Auto merge of #8068 - ehuss:bcx-units, r=alexcrichton,ehuss

Refactor BuildContext

This restructures the "front end" of the compile process so that the `UnitGraph` can be accessed by API users. Essentially, the `BuildContext` contains the result of generating the `UnitGraph`, and other bits of information collected along the way. This logically separates the build process into two phases: (1) generate the `UnitGraph` and `BuildContext` and (2) pass the `BuildContext` to `Context` which performs the actual compilation.

The main challenge here is dealing with the references and lifetimes. The old code kept a bunch of things on the stack with various layers of references. Beside reorganizing things, the big change is to wrap `Package` and `Target` in `Rc`. This still requires the `UnitInterner` to be passed in and kept alive. It is possible to avoid that by placing all `Unit`s in `Rc`, but that had a roughly 5% performance hit (on fresh builds) because Units are very optimized to be used as hashable keys, and `Rc` loses those optimizations.

src/bin/cargo/commands/build.rs

@@ -65,12 +65,12 @@ pub fn exec(config: &mut Config, args: &ArgMatches<'_>) -> CliResult {
     )?;
 
     if let Some(out_dir) = args.value_of_path("out-dir", config) {
-        compile_opts.export_dir = Some(out_dir);
+        compile_opts.build_config.export_dir = Some(out_dir);
     } else if let Some(out_dir) = config.build_config()?.out_dir.as_ref() {
         let out_dir = out_dir.resolve_path(config);
-        compile_opts.export_dir = Some(out_dir);
+        compile_opts.build_config.export_dir = Some(out_dir);
     }
-    if compile_opts.export_dir.is_some() {
+    if compile_opts.build_config.export_dir.is_some() {
         config
             .cli_unstable()
             .fail_if_stable_opt("--out-dir", 6790)?;

src/cargo/core/compiler/build_config.rs

@@ -4,6 +4,7 @@ use crate::util::ProcessBuilder;
 use crate::util::{CargoResult, Config, RustfixDiagnosticServer};
 use serde::ser;
 use std::cell::RefCell;
+use std::path::PathBuf;
 
 /// Configuration information for a rustc build.
 #[derive(Debug)]
@@ -26,7 +27,15 @@ pub struct BuildConfig {
     pub unit_graph: bool,
     /// An optional override of the rustc process for primary units
     pub primary_unit_rustc: Option<ProcessBuilder>,
+    /// A thread used by `cargo fix` to receive messages on a socket regarding
+    /// the success/failure of applying fixes.
     pub rustfix_diagnostic_server: RefCell<Option<RustfixDiagnosticServer>>,
+    /// The directory to copy final artifacts to. Note that even if `out_dir` is
+    /// set, a copy of artifacts still could be found a `target/(debug\release)`
+    /// as usual.
+    // Note that, although the cmd-line flag name is `out-dir`, in code we use
+    // `export_dir`, to avoid confusion with out dir at `target/debug/deps`.
+    pub export_dir: Option<PathBuf>,
 }
 
 impl BuildConfig {
@@ -70,6 +79,7 @@ impl BuildConfig {
             unit_graph: false,
             primary_unit_rustc: None,
             rustfix_diagnostic_server: RefCell::new(None),
+            export_dir: None,
         })
     }
 

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

@@ -1,5 +1,5 @@
-use crate::core::compiler::unit::UnitInterner;
-use crate::core::compiler::{BuildConfig, BuildOutput, CompileKind, Unit};
+use crate::core::compiler::unit_graph::UnitGraph;
+use crate::core::compiler::{BuildConfig, CompileKind, Unit};
 use crate::core::profiles::Profiles;
 use crate::core::{InternedString, Workspace};
 use crate::core::{PackageId, PackageSet};
@@ -8,7 +8,6 @@ use crate::util::errors::CargoResult;
 use crate::util::Rustc;
 use std::collections::HashMap;
 use std::path::PathBuf;
-use std::str;
 
 mod target_info;
 pub use self::target_info::{FileFlavor, RustcTargetData, TargetInfo};
@@ -27,37 +26,40 @@ pub struct BuildContext<'a, 'cfg> {
     pub profiles: Profiles,
     pub build_config: &'a BuildConfig,
     /// Extra compiler args for either `rustc` or `rustdoc`.
-    pub extra_compiler_args: HashMap<Unit<'a>, Vec<String>>,
+    pub extra_compiler_args: HashMap<Unit, Vec<String>>,
     /// Package downloader.
-    pub packages: &'a PackageSet<'cfg>,
-
-    /// Source of interning new units as they're created.
-    pub units: &'a UnitInterner<'a>,
-
+    ///
+    /// This holds ownership of the `Package` objects.
+    pub packages: PackageSet<'cfg>,
     /// Information about rustc and the target platform.
     pub target_data: RustcTargetData,
+    /// The root units of `unit_graph` (units requested on the command-line).
+    pub roots: Vec<Unit>,
+    /// The dependency graph of units to compile.
+    pub unit_graph: UnitGraph,
 }
 
