WIP: Add a general mechanism for setting rustflags in Cargo for the current crate only

src/bin/cargo/commands/bench.rs

@@ -48,6 +48,7 @@ pub fn cli() -> App {
         ))
         .arg_unit_graph()
         .arg_timings()
+        .arg_rustflags()
         .after_help("Run `cargo help bench` for more detailed information.\n")
 }
 

src/bin/cargo/commands/build.rs

@@ -45,6 +45,7 @@ pub fn cli() -> App {
         .arg_unit_graph()
         .arg_future_incompat_report()
         .arg_timings()
+        .arg_rustflags()
         .after_help("Run `cargo help build` for more detailed information.\n")
 }
 

src/bin/cargo/commands/check.rs

@@ -37,6 +37,7 @@ pub fn cli() -> App {
         .arg_unit_graph()
         .arg_future_incompat_report()
         .arg_timings()
+        .arg_rustflags()
         .after_help("Run `cargo help check` for more detailed information.\n")
 }
 

src/bin/cargo/commands/doc.rs

@@ -40,6 +40,7 @@ pub fn cli() -> App {
         .arg_ignore_rust_version()
         .arg_unit_graph()
         .arg_timings()
+        .arg_rustflags()
         .after_help("Run `cargo help doc` for more detailed information.\n")
 }
 

src/bin/cargo/commands/fix.rs

@@ -54,6 +54,7 @@ pub fn cli() -> App {
         ))
         .arg_ignore_rust_version()
         .arg_timings()
+        .arg_rustflags()
         .after_help("Run `cargo help fix` for more detailed information.\n")
 }
 

src/bin/cargo/commands/install.rs

@@ -82,6 +82,7 @@ pub fn cli() -> App {
         )
         .arg_message_format()
         .arg_timings()
+        .arg_rustflags()
         .after_help("Run `cargo help install` for more detailed information.\n")
 }
 

src/bin/cargo/commands/package.rs

@@ -35,6 +35,7 @@ pub fn cli() -> App {
         )
         .arg_manifest_path()
         .arg_jobs()
+        .arg_rustflags()
         .after_help("Run `cargo help package` for more detailed information.\n")
 }
 

src/bin/cargo/commands/run.rs

@@ -32,6 +32,7 @@ pub fn cli() -> App {
         .arg_unit_graph()
         .arg_ignore_rust_version()
         .arg_timings()
+        .arg_rustflags()
         .after_help("Run `cargo help run` for more detailed information.\n")
 }
 

src/bin/cargo/commands/test.rs

@@ -56,6 +56,7 @@ pub fn cli() -> App {
         .arg_unit_graph()
         .arg_future_incompat_report()
         .arg_timings()
+        .arg_rustflags()
         .after_help(
             "Run `cargo help test` for more detailed information.\n\
              Run `cargo test -- --help` for test binary options.\n",

src/cargo/core/compiler/fingerprint.rs

@@ -1302,13 +1302,16 @@ fn calculate_normal(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Finger
     // Fill out a bunch more information that we'll be tracking typically
     // hashed to take up less space on disk as we just need to know when things
     // change.
-    let extra_flags = if unit.mode.is_doc() {
+    let mut rustflags = if unit.mode.is_doc() {
         cx.bcx.rustdocflags_args(unit)
     } else {
         cx.bcx.rustflags_args(unit)
     }
     .to_vec();
 
+    // Append the command line user specified RUSTFLAGS to the env var or config RUSTFLAGS.
+    rustflags.extend(unit.rustflags.iter().map(InternedString::to_string));
+
     let profile_hash = util::hash_u64((
         &unit.profile,
         unit.mode,
@@ -1345,7 +1348,7 @@ fn calculate_normal(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Finger
         metadata,
         config: config.finish(),
         compile_kind,
-        rustflags: extra_flags,
+        rustflags,
         fs_status: FsStatus::Stale,
         outputs,
     })

src/cargo/core/compiler/mod.rs

@@ -241,9 +241,15 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
     let dep_info_loc = fingerprint::dep_info_loc(cx, unit);
 
     rustc.args(cx.bcx.rustflags_args(unit));
+
+    // Append any user specified rustflags on the command line
+    // via the --rustflag argument.
+    rustc.args(&unit.rustflags);
+
     if cx.bcx.config.cli_unstable().binary_dep_depinfo {
         rustc.arg("-Z").arg("binary-dep-depinfo");
     }
+
     let mut output_options = OutputOptions::new(cx, unit);
     let package_id = unit.pkg.package_id();
     let target = Target::clone(&unit.target);

