fix: Sql query recording in extended Prisma clients

src/hooks/prisma.ts

@@ -1,6 +1,6 @@
 import assert from "node:assert";
 
-import { ESTree } from "meriyah";
+import type { ESTree } from "meriyah";
 import type prisma from "@prisma/client";
 
 import type * as AppMap from "../AppMap";
@@ -10,15 +10,39 @@ import { FunctionInfo } from "../registry";
 import config from "../config";
 
 export default function prismaHook(mod: typeof prisma, id?: string) {
+  assert(mod.PrismaClient != null);
+  // (1) Prisma Queries: We proxy prismaClient._request method in order to record
+  // prisma queries (not sqls) as appmap function call events.
+  // (2) SQL Queries: We have to change config parameters (logLevel, logQueries)
+  // and register a prismaClient.$on("query") handler to record sql queries.
+  // We have to do it by proxying mod.PrismaClient here, since it turned out that
+  // it's too late to do it inside the first invocation of the _request method,
+  // because $on is (becomes?) undefined in extended prisma clients.
+  // https://www.prisma.io/docs/orm/reference/prisma-client-reference#remarks-37
+
+  // Normally, we "Cannot assign to 'PrismaClient' because it is a read-only property."
+  // Fortunately with this hack it can be done.
+  const modHacked = mod as unknown as { PrismaClient: unknown };
+  modHacked.PrismaClient = new Proxy(mod.PrismaClient, {
+    construct(target, argArray, newTarget): object {
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-unsafe-argument
+      const result = Reflect.construct(target, argArray, newTarget);
+      if (!hookAttached) {
+        hookAttached = true;
+        attachSqlHook(result);
+      }
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-return
+      return result;
+    },
+  });
+
   // Imported PrismaClient type does not have _request method in type definition.
   // But we have it in runtime.
-  console.log("MOD", mod);
-  assert(mod.PrismaClient != null);
   const PC = mod.PrismaClient as { prototype: unknown };
   const proto = PC.prototype;
   assert(proto != null && typeof proto === "object");
   assert("_request" in proto);
-  proto._request = createProxy(
+  proto._request = createPrismaClientMethodProxy(
     proto._request as (...args: unknown[]) => unknown,
     id ?? "@prisma/client",
   );
@@ -77,45 +101,16 @@ function getFunctionInfo(model: string, action: string, moduleId: string) {
   return functionInfos.get(key)!;
 }
 
-function createProxy<T extends (...args: unknown[]) => unknown>(
+function createPrismaClientMethodProxy<T extends (...args: unknown[]) => unknown>(
   prismaClientMethod: T,
   moduleId: string,
 ) {
   return new Proxy(prismaClientMethod, {
     apply(target, thisArg: unknown, argArray: Parameters<T>) {
-      if (!hookAttached) {
-        hookAttached = true;
-        assert(
-          thisArg != null &&
-            typeof thisArg === "object" &&
-            "_engine" in thisArg &&
-            thisArg._engine != null &&
-            typeof thisArg._engine === "object" &&
-            "config" in thisArg._engine &&
-            thisArg._engine.config != null &&
-            typeof thisArg._engine.config === "object" &&
-            "logLevel" in thisArg._engine.config &&
-            "logQueries" in thisArg._engine.config &&
-            "activeProvider" in thisArg._engine.config &&
-            typeof thisArg._engine.config.activeProvider == "string",
-        );
-
-        const dbType = thisArg._engine.config.activeProvider;
-        thisArg._engine.config.logLevel = "query";
-        thisArg._engine.config.logQueries = true;
-        assert("$on" in thisArg && typeof thisArg.$on === "function");
-        thisArg.$on("query", (queryEvent: QueryEvent) => {
-          const call = recording.sqlQuery(dbType, queryEvent.query);
-          const elapsedSec = queryEvent.duration / 1000.0;
-          recording.functionReturn(call.id, undefined, elapsedSec);
-        });
-      }
-
       // Report Prisma query as a function call, if suitable
       let prismaCall: AppMap.FunctionCallEvent | undefined;
       if (argArray?.length > 0) {
         const requestParams = argArray[0] as PrismaRequestParams;
-
         if (requestParams.action && requestParams.model) {
           prismaCall = recording.functionCall(
             getFunctionInfo(requestParams.model, requestParams.action, moduleId),
@@ -141,3 +136,30 @@ function createProxy<T extends (...args: unknown[]) => unknown>(
     },
   });
 }
+
+function attachSqlHook(thisArg: unknown) {
+  assert(
+    thisArg != null &&
+      typeof thisArg === "object" &&
+      "_engine" in thisArg &&
+      thisArg._engine != null &&
+      typeof thisArg._engine === "object" &&
+      "config" in thisArg._engine &&
+      thisArg._engine.config != null &&
+      typeof thisArg._engine.config === "object" &&
+      "logLevel" in thisArg._engine.config &&
+      "logQueries" in thisArg._engine.config &&
+      "activeProvider" in thisArg._engine.config &&
+      typeof thisArg._engine.config.activeProvider == "string",
+  );
+
+  const dbType = thisArg._engine.config.activeProvider;
+  thisArg._engine.config.logLevel = "query";
+  thisArg._engine.config.logQueries = true;
+  assert("$on" in thisArg && typeof thisArg.$on === "function");
+  thisArg.$on("query", (queryEvent: QueryEvent) => {
+    const call = recording.sqlQuery(dbType, queryEvent.query);
+    const elapsedSec = queryEvent.duration / 1000.0;
+    recording.functionReturn(call.id, undefined, elapsedSec);
+  });
+}