From 2f564db18874ee11bce10926fe43e88d2f0f26da Mon Sep 17 00:00:00 2001
From: Daniel Lee <taeold@gmail.com>
Date: Tue, 27 May 2025 20:45:56 -0700
Subject: [PATCH 1/6] WIP

---
 src/deploy/functions/runtimes/index.ts      |  2 +
 src/deploy/functions/runtimes/node/index.ts | 71 ++++++++++++++++++++-
 src/emulator/functionsEmulator.ts           | 39 ++++++++---
 src/emulator/functionsEmulatorRuntime.ts    | 13 +++-
 4 files changed, 112 insertions(+), 13 deletions(-)

diff --git a/src/deploy/functions/runtimes/index.ts b/src/deploy/functions/runtimes/index.ts
index cb3aa66d1ab..207495d969e 100644
--- a/src/deploy/functions/runtimes/index.ts
+++ b/src/deploy/functions/runtimes/index.ts
@@ -67,6 +67,8 @@ export interface DelegateContext {
   // Absolute path of the source directory.
   sourceDir: string;
   runtime?: supported.Runtime;
+  // Whether this delegate is being created for the emulator
+  isEmulator?: boolean;
 }
 
 type Factory = (context: DelegateContext) => Promise<RuntimeDelegate | undefined>;
diff --git a/src/deploy/functions/runtimes/node/index.ts b/src/deploy/functions/runtimes/node/index.ts
index 2649e59821e..9802164d95d 100644
--- a/src/deploy/functions/runtimes/node/index.ts
+++ b/src/deploy/functions/runtimes/node/index.ts
@@ -25,6 +25,37 @@ import * as versioning from "./versioning";
 import * as parseTriggers from "./parseTriggers";
 import { fileExistsSync } from "../../../../fsutils";
 
+/**
+ * Get the TypeScript source entry point for a functions directory.
+ * Used by the emulator to load TypeScript directly with tsx.
+ */
+export function getTypeScriptEntryPoint(functionsDir: string): string | null {
+  // Check if this is a TypeScript project
+  const tsconfigPath = path.join(functionsDir, "tsconfig.json");
+  if (!fileExistsSync(tsconfigPath)) {
+    return null;
+  }
+
+  try {
+    // Resolve the actual main file path
+    const mainPath = require.resolve(functionsDir);
+    // Transform compiled JS path to TypeScript source
+    // e.g., /path/to/project/lib/index.js -> /path/to/project/src/index.ts
+    const tsSourcePath = mainPath
+      .replace(/\/lib\//, '/src/')
+      .replace(/\.js$/, '.ts');
+    
+    // Check if TypeScript source exists
+    if (fileExistsSync(tsSourcePath)) {
+      return tsSourcePath;
+    }
+  } catch (e) {
+    // Failed to resolve, return null
+  }
+  
+  return null;
+}
+
 // The versions of the Firebase Functions SDK that added support for the container contract.
 const MIN_FUNCTIONS_SDK_VERSION = "3.20.0";
 
@@ -54,7 +85,7 @@ export async function tryCreateDelegate(context: DelegateContext): Promise<Deleg
     throw new FirebaseError(`Unexpected runtime ${runtime}`);
   }
 
-  return new Delegate(context.projectId, context.projectDir, context.sourceDir, runtime);
+  return new Delegate(context.projectId, context.projectDir, context.sourceDir, runtime, context.isEmulator);
 }
 
 // TODO(inlined): Consider moving contents in parseRuntimeAndValidateSDK and validate around.
@@ -69,6 +100,7 @@ export class Delegate {
     private readonly projectDir: string,
     private readonly sourceDir: string,
     public readonly runtime: supported.Runtime,
+    private readonly isEmulator: boolean = false,
   ) {}
 
   // Using a caching interface because we (may/will) eventually depend on the SDK version
@@ -90,6 +122,24 @@ export class Delegate {
     return this._bin;
   }
 
