Write lint to check for dashmaps entries being held

Signed-off-by: Marcel Müller <neikos@neikos.email>

.config/hakari.toml

@@ -0,0 +1,27 @@
+# This file contains settings for `cargo hakari`.
+# See https://docs.rs/cargo-hakari/latest/cargo_hakari/config for a full list of options.
+
+hakari-package = "hakari"
+
+# Format version for hakari's output. Version 4 requires cargo-hakari 0.9.22 or above.
+dep-format-version = "4"
+
+# Setting workspace.resolver = "2" or higher in the root Cargo.toml is HIGHLY recommended.
+# Hakari works much better with the v2 resolver. (The v2 and v3 resolvers are identical from
+# hakari's perspective, so you're welcome to set either.)
+#
+# For more about the new feature resolver, see:
+# https://blog.rust-lang.org/2021/03/25/Rust-1.51.0.html#cargos-new-feature-resolver
+resolver = "2"
+
+# Add triples corresponding to platforms commonly used by developers here.
+# https://doc.rust-lang.org/rustc/platform-support.html
+platforms = [
+    # "x86_64-unknown-linux-gnu",
+    # "x86_64-apple-darwin",
+    # "aarch64-apple-darwin",
+    # "x86_64-pc-windows-msvc",
+]
+
+# Write out exact versions rather than a semver range. (Defaults to false.)
+# exact-versions = true

.gitignore

@@ -1 +1,6 @@
 .direnv/
+
+
+# Added by cargo
+
+/target

Cargo.toml

@@ -0,0 +1,12 @@
+[workspace]
+
+members = [ "hakari" , "lints/*" ]
+
+resolver = "2"
+
+[workspace.package]
+version = "0.1.0"
+edition = "2021"
+
+[workspace.metadata.crane]
+name = "dylints-various"

flake.lock

@@ -31,11 +31,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1741084643,
+        "lastModified": 1741089216,
-        "narHash": "sha256-pohp+9ekX2rBuoew8MNoqkZKaez6q4n+8j/K6SSfTrE=",
+        "narHash": "sha256-5ZBaJ0XvjakoZwpHPj6oGzwCcCrcREQlNuDklQfZAxQ=",
         "owner": "TheNeikos",
         "repo": "nix-dylint",
-        "rev": "c88fde3de47277b3d0c1f16f740ff8ceb079e161",
+        "rev": "7ca821aada8b6fd82a5c422cd1eb821eb208f8ae",
         "type": "github"
       },
       "original": {

flake.nix

@@ -32,6 +32,9 @@
           ];
         };
 
+        inherit (pkgs) lib;
+
+        toolchain = (builtins.fromTOML (builtins.readFile ./rust-toolchain.toml)).toolchain.channel;
         rustTarget = pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
 
         dylintLib = inputs.dylint.mkLib {
@@ -39,7 +42,61 @@
           inherit (inputs) crane;
         };
 
-        lints = [ ];
+        craneLib = (inputs.crane.mkLib pkgs).overrideToolchain rustTarget;
+
+        src = craneLib.cleanCargoSource ./.;
+
+        commonLintArgs = {
+          inherit src;
+          strictDeps = true;
+
+          buildInputs = [ pkgs.openssl ];
+          nativeBuildInputs = [ pkgs.pkg-config ];
+
+          DOCS_RS = "true";
+          RUSTUP_TOOLCHAIN = toolchain;
+        };
+
+        cargoArtifacts = craneLib.buildDepsOnly commonLintArgs;
+
+        individualLintArgs = commonLintArgs // {
+          inherit cargoArtifacts;
+          inherit (craneLib.crateNameFromCargoToml { inherit src; }) version;
+
+          doCheck = false;
+        };
+
+        fileSetForCrate =
+          crate:
+          lib.fileset.toSource {
+            root = ./.;
+            fileset = lib.fileset.unions [
+              ./Cargo.lock
+              ./Cargo.toml
+              (craneLib.fileset.commonCargoSources ./hakari)
+              (craneLib.fileset.commonCargoSources crate)
+            ];
+          };
+
+        dashmap-ref = craneLib.buildPackage (
+          individualLintArgs
+          // {
+            pname = "dashmap-ref";
+            cargoExtraArgs = "-p dashmap-ref";
+            src = fileSetForCrate ./lints/dashmap-ref;
+
+            postFixup = ''
+              mv $out/lib/libdashmap_ref{.so,@$RUSTUP_TOOLCHAIN.so}
+            '';
+          }
+        );
+
+        lints = [
+          {
+            inherit toolchain;
+            package = dashmap-ref;
+          }
+        ];
         dylint = dylintLib.mkDylint { inherit lints; };
       in
       {
@@ -47,7 +104,14 @@
           nativeBuildInputs = [
             rustTarget
             dylint
+
+            pkgs.cargo-hakari
+            pkgs.openssl
+            pkgs.pkg-config
           ];
+
+          DYLINT_DRIVER_PATH = dylint.passthru.DYLINT_DRIVER_PATH;
+          RUSTUP_TOOLCHAIN = toolchain;
         };
       }
     );

