feat: implement warnings on NeverClones that implement Copy

libs/pavexc/src/compiler/analyses/cloning.rs

@@ -110,3 +110,94 @@ fn must_be_clonable(
         .build();
     diagnostics.push(diagnostic);
 }
+
+/// Check all types whose cloning strategy is set to "NeverClone" are not Copy.
+
+#[tracing::instrument(
+    name = "If cloning is not allowed, types should not be copyable",
+    skip_all
+)]
+
+pub(crate) fn never_clones_should_not_be_copyable<'a>(
+    component_db: &ComponentDb,
+    computation_db: &ComputationDb,
+    krate_collection: &CrateCollection,
+    diagnostics: &mut crate::diagnostic::DiagnosticSink,
+) {
+    let copy = process_framework_path("core::marker::Copy", krate_collection);
+
+    let ResolvedType::ResolvedPath(copy) = copy else {
+        unreachable!()
+    };
+
+    for (id, _) in component_db.iter() {
+        let hydrated = component_db.hydrated_component(id, computation_db);
+        match hydrated {
+            HydratedComponent::Constructor(_) | HydratedComponent::PrebuiltType(_) => {
+                if component_db.cloning_strategy(id) != CloningStrategy::NeverClone {
+                    continue;
+                }
+            }
+            _ => {
+                continue;
+            }
+        };
+
+        let Some(output_type) = hydrated.output_type() else {
+            continue;
+        };
+
+        if let Ok(()) = assert_trait_is_implemented(krate_collection, output_type, &copy) {
+            should_not_be_never_clone(output_type, id, component_db, computation_db, diagnostics);
+        }
+    }
+}
+
+fn should_not_be_never_clone(
+    type_: &ResolvedType,
+    id: ComponentId,
+    db: &ComponentDb,
+    computation_db: &ComputationDb,
+    diagnostics: &mut crate::diagnostic::DiagnosticSink,
+) {
+    let id = db.derived_from(&id).unwrap_or(id);
+    let user_id = db.user_component_id(id).unwrap();
+    let kind = db.user_db()[user_id].kind();
+    let registration = db.registration(user_id);
+    let source = diagnostics.annotated(
+        db.registration_target(user_id),
+        format!("The {kind} was registered here"),
+    );
+
+    let (clone_if_necessary, never_clone) = if registration.kind.is_attribute() {
+        ("clone_if_necessary", "never_clone")
+    } else {
+        ("CloneIfNecessary", "NeverClone")
+    };
+
+    let output_type = type_.display_for_error();
+    let warning_msg = match kind {
+        ComponentKind::Constructor => {
+            let callable_path = &computation_db[user_id].path;
+            format!(
+                "`{output_type}` implements `Copy`, but its constructor, `{callable_path}`, is marked as `{never_clone}`."
+            )
+        }
+        ComponentKind::PrebuiltType => {
+            format!("`{output_type}` implements `Copy`, but it's marked as `{never_clone}`.")
+        }
+        _ => unreachable!(),
+    };
+
+    let help = format!(
+        "Either set the cloning strategy to `{clone_if_necessary}` or remove `Copy` for `{output_type}`",
+    );
+
+    let diagnostic = CompilerDiagnostic::builder(anyhow::anyhow!(warning_msg))
+        .severity(miette::Severity::Warning)
+        .optional_source(source)
+        .help(help)
+        .build();
+
+    diagnostics.push(diagnostic);
+}

libs/pavexc/src/compiler/app.rs

@@ -14,7 +14,9 @@ use crate::compiler::analyses::application_state::ApplicationState;
 use crate::compiler::analyses::call_graph::{
     ApplicationStateCallGraph, application_state_call_graph,
 };
-use crate::compiler::analyses::cloning::clonables_can_be_cloned;
+use crate::compiler::analyses::cloning::{
+    clonables_can_be_cloned, never_clones_should_not_be_copyable,
+};
 use crate::compiler::analyses::components::{ComponentDb, ComponentId};
 use crate::compiler::analyses::computations::ComputationDb;
 use crate::compiler::analyses::config_types::ConfigTypeDb;
@@ -116,6 +118,12 @@ impl App {
             &krate_collection,
             &mut diagnostics,
         );
+        never_clones_should_not_be_copyable(
+            &component_db,
+            &computation_db,
+            &krate_collection,
+            &mut diagnostics,
+        );
         exit_on_errors!(diagnostics);
         let handler_id2pipeline = {
             let handler_ids: BTreeSet<_> = router.handler_ids();

libs/ui_tests/Cargo.toml

@@ -11,6 +11,8 @@ members = [
   "annotations/non_existing_dependency/generated_app",
   "app_builder",
   "app_builder/generated_app",
+  "blueprint/common/a_warning_is_emitted_for_copyable_never_clone",
+  "blueprint/common/a_warning_is_emitted_for_copyable_never_clone/generated_app",
   "blueprint/common/async_callable_are_supported",
   "blueprint/common/async_callable_are_supported/generated_app",
   "blueprint/common/cannot_return_the_unit_type",

libs/ui_tests/blueprint/common/a_warning_is_emitted_for_copyable_never_clone/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "app_cd2e094a"
+version = "0.1.0"
+edition.workspace = true
+
+[lints.rust.unexpected_cfgs]
+level = "allow"
+check-cfg = ["cfg(pavex_ide_hint)"]
+
+[dependencies]
+workspace_hack = { version = "0.1", path = "../../../workspace_hack" }
+
+[dependencies.pavex]
+workspace = true
+
+[dependencies.pavex_cli_client]
+workspace = true

libs/ui_tests/blueprint/common/a_warning_is_emitted_for_copyable_never_clone/diagnostics.dot