+  private isTypeScriptProject(): boolean {
+    const tsconfigPath = path.join(this.sourceDir, "tsconfig.json");
+    return fileExistsSync(tsconfigPath);
+  }
+
+  private getTsxPath(): string | null {
+    try {
+      // Try to find tsx in the project's node_modules
+      const tsxPath = require.resolve("tsx/cli", { paths: [this.sourceDir] });
+      return tsxPath;
+    } catch (e) {
+      // tsx not found
+      return null;
+    }
+  }
+
+
+
   getNodeBinary(): string {
     const requestedVersion = semver.coerce(this.runtime);
     if (!requestedVersion) {
@@ -99,6 +149,25 @@ export class Delegate {
     }
     const hostVersion = process.versions.node;
 
+    // Check if this is a TypeScript project and tsx is available (only in emulator)
+    if (this.isEmulator && this.isTypeScriptProject()) {
+      const tsxPath = this.getTsxPath();
+      if (tsxPath) {
+        logLabeledSuccess(
+          "functions",
+          "TypeScript project detected. Using tsx for automatic TypeScript compilation.",
+        );
+        return tsxPath;
+      } else {
+        logLabeledWarning(
+          "functions",
+          "TypeScript project detected but tsx is not installed. " +
+          "Consider running 'npm install --save-dev tsx' for automatic TypeScript compilation. " +
+          "Falling back to standard node runtime.",
+        );
+      }
+    }
+
     const localNodePath = path.join(this.sourceDir, "node_modules/node");
     const localNodeVersion = versioning.findModuleVersion("node", localNodePath);
 
diff --git a/src/emulator/functionsEmulator.ts b/src/emulator/functionsEmulator.ts
index c8f69de5343..c3d08f8d435 100644
--- a/src/emulator/functionsEmulator.ts
+++ b/src/emulator/functionsEmulator.ts
@@ -54,6 +54,7 @@ import { functionIdsAreValid } from "../deploy/functions/validate";
 import { Extension, ExtensionSpec, ExtensionVersion } from "../extensions/types";
 import { accessSecretVersion } from "../gcp/secretManager";
 import * as runtimes from "../deploy/functions/runtimes";
+import { getTypeScriptEntryPoint } from "../deploy/functions/runtimes/node";
 import * as backend from "../deploy/functions/backend";
 import * as functionsEnv from "../functions/env";
 import { AUTH_BLOCKING_EVENTS, BEFORE_CREATE_EVENT } from "../functions/events/v1";
@@ -131,7 +132,7 @@ export interface FunctionsEmulatorArgs {
  * IPC connection info of a Function Runtime.
  */
 export class IPCConn {
-  constructor(readonly socketPath: string) {}
+  constructor(readonly socketPath: string) { }
 
   httpReqOpts(): http.RequestOptions {
     return {
@@ -147,7 +148,7 @@ export class TCPConn {
   constructor(
     readonly host: string,
     readonly port: number,
-  ) {}
+  ) { }
 
   httpReqOpts(): http.RequestOptions {
     return {
@@ -244,7 +245,7 @@ export class FunctionsEmulator implements EmulatorInstance {
       if (maybeNodeCodebases.length > 1 && typeof this.args.debugPort === "number") {
         throw new FirebaseError(
           "Cannot debug on a single port with multiple codebases. " +
-            "Use --inspect-functions=true to assign dynamic ports to each codebase",
+          "Use --inspect-functions=true to assign dynamic ports to each codebase",
         );
       }
       this.args.disabledRuntimeFeatures = this.args.disabledRuntimeFeatures || {};
@@ -529,6 +530,7 @@ export class FunctionsEmulator implements EmulatorInstance {
         projectDir: this.args.projectDir,
         sourceDir: emulatableBackend.functionsDir,
         runtime: emulatableBackend.runtime,
+        isEmulator: true,
       };
       const runtimeDelegate = await runtimes.getRuntimeDelegate(runtimeDelegateContext);
       logger.debug(`Validating ${runtimeDelegate.language} source`);
@@ -1522,9 +1524,9 @@ export class FunctionsEmulator implements EmulatorInstance {
         "ERROR",
         "functions",
         "Unable to access secret environment variables from Google Cloud Secret Manager. " +
-          "Make sure the credential used for the Functions Emulator have access " +
-          `or provide override values in ${secretPath}:\n\t` +
-          errs.join("\n\t"),
+        "Make sure the credential used for the Functions Emulator have access " +
+        `or provide override values in ${secretPath}:\n\t` +
+        errs.join("\n\t"),
       );
     }
 