hakari/.gitattributes

@@ -0,0 +1,4 @@
+# Avoid putting conflict markers in the generated Cargo.toml file, since their presence breaks
+# Cargo.
+# Also do not check out the file as CRLF on Windows, as that's what hakari needs.
+Cargo.toml merge=binary -crlf

hakari/Cargo.toml

@@ -0,0 +1,36 @@
+# This file is generated by `cargo hakari`.
+# To regenerate, run:
+#     cargo hakari generate
+
+[package]
+name = "hakari"
+version = "0.1.0"
+edition = "2021"
+description = "workspace-hack package, managed by hakari"
+# You can choose to publish this crate: see https://docs.rs/cargo-hakari/latest/cargo_hakari/publishing.
+publish = false
+
+# The parts of the file between the BEGIN HAKARI SECTION and END HAKARI SECTION comments
+# are managed by hakari.
+
+### BEGIN HAKARI SECTION
+[dependencies]
+aho-corasick = { version = "1" }
+dylint_internal = { version = "4", default-features = false, features = ["config", "git", "packaging", "rustup", "sed"] }
+log = { version = "0.4", default-features = false, features = ["std"] }
+regex-automata = { version = "0.4", default-features = false, features = ["dfa-onepass", "hybrid", "meta", "nfa", "perf", "unicode"] }
+regex-syntax = { version = "0.8" }
+serde = { version = "1", features = ["derive"] }
+smallvec = { version = "1", default-features = false, features = ["const_generics", "union"] }
+
+[build-dependencies]
+aho-corasick = { version = "1" }
+dylint_internal = { version = "4", default-features = false, features = ["config", "git", "packaging", "rustup", "sed"] }
+log = { version = "0.4", default-features = false, features = ["std"] }
+regex-automata = { version = "0.4", default-features = false, features = ["dfa-onepass", "hybrid", "meta", "nfa", "perf", "unicode"] }
+regex-syntax = { version = "0.8" }
+serde = { version = "1", features = ["derive"] }
+smallvec = { version = "1", default-features = false, features = ["const_generics", "union"] }
+syn = { version = "2", features = ["extra-traits", "fold", "visit"] }
+
+### END HAKARI SECTION

hakari/build.rs

@@ -0,0 +1,2 @@
+// A build script is required for cargo to consider build dependencies.
+fn main() {}

hakari/src/lib.rs

@@ -0,0 +1 @@
+// This is a stub lib.rs.

lints/dashmap-ref/.cargo/config.toml

@@ -0,0 +1,6 @@
+[target.'cfg(all())']
+rustflags = ["-C", "linker=dylint-link"]
+
+# For Rust versions 1.74.0 and onward, the following alternative can be used
+# (see https://github.com/rust-lang/cargo/pull/12535):
+# linker = "dylint-link"

lints/dashmap-ref/.gitignore

@@ -0,0 +1 @@
+/target

lints/dashmap-ref/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "dashmap-ref"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[lib]
+crate-type = ["cdylib"]
+
+[[example]]
+name = "ui"
+path = "ui/main.rs"
+
+[dependencies]
+clippy_utils = { git = "https://github.com/rust-lang/rust-clippy", rev = "19e305bb57a7595f2a8d81f521c0dd8bf854e739" }
+dylint_linting = "4.0.0"
+hakari = { version = "0.1", path = "../../hakari" }
+
+[dev-dependencies]
+dashmap = "6"
+dylint_testing = "4.0.0"
+
+[package.metadata.rust-analyzer]
+rustc_private = true

lints/dashmap-ref/README.md

@@ -0,0 +1,21 @@
+# template
+
+### What it does
+
+### Why is this bad?
+
+### Known problems
+
+Remove if none.
+
+### Example
+
+```rust
+// example code where a warning is issued
+```
+
+Use instead:
+
+```rust
+// example code that does not raise a warning
+```

