derive-typescript: fail on unexpected requests

Specifically, this ensures a derivation is failed and restarted if it
sees a second Request.Open, as happens today (we need to handle this
properly).

Also add handling for Request.Reqest, which happens during catalog
tests.

crates/derive-typescript/src/codegen/main.ts.template

@@ -59,7 +59,8 @@ for await (const line of stdin) {
         flush?: Record<string, never>,
         startCommit?: {
             runtimeCheckpoint: any,
-        }
+        },
+        reset?: {}
     };
 
     if (request.read) {
@@ -83,5 +84,9 @@ for await (const line of stdin) {
     } else if (request.startCommit) {
         const startedCommit = derivation.startCommit(request.startCommit);
         await emit({ startedCommit: startedCommit })
+    } else if (request.reset) {
+        await derivation.reset();
+    } else {
+        throw new Error(`unexpected request: ${JSON.stringify(request)}`);
     }
 }

crates/derive-typescript/src/codegen/mod.rs

@@ -72,6 +72,9 @@ export abstract class IDerivation {{
         return [];
     }}
 
+    // reset is called only when running catalog tests, and must reset any internal state.
+    async reset() {{ }}
+
     // startCommit is notified of a runtime commit in progress, and returns an optional
     // connector state update to be committed.
     startCommit(_startCommit: {{ runtimeCheckpoint: unknown }}): {{ state?: {{ updated: unknown, mergePatch: boolean }} }} {{
@@ -88,7 +91,7 @@ export abstract class IDerivation {{
         write!(
             w,
             r#"
-    abstract {method_name}(source: {{ doc: {source_name} }}): Document[];"#,
+    abstract {method_name}(read: {{ doc: {source_name} }}): Document[];"#,
         )
         .unwrap();
     }