Auto merge of #14205 - gmorenz:links_overrides_in_unit, r=weihanglo

Fix passing of links-overrides with target-applies-to-host and an implicit target

### What does this PR try to resolve?

This fixes the link-overrides half of #14195, both the panic, and the fact that the field is being discarded, the latter of which caused the former as discussed in [the issue](https://github.com/rust-lang/cargo/issues/14195#issuecomment-2211481773).

It does so following the blueprint laid out in #13900 - which is also in my opinion the current best summary of the broader context.

### How should we test and review this PR?

For reviewing, comparing to the changes in #13900 might be useful.

### Additional information

I'm pushing a PR for the other half of #14195 simultaneously. I thought it better to keep the PRs small since they're independent, though if merged simultaneously there will be a conflict over the ordering of fields in `Unit`.

src/cargo/core/compiler/build_context/target_info.rs

@@ -8,9 +8,7 @@
 //! * [`TargetInfo::rustc_outputs`] to get a list of supported file types.
 
 use crate::core::compiler::apply_env_config;
-use crate::core::compiler::{
+use crate::core::compiler::{BuildRunner, CompileKind, CompileMode, CompileTarget, CrateType};
-    BuildOutput, BuildRunner, CompileKind, CompileMode, CompileTarget, CrateType,
-};
 use crate::core::{Dependency, Package, Target, TargetKind, Workspace};
 use crate::util::context::{GlobalContext, StringList, TargetConfig};
 use crate::util::interning::InternedString;
@@ -1038,14 +1036,6 @@ impl<'gctx> RustcTargetData<'gctx> {
             CompileKind::Target(s) => &self.target_config[&s],
         }
     }
-
-    /// If a build script is overridden, this returns the `BuildOutput` to use.
-    ///
-    /// `lib_name` is the `links` library name and `kind` is whether it is for
-    /// Host or Target.
-    pub fn script_override(&self, lib_name: &str, kind: CompileKind) -> Option<&BuildOutput> {
-        self.target_config(kind).links_overrides.get(lib_name)
-    }
 }
 
 /// Structure used to deal with Rustdoc fingerprinting

src/cargo/core/compiler/custom_build.rs

@@ -61,7 +61,7 @@ const OLD_CARGO_WARNING_SYNTAX: &str = "cargo:warning=";
 /// [the doc]: https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#cargo-warning
 const NEW_CARGO_WARNING_SYNTAX: &str = "cargo::warning=";
 /// Contains the parsed output of a custom build script.
-#[derive(Clone, Debug, Hash, Default)]
+#[derive(Clone, Debug, Hash, Default, PartialEq, Eq, PartialOrd, Ord)]
 pub struct BuildOutput {
     /// Paths to pass to rustc with the `-L` flag.
     pub library_paths: Vec<PathBuf>,
@@ -160,7 +160,7 @@ pub struct BuildDeps {
 /// See the [build script documentation][1] for more.
 ///
 /// [1]: https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#cargorustc-link-argflag
-#[derive(Clone, Hash, Debug, PartialEq, Eq)]
+#[derive(Clone, Hash, Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub enum LinkArgTarget {
     /// Represents `cargo::rustc-link-arg=FLAG`.
     All,
@@ -1168,11 +1168,7 @@ pub fn build_map(build_runner: &mut BuildRunner<'_, '_>) -> CargoResult<()> {
         // If there is a build script override, pre-fill the build output.
         if unit.mode.is_run_custom_build() {
             if let Some(links) = unit.pkg.manifest().links() {
-                if let Some(output) = build_runner
+                if let Some(output) = unit.links_overrides.get(links) {
-                    .bcx
-                    .target_data
-                    .script_override(links, unit.kind)
-                {
                     let metadata = build_runner.get_run_build_script_metadata(unit);
                     build_runner.build_script_outputs.lock().unwrap().insert(
                         unit.pkg.package_id(),

src/cargo/core/compiler/standard_lib.rs

@@ -219,6 +219,7 @@ pub fn generate_std_roots(
                 features.clone(),
                 target_data.info(*kind).rustflags.clone(),
                 target_data.info(*kind).rustdocflags.clone(),
+                target_data.target_config(*kind).links_overrides.clone(),
                 /*is_std*/ true,
                 /*dep_hash*/ 0,
                 IsArtifact::No,

src/cargo/core/compiler/unit.rs

@@ -9,13 +9,15 @@ use crate::util::hex::short_hash;
 use crate::util::interning::InternedString;
 use crate::util::GlobalContext;
 use std::cell::RefCell;
-use std::collections::HashSet;
+use std::collections::{BTreeMap, HashSet};
 use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::ops::Deref;
 use std::rc::Rc;
 use std::sync::Arc;
 
