fix: error stack traces in transpiled TypeScript (#740)

* fix: error stack traces in transpiled TypeScript

Example code:

```ts
interface User {
  name: string;
  email: string;
}

const err: Error = new Error("boom!"); throw err;
```

Deno output:

```
error: Uncaught (in promise) Error: boom!
const err: Error = new Error("boom!"); throw err;
                   ^
    at file:///project/x.ts:6:20

Zinnia before this change - notice the missing `: Error` text
and wrong source code line & column numbers:

```
error: Uncaught (in promise) Error: boom!
const err = new Error("boom!");
            ^
    at file:///project/x.ts:1:13
```

Zinnia after this change (same output as from Deno):

```
error: Uncaught (in promise) Error: boom!
const err: Error = new Error("boom!"); throw err;
                   ^
    at file:///project/x.ts:6:20
```

---------

Signed-off-by: Miroslav Bajtoš <oss@bajtos.net>

Author: bajtos

.prettierignore

@@ -1,6 +1,7 @@
 /runtime/vendored
 /runtime/js/vendored
 target
+/runtime/tests/js/typescript_fixtures/typescript_stack_trace.ts
 
 # Let's keep LICENSE.md in the same formatting as we use in other PL repositories
 LICENSE.md

runtime/module_loader.rs

@@ -1,6 +1,8 @@
+use std::borrow::Cow;
+use std::cell::RefCell;
 use std::collections::HashMap;
 use std::path::{Path, PathBuf};
-use std::sync::{Arc, RwLock};
+use std::rc::Rc;
 
 use deno_ast::{MediaType, ParseParams};
 use deno_core::anyhow::anyhow;
@@ -21,7 +23,9 @@ use deno_core::anyhow::Result;
 pub struct ZinniaModuleLoader {
     module_root: Option<PathBuf>,
     // Cache mapping file_name to source_code
-    code_cache: Arc<RwLock<HashMap<String, String>>>,
+    code_cache: Rc<RefCell<HashMap<String, String>>>,
+    // Cache mapping module_specifier string to source_map bytes
+    source_maps: Rc<RefCell<HashMap<String, Vec<u8>>>>,
 }
 
 impl ZinniaModuleLoader {
@@ -34,7 +38,8 @@ impl ZinniaModuleLoader {
 
         Ok(Self {
             module_root,
-            code_cache: Arc::new(RwLock::new(HashMap::new())),
+            code_cache: Rc::new(RefCell::new(HashMap::new())),
+            source_maps: Rc::new(RefCell::new(HashMap::new())),
         })
     }
 }
@@ -79,6 +84,7 @@ impl ModuleLoader for ZinniaModuleLoader {
         let module_root = self.module_root.clone();
         let maybe_referrer = maybe_referrer.cloned();
         let code_cache = self.code_cache.clone();
+        let source_maps = self.source_maps.clone();
         let module_load = async move {
             let spec_str = module_specifier.as_str();
 
@@ -188,6 +194,10 @@ impl ModuleLoader for ZinniaModuleLoader {
 
             let code = read_file_to_string(&module_path).await?;
 
+            code_cache
+                .borrow_mut()
+                .insert(spec_str.to_string(), code.clone());
+
             let code = if should_transpile {
                 let parsed = deno_ast::parse_module(ParseParams {
                     specifier: module_specifier.clone(),
@@ -198,30 +208,34 @@ impl ModuleLoader for ZinniaModuleLoader {
                     maybe_syntax: None,
                 })
                 .map_err(JsErrorBox::from_err)?;
-                parsed
+                let res = parsed
                     .transpile(
                         &deno_ast::TranspileOptions {
                             imports_not_used_as_values: deno_ast::ImportsNotUsedAsValues::Error,
                             verbatim_module_syntax: true,
                             ..Default::default()
                         },
                         &Default::default(),
-                        &Default::default(),
+                        &deno_ast::EmitOptions {
+                            source_map: deno_ast::SourceMapOption::Separate,
+                            inline_sources: true,
+                            ..Default::default()
+                        },
                     )
                     .map_err(JsErrorBox::from_err)?
-                    .into_source()
-                    .text
+                    .into_source();
+
+                if let Some(source_map) = res.source_map {
+                    source_maps
+                        .borrow_mut()
