Support per-pkg-target for -Zbuild-std, take two

This is a simplified minimal change, which changes the build-std to
iterate over the packages to collect a list of targets std should be
built for. Does the iterating over packages part have issues with
artifact dependencies? I am not very familiar with artifact deps to
know so any help would be appreciated. But it should be fine for now
since artifact dependencies don't work with build-std yet. #10444

src/cargo/core/compiler/standard_lib.rs

@@ -10,6 +10,7 @@ use crate::core::{Dependency, PackageId, PackageSet, Resolve, SourceId, Workspac
 use crate::ops::{self, Packages};
 use crate::util::errors::CargoResult;
 use crate::Config;
+use std::collections::hash_map::Entry;
 use std::collections::{HashMap, HashSet};
 use std::path::PathBuf;
 
@@ -168,7 +169,8 @@ pub fn generate_std_roots(
     crates: &[String],
     std_resolve: &Resolve,
     std_features: &ResolvedFeatures,
-    kinds: &[CompileKind],
+    requested_kinds: &[CompileKind],
+    explicit_host_kind: CompileKind,
     package_set: &PackageSet<'_>,
     interner: &UnitInterner,
     profiles: &Profiles,
@@ -182,41 +184,62 @@ pub fn generate_std_roots(
     let std_pkgs = package_set.get_many(std_ids)?;
     // Generate a map of Units for each kind requested.
     let mut ret = HashMap::new();
-    for pkg in std_pkgs {
-        let lib = pkg
-            .targets()
-            .iter()
-            .find(|t| t.is_lib())
-            .expect("std has a lib");
-        // I don't think we need to bother with Check here, the difference
-        // in time is minimal, and the difference in caching is
-        // significant.
-        let mode = CompileMode::Build;
-        let features = std_features.activated_features(pkg.package_id(), FeaturesFor::NormalOrDev);
-        for kind in kinds {
-            let list = ret.entry(*kind).or_insert_with(Vec::new);
-            let unit_for = UnitFor::new_normal(*kind);
+
+    // Get information for the list of packages for standard library
+    let std_pkg_infos: Vec<_> = std_pkgs
+        .iter()
+        .map(|pkg| {
+            let lib = pkg
+                .targets()
+                .iter()
+                .find(|t| t.is_lib())
+                .expect("std has a lib");
+            let features =
+                std_features.activated_features(pkg.package_id(), FeaturesFor::NormalOrDev);
+            let unit_for = UnitFor::new_normal(explicit_host_kind);
+            (pkg, lib, unit_for, features)
+        })
+        .collect();
+
+    // Iterate over all packages over the package set to find all targets requested.
+    for kind in package_set
+        .packages()
+        .flat_map(|pkg| pkg.explicit_kinds(requested_kinds, explicit_host_kind))
+    {
+        let e = match ret.entry(kind) {
+            Entry::Vacant(e) => e,
+            Entry::Occupied(_) => continue,
+        };
+
+        let units = std_pkg_infos.iter().map(|(pkg, lib, unit_for, features)| {
+            // I don't think we need to bother with Check here, the difference
+            // in time is minimal, and the difference in caching is
+            // significant.
+            let mode = CompileMode::Build;
             let profile = profiles.get_profile(
                 pkg.package_id(),
                 /*is_member*/ false,
                 /*is_local*/ false,
-                unit_for,
-                *kind,
+                *unit_for,
+                kind,
             );
-            list.push(interner.intern(
+            interner.intern(
                 pkg,
                 lib,
                 profile,
-                *kind,
+                kind,
                 mode,
                 features.clone(),
                 /*is_std*/ true,
                 /*dep_hash*/ 0,
                 IsArtifact::No,
                 None,
-            ));
-        }
+            )
+        });
+
+        e.insert(units.collect());
     }
+
     Ok(ret)
 }
 

src/cargo/core/package.rs

@@ -185,6 +185,28 @@ impl Package {
         self.targets().iter().any(|t| t.is_custom_build())
     }
 
+    /// Returns explicit kinds either forced by `forced-target` in `Cargo.toml`,
+    /// fallback to `default-target`, or specified in cli parameters.
+    pub fn explicit_kinds(
+        &self,
+        requested_kinds: &[CompileKind],
+        explicit_host_kind: CompileKind,
+    ) -> Vec<CompileKind> {
+        if let Some(k) = self.manifest().forced_kind() {
+            vec![k]
+        } else {
+            requested_kinds
+                .iter()
+                .map(|kind| match kind {
+                    CompileKind::Host => {
+                        self.manifest().default_kind().unwrap_or(explicit_host_kind)
+                    }
+                    CompileKind::Target(t) => CompileKind::Target(*t),
+                })
+                .collect()
+        }
+    }
+
     pub fn map_source(self, to_replace: SourceId, replace_with: SourceId) -> Package {
         Package {
             inner: Rc::new(PackageInner {

src/cargo/ops/cargo_compile/mod.rs

@@ -341,14 +341,6 @@ pub fn create_bcx<'a, 'cfg>(
     // assuming `--target $HOST` was specified. See
     // `rebuild_unit_graph_shared` for more on why this is done.
     let explicit_host_kind = CompileKind::Target(CompileTarget::new(&target_data.rustc.host)?);
-    let explicit_host_kinds: Vec<_> = build_config
-        .requested_kinds
-        .iter()
-        .map(|kind| match kind {
-            CompileKind::Host => explicit_host_kind,
-            CompileKind::Target(t) => CompileKind::Target(*t),
-        })
-        .collect();
 
