Auto merge of #5228 - phil-opp:target-spec, r=alexcrichton

Add support for absolute target.json paths

Builds upon https://github.com/rust-lang/rust/pull/49019 with the goal to provide a solution to https://github.com/rust-lang/cargo/issues/4905.

This PR does two things:

~~1. It appends a hash of the target path to the target folder name if a `*.json` path is passed as `--target`, like it's done in https://github.com/rust-lang/rust/pull/49019. This helps differentiating targets with the same JSON file name and avoids sysroot clashes in `xargo`.~~ See https://github.com/rust-lang/cargo/pull/5228#discussion_r176827531
2. It canonicalizes the passed target path (if it's a `*.json` path), so that the path stays valid when building dependencies and setting the `RUST_TARGET_PATH` environment variable is no longer necessary.

src/cargo/ops/cargo_compile.rs

@@ -24,7 +24,7 @@
 
 use std::collections::{HashMap, HashSet};
 use std::default::Default;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
 use core::{Package, Source, Target};
@@ -32,7 +32,7 @@ use core::{PackageId, PackageIdSpec, Profile, Profiles, TargetKind, Workspace};
 use core::resolver::{Method, Resolve};
 use ops::{self, BuildOutput, DefaultExecutor, Executor};
 use util::config::Config;
-use util::{profile, CargoResult};
+use util::{profile, CargoResult, CargoResultExt};
 
 /// Contains information about how a package should be compiled.
 #[derive(Debug)]
@@ -235,7 +235,17 @@ pub fn compile_ws<'a>(
         ref target_rustc_args,
     } = *options;
 
-    let target = target.clone();
+    let target = match target {
+        &Some(ref target) if target.ends_with(".json") => {
+            let path = Path::new(target)
+                .canonicalize()
+                .chain_err(|| format_err!("Target path {:?} is not a valid file", target))?;
+            Some(path.into_os_string()
+                .into_string()
+                .map_err(|_| format_err!("Target path is not valid unicode"))?)
+        }
+        other => other.clone(),
+    };
 
     if jobs == Some(0) {
         bail!("jobs must be at least 1")

tests/testsuite/custom_target.rs

@@ -0,0 +1,170 @@
+use cargotest::is_nightly;
+use cargotest::support::{execs, project};
+use hamcrest::assert_that;
+
+#[test]
+fn custom_target_minimal() {
+    if !is_nightly() {
+        return;
+    }
+    let p = project("foo")
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+
+            name = "foo"
+            version = "0.0.1"
+            authors = ["author@example.com"]
+        "#,
+        )
+        .file(
+            "src/lib.rs",
+            r#"
+            #![feature(no_core)]
+            #![feature(lang_items)]
+            #![no_core]
+
+            pub fn foo() -> u32 {
+                42
+            }
+
+            #[lang = "sized"]
+            pub trait Sized {
+                // Empty.
+            }
+            #[lang = "copy"]
+            pub trait Copy {
+                // Empty.
+            }
+        "#,
+        )
+        .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();
+
+    assert_that(
+        p.cargo("build")
+            .arg("--lib")
+            .arg("--target")
+            .arg("custom-target.json")
+            .arg("-v"),
+        execs().with_status(0),
+    );
+    assert_that(
+        p.cargo("build")
+            .arg("--lib")
+            .arg("--target")
+            .arg("src/../custom-target.json")
+            .arg("-v"),
+        execs().with_status(0),
+    );
+}
+
+#[test]
+fn custom_target_dependency() {
+    if !is_nightly() {
+        return;
+    }
+    let p = project("foo")
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+
+            name = "foo"
+            version = "0.0.1"
+            authors = ["author@example.com"]
+
+            [dependencies]
+            bar = { path = "bar" }
+        "#,
+        )
+        .file(
+            "src/lib.rs",
+            r#"
+            #![feature(no_core)]
+            #![feature(lang_items)]
+            #![feature(optin_builtin_traits)]
+            #![no_core]
+
+            extern crate bar;
+
+            pub fn foo() -> u32 {
+                bar::bar()
+            }
+
+            #[lang = "freeze"]
+            unsafe auto trait Freeze {}
+        "#,
+        )
+        .file(
+            "bar/Cargo.toml",
+            r#"
+            [package]
+
+            name = "bar"
+            version = "0.0.1"
+            authors = ["author@example.com"]
+        "#,
+        )
+        .file(
+            "bar/src/lib.rs",
+            r#"
+            #![feature(no_core)]
+            #![feature(lang_items)]
+            #![no_core]
+
+            pub fn bar() -> u32 {
+                42
+            }
+
+            #[lang = "sized"]
+            pub trait Sized {
+                // Empty.
+            }
+            #[lang = "copy"]
+            pub trait Copy {
+                // Empty.
+            }
+        "#,
+        )
+        .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();
+
+    assert_that(
+        p.cargo("build")
+            .arg("--lib")
+            .arg("--target")
+            .arg("custom-target.json")
+            .arg("-v"),
+        execs().with_status(0),
+    );
+}

tests/testsuite/main.rs

@@ -43,6 +43,7 @@ mod config;
 mod corrupt_git;
 mod cross_compile;
 mod cross_publish;
+mod custom_target;
 mod death;
 mod dep_info;
 mod directory;