Improve reporting of "fn is not a function" error

packages/cli/CHANGELOG.md

@@ -1,5 +1,13 @@
 # @openfn/cli
 
+## 1.30.4
+
+### Patch Changes
+
+- 0ed97be: Improve error reporting to resolve the dreaded "fn is not a function" error that occurs when writing `console.log()` at the top of job code
+- Updated dependencies [0ed97be]
+  - @openfn/runtime@1.8.5
+
 ## 1.30.3
 
 ### Patch Changes

packages/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@openfn/cli",
-  "version": "1.30.3",
+  "version": "1.30.4",
   "description": "CLI devtools for the OpenFn toolchain",
   "engines": {
     "node": ">=18",

packages/engine-multi/CHANGELOG.md

@@ -1,5 +1,12 @@
 # engine-multi
 
+## 1.10.6
+
+### Patch Changes
+
+- Updated dependencies [0ed97be]
+  - @openfn/runtime@1.8.5
+
 ## 1.10.5
 
 ### Patch Changes

packages/engine