src/cargo/core/compiler/standard_lib.rs

@@ -214,6 +214,8 @@ pub fn generate_std_roots(
                 *kind,
                 mode,
                 features.clone(),
+                /*rustflags*/
+                Default::default(), // Setting command line rustflags for the standard library is not supported
                 /*is_std*/ true,
                 /*dep_hash*/ 0,
                 IsArtifact::No,

src/cargo/core/compiler/unit.rs

@@ -55,6 +55,8 @@ pub struct UnitInner {
     /// The `cfg` features to enable for this unit.
     /// This must be sorted.
     pub features: Vec<InternedString>,
+    /// The rustflags to set for this unit.
+    pub rustflags: Vec<InternedString>,
     // 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,
@@ -181,6 +183,7 @@ impl UnitInterner {
         kind: CompileKind,
         mode: CompileMode,
         features: Vec<InternedString>,
+        rustflags: Vec<InternedString>,
         is_std: bool,
         dep_hash: u64,
         artifact: IsArtifact,
@@ -213,6 +216,7 @@ impl UnitInterner {
             kind,
             mode,
             features,
+            rustflags,
             is_std,
             dep_hash,
             artifact,

src/cargo/core/compiler/unit_dependencies.rs

@@ -284,6 +284,7 @@ fn compute_deps(
                 unit,
                 dep_pkg,
                 dep_lib,
+                /*rustflags*/ Default::default(),
                 dep_unit_for,
                 unit.kind,
                 mode,
@@ -295,6 +296,7 @@ fn compute_deps(
                 unit,
                 dep_pkg,
                 dep_lib,
+                /*rustflags*/ Default::default(),
                 dep_unit_for,
                 CompileKind::Host,
                 mode,
@@ -307,6 +309,7 @@ fn compute_deps(
                 unit,
                 dep_pkg,
                 dep_lib,
+                /*rustflags*/ Default::default(),
                 dep_unit_for,
                 unit.kind.for_target(dep_lib),
                 mode,
@@ -377,6 +380,7 @@ fn compute_deps(
                         unit,
                         &unit.pkg,
                         t,
+                        /*rustflags*/ Default::default(),
                         UnitFor::new_normal(unit_for.root_compile_kind()),
                         unit.kind.for_target(t),
                         CompileMode::Build,
@@ -479,6 +483,7 @@ fn compute_deps_custom_build(
         unit,
         &unit.pkg,
         &unit.target,
+        /*rustflags*/ Default::default(),
         script_unit_for,
         // Build scripts always compiled for the host.
         CompileKind::Host,
@@ -568,6 +573,7 @@ fn artifact_targets_to_unit_deps(
                                     target
                                         .clone()
                                         .set_kind(TargetKind::Lib(vec![target_kind.clone()])),
+                                    /*rustflags*/ Default::default(),
                                     parent_unit_for,
                                     compile_kind,
                                     CompileMode::Build,
@@ -580,6 +586,7 @@ fn artifact_targets_to_unit_deps(
                         parent,
                         artifact_pkg,
                         target,
+                        /*rustflags*/ Default::default(),
                         parent_unit_for,
                         compile_kind,
                         CompileMode::Build,
@@ -655,6 +662,7 @@ fn compute_deps_doc(
             unit,
             dep_pkg,
             dep_lib,
+            /*rustflags*/ Default::default(),
             dep_unit_for,
             unit.kind.for_target(dep_lib),
             mode,
@@ -669,6 +677,7 @@ fn compute_deps_doc(
                     unit,
                     dep_pkg,
                     dep_lib,
+                    /*rustflags*/ Default::default(),
                     dep_unit_for,
                     unit.kind.for_target(dep_lib),
                     unit.mode,
@@ -699,6 +708,7 @@ fn compute_deps_doc(
                 unit,
                 &unit.pkg,
                 lib,
+                /*rustflags*/ Default::default(),
                 dep_unit_for,
                 unit.kind.for_target(lib),
                 unit.mode,
@@ -717,6 +727,7 @@ fn compute_deps_doc(
                 scrape_unit,
                 &scrape_unit.pkg,
                 &scrape_unit.target,
+                /*rustflags*/ Default::default(),
                 unit_for,
                 scrape_unit.kind,
                 scrape_unit.mode,
@@ -740,11 +751,15 @@ fn maybe_lib(
         .map(|t| {
             let mode = check_or_build_mode(unit.mode, t);
             let dep_unit_for = unit_for.with_dependency(unit, t, unit_for.root_compile_kind());
+
+            // When adding the lib targets for the current unit also pass down the user specified
+            // rustflags for the package.
             new_unit_dep(
                 state,
                 unit,
                 &unit.pkg,
                 t,
+                unit.rustflags.clone(),
                 dep_unit_for,
                 unit.kind.for_target(t),
                 mode,
@@ -805,6 +820,7 @@ fn dep_build_script(
                 unit,
                 &unit.pkg,
                 t,
+                Default::default(),
                 script_unit_for,
                 unit.kind,
                 CompileMode::RunCustomBuild,
@@ -839,6 +855,7 @@ fn new_unit_dep(
     parent: &Unit,
     pkg: &Package,
     target: &Target,
+    rustflags: Vec<InternedString>,
     unit_for: UnitFor,
     kind: CompileKind,
     mode: CompileMode,
@@ -853,7 +870,7 @@ fn new_unit_dep(
         kind,
     );
     new_unit_dep_with_profile(
-        state, parent, pkg, target, unit_for, kind, mode, profile, artifact,
+        state, parent, pkg, target, rustflags, unit_for, kind, mode, profile, artifact,
     )
 }
 
