feat: Error when code injection fails

src/error.rs

@@ -6,33 +6,17 @@ use std::fmt::{self, Display, Formatter};
 
 #[derive(Debug)]
 pub enum OrchestrionError {
-    IoError(std::io::Error),
-    StrError(String),
+    InjectionMatchFailure,
 }
 
-impl From<std::io::Error> for OrchestrionError {
-    fn from(e: std::io::Error) -> Self {
-        OrchestrionError::IoError(e)
-    }
-}
-
-impl From<String> for OrchestrionError {
-    fn from(s: String) -> Self {
-        OrchestrionError::StrError(s)
-    }
-}
-
-impl From<&str> for OrchestrionError {
-    fn from(s: &str) -> Self {
-        OrchestrionError::StrError(s.to_string())
-    }
-}
+impl std::error::Error for OrchestrionError {}
 
 impl Display for OrchestrionError {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         match self {
-            OrchestrionError::IoError(e) => write!(f, "IO error: {e}"),
-            OrchestrionError::StrError(s) => write!(f, "String error: {s}"),
+            OrchestrionError::InjectionMatchFailure => {
+                write!(f, "Injection match failed")
+            }
         }
     }
 }

src/instrumentation.rs

@@ -32,6 +32,7 @@ pub struct Instrumentation {
     config: InstrumentationConfig,
     count: usize,
     is_correct_class: bool,
+    has_injected: bool,
 }
 
 impl Instrumentation {
@@ -41,14 +42,24 @@ impl Instrumentation {
             config,
             count: 0,
             is_correct_class: false,
+            has_injected: false,
         }
     }
 
+    #[must_use]
+    pub fn has_injected(&self) -> bool {
+        self.has_injected
+    }
+
     pub(crate) fn reset(&mut self) {
         self.count = 0;
         self.is_correct_class = false;
     }
 
+    pub(crate) fn reset_has_injected(&mut self) {
+        self.has_injected = false;
+    }
+
     fn new_fn(&self, body: BlockStmt) -> ArrowExpr {
         ArrowExpr {
             params: vec![],
@@ -114,6 +125,8 @@ impl Instrumentation {
                 trace = trace_ident
             ),
         ];
+
+        self.has_injected = true;
     }
 
     fn insert_constructor_tracing(&mut self, body: &mut BlockStmt) {
@@ -160,6 +173,8 @@ impl Instrumentation {
             quote!("const $ctx = { arguments };" as Stmt, ctx = ctx_ident,),
             try_catch,
         ];
+
+        self.has_injected = true;
     }
 
     fn trace_expr_or_count(&mut self, func_expr: &mut FnExpr, name: &Atom) -> bool {

src/lib.rs

@@ -47,6 +47,8 @@ pub use instrumentation::*;
 mod function_query;
 pub use function_query::*;
 
+use crate::error::OrchestrionError;
+
 #[cfg(feature = "wasm")]
 pub mod wasm;
 
@@ -112,6 +114,19 @@ impl InstrumentationVisitor {
         !self.instrumentations.is_empty()
     }
 
+    #[must_use]
+    pub fn has_injected(&self) -> bool {
+        self.instrumentations
+            .iter()
+            .any(Instrumentation::has_injected)
+    }
+
+    pub fn reset_has_injected(&mut self) {
+        for instr in &mut self.instrumentations {
+            instr.reset_has_injected();
+        }
+    }
+
     /// Transform the given JavaScript code.
     /// # Errors
     /// Returns an error if the transformation fails.
@@ -125,7 +140,7 @@ impl InstrumentationVisitor {
         )));
 
         #[allow(clippy::redundant_closure_for_method_calls)]
-        Ok(try_with_handler(
+        let result = try_with_handler(
             compiler.cm.clone(),
             HandlerOpts {
                 color: ColorConfig::Never,
@@ -165,10 +180,20 @@ impl InstrumentationVisitor {
                         ..Default::default()
                     },
                 )?;
+
                 Ok(result.code)
             },
         )
-        .map_err(|e| e.to_pretty_error())?)
+        .map_err(|e| e.to_pretty_error())?;
+
+        let has_injected = self.has_injected();
+        self.reset_has_injected();
+
+        if has_injected {
+            Ok(result)
+        } else {
+            Err(Box::new(OrchestrionError::InjectionMatchFailure))
+        }
     }
 }
 

src/wasm.rs

@@ -1,5 +1,7 @@
-use crate::*;
-use wasm_bindgen::{prelude::wasm_bindgen, JsValue};
+use crate::{Config, InstrumentationConfig, InstrumentationVisitor, Instrumentor};
+use std::path::PathBuf;
+use swc::config::IsModule;
+use wasm_bindgen::prelude::*;
 