+use super::BuildOutput;
+
 /// All information needed to define a unit.
 ///
 /// A unit is an object that has enough information so that cargo knows how to build it.
@@ -82,6 +84,12 @@ pub struct UnitInner {
     /// [`BuildContext::extra_args_for`]: crate::core::compiler::build_context::BuildContext::extra_args_for
     /// [`TargetInfo.rustdocflags`]: crate::core::compiler::build_context::TargetInfo::rustdocflags
     pub rustdocflags: Arc<[String]>,
+    /// Build script override for the given library name.
+    ///
+    /// Any package with a `links` value for the given library name will skip
+    /// running its build script and instead use the given output from the
+    /// config file.
+    pub links_overrides: Rc<BTreeMap<String, BuildOutput>>,
     // if `true`, the dependency is an artifact dependency, requiring special handling when
     // calculating output directories, linkage and environment variables provided to builds.
     pub artifact: IsArtifact,
@@ -176,6 +184,7 @@ impl fmt::Debug for Unit {
             .field("features", &self.features)
             .field("rustflags", &self.rustflags)
             .field("rustdocflags", &self.rustdocflags)
+            .field("links_overrides", &self.links_overrides)
             .field("artifact", &self.artifact.is_true())
             .field(
                 "artifact_target_for_features",
@@ -225,6 +234,7 @@ impl UnitInterner {
         features: Vec<InternedString>,
         rustflags: Arc<[String]>,
         rustdocflags: Arc<[String]>,
+        links_overrides: Rc<BTreeMap<String, BuildOutput>>,
         is_std: bool,
         dep_hash: u64,
         artifact: IsArtifact,
@@ -260,6 +270,7 @@ impl UnitInterner {
             features,
             rustflags,
             rustdocflags,
+            links_overrides,
             is_std,
             dep_hash,
             artifact,

src/cargo/core/compiler/unit_dependencies.rs

@@ -457,11 +457,7 @@ fn compute_deps_custom_build(
     state: &State<'_, '_>,
 ) -> CargoResult<Vec<UnitDep>> {
     if let Some(links) = unit.pkg.manifest().links() {
-        if state
+        if unit.links_overrides.get(links).is_some() {
-            .target_data
-            .script_override(links, unit.kind)
-            .is_some()
-        {
             // Overridden build scripts don't have any dependencies.
             return Ok(Vec::new());
         }
@@ -861,6 +857,11 @@ fn new_unit_dep_with_profile(
         features,
         state.target_data.info(kind).rustflags.clone(),
         state.target_data.info(kind).rustdocflags.clone(),
+        state
+            .target_data
+            .target_config(kind)
+            .links_overrides
+            .clone(),
         state.is_std,
         /*dep_hash*/ 0,
         artifact.map_or(IsArtifact::No, |_| IsArtifact::Yes),

src/cargo/ops/cargo_compile/mod.rs

@@ -698,6 +698,7 @@ fn traverse_and_share(
             unit.features.clone(),
             unit.rustflags.clone(),
             unit.rustdocflags.clone(),
+            unit.links_overrides.clone(),
             unit.is_std,
             unit.dep_hash,
             unit.artifact,
@@ -725,6 +726,7 @@ fn traverse_and_share(
         unit.features.clone(),
         unit.rustflags.clone(),
         unit.rustdocflags.clone(),
+        unit.links_overrides.clone(),
         unit.is_std,
         new_dep_hash,
         unit.artifact,
@@ -888,6 +890,7 @@ fn override_rustc_crate_types(
             unit.features.clone(),
             unit.rustflags.clone(),
             unit.rustdocflags.clone(),
+            unit.links_overrides.clone(),
             unit.is_std,
             unit.dep_hash,
             unit.artifact,

src/cargo/ops/cargo_compile/unit_generator.rs

@@ -173,6 +173,7 @@ impl<'a> UnitGenerator<'a, '_> {
                     features.clone(),
                     self.target_data.info(kind).rustflags.clone(),
                     self.target_data.info(kind).rustdocflags.clone(),
+                    self.target_data.target_config(kind).links_overrides.clone(),
                     /*is_std*/ false,
                     /*dep_hash*/ 0,
                     IsArtifact::No,

src/cargo/util/context/target.rs

@@ -4,6 +4,7 @@ use crate::util::CargoResult;
 use serde::Deserialize;
 use std::collections::{BTreeMap, HashMap};
 use std::path::PathBuf;
+use std::rc::Rc;
 
 /// Config definition of a `[target.'cfg(…)']` table.
 ///
@@ -36,7 +37,7 @@ pub struct TargetConfig {
     /// Any package with a `links` value for the given library name will skip
     /// running its build script and instead use the given output from the
     /// config file.
-    pub links_overrides: BTreeMap<String, BuildOutput>,
+    pub links_overrides: Rc<BTreeMap<String, BuildOutput>>,
 }
 
 /// Loads all of the `target.'cfg()'` tables.
@@ -128,7 +129,7 @@ fn load_config_table(gctx: &GlobalContext, prefix: &str) -> CargoResult<TargetCo
         rustflags,
         rustdocflags,
         linker,
-        links_overrides,
+        links_overrides: Rc::new(links_overrides),
     })
 }
 

tests/testsuite/build_script.rs

@@ -5777,3 +5777,41 @@ hello
 "#]])
         .run();
 }
+
+#[cargo_test]
+fn links_overrides_with_target_applies_to_host() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "mylib-sys"
+                edition = "2021"
+                version = "0.0.1"
+                authors = []
+                links = "mylib"
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .file("build.rs", "bad file")
+        .build();
+
+    p.cargo("build -v")
+        .masquerade_as_nightly_cargo(&["target-applies-to-host"])
+        .args(&[
+            "-Ztarget-applies-to-host",
+            "--config",
+            "target-applies-to-host=false",
+        ])
+        .args(&[
+            "--config",
+            &format!(r#"target.{}.mylib.rustc-link-search=["foo"]"#, rustc_host()),
+        ])
+        .with_stderr_data(str![[r#"
+[COMPILING] mylib-sys v0.0.1 ([ROOT]/foo)
+[RUNNING] `rustc --crate-name mylib_sys [..] -L foo`
+[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
+
+"#]])
+        .run();
+}