@@ -1566,7 +1568,7 @@ export class FunctionsEmulator implements EmulatorInstance {
               "SUCCESS",
               "functions",
               `Using debug port ${port} for functions codebase ${backend.codebase}. ` +
-                "You may need to add manually add this port to your inspector.",
+              "You may need to add manually add this port to your inspector.",
             );
           }
         }
@@ -1586,8 +1588,8 @@ export class FunctionsEmulator implements EmulatorInstance {
         "WARN_ONCE",
         "functions",
         "Detected yarn@2 with PnP. " +
-          "Cloud Functions for Firebase requires a node_modules folder to work correctly and is therefore incompatible with PnP. " +
-          "See https://yarnpkg.com/getting-started/migration#step-by-step for more information.",
+        "Cloud Functions for Firebase requires a node_modules folder to work correctly and is therefore incompatible with PnP. " +
+        "See https://yarnpkg.com/getting-started/migration#step-by-step for more information.",
       );
     }
 
@@ -1595,11 +1597,26 @@ export class FunctionsEmulator implements EmulatorInstance {
     if (!bin) {
       throw new Error(
         `No binary associated with ${backend.functionsDir}. ` +
-          "Make sure function runtime is configured correctly in firebase.json.",
+        "Make sure function runtime is configured correctly in firebase.json.",
       );
     }
 
     const socketPath = getTemporarySocketPath();
+    
+    // Check if we're using tsx and get TypeScript entry point
+    let functionsEntryPoint: string | undefined;
+    if (backend.bin && backend.bin.includes("tsx")) {
+      const tsEntryPoint = getTypeScriptEntryPoint(backend.functionsDir);
+      if (tsEntryPoint) {
+        functionsEntryPoint = tsEntryPoint;
+        this.logger.logLabeled(
+          "DEBUG",
+          "functions",
+          `Using TypeScript source from ${tsEntryPoint}`,
+        );
+      }
+    }
+    
     const childProcess = spawn(bin, args, {
       cwd: backend.functionsDir,
       env: {
@@ -1608,6 +1625,8 @@ export class FunctionsEmulator implements EmulatorInstance {
         ...process.env,
         ...envs,
         PORT: socketPath,
+        // Pass the resolved entry point if we found one
+        ...(functionsEntryPoint ? { FUNCTIONS_ENTRY_POINT: functionsEntryPoint } : {}),
       },
       stdio: ["pipe", "pipe", "pipe", "ipc"],
     });
diff --git a/src/emulator/functionsEmulatorRuntime.ts b/src/emulator/functionsEmulatorRuntime.ts
index 8720c3b08ab..0575c1c1f3e 100644
--- a/src/emulator/functionsEmulatorRuntime.ts
+++ b/src/emulator/functionsEmulatorRuntime.ts
@@ -906,15 +906,24 @@ async function initializeRuntime(): Promise<void> {
 
 async function loadTriggers(): Promise<any> {
   let triggerModule;
+  
+  // Check if we have an override entry point (e.g., for TypeScript with tsx)
+  const entryPoint = process.env.FUNCTIONS_ENTRY_POINT;
+  
   try {
-    triggerModule = require(process.cwd());
+    if (entryPoint) {
+      logDebug(`Loading functions from specified entry point: ${entryPoint}`);
+      triggerModule = require(entryPoint);
+    } else {
+      triggerModule = require(process.cwd());
+    }
   } catch (err: any) {
     if (err.code !== "ERR_REQUIRE_ESM") {
       // Try to run diagnostics to see what could've gone wrong before rethrowing the error.
       await moduleResolutionDetective(err);
       throw err;
     }
-    const modulePath = require.resolve(process.cwd());
+    const modulePath = entryPoint || require.resolve(process.cwd());
     // Resolve module path to file:// URL. Required for windows support.
     const moduleURL = pathToFileURL(modulePath).href;
     triggerModule = await dynamicImport(moduleURL);