@@ -0,0 +1,75 @@
+digraph "GET / - 0" {
+    0 [ label = "0| app_cd2e094a::B"]
+    1 [ label = "1| crate::route_0::Next0(app_cd2e094a::B) -> crate::route_0::Next0"]
+    2 [ label = "2| pavex::middleware::Next::new(crate::route_0::Next0) -> pavex::middleware::Next<crate::route_0::Next0>"]
+    3 [ label = "3| pavex::middleware::wrap_noop(pavex::middleware::Next<crate::route_0::Next0>) -> pavex::response::Response"]
+    4 [ label = "4| <pavex::response::Response as pavex::response::IntoResponse>::into_response(pavex::response::Response) -> pavex::response::Response"]
+    2 -> 3 [ ]
+    1 -> 2 [ ]
+    0 -> 1 [ ]
+    3 -> 4 [ ]
+}
+
+digraph "GET / - 1" {
+    0 [ label = "0| app_cd2e094a::B"]
+    1 [ label = "1| app_cd2e094a::a() -> app_cd2e094a::A"]
+    2 [ label = "2| app_cd2e094a::handler_1(app_cd2e094a::A, app_cd2e094a::B) -> pavex::response::Response"]
+    3 [ label = "3| <pavex::response::Response as pavex::response::IntoResponse>::into_response(pavex::response::Response) -> pavex::response::Response"]
+    0 -> 2 [ ]
+    1 -> 2 [ ]
+    2 -> 3 [ ]
+}
+
+digraph "GET /2 - 0" {
+    0 [ label = "0| app_cd2e094a::A1"]
+    1 [ label = "1| app_cd2e094a::B1"]
+    2 [ label = "2| crate::route_1::Next0(app_cd2e094a::B1, app_cd2e094a::A1) -> crate::route_1::Next0"]
+    3 [ label = "3| pavex::middleware::Next::new(crate::route_1::Next0) -> pavex::middleware::Next<crate::route_1::Next0>"]
+    4 [ label = "4| pavex::middleware::wrap_noop(pavex::middleware::Next<crate::route_1::Next0>) -> pavex::response::Response"]
+    5 [ label = "5| <pavex::response::Response as pavex::response::IntoResponse>::into_response(pavex::response::Response) -> pavex::response::Response"]
+    3 -> 4 [ ]
+    2 -> 3 [ ]
+    0 -> 2 [ ]
+    1 -> 2 [ ]
+    4 -> 5 [ ]
+}
+
+digraph "GET /2 - 1" {
+    0 [ label = "0| app_cd2e094a::B1"]
+    1 [ label = "1| app_cd2e094a::A1"]
+    2 [ label = "2| app_cd2e094a::handler_2(app_cd2e094a::A1, app_cd2e094a::B1) -> pavex::response::Response"]
+    3 [ label = "3| <pavex::response::Response as pavex::response::IntoResponse>::into_response(pavex::response::Response) -> pavex::response::Response"]
+    0 -> 2 [ ]
+    1 -> 2 [ ]
+    2 -> 3 [ ]
+}
+
+digraph "* * - 0" {
+    0 [ label = "0| &pavex::router::AllowedMethods"]
+    1 [ label = "1| crate::route_2::Next0(&'a pavex::router::AllowedMethods) -> crate::route_2::Next0<'a>"]
+    2 [ label = "2| pavex::middleware::Next::new(crate::route_2::Next0<'a>) -> pavex::middleware::Next<crate::route_2::Next0<'a>>"]
+    3 [ label = "3| pavex::middleware::wrap_noop(pavex::middleware::Next<crate::route_2::Next0<'a>>) -> pavex::response::Response"]
+    4 [ label = "4| <pavex::response::Response as pavex::response::IntoResponse>::into_response(pavex::response::Response) -> pavex::response::Response"]
+    2 -> 3 [ ]
+    1 -> 2 [ ]
+    3 -> 4 [ ]
+    0 -> 1 [ ]
+}
+
+digraph "* * - 1" {
+    0 [ label = "0| &pavex::router::AllowedMethods"]
+    1 [ label = "1| pavex::router::default_fallback(&pavex::router::AllowedMethods) -> pavex::response::Response"]
+    2 [ label = "2| <pavex::response::Response as pavex::response::IntoResponse>::into_response(pavex::response::Response) -> pavex::response::Response"]
+    1 -> 2 [ ]
+    0 -> 1 [ ]
+}
+
+digraph app_state {
+    0 [ label = "0| app_cd2e094a::b1() -> app_cd2e094a::B1"]
+    1 [ label = "1| app_cd2e094a::b() -> app_cd2e094a::B"]
+    2 [ label = "2| app_cd2e094a::a1() -> app_cd2e094a::A1"]
+    3 [ label = "3| crate::ApplicationState(app_cd2e094a::A1, app_cd2e094a::B, app_cd2e094a::B1) -> crate::ApplicationState"]
+    0 -> 3 [ ]
+    1 -> 3 [ ]
+    2 -> 3 [ ]
+}