Enable backtraces in turbopack integration tests (#89935)

## Enable Rust backtraces in CI tests

### What?
Added `RUST_BACKTRACE=1` environment variable to all Turbopack-related test workflows.

### Why?
This change enables detailed Rust backtraces when Turbopack encounters errors during CI tests, making it easier to diagnose and fix issues that occur in the Rust components.

Notably, some assertions/panics are about detecting race conditions, e.g.
```
thread 'tokio-runtime-worker' (1056161) panicked at turbopack/crates/turbo-tasks-backend/src/backend/operation/mod.rs:426:13:
Concurrent task lock acquisition detected. This is not allowed and indicates a bug. It can lead to deadlocks.
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

Rather than painfully attempting to reproduce locally we can just run with the env var all the time and perhaps that will be enough to figure out rare issues

Author: lukesandberg

.github/workflows/build_and_test.yml

@@ -256,6 +256,7 @@ jobs:
         export NEXT_TEST_MODE=dev
         export NEXT_TEST_REACT_VERSION="${{ matrix.react }}"
         export __NEXT_EXPERIMENTAL_STRICT_ROUTE_TYPES=true
+        export RUST_BACKTRACE=1
 
         node run-tests.js \
           --test-pattern '^(test\/(development|e2e))/.*\.test\.(js|jsx|ts|tsx)$' \
@@ -287,6 +288,7 @@ jobs:
         export TURBOPACK_DEV=1
         export NEXT_TEST_REACT_VERSION="${{ matrix.react }}"
         export __NEXT_EXPERIMENTAL_STRICT_ROUTE_TYPES=true
+        export RUST_BACKTRACE=1
 
         node run-tests.js \
           --timings \
@@ -318,6 +320,7 @@ jobs:
         export NEXT_TEST_MODE=start
         export NEXT_TEST_REACT_VERSION="${{ matrix.react }}"
         export __NEXT_EXPERIMENTAL_STRICT_ROUTE_TYPES=true
+        export RUST_BACKTRACE=1
 
         node run-tests.js --timings -g ${{ matrix.group }} --type production
       stepName: 'test-turbopack-production-react-${{ matrix.react }}-${{ matrix.group }}'
@@ -346,6 +349,7 @@ jobs:
         export TURBOPACK_BUILD=1
         export NEXT_TEST_REACT_VERSION="${{ matrix.react }}"
         export __NEXT_EXPERIMENTAL_STRICT_ROUTE_TYPES=true
+        export RUST_BACKTRACE=1
 
         node run-tests.js \
           --timings \

.github/workflows/turbopack-nextjs-build-integration-tests.yml

@@ -13,7 +13,7 @@ jobs:
       name: turbopack-production
       test_type: production
       run_before_test: |
-        export IS_TURBOPACK_TEST=1 TURBOPACK_BUILD=1
+        export IS_TURBOPACK_TEST=1 TURBOPACK_BUILD=1 RUST_BACKTRACE=1
       # Failing tests take longer (due to timeouts and retries). Since we have
       # many failing tests, we need smaller groups and longer timeouts, in case
       # a group gets stuck with a cluster of failing tests.

.github/workflows/turbopack-nextjs-dev-integration-tests.yml

@@ -13,5 +13,5 @@ jobs:
       name: turbopack-development
       test_type: development
       run_before_test: |
-        export IS_TURBOPACK_TEST=1 TURBOPACK_DEV=1
+        export IS_TURBOPACK_TEST=1 TURBOPACK_DEV=1 RUST_BACKTRACE=1
     secrets: inherit

turbopack/crates/turbopack-ecmascript-plugins/src/transform/swc_ecma_transform_plugins.rs

@@ -299,9 +299,22 @@ impl CustomTransformer for SwcEcmaTransformPluginsTransformer {
                         Err(e) => {
                             use turbopack_core::issue::IssueExt;
 
+                            // Format the error chain without backtrace.
+                            // Using `{:?}` would include the backtrace when
+                            // RUST_BACKTRACE=1, which is not useful in
+                            // user-facing error messages.
+                            let mut description = e.to_string();
+                            let mut causes = e.chain().skip(1).peekable();
+                            if causes.peek().is_some() {
+                                description.push_str("\n\nCaused by:");
+                                for (i, cause) in causes.enumerate() {
+                                    description.push_str(&format!("\n    {i}: {cause}"));
+                                }
+                            }
+
                             SwcEcmaTransformFailureIssue {
                                 file_path: ctx.file_path.clone(),
-                                description: StyledString::Text(format!("{:?}", e).into()),
+                                description: StyledString::Text(description.into()),
                             }
                             .resolved_cell()
                             .emit();