From f47685c6020cf3a9b5cec21e2c6eef02c7303ec6 Mon Sep 17 00:00:00 2001
From: Mofei Zhang <feifei0@meta.com>
Date: Sun, 12 Nov 2023 14:56:10 -0500
Subject: [PATCH] [be] Flag and test for unexpected exceptions during
 compilations

---
 .../src/Entrypoint/Pipeline.ts                |  9 ++++++++
 .../src/HIR/Environment.ts                    |  6 +++++
 ...le-unexpected-exception-pipeline.expect.md | 23 +++++++++++++++++++
 ...or.handle-unexpected-exception-pipeline.ts |  8 +++++++
 4 files changed, 46 insertions(+)
 create mode 100644 compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.handle-unexpected-exception-pipeline.expect.md
 create mode 100644 compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.handle-unexpected-exception-pipeline.ts

diff --git a/compiler/packages/babel-plugin-react-forget/src/Entrypoint/Pipeline.ts b/compiler/packages/babel-plugin-react-forget/src/Entrypoint/Pipeline.ts
index 9c2fe645f7..d28aa283ae 100644
--- a/compiler/packages/babel-plugin-react-forget/src/Entrypoint/Pipeline.ts
+++ b/compiler/packages/babel-plugin-react-forget/src/Entrypoint/Pipeline.ts
@@ -361,6 +361,15 @@ function* runWithEnvironment(
   const ast = codegenReactiveFunction(reactiveFunction).unwrap();
   yield log({ kind: "ast", name: "Codegen", value: ast });
 
+  /**
+   * This flag should be only set for unit / fixture tests to check
+   * that Forget correctly handles unexpected errors (e.g. exceptions
+   * thrown by babel functions or other unexpected exceptions).
+   */
+  if (env.config.throwUnknownException__testonly) {
+    throw new Error("unexpected error");
+  }
+
   return ast;
 }
 
diff --git a/compiler/packages/babel-plugin-react-forget/src/HIR/Environment.ts b/compiler/packages/babel-plugin-react-forget/src/HIR/Environment.ts
index 25cd81de3f..40eca65b5e 100644
--- a/compiler/packages/babel-plugin-react-forget/src/HIR/Environment.ts
+++ b/compiler/packages/babel-plugin-react-forget/src/HIR/Environment.ts
@@ -281,6 +281,12 @@ const EnvironmentConfigSchema = z.object({
    * Intended for use in demo purposes (incl playground)
    */
   enableMemoizationComments: z.boolean().default(false),
+
+  /**
+   * [TESTING ONLY] Throw an unknown exception during compilation to
+   * simulate unexpected exceptions e.g. errors from babel functions.
+   */
+  throwUnknownException__testonly: z.boolean().default(false),
 });
 
 export type EnvironmentConfig = z.infer<typeof EnvironmentConfigSchema>;
diff --git a/compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.handle-unexpected-exception-pipeline.expect.md b/compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.handle-unexpected-exception-pipeline.expect.md
new file mode 100644
index 0000000000..996bae3a74
--- /dev/null
+++ b/compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.handle-unexpected-exception-pipeline.expect.md
@@ -0,0 +1,23 @@
+
+## Input
+
+```javascript
+// @throwUnknownException__testonly:true
+
+function Component() {}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [],
+};
+
+```
+
+
+## Error
+
+```
+unexpected error
+```
+          
+      
\ No newline at end of file
diff --git a/compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.handle-unexpected-exception-pipeline.ts b/compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.handle-unexpected-exception-pipeline.ts
new file mode 100644
index 0000000000..4a341c4e47
--- /dev/null
+++ b/compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.handle-unexpected-exception-pipeline.ts
@@ -0,0 +1,8 @@
+// @throwUnknownException__testonly:true
+
+function Component() {}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [],
+};