+                        .insert(module_specifier.to_string(), source_map.into_bytes());
+                }
+
+                res.text
             } else {
                 code
             };
 
-            code_cache
-                .write()
-                .map_err(|_| {
-                    JsErrorBox::generic("Unexpected internal error: code_cache lock was poisoned")
-                })?
-                .insert(spec_str.to_string(), code.clone());
-
             let sandboxed_module_specifier = ModuleSpecifier::from_file_path(&sandboxed_path)
                 .map_err(|_| {
                     let msg = format!(
@@ -245,9 +259,16 @@ impl ModuleLoader for ZinniaModuleLoader {
         ModuleLoadResponse::Async(module_load.boxed_local())
     }
 
+    fn get_source_map(&self, specifier: &str) -> Option<Cow<[u8]>> {
+        self.source_maps
+            .borrow()
+            .get(specifier)
+            .map(|v| v.clone().into())
+    }
+
     fn get_source_mapped_source_line(&self, file_name: &str, line_number: usize) -> Option<String> {
         log::debug!("get_source_mapped_source_line {file_name}:{line_number}");
-        let code_cache = self.code_cache.read().ok()?;
+        let code_cache = self.code_cache.borrow();
         let code = code_cache.get(file_name)?;
 
         // Based on Deno cli/module_loader.rs

runtime/tests/js/typescript_fixtures/typescript_stack_trace.ts

@@ -0,0 +1,14 @@
+// This TypeScript-only block of code is removed during transpilation. A naive solution that removes
+// the TypeScript code instead of replacing it with whitespace and does not apply source maps to error
+// stack traces will lead to incorrect line numbers in error stack traces.
+interface User {
+  name: string;
+  email: string;
+}
+
+// The part `: Error` changes the source column number
+// between the TypeScript original and the transpiled code.
+//
+// Throw the error so that the test can verify source code line & column numbers
+// in the stack trace frames but also the source code of the line throwing the exception.
+const error: Error = new Error(); throw error;

runtime/tests/runtime_integration_tests.rs

@@ -8,6 +8,7 @@ use std::rc::Rc;
 
 use anyhow::{anyhow, Context};
 use deno_core::ModuleSpecifier;
+use zinnia_runtime::fmt_errors::format_js_error;
 use zinnia_runtime::{any_and_jserrorbox_downcast_ref, CoreError, RecordingReporter};
 use zinnia_runtime::{anyhow, deno_core, run_js_module, AnyError, BootstrapOptions};
 
@@ -94,6 +95,36 @@ js_tests!(ipfs_retrieval_tests);
 test_runner_tests!(passing_tests);
 test_runner_tests!(failing_tests expect_failure);
 
+#[tokio::test]
+async fn typescript_stack_trace_test() -> Result<(), AnyError> {
+    let (_, run_error) = run_js_test_file("typescript_fixtures/typescript_stack_trace.ts").await?;
+    let error = run_error.ok_or_else(|| {
+        anyhow!("The script was expected to throw an error. Success was reported instead.")
+    })?;
+
+    if let Some(CoreError::Js(e)) = any_and_jserrorbox_downcast_ref::<CoreError>(&error) {
+        let actual_error = format_js_error(e);
+        // Strip ANSI codes (colors, styles)
+        let actual_error = console_static_text::ansi::strip_ansi_codes(&actual_error);
+        // Replace current working directory in stack trace file paths with a fixed placeholder
+        let cwd_url = ModuleSpecifier::from_file_path(std::env::current_dir().unwrap()).unwrap();
+        let actual_error = actual_error.replace(cwd_url.as_str(), "file:///project-root");
+        // Normalize line endings to Unix style (LF only)
+        let actual_error = actual_error.replace("\r\n", "\n");
+
+        let expected_error = r#"
+Uncaught (in promise) Error
+const error: Error = new Error(); throw error;
+                     ^
+    at file:///project-root/tests/js/typescript_fixtures/typescript_stack_trace.ts:14:22
+"#;
+        assert_eq!(actual_error.trim(), expected_error.trim());
+    } else {
+        panic!("The script threw unexpected error: {}", error);
+    }
+    Ok(())
+}
+
 #[tokio::test]
 async fn source_code_paths_when_no_module_root() -> Result<(), AnyError> {
     let (activities, run_error) =