 impl<'a, 'cfg> BuildContext<'a, 'cfg> {
     pub fn new(
         ws: &'a Workspace<'cfg>,
-        packages: &'a PackageSet<'cfg>,
-        config: &'cfg Config,
+        packages: PackageSet<'cfg>,
         build_config: &'a BuildConfig,
         profiles: Profiles,
-        units: &'a UnitInterner<'a>,
-        extra_compiler_args: HashMap<Unit<'a>, Vec<String>>,
+        extra_compiler_args: HashMap<Unit, Vec<String>>,
         target_data: RustcTargetData,
+        roots: Vec<Unit>,
+        unit_graph: UnitGraph,
     ) -> CargoResult<BuildContext<'a, 'cfg>> {
         Ok(BuildContext {
             ws,
+            config: ws.config(),
             packages,
-            config,
             build_config,
             profiles,
             extra_compiler_args,
-            units,
             target_data,
+            roots,
+            unit_graph,
         })
     }
 
@@ -89,30 +91,19 @@ impl<'a, 'cfg> BuildContext<'a, 'cfg> {
         self.build_config.jobs
     }
 
-    pub fn rustflags_args(&self, unit: &Unit<'_>) -> &[String] {
+    pub fn rustflags_args(&self, unit: &Unit) -> &[String] {
         &self.target_data.info(unit.kind).rustflags
     }
 
-    pub fn rustdocflags_args(&self, unit: &Unit<'_>) -> &[String] {
+    pub fn rustdocflags_args(&self, unit: &Unit) -> &[String] {
         &self.target_data.info(unit.kind).rustdocflags
     }
 
     pub fn show_warnings(&self, pkg: PackageId) -> bool {
         pkg.source_id().is_path() || self.config.extra_verbose()
     }
 
-    pub fn extra_args_for(&self, unit: &Unit<'a>) -> Option<&Vec<String>> {
+    pub fn extra_args_for(&self, unit: &Unit) -> Option<&Vec<String>> {
         self.extra_compiler_args.get(unit)
     }
-
-    /// 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_data
-            .target_config(kind)
-            .links_overrides
-            .get(lib_name)
-    }
 }

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

@@ -1,5 +1,4 @@
-use crate::core::compiler::CompileKind;
-use crate::core::compiler::CompileTarget;
+use crate::core::compiler::{BuildOutput, CompileKind, CompileTarget};
 use crate::core::{Dependency, TargetKind, Workspace};
 use crate::util::config::{Config, StringList, TargetConfig};
 use crate::util::{CargoResult, CargoResultExt, ProcessBuilder, Rustc};
@@ -583,4 +582,12 @@ impl RustcTargetData {
             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)
+    }
 }

src/cargo/core/compiler/build_plan.rs

@@ -45,7 +45,7 @@ struct SerializedBuildPlan {
 }
 
 impl Invocation {
-    pub fn new(unit: &Unit<'_>, deps: Vec<usize>) -> Invocation {
+    pub fn new(unit: &Unit, deps: Vec<usize>) -> Invocation {
         let id = unit.pkg.package_id();
         Invocation {
             package_name: id.name().to_string(),
@@ -109,7 +109,7 @@ impl BuildPlan {
         }
     }
 
-    pub fn add<'a>(&mut self, cx: &Context<'a, '_>, unit: &Unit<'a>) -> CargoResult<()> {
+    pub fn add(&mut self, cx: &Context<'_, '_>, unit: &Unit) -> CargoResult<()> {
         let id = self.plan.invocations.len();
         self.invocation_map.insert(unit.buildkey(), id);
         let deps = cx

src/cargo/core/compiler/compilation.rs

@@ -86,10 +86,7 @@ pub struct Compilation<'cfg> {
 }
 
 impl<'cfg> Compilation<'cfg> {
-    pub fn new<'a>(
-        bcx: &BuildContext<'a, 'cfg>,
-        default_kind: CompileKind,
-    ) -> CargoResult<Compilation<'cfg>> {
+    pub fn new<'a>(bcx: &BuildContext<'a, 'cfg>) -> CargoResult<Compilation<'cfg>> {
         let mut rustc = bcx.rustc().process();
         let mut primary_rustc_process = bcx.build_config.primary_unit_rustc.clone();
         let mut rustc_workspace_wrapper_process = bcx.rustc().workspace_process();
@@ -103,6 +100,7 @@ impl<'cfg> Compilation<'cfg> {
             }
         }
 
+        let default_kind = bcx.build_config.requested_kind;
         Ok(Compilation {
             // TODO: deprecated; remove.
             native_dirs: BTreeSet::new(),