 #[wasm_bindgen]
 pub struct InstrumentationMatcher(Instrumentor);
@@ -31,11 +33,11 @@ pub struct Transformer(InstrumentationVisitor);
 #[wasm_bindgen]
 impl Transformer {
     #[wasm_bindgen]
-    pub fn transform(&mut self, contents: &str, is_module: bool) -> Result<String, JsValue> {
+    pub fn transform(&mut self, contents: &str, is_module: bool) -> Result<String, JsError> {
         let is_module = IsModule::Bool(is_module);
         self.0
             .transform(contents, is_module)
-            .map_err(|e| JsValue::from_str(&e.to_string()))
+            .map_err(|e| JsError::new(&e.to_string()))
     }
 }
 

tests/common/mod.rs

@@ -27,13 +27,11 @@ pub fn transpile_and_test(test_file: &str, mjs: bool, config: Config) {
     let mut contents = String::new();
     file.read_to_string(&mut contents).unwrap();
 
-    let result = instrumentations
-        .transform(&contents, IsModule::Bool(mjs))
-        .unwrap();
-
-    let instrumented_file = test_dir.join(format!("instrumented.{}", extension));
-    let mut file = std::fs::File::create(&instrumented_file).unwrap();
-    file.write_all(result.as_bytes()).unwrap();
+    if let Ok(result) = instrumentations.transform(&contents, IsModule::Bool(mjs)) {
+        let instrumented_file = test_dir.join(format!("instrumented.{}", extension));
+        let mut file = std::fs::File::create(&instrumented_file).unwrap();
+        file.write_all(result.as_bytes()).unwrap();
+    }
 
     let test_file = format!("test.{}", extension);
     Command::new("node")

tests/injection_failure/mod.mjs

@@ -0,0 +1,9 @@
+/**
+ * Unless explicitly stated otherwise all files in this repository are licensed under the Apache-2.0 License.
+ * This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2025 Datadog, Inc.
+ **/
+const fetch = async function (url) {
+  return 42;
+}
+
+export { fetch };

tests/injection_failure/mod.rs

@@ -0,0 +1,15 @@
+use crate::common::*;
+use orchestrion_js::*;
+
+#[test]
+fn injection_failure() {
+    transpile_and_test(
+        file!(),
+        true,
+        Config::new_single(InstrumentationConfig::new(
+            "some_expr",
+            test_module_matcher(),
+            FunctionQuery::function_expression("some", FunctionKind::Async),
+        )),
+    );
+}

tests/injection_failure/test.mjs

@@ -0,0 +1,9 @@
+/**
+ * Unless explicitly stated otherwise all files in this repository are licensed under the Apache-2.0 License.
+ * This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2025 Datadog, Inc.
+ **/
+import { existsSync } from 'node:fs'
+import { assert } from '../common/preamble.js';
+
+const instrumented = existsSync('./instrumented.js');
+assert.strictEqual(instrumented, false, 'instrumented.js should not exist');

tests/instrumentor_test.rs

@@ -14,6 +14,7 @@ mod decl_mjs_mismatched_type;
 mod expr_cjs;
 mod expr_mjs;
 mod index_cjs;
+mod injection_failure;
 mod multiple_class_method_cjs;
 mod multiple_load_cjs;
 mod object_method_cjs;

tests/wasm/testdata/no-match.mjs

@@ -0,0 +1,9 @@
+export class Down {
+	constructor() {
+		console.log('constructor')
+	}
+
+	fetch() {
+		console.log('fetch')
+	}
+}

tests/wasm/tests.mjs

@@ -40,3 +40,9 @@ const outputCjs = matchedTransforms.transform(originalCjs.toString('utf8'), fals
 
 const expectedCjs = await fs.readFile(path.join(import.meta.dirname, './testdata/expected-cjs.js'))
 assert.strictEqual(outputCjs, expectedCjs.toString('utf8'));
+
+const noMatch = await fs.readFile(path.join(import.meta.dirname, './testdata/no-match.mjs'));
+
+assert.throws(() => {
+    matchedTransforms.transform(noMatch.toString('utf8'), true);
+}, { message: "Injection match failed" });