From a0324d2bdaa1873a72dd19676a9c11cd93d54fed Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Thu, 10 Sep 2026 21:37:47 +0000
Subject: [PATCH] test(swc-plugin): verify class-name preservation at runtime
 (#4015)

Signed-off-by: Nathan Rajlich <n@n8.io>
---
 .changeset/swc-class-name-runtime-tests.md    |   4 +
 .../transform/tests/class_names.rs            | 107 ++++++++++++++++++
 2 files changed, 111 insertions(+)
 create mode 100644 .changeset/swc-class-name-runtime-tests.md
 create mode 100644 packages/swc-plugin-workflow/transform/tests/class_names.rs

diff --git a/.changeset/swc-class-name-runtime-tests.md b/.changeset/swc-class-name-runtime-tests.md
new file mode 100644
index 0000000000..969c4362f0
--- /dev/null
+++ b/.changeset/swc-class-name-runtime-tests.md
@@ -0,0 +1,4 @@
+---
+---
+
+Add runtime regression tests for class names and registration identity in both compiler transform modes, with no package release.
diff --git a/packages/swc-plugin-workflow/transform/tests/class_names.rs b/packages/swc-plugin-workflow/transform/tests/class_names.rs
new file mode 100644
index 0000000000..de0ec62c89
--- /dev/null
+++ b/packages/swc-plugin-workflow/transform/tests/class_names.rs
@@ -0,0 +1,107 @@
+use std::process::Command;
+use swc_core::ecma::{transforms::testing::Tester, visit::visit_mut_pass};
+use swc_workflow::{StepTransform, TransformMode};
+
+fn assert_class_names(mode: TransformMode) {
+    for members in [
+        r#"async run() { 'use step'; return 42; }"#,
+        r#"
+        static [Symbol.for('workflow-serialize')](instance) { return {}; }
+        static [Symbol.for('workflow-deserialize')](data) { return new this(); }
+        "#,
+    ] {
+        let source = r#"
+            import assert from 'node:assert/strict';
+
+            globalThis[Symbol.for('WORKFLOW_USE_STEP')] = () => function proxy() {};
+
+            var C = class { static initialName = this.name; __MEMBERS__ };
+            let LetClass = class { __MEMBERS__ };
+            const ConstClass = class { __MEMBERS__ };
+            var Alpha = class { __MEMBERS__ }, Beta = class { __MEMBERS__ };
+            var Parenthesized = (class { __MEMBERS__ });
+            let Assigned;
+            Assigned = class { __MEMBERS__ };
+            var Explicit = class InternalName { __MEMBERS__ };
+            const objects = {
+                Key: class { __MEMBERS__ },
+                'key-with-dashes': class { __MEMBERS__ },
+            };
+            const array = [class { __MEMBERS__ }];
+            const conditional = true ? class { __MEMBERS__ } : null;
+            function capture(value) { return value; }
+            const argument = capture(class { __MEMBERS__ });
+
+            const classes = [
+                [C, 'C'],
+                [LetClass, 'LetClass'],
+                [ConstClass, 'ConstClass'],
+                [Alpha, 'Alpha'],
+                [Beta, 'Beta'],
+                [Parenthesized, 'Parenthesized'],
+                [Assigned, 'Assigned'],
+                [Explicit, 'InternalName'],
+                [objects.Key, 'Key'],
+                [objects['key-with-dashes'], 'key-with-dashes'],
+                [array[0], ''],
+                [conditional, ''],
+                [argument, ''],
+            ];
+            assert.equal(C.initialName, 'C');
+            for (const [cls, name] of classes) {
+                assert.equal(cls.name, name);
+                assert.deepEqual(Object.getOwnPropertyDescriptor(cls, 'name'), {
+                    value: name,
+                    writable: false,
+                    enumerable: false,
+                    configurable: true,
+                });
+            }
+        "#
+        .replace("__MEMBERS__", members);
+
+        let code = Tester::run(|tester| {
+            let program = tester.apply_transform(
+                visit_mut_pass(StepTransform::new(mode.clone(), "input.js".into(), None)),
+                "input.js",
+                Default::default(),
+                Some(true),
+                &source,
+            )?;
+            Ok(tester.print(&program, &tester.comments.clone()))
+        });
+
+        // Execute both the original and freshly transformed source, rather
+        // than relying on snapshots of the generated class identifiers.
+        let registered = format!(
+            r#"{code}
+            const registry = globalThis[Symbol.for('workflow-class-registry')];
+            for (const [cls] of classes) {{
+                assert.equal(typeof cls.classId, 'string');
+                assert.equal(registry.get(cls.classId), cls);
+            }}
+            "#
+        );
+        for (label, code) in [("original", &source), ("transformed", &registered)] {
+            let output = Command::new("node")
+                .args(["--input-type=module", "--eval", code])
+                .output()
+                .expect("Node.js is required for class-name runtime tests");
+            assert!(
+                output.status.success(),
+                "{label} {mode:?}: {}\n{code}",
+                String::from_utf8_lossy(&output.stderr)
+            );
+        }
+    }
+}
+
+#[test]
+fn inferred_class_names_step_mode() {
+    assert_class_names(TransformMode::Step);
+}
+
+#[test]
+fn inferred_class_names_workflow_mode() {
+    assert_class_names(TransformMode::Workflow);
+}