Panic beaviour in profile can be specified if using custom harness

It's libtest that requires tests to be always unwound.
For custom harnesses they don't need such a requirement.
Cargo relaxes it a bit in profile settings.

Author: weihanglo

src/cargo/core/compiler/unit_dependencies.rs

@@ -211,9 +211,9 @@ fn deps_of_roots(roots: &[Unit], state: &mut State<'_, '_>) -> CargoResult<()> {
             if unit.target.proc_macro() {
                 // Special-case for proc-macros, which are forced to for-host
                 // since they need to link with the proc_macro crate.
-                UnitFor::new_host_test(state.config, root_compile_kind)
+                UnitFor::new_host_test(state.config, &unit.target, root_compile_kind)
             } else {
-                UnitFor::new_test(state.config, root_compile_kind)
+                UnitFor::new_test(state.config, &unit.target, root_compile_kind)
             }
         } else if unit.target.is_custom_build() {
             // This normally doesn't happen, except `clean` aggressively

src/cargo/core/profiles.rs

@@ -921,19 +921,24 @@ impl UnitFor {
     /// whether `panic=abort` is supported for tests. Historical versions of
     /// rustc did not support this, but newer versions do with an unstable
     /// compiler flag.
-    pub fn new_test(config: &Config, root_compile_kind: CompileKind) -> UnitFor {
+    ///
+    /// Moreover, `target` is taken here for determining whether the test is
+    /// driven by libtest harness. Cargo relaxes the panic behaviour if it is
+    /// a custom harness, which is not required to be always unwound.
+    pub fn new_test(config: &Config, target: &Target, root_compile_kind: CompileKind) -> UnitFor {
+        // We're testing out an unstable feature (`-Zpanic-abort-tests`)
+        // which inherits the panic setting from the dev/release profile
+        // (basically avoid recompiles) but historical defaults required
+        // that we always unwound.
+        let panic_setting = if config.cli_unstable().panic_abort_tests || !target.harness() {
+            PanicSetting::ReadProfile
+        } else {
+            PanicSetting::AlwaysUnwind
+        };
         UnitFor {
             host: false,
             host_features: false,
-            // We're testing out an unstable feature (`-Zpanic-abort-tests`)
-            // which inherits the panic setting from the dev/release profile
-            // (basically avoid recompiles) but historical defaults required
-            // that we always unwound.
-            panic_setting: if config.cli_unstable().panic_abort_tests {
-                PanicSetting::ReadProfile
-            } else {
-                PanicSetting::AlwaysUnwind
-            },
+            panic_setting,
             root_compile_kind,
             artifact_target_for_features: None,
         }
@@ -942,8 +947,14 @@ impl UnitFor {
     /// This is a special case for unit tests of a proc-macro.
     ///
     /// Proc-macro unit tests are forced to be run on the host.
-    pub fn new_host_test(config: &Config, root_compile_kind: CompileKind) -> UnitFor {
-        let mut unit_for = UnitFor::new_test(config, root_compile_kind);
+    ///
+    /// See [`UnitFor::new_test`] for more.
+    pub fn new_host_test(
+        config: &Config,
+        target: &Target,
+        root_compile_kind: CompileKind,
+    ) -> UnitFor {
+        let mut unit_for = UnitFor::new_test(config, target, root_compile_kind);
         unit_for.host = true;
         unit_for.host_features = true;
         unit_for

src/cargo/ops/cargo_compile/mod.rs

@@ -678,7 +678,7 @@ fn generate_targets(
                 //
                 // Forcing the lib to be compiled three times during `cargo
                 // test` is probably also not desirable.
-                UnitFor::new_test(config, *kind)
+                UnitFor::new_test(config, &target, *kind)
             } else if target.for_host() {
                 // Proc macro / plugin should not have `panic` set.
                 UnitFor::new_compiler(*kind)