From 4e56d7896abc476a00942972275befcf353d9e3c Mon Sep 17 00:00:00 2001
From: Daniel Young Lee <danielylee@google.com>
Date: Wed, 28 May 2025 17:15:20 -0700
Subject: [PATCH 2/6] Use FUNCTION_SOURCE instead for functions-framework
 compatibility

---
 src/deploy/functions/runtimes/node/index.ts | 22 ++++++------
 src/emulator/functionsEmulator.ts           | 38 +++++++++------------
 src/emulator/functionsEmulatorRuntime.ts    |  6 ++--
 3 files changed, 32 insertions(+), 34 deletions(-)

diff --git a/src/deploy/functions/runtimes/node/index.ts b/src/deploy/functions/runtimes/node/index.ts
index 9802164d95d..11326d422ed 100644
--- a/src/deploy/functions/runtimes/node/index.ts
+++ b/src/deploy/functions/runtimes/node/index.ts
@@ -41,10 +41,8 @@ export function getTypeScriptEntryPoint(functionsDir: string): string | null {
     const mainPath = require.resolve(functionsDir);
     // Transform compiled JS path to TypeScript source
     // e.g., /path/to/project/lib/index.js -> /path/to/project/src/index.ts
-    const tsSourcePath = mainPath
-      .replace(/\/lib\//, '/src/')
-      .replace(/\.js$/, '.ts');
-    
+    const tsSourcePath = mainPath.replace(/\/lib\//, "/src/").replace(/\.js$/, ".ts");
+
     // Check if TypeScript source exists
     if (fileExistsSync(tsSourcePath)) {
       return tsSourcePath;
@@ -52,7 +50,7 @@ export function getTypeScriptEntryPoint(functionsDir: string): string | null {
   } catch (e) {
     // Failed to resolve, return null
   }
-  
+
   return null;
 }
 
@@ -85,7 +83,13 @@ export async function tryCreateDelegate(context: DelegateContext): Promise<Deleg
     throw new FirebaseError(`Unexpected runtime ${runtime}`);
   }
 
-  return new Delegate(context.projectId, context.projectDir, context.sourceDir, runtime, context.isEmulator);
+  return new Delegate(
+    context.projectId,
+    context.projectDir,
+    context.sourceDir,
+    runtime,
+    context.isEmulator,
+  );
 }
 
 // TODO(inlined): Consider moving contents in parseRuntimeAndValidateSDK and validate around.
@@ -138,8 +142,6 @@ export class Delegate {
     }
   }
 
-
-
   getNodeBinary(): string {
     const requestedVersion = semver.coerce(this.runtime);
     if (!requestedVersion) {
@@ -162,8 +164,8 @@ export class Delegate {
         logLabeledWarning(
           "functions",
           "TypeScript project detected but tsx is not installed. " +
-          "Consider running 'npm install --save-dev tsx' for automatic TypeScript compilation. " +
-          "Falling back to standard node runtime.",
+            "Consider running 'npm install --save-dev tsx' for automatic TypeScript compilation. " +
+            "Falling back to standard node runtime.",
         );
       }
     }
diff --git a/src/emulator/functionsEmulator.ts b/src/emulator/functionsEmulator.ts
index c3d08f8d435..455d4ce3d08 100644
--- a/src/emulator/functionsEmulator.ts
+++ b/src/emulator/functionsEmulator.ts
@@ -132,7 +132,7 @@ export interface FunctionsEmulatorArgs {
  * IPC connection info of a Function Runtime.
  */
 export class IPCConn {
-  constructor(readonly socketPath: string) { }
+  constructor(readonly socketPath: string) {}
 
   httpReqOpts(): http.RequestOptions {
     return {
@@ -148,7 +148,7 @@ export class TCPConn {
   constructor(
     readonly host: string,
     readonly port: number,
-  ) { }
+  ) {}
 