@@ -862,6 +879,7 @@ fn new_unit_dep_with_profile(
     parent: &Unit,
     pkg: &Package,
     target: &Target,
+    rustflags: Vec<InternedString>,
     unit_for: UnitFor,
     kind: CompileKind,
     mode: CompileMode,
@@ -885,6 +903,7 @@ fn new_unit_dep_with_profile(
         kind,
         mode,
         features,
+        rustflags,
         state.is_std,
         /*dep_hash*/ 0,
         artifact.map_or(IsArtifact::No, |_| IsArtifact::Yes),

src/cargo/ops/cargo_compile.rs

@@ -62,6 +62,8 @@ pub struct CompileOptions {
     pub build_config: BuildConfig,
     /// Feature flags requested by the user.
     pub cli_features: CliFeatures,
+    /// Rustflags requested by the user.
+    pub rustflags: Vec<InternedString>,
     /// A set of packages to build.
     pub spec: Packages,
     /// Filter to apply to the root package to select which targets will be
@@ -91,6 +93,7 @@ impl CompileOptions {
         Ok(CompileOptions {
             build_config: BuildConfig::new(config, jobs, keep_going, &[], mode)?,
             cli_features: CliFeatures::new_all(false),
+            rustflags: Vec::new(),
             spec: ops::Packages::Packages(Vec::new()),
             filter: CompileFilter::Default {
                 required_features_filterable: false,
@@ -335,6 +338,7 @@ pub fn create_bcx<'a, 'cfg>(
         ref build_config,
         ref spec,
         ref cli_features,
+        ref rustflags,
         ref filter,
         ref target_rustdoc_args,
         ref target_rustc_args,
@@ -492,6 +496,7 @@ pub fn create_bcx<'a, 'cfg>(
         &resolve,
         &workspace_resolve,
         &resolved_features,
+        &rustflags,
         &pkg_set,
         &profiles,
         interner,
@@ -532,6 +537,7 @@ pub fn create_bcx<'a, 'cfg>(
                 &resolve,
                 &workspace_resolve,
                 &resolved_features,
+                &rustflags,
                 &pkg_set,
                 &profiles,
                 interner,
@@ -983,6 +989,7 @@ fn generate_targets(
     resolve: &Resolve,
     workspace_resolve: &Option<Resolve>,
     resolved_features: &features::ResolvedFeatures,
+    rustflags: &Vec<InternedString>,
     package_set: &PackageSet<'_>,
     profiles: &Profiles,
     interner: &UnitInterner,
@@ -1082,13 +1089,23 @@ fn generate_targets(
                 unit_for,
                 *kind,
             );
+
+            // Doc units will not set the user specified rustflags since these use
+            // rustdoc specific flags instead.
+            let rustflags = if target_mode.is_doc() {
+                Default::default()
+            } else {
+                rustflags.clone()
+            };
+
             let unit = interner.intern(
                 pkg,
                 target,
                 profile,
                 kind.for_target(target),
                 target_mode,
                 features.clone(),
+                rustflags.clone(),
                 /*is_std*/ false,
                 /*dep_hash*/ 0,
                 IsArtifact::No,
@@ -1672,6 +1689,7 @@ fn traverse_and_share(
         new_kind,
         unit.mode,
         unit.features.clone(),
+        unit.rustflags.clone(),
         unit.is_std,
         new_dep_hash,
         unit.artifact,
@@ -1913,6 +1931,7 @@ fn override_rustc_crate_types(
             unit.kind,
             unit.mode,
             unit.features.clone(),
+            unit.rustflags.clone(),
             unit.is_std,
             unit.dep_hash,
             unit.artifact,

src/cargo/ops/cargo_package.rs

@@ -822,6 +822,7 @@ fn run_verify(
                 CompileMode::Build,
             )?,
             cli_features: opts.cli_features.clone(),
+            rustflags: Vec::new(),
             spec: ops::Packages::Packages(Vec::new()),
             filter: ops::CompileFilter::Default {
                 required_features_filterable: true,