fix: Add -Zjson-target-spec on Cargo calls where needed

crates/project-model/src/build_dependencies.rs

@@ -459,9 +459,7 @@ impl WorkspaceBuildScripts {
                     cmd.arg(target_dir.as_ref());
                 }
 
-                if let Some(target) = &config.target {
-                    cmd.args(["--target", target]);
-                }
+                toolchain::cargo_use_targets(&mut cmd, config.target.as_slice());
                 let mut lockfile_copy = None;
                 if let Some(toolchain) = toolchain {
                     let lockfile_path =

crates/project-model/src/toolchain_info/target_data.rs

@@ -55,9 +55,7 @@ pub fn get(
             let mut cmd = sysroot.tool(Tool::Cargo, cargo_toml.parent(), extra_env);
             cmd.env("RUSTC_BOOTSTRAP", "1");
             cmd.args(["rustc", "-Z", "unstable-options"]).args(RUSTC_ARGS);
-            if let Some(target) = target {
-                cmd.args(["--target", target]);
-            }
+            toolchain::cargo_use_targets(&mut cmd, target.as_slice());
             cmd.args(["--", "-Z", "unstable-options"]);
             match utf8_stdout(&mut cmd) {
                 Ok(output) => return process(output),

crates/rust-analyzer/src/flycheck.rs

@@ -64,9 +64,7 @@ pub(crate) enum Target {
 
 impl CargoOptions {
     pub(crate) fn apply_on_command(&self, cmd: &mut Command, ws_target_dir: Option<&Utf8Path>) {
-        for target in &self.target_tuples {
-            cmd.args(["--target", target.as_str()]);
-        }
+        toolchain::cargo_use_targets(cmd, &self.target_tuples);
         if self.all_targets {
             if self.set_test {
                 cmd.arg("--all-targets");

crates/toolchain/src/lib.rs

@@ -143,3 +143,16 @@ pub fn probe_for_binary(path: Utf8PathBuf) -> Option<Utf8PathBuf> {
     };
     iter::once(path).chain(with_extension).find(|it| it.is_file())
 }
+
+/// Uses targets in a Cargo process.
+pub fn cargo_use_targets(cmd: &mut Command, targets: impl IntoIterator<Item = impl AsRef<str>>) {
+    let mut has_target_json = false;
+    for target in targets {
+        let target = target.as_ref();
+        cmd.args(["--target", target]);
+        has_target_json |= target.ends_with(".json");
+    }
+    if has_target_json {
+        cmd.arg("-Zjson-target-spec");
+    }
+}