   httpReqOpts(): http.RequestOptions {
     return {
@@ -245,7 +245,7 @@ export class FunctionsEmulator implements EmulatorInstance {
       if (maybeNodeCodebases.length > 1 && typeof this.args.debugPort === "number") {
         throw new FirebaseError(
           "Cannot debug on a single port with multiple codebases. " +
-          "Use --inspect-functions=true to assign dynamic ports to each codebase",
+            "Use --inspect-functions=true to assign dynamic ports to each codebase",
         );
       }
       this.args.disabledRuntimeFeatures = this.args.disabledRuntimeFeatures || {};
@@ -1524,9 +1524,9 @@ export class FunctionsEmulator implements EmulatorInstance {
         "ERROR",
         "functions",
         "Unable to access secret environment variables from Google Cloud Secret Manager. " +
-        "Make sure the credential used for the Functions Emulator have access " +
-        `or provide override values in ${secretPath}:\n\t` +
-        errs.join("\n\t"),
+          "Make sure the credential used for the Functions Emulator have access " +
+          `or provide override values in ${secretPath}:\n\t` +
+          errs.join("\n\t"),
       );
     }
 
@@ -1568,7 +1568,7 @@ export class FunctionsEmulator implements EmulatorInstance {
               "SUCCESS",
               "functions",
               `Using debug port ${port} for functions codebase ${backend.codebase}. ` +
-              "You may need to add manually add this port to your inspector.",
+                "You may need to add manually add this port to your inspector.",
             );
           }
         }
@@ -1588,8 +1588,8 @@ export class FunctionsEmulator implements EmulatorInstance {
         "WARN_ONCE",
         "functions",
         "Detected yarn@2 with PnP. " +
-        "Cloud Functions for Firebase requires a node_modules folder to work correctly and is therefore incompatible with PnP. " +
-        "See https://yarnpkg.com/getting-started/migration#step-by-step for more information.",
+          "Cloud Functions for Firebase requires a node_modules folder to work correctly and is therefore incompatible with PnP. " +
+          "See https://yarnpkg.com/getting-started/migration#step-by-step for more information.",
       );
     }
 
@@ -1597,26 +1597,22 @@ export class FunctionsEmulator implements EmulatorInstance {
     if (!bin) {
       throw new Error(
         `No binary associated with ${backend.functionsDir}. ` +
-        "Make sure function runtime is configured correctly in firebase.json.",
+          "Make sure function runtime is configured correctly in firebase.json.",
       );
     }
 
     const socketPath = getTemporarySocketPath();
-    
+
     // Check if we're using tsx and get TypeScript entry point
-    let functionsEntryPoint: string | undefined;
+    let overrideFunctionSource: string | undefined;
     if (backend.bin && backend.bin.includes("tsx")) {
       const tsEntryPoint = getTypeScriptEntryPoint(backend.functionsDir);
       if (tsEntryPoint) {
-        functionsEntryPoint = tsEntryPoint;
-        this.logger.logLabeled(
-          "DEBUG",
-          "functions",
-          `Using TypeScript source from ${tsEntryPoint}`,
-        );
+        overrideFunctionSource = tsEntryPoint;
+        this.logger.logLabeled("DEBUG", "functions", `Using TypeScript source in ${tsEntryPoint}`);
       }
     }
-    
+
     const childProcess = spawn(bin, args, {
       cwd: backend.functionsDir,
       env: {
@@ -1625,8 +1621,8 @@ export class FunctionsEmulator implements EmulatorInstance {
         ...process.env,
         ...envs,
         PORT: socketPath,
-        // Pass the resolved entry point if we found one
-        ...(functionsEntryPoint ? { FUNCTIONS_ENTRY_POINT: functionsEntryPoint } : {}),
+        // Overried the entry point we have any
+        ...(overrideFunctionSource ? { FUNCTIONS_SOURCE: overrideFunctionSource } : {}),
       },
       stdio: ["pipe", "pipe", "pipe", "ipc"],
     });
diff --git a/src/emulator/functionsEmulatorRuntime.ts b/src/emulator/functionsEmulatorRuntime.ts
index 0575c1c1f3e..a6a2a4fc1ab 100644
--- a/src/emulator/functionsEmulatorRuntime.ts
+++ b/src/emulator/functionsEmulatorRuntime.ts
@@ -906,10 +906,10 @@ async function initializeRuntime(): Promise<void> {
 