lints/dashmap-ref/src/lib.rs

@@ -0,0 +1,142 @@
+#![feature(rustc_private)]
+#![feature(let_chains)]
+
+extern crate rustc_hir;
+extern crate rustc_middle;
+extern crate rustc_span;
+
+use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::match_any_def_paths;
+use rustc_hir as hir;
+use rustc_hir::def_id::DefId;
+use rustc_lint::LateContext;
+use rustc_lint::LateLintPass;
+use rustc_middle::mir::CoroutineLayout;
+use rustc_middle::ty::Adt;
+use rustc_middle::ty::Ty;
+use rustc_span::sym;
+
+dylint_linting::declare_late_lint! {
+    /// ### What it does
+    /// Check whether a DashMap reference is held across an await point.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// This can cause issues as the dashmap may deadlock
+    ///
+    /// ### Known problems
+    ///
+    /// Remove if none.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// // example code where a warning is issued
+    /// ```
+    ///
+    /// Use instead:
+    ///
+    /// ```rust
+    /// // example code that does not raise a warning
+    /// ```
+    pub DASHMAP_REF,
+    Warn,
+    "Check whether a dashmap reference is held over an await point"
+}
+
+const DASHMAP_REF_GUARD: [&str; 4] = ["dashmap", "mapref", "one", "Ref"];
+const DASHMAP_REF_MUT_GUARD: [&str; 4] = ["dashmap", "mapref", "one", "RefMut"];
+const DASHMAP_ENTRY_GUARD: [&str; 4] = ["dashmap", "mapref", "entry", "Entry"];
+const DASHMAP_ITER: [&str; 3] = ["dashmap", "iter", "Iter"];
+const DASHMAP_ITER_MUT: [&str; 3] = ["dashmap", "iter", "IterMut"];
+
+impl LateLintPass<'_> for DashmapRef {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'_ hir::Expr<'_>) {
+        if let hir::ExprKind::Closure(hir::Closure {
+            def_id,
+            kind:
+                hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
+                    hir::CoroutineDesugaring::Async,
+                    _,
+                )),
+            ..
+        }) = expr.kind
+        {
+            if let Some(coroutine_layout) = cx.tcx.mir_coroutine_witnesses(*def_id) {
+                check_interior_types(cx, coroutine_layout);
+            }
+        }
+    }
+}
+
+fn check_interior_types(cx: &LateContext<'_>, coroutine: &CoroutineLayout<'_>) {
+    for (ty_index, ty_cause) in coroutine.field_tys.iter_enumerated() {
+        if let Adt(adt, _) = ty_cause.ty.kind() {
+            let await_points = || {
+                coroutine
+                    .variant_source_info
+                    .iter_enumerated()
+                    .filter_map(|(variant, source_info)| {
+                        coroutine.variant_fields[variant]
+                            .raw
+                            .contains(&ty_index)
+                            .then_some(source_info.span)
+                    })
+                    .collect::<Vec<_>>()
+            };
+
+            if is_dashmap_ref(cx, adt.did(), &ty_cause.ty) {
+                span_lint_and_then(
+                    cx,
+                    DASHMAP_REF,
+                    ty_cause.source_info.span,
+                    "this dashmap reference is held \
+                    across an 'await' point. Either drop it before the 'await', \
+                    or read it again afterwards.",
+                    |diag| {
+                        diag.span_note(
+                            await_points(),
+                            "these are all the await points this ref is held through",
+                        );
+                    },
+                );
+            }
+        }
+    }
+}
+
+fn is_dashmap_ref(cx: &LateContext<'_>, def_id: DefId, ty: &Ty<'_>) -> bool {
+    if let Adt(adt, args) = ty.kind() {
+        if let Some(ty) = cx
+            .tcx
+            .is_diagnostic_item(sym::Option, adt.did())
+            .then(|| args.type_at(0))
+        {
+            if let Adt(adt, ..) = ty.kind() {
+                is_dashmap_ref(cx, adt.did(), &ty)
+            } else {
+                false
+            }
+        } else {
+            match_any_def_paths(
+                cx,
+                def_id,
+                &[
+                    &DASHMAP_REF_GUARD,
+                    &DASHMAP_REF_MUT_GUARD,
+                    &DASHMAP_ENTRY_GUARD,
+                    &DASHMAP_ITER,
+                    &DASHMAP_ITER_MUT,
+                ],
+            )
+            .is_some()
+        }
+    } else {
+        false
+    }
+}
+
+#[test]
+fn ui() {
+    dylint_testing::ui_test_example(env!("CARGO_PKG_NAME"), "ui");
+}

lints/dashmap-ref/ui/main.rs

@@ -0,0 +1,50 @@
+#[expect(unused_must_use)]
+fn main() {
+    held_across();
+    held_across_multiple();
+    dropped_before();
+    all_kinds();
+}
+
+async fn held_across() {
+    let map = dashmap::DashMap::<String, String>::default();
+
+    let reference = map.get("Hello");
+
+    std::future::pending::<()>().await;
+
+    println!("{reference:?}");
+}
+
+async fn held_across_multiple() {
+    let map = dashmap::DashMap::<String, String>::default();
+
+    let _reference = map.get("Hello");
+
+    std::future::pending::<()>().await;
+
+    std::future::pending::<()>().await;
+}
+
+async fn dropped_before() {
+    let map = dashmap::DashMap::<String, String>::default();
+
+    let _ = map.get("Hello");
+
+    std::future::pending::<()>().await;
+}
+
+async fn all_kinds() {
+    let map = dashmap::DashMap::<String, String>::default();
+
+    let _ref = map.get("Hello");
+    let _ref_mut = map.get_mut("Hello");
+    let _entry = map.entry("Hello".to_string());
+    let _opt_entry = map.try_entry("Hello".to_string());
+    let _iter_entry = map.iter();
+    let _iter_mut_entry = map.iter_mut();
+    let _direct_ref = map.get("Hello").unwrap();
+    let _direct_ref_mut = map.get_mut("Hello").unwrap();
+
+    std::future::pending::<()>().await;
+}

