3b1b355 in rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
30 0x00007ffff3b9c297 in rustc_span::with_source_map () from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
31 0x00007ffff3b1caab in rustc_interface::interface::create_compiler_and_run ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
32 0x00007ffff3bc92e0 in scoped_tls::ScopedKey<T>::set () from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
33 0x00007ffff3bd01a6 in std::sys_common::backtrace::__rust_begin_short_backtrace ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
34 0x00007ffff3b23f4a in core::ops::function::FnOnce::call_once{{vtable-shim}} ()
   from /home/ebroto/.rustup/toolchains/nightly-2020-12-14-x86_64-unknown-linux-gnu/lib/librustc_driver-17b8b01089c6566b.so
35 0x00007ffff32c947a in <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once () at /rustc/803c60218ffac3384b0063c1b87ae7944163bba7/library/alloc/src/boxed.rs:1328
36 <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once () at /rustc/803c60218ffac3384b0063c1b87ae7944163bba7/library/alloc/src/boxed.rs:1328
37 std::sys::unix::thread::Thread::new::thread_start () at library/std/src/sys/unix/thread.rs:71
38 0x00007ffff31cafb7 in start_thread (arg=<optimized out>) at pthread_create.c:486
39 0x00007ffff2fb72cf in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

ebroto on 15 Dec 2020

Do you know why clippy did not properly panic here?
The fact that it only threw a bad exit status without giving details is a bit scary imo.

matthiaskrgr on 15 Dec 2020

@matthiaskrgr yep, that happened because of two reasons:
1) When parsing doctests, we throw away any diagnostic emitted by the parser. This makes sense as we only care about valid Rust code, but...
2) When a fatal error is raised when parsing, a panic starts unwinding the stack unti we reach rustc_driver::catch_with_exit_code. There, if the panic was started by a fatal error, it is assumed the message was printed and that it's not an ICE, so the panic hook is not executed.

The PR adds a call to rustc_driver::catch_fatal_errors to avoid propagating the panic until catch_with_exit_code in driver.rs.

Note that stack unwinding is used during "normal operation", a fatal error is not an ICE.

ebroto on 16 Dec 2020

👍1

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