 async function loadTriggers(): Promise<any> {
   let triggerModule;
-  
+
   // Check if we have an override entry point (e.g., for TypeScript with tsx)
-  const entryPoint = process.env.FUNCTIONS_ENTRY_POINT;
-  
+  const entryPoint = process.env.FUNCTIONS_SOURCE;
+
   try {
     if (entryPoint) {
       logDebug(`Loading functions from specified entry point: ${entryPoint}`);

From 9a5559f29e0cc2a0fd044346883d2c06597a95a1 Mon Sep 17 00:00:00 2001
From: Daniel Young Lee <danielylee@google.com>
Date: Wed, 28 May 2025 17:22:03 -0700
Subject: [PATCH 3/6] Add tsx to TS templates.

---
 templates/init/functions/typescript/package.lint.json   | 3 ++-
 templates/init/functions/typescript/package.nolint.json | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/templates/init/functions/typescript/package.lint.json b/templates/init/functions/typescript/package.lint.json
index c2d4f5493e6..57deecb2036 100644
--- a/templates/init/functions/typescript/package.lint.json
+++ b/templates/init/functions/typescript/package.lint.json
@@ -25,7 +25,8 @@
     "eslint-config-google": "^0.14.0",
     "eslint-plugin-import": "^2.25.4",
     "firebase-functions-test": "^3.1.0",
-    "typescript": "^5.7.3"
+    "typescript": "^5.7.3",
+    "tsx": "^4.19.4"
   },
   "private": true
 }
diff --git a/templates/init/functions/typescript/package.nolint.json b/templates/init/functions/typescript/package.nolint.json
index 066161c31cd..5ce934823b2 100644
--- a/templates/init/functions/typescript/package.nolint.json
+++ b/templates/init/functions/typescript/package.nolint.json
@@ -19,7 +19,8 @@
   },
   "devDependencies": {
     "typescript": "^5.7.3",
-    "firebase-functions-test": "^3.1.0"
+    "firebase-functions-test": "^3.1.0",
+    "tsx": "^4.19.4"
   },
   "private": true
 }

From 6bdc36c04c19b1dffe111485c0a46666d51149ce Mon Sep 17 00:00:00 2001
From: Daniel Young Lee <danielylee@google.com>
Date: Wed, 28 May 2025 17:45:03 -0700
Subject: [PATCH 4/6] Add changelog.

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9f0e1e973fc..30c6f1f9742 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,3 +3,4 @@
 - Fixed crash when starting the App Hosting emulator in certain applications (#8624)
 - Fixed issue where, with `webframeworks` enabled, `firebase init hosting` re-prompts users for source. (#8587)
 - Update typescript version in functions template to avoid build issue with @google-cloud/storage depedency (#8194)
+- Added support for loading TypeScript functions using tsx in the Functions Emulator. (#8663)

From 0bf32f610be2aa19d47652b4c59085b28e03664e Mon Sep 17 00:00:00 2001
From: Daniel Lee <danielylee@google.com>
Date: Wed, 28 May 2025 19:21:44 -0700
Subject: [PATCH 5/6] Update src/emulator/functionsEmulator.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 src/emulator/functionsEmulator.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/emulator/functionsEmulator.ts b/src/emulator/functionsEmulator.ts
index 455d4ce3d08..d7908c8bfa7 100644
--- a/src/emulator/functionsEmulator.ts
+++ b/src/emulator/functionsEmulator.ts
@@ -1621,7 +1621,7 @@ export class FunctionsEmulator implements EmulatorInstance {
         ...process.env,
         ...envs,
         PORT: socketPath,
-        // Overried the entry point we have any
+        // Override the entry point if we have any
         ...(overrideFunctionSource ? { FUNCTIONS_SOURCE: overrideFunctionSource } : {}),
       },
       stdio: ["pipe", "pipe", "pipe", "ipc"],

From bfe715021cb482aceeabb308bb5ef8239ad8df03 Mon Sep 17 00:00:00 2001
From: Daniel Young Lee <danielylee@google.com>
Date: Thu, 29 May 2025 10:38:11 -0700
Subject: [PATCH 6/6] Nits.