     // Passing `build_config.requested_kinds` instead of
     // `explicit_host_kinds` here so that `generate_root_units` can do
@@ -393,7 +385,8 @@ pub fn create_bcx<'a, 'cfg>(
             &crates,
             std_resolve,
             std_features,
-            &explicit_host_kinds,
+            &build_config.requested_kinds,
+            explicit_host_kind,
             &pkg_set,
             interner,
             &profiles,

src/cargo/ops/cargo_compile/unit_generator.rs

@@ -111,20 +111,7 @@ impl<'a> UnitGenerator<'a, '_> {
         // why this is done. However, if the package has its own
         // `package.target` key, then this gets used instead of
         // `$HOST`
-        let explicit_kinds = if let Some(k) = pkg.manifest().forced_kind() {
-            vec![k]
-        } else {
-            self.requested_kinds
-                .iter()
-                .map(|kind| match kind {
-                    CompileKind::Host => pkg
-                        .manifest()
-                        .default_kind()
-                        .unwrap_or(self.explicit_host_kind),
-                    CompileKind::Target(t) => CompileKind::Target(*t),
-                })
-                .collect()
-        };
+        let explicit_kinds = pkg.explicit_kinds(self.requested_kinds, self.explicit_host_kind);
 
         explicit_kinds
             .into_iter()

tests/build-std/main.rs

@@ -227,3 +227,50 @@ fn custom_test_framework() {
         .build_std_arg("core")
         .run();
 }
+
+/// like cross-custom but uses per-package-target instead
+#[cargo_test(build_std_real)]
+fn per_package_target() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                cargo-features = ["per-package-target"]
+                [package]
+                name = "foo"
+                version = "0.1.0"
+                edition = "2018"
+                default-target = "custom-target.json"
+                # [target.custom-target.dependencies] <-- not sure why this doesn't work
+                [dependencies]
+                dep = { path = "dep" }
+            "#,
+        )
+        .file(
+            "src/lib.rs",
+            "#![no_std] pub fn f() -> u32 { dep::answer() }",
+        )
+        .file("dep/Cargo.toml", &basic_manifest("dep", "0.1.0"))
+        .file("dep/src/lib.rs", "#![no_std] pub fn answer() -> u32 { 42 }")
+        .file(
+            "custom-target.json",
+            r#"
+            {
+                "llvm-target": "x86_64-unknown-none-gnu",
+                "data-layout": "e-m:e-i64:64-f80:128-n8:16:32:64-S128",
+                "arch": "x86_64",
+                "target-endian": "little",
+                "target-pointer-width": "64",
+                "target-c-int-width": "32",
+                "os": "none",
+                "linker-flavor": "ld.lld"
+            }
+            "#,
+        )
+        .build();
+
+    p.cargo("build -v")
+        .build_std_arg("core")
+        .target_host()
+        .run();
+}

tests/testsuite/mock-std/library/proc_macro/src/lib.rs

@@ -1,10 +1,15 @@
 #![feature(staged_api)]
 #![stable(since = "1.0.0", feature = "dummy")]
 
+
 extern crate proc_macro;
 
+// Don't re-export everything in the root so that the mock std can be distinguished from the real one.
 #[stable(since = "1.0.0", feature = "dummy")]
-pub use proc_macro::*;
+pub mod exported {
+    #[stable(since = "1.0.0", feature = "dummy")]
+    pub use proc_macro::*;
+}
 
 #[stable(since = "1.0.0", feature = "dummy")]
 pub fn custom_api() {

tests/testsuite/standard_lib.rs

@@ -371,11 +371,104 @@ fn target_proc_macro() {
                 }
             "#,
         )
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "pm"
+                version = "0.1.0"
+                [lib]
+                proc-macro = true
+            "#,
+        )
         .build();
 
     p.cargo("build -v").build_std(&setup).target_host().run();
 }
 
+// We already have `basic` which uses `proc_macro::custom_api()`. This case attempts to use
+// `TokenStream` which would error because we are using the sysroot version.
+#[cargo_test(build_std_mock)]
+fn non_proc_macro_crate_uses_non_sysroot_proc_macro() {
+    let setup = setup();
+
+    let p = project()
+        .file(
+            "src/lib.rs",
+            r#"
+                extern crate proc_macro;
+                fn f() {
+                    let _ts = proc_macro::TokenStream::new();
+                }
+            "#,
+        )
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "pm"
+                version = "0.1.0"
+            "#,
+        )
+        .build();
+
+    p.cargo("build -v").build_std(&setup).run_expect_error();
+}
+
+#[cargo_test(build_std_mock)]
+fn intergrated_proc_macro() {
+    let setup = setup();
+
+    let p = project()
+        .file(
+            "src/main.rs",
+            r#"
+                fn main() {
+                    println!("The answer is {}", pm::m!());
+                }
+            "#,
+        )
+        .file(
+            "pm/src/lib.rs",
+            r#"
+                extern crate proc_macro;
+                use proc_macro::TokenStream;
+                #[proc_macro]
+                pub fn m(_item: TokenStream) -> TokenStream {
+                   "42".parse().unwrap()
+                }
+            "#,
+        )
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.0"
+                [workspace]
+                members = ["pm"]
+                [dependencies]
+                pm = { path = "./pm" }
+            "#,
+        )
+        .file(
+            "pm/Cargo.toml",
+            r#"
+                [package]
+                name = "pm"
+                version = "0.1.0"
+                [lib]
+                proc-macro = true
+            "#,
+        )
+        .build();
+
+    p.cargo("run -v")
+        .build_std(&setup)
+        .with_stdout_contains("The answer is 42")
+        .run();
+}
+
 #[cargo_test(build_std_mock)]
 fn bench() {
     let setup = setup();