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Merged
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Aug 26, 2025
Merged

test: avoid hardcoded target spec json #15880

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23 changes: 23 additions & 0 deletions crates/cargo-test-support/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,7 @@ use std::fs;
use std::os;
use std::path::{Path, PathBuf};
use std::process::{Command, Output};
use std::sync::LazyLock;
use std::sync::OnceLock;
use std::thread::JoinHandle;
use std::time::{self, Duration};
Expand Down Expand Up @@ -1264,6 +1265,28 @@ pub fn basic_lib_manifest(name: &str) -> String {
)
}

/// Gets a valid target spec JSON from rustc.
///
/// To avoid any hardcoded value, this fetches `x86_64-unknown-none` target
/// spec JSON directly from `rustc`, as Cargo shouldn't know the JSON schema.
pub fn target_spec_json() -> &'static str {
static TARGET_SPEC_JSON: LazyLock<String> = LazyLock::new(|| {
let json = std::process::Command::new("rustc")
.env("RUSTC_BOOTSTRAP", "1")
.arg("--print")
.arg("target-spec-json")
.arg("-Zunstable-options")
.arg("--target")
.arg("x86_64-unknown-none")
.output()
.expect("rustc --print target-spec-json")
.stdout;
String::from_utf8(json).expect("utf8 target spec json")
});

TARGET_SPEC_JSON.as_str()
}

struct RustcInfo {
verbose_version: String,
host: String,
Expand Down
41 changes: 9 additions & 32 deletions tests/build-std/main.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,13 @@

#![allow(clippy::disallowed_methods)]

use cargo_test_support::{Execs, basic_manifest, paths, project, rustc_host, str};
use cargo_test_support::Execs;
use cargo_test_support::basic_manifest;
use cargo_test_support::paths;
use cargo_test_support::project;
use cargo_test_support::rustc_host;
use cargo_test_support::str;
use cargo_test_support::target_spec_json;
use cargo_test_support::{Project, prelude::*};
use std::env;
use std::path::{Path, PathBuf};
Expand Down Expand Up @@ -262,20 +268,7 @@ fn cross_custom() {
)
.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-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
"arch": "x86_64",
"target-endian": "little",
"target-pointer-width": "64",
"os": "none",
"linker-flavor": "ld.lld"
}
"#,
)
.file("custom-target.json", target_spec_json())
.build();

p.cargo("build --target custom-target.json -v")
Expand All @@ -302,23 +295,7 @@ fn custom_test_framework() {
}
"#,
)
.file(
"target.json",
r#"
{
"llvm-target": "x86_64-unknown-none-gnu",
"data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
"arch": "x86_64",
"target-endian": "little",
"target-pointer-width": "64",
"os": "none",
"linker-flavor": "ld.lld",
"linker": "rust-lld",
"executables": true,
"panic-strategy": "abort"
}
"#,
)
.file("target.json", target_spec_json())
.build();

// This is a bit of a hack to use the rust-lld that ships with most toolchains.
Expand Down
33 changes: 11 additions & 22 deletions tests/testsuite/custom_target.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,10 @@
use std::fs;

use crate::prelude::*;
use cargo_test_support::{basic_manifest, project, str};
use cargo_test_support::basic_manifest;
use cargo_test_support::project;
use cargo_test_support::str;
use cargo_test_support::target_spec_json;

const MINIMAL_LIB: &str = r#"
#![allow(internal_features)]
Expand Down Expand Up @@ -31,20 +34,6 @@ pub trait Copy {
}
"#;

const SIMPLE_SPEC: &str = r#"
{
"llvm-target": "x86_64-unknown-none-gnu",
"data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
"arch": "x86_64",
"target-endian": "little",
"target-pointer-width": "64",
"os": "none",
"linker-flavor": "ld.lld",
"linker": "rust-lld",
"executables": true
}
"#;

#[cargo_test(nightly, reason = "requires features no_core, lang_items")]
fn custom_target_minimal() {
let p = project()
Expand All @@ -59,7 +48,7 @@ fn custom_target_minimal() {
"
.replace("__MINIMAL_LIB__", MINIMAL_LIB),
)
.file("custom-target.json", SIMPLE_SPEC)
.file("custom-target.json", target_spec_json())
.build();

p.cargo("build --lib --target custom-target.json -v").run();
Expand Down Expand Up @@ -127,7 +116,7 @@ fn custom_target_dependency() {
"
.replace("__MINIMAL_LIB__", MINIMAL_LIB),
)
.file("custom-target.json", SIMPLE_SPEC)
.file("custom-target.json", target_spec_json())
.build();

p.cargo("build --lib --target custom-target.json -v").run();
Expand All @@ -146,7 +135,7 @@ fn custom_bin_target() {
"
.replace("__MINIMAL_LIB__", MINIMAL_LIB),
)
.file("custom-bin-target.json", SIMPLE_SPEC)
.file("custom-bin-target.json", target_spec_json())
.build();

p.cargo("build --target custom-bin-target.json -v").run();
Expand All @@ -167,7 +156,7 @@ fn changing_spec_rebuilds() {
"
.replace("__MINIMAL_LIB__", MINIMAL_LIB),
)
.file("custom-target.json", SIMPLE_SPEC)
.file("custom-target.json", target_spec_json())
.build();

p.cargo("build --lib --target custom-target.json -v").run();
Expand Down Expand Up @@ -212,7 +201,7 @@ fn changing_spec_relearns_crate_types() {
"#,
)
.file("src/lib.rs", MINIMAL_LIB)
.file("custom-target.json", SIMPLE_SPEC)
.file("custom-target.json", target_spec_json())
.build();

p.cargo("build --lib --target custom-target.json -v")
Expand Down Expand Up @@ -254,8 +243,8 @@ fn custom_target_ignores_filepath() {
"
.replace("__MINIMAL_LIB__", MINIMAL_LIB),
)
.file("b/custom-target.json", SIMPLE_SPEC)
.file("a/custom-target.json", SIMPLE_SPEC)
.file("b/custom-target.json", target_spec_json())
.file("a/custom-target.json", target_spec_json())
.build();

// Should build the library the first time.
Expand Down
17 changes: 7 additions & 10 deletions tests/testsuite/rustc.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,12 @@
//! Tests for the `cargo rustc` command.

use crate::prelude::*;
use cargo_test_support::{basic_bin_manifest, basic_lib_manifest, basic_manifest, project, str};
use cargo_test_support::basic_bin_manifest;
use cargo_test_support::basic_lib_manifest;
use cargo_test_support::basic_manifest;
use cargo_test_support::project;
use cargo_test_support::str;
use cargo_test_support::target_spec_json;

#[cargo_test]
fn build_lib_for_foo() {
Expand Down Expand Up @@ -820,15 +825,7 @@ windows
fn rustc_with_print_cfg_config_toml_env() {
let p = project()
.file("Cargo.toml", &basic_bin_manifest("foo"))
.file(
"targets/best-target.json",
r#"{
"llvm-target": "x86_64-unknown-none",
"target-pointer-width": "64",
"data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
"arch": "x86_64"
}"#,
)
.file("targets/best-target.json", target_spec_json())
.file(
".cargo/config.toml",
r#"
Expand Down
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