---
 src/deploy/functions/runtimes/node/index.ts | 11 ++++-------
 src/emulator/functionsEmulator.ts           |  4 ++--
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/src/deploy/functions/runtimes/node/index.ts b/src/deploy/functions/runtimes/node/index.ts
index 11326d422ed..8414a7451f0 100644
--- a/src/deploy/functions/runtimes/node/index.ts
+++ b/src/deploy/functions/runtimes/node/index.ts
@@ -30,25 +30,23 @@ import { fileExistsSync } from "../../../../fsutils";
  * Used by the emulator to load TypeScript directly with tsx.
  */
 export function getTypeScriptEntryPoint(functionsDir: string): string | null {
-  // Check if this is a TypeScript project
   const tsconfigPath = path.join(functionsDir, "tsconfig.json");
   if (!fileExistsSync(tsconfigPath)) {
     return null;
   }
 
   try {
-    // Resolve the actual main file path
     const mainPath = require.resolve(functionsDir);
     // Transform compiled JS path to TypeScript source
     // e.g., /path/to/project/lib/index.js -> /path/to/project/src/index.ts
     const tsSourcePath = mainPath.replace(/\/lib\//, "/src/").replace(/\.js$/, ".ts");
 
-    // Check if TypeScript source exists
     if (fileExistsSync(tsSourcePath)) {
       return tsSourcePath;
     }
   } catch (e) {
-    // Failed to resolve, return null
+    logger.debug("Failed to resolve TS entrypoint", e);
+    // Fail-safe and fallback to assuming JS codebase.
   }
 
   return null;
@@ -133,13 +131,12 @@ export class Delegate {
 
   private getTsxPath(): string | null {
     try {
-      // Try to find tsx in the project's node_modules
       const tsxPath = require.resolve("tsx/cli", { paths: [this.sourceDir] });
       return tsxPath;
     } catch (e) {
-      // tsx not found
-      return null;
+      // tsx not found. fail-safe
     }
+    return null;
   }
 
   getNodeBinary(): string {
diff --git a/src/emulator/functionsEmulator.ts b/src/emulator/functionsEmulator.ts
index d7908c8bfa7..7bb137983dc 100644
--- a/src/emulator/functionsEmulator.ts
+++ b/src/emulator/functionsEmulator.ts
@@ -54,7 +54,7 @@ import { functionIdsAreValid } from "../deploy/functions/validate";
 import { Extension, ExtensionSpec, ExtensionVersion } from "../extensions/types";
 import { accessSecretVersion } from "../gcp/secretManager";
 import * as runtimes from "../deploy/functions/runtimes";
-import { getTypeScriptEntryPoint } from "../deploy/functions/runtimes/node";
+import * as node from "../deploy/functions/runtimes/node";
 import * as backend from "../deploy/functions/backend";
 import * as functionsEnv from "../functions/env";
 import { AUTH_BLOCKING_EVENTS, BEFORE_CREATE_EVENT } from "../functions/events/v1";
@@ -1606,7 +1606,7 @@ export class FunctionsEmulator implements EmulatorInstance {
     // Check if we're using tsx and get TypeScript entry point
     let overrideFunctionSource: string | undefined;
     if (backend.bin && backend.bin.includes("tsx")) {
-      const tsEntryPoint = getTypeScriptEntryPoint(backend.functionsDir);
+      const tsEntryPoint = node.getTypeScriptEntryPoint(backend.functionsDir);
       if (tsEntryPoint) {
         overrideFunctionSource = tsEntryPoint;
         this.logger.logLabeled("DEBUG", "functions", `Using TypeScript source in ${tsEntryPoint}`);