lints/dashmap-ref/ui/main.stderr

@@ -0,0 +1,126 @@
+warning: this dashmap reference is held across an 'await' point. Either drop it before the 'await', or read it again afterwards.
+  --> $DIR/main.rs:12:9
+   |
+LL |     let reference = map.get("Hello");
+   |         ^^^^^^^^^
+   |
+note: these are all the await points this ref is held through
+  --> $DIR/main.rs:14:34
+   |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+   = note: `#[warn(dashmap_ref)]` on by default
+
+warning: this dashmap reference is held across an 'await' point. Either drop it before the 'await', or read it again afterwards.
+  --> $DIR/main.rs:22:9
+   |
+LL |     let _reference = map.get("Hello");
+   |         ^^^^^^^^^^
+   |
+note: these are all the await points this ref is held through
+  --> $DIR/main.rs:24:34
+   |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+LL |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+
+warning: this dashmap reference is held across an 'await' point. Either drop it before the 'await', or read it again afterwards.
+  --> $DIR/main.rs:40:9
+   |
+LL |     let _ref = map.get("Hello");
+   |         ^^^^
+   |
+note: these are all the await points this ref is held through
+  --> $DIR/main.rs:49:34
+   |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+
+warning: this dashmap reference is held across an 'await' point. Either drop it before the 'await', or read it again afterwards.
+  --> $DIR/main.rs:41:9
+   |
+LL |     let _ref_mut = map.get_mut("Hello");
+   |         ^^^^^^^^
+   |
+note: these are all the await points this ref is held through
+  --> $DIR/main.rs:49:34
+   |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+
+warning: this dashmap reference is held across an 'await' point. Either drop it before the 'await', or read it again afterwards.
+  --> $DIR/main.rs:42:9
+   |
+LL |     let _entry = map.entry("Hello".to_string());
+   |         ^^^^^^
+   |
+note: these are all the await points this ref is held through
+  --> $DIR/main.rs:49:34
+   |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+
+warning: this dashmap reference is held across an 'await' point. Either drop it before the 'await', or read it again afterwards.
+  --> $DIR/main.rs:43:9
+   |
+LL |     let _opt_entry = map.try_entry("Hello".to_string());
+   |         ^^^^^^^^^^
+   |
+note: these are all the await points this ref is held through
+  --> $DIR/main.rs:49:34
+   |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+
+warning: this dashmap reference is held across an 'await' point. Either drop it before the 'await', or read it again afterwards.
+  --> $DIR/main.rs:44:9
+   |
+LL |     let _iter_entry = map.iter();
+   |         ^^^^^^^^^^^
+   |
+note: these are all the await points this ref is held through
+  --> $DIR/main.rs:49:34
+   |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+
+warning: this dashmap reference is held across an 'await' point. Either drop it before the 'await', or read it again afterwards.
+  --> $DIR/main.rs:45:9
+   |
+LL |     let _iter_mut_entry = map.iter_mut();
+   |         ^^^^^^^^^^^^^^^
+   |
+note: these are all the await points this ref is held through
+  --> $DIR/main.rs:49:34
+   |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+
+warning: this dashmap reference is held across an 'await' point. Either drop it before the 'await', or read it again afterwards.
+  --> $DIR/main.rs:46:9
+   |
+LL |     let _direct_ref = map.get("Hello").unwrap();
+   |         ^^^^^^^^^^^
+   |
+note: these are all the await points this ref is held through
+  --> $DIR/main.rs:49:34
+   |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+
+warning: this dashmap reference is held across an 'await' point. Either drop it before the 'await', or read it again afterwards.
+  --> $DIR/main.rs:47:9
+   |
+LL |     let _direct_ref_mut = map.get_mut("Hello").unwrap();
+   |         ^^^^^^^^^^^^^^^
+   |
+note: these are all the await points this ref is held through
+  --> $DIR/main.rs:49:34
+   |
+LL |     std::future::pending::<()>().await;
+   |                                  ^^^^^
+
+warning: 10 warnings emitted
+

rust-toolchain.toml

@@ -1,2 +1,3 @@
 [toolchain]
-channel = "1.85.0"
+channel = "nightly-2025-01-09"
+components = ["llvm-tools-preview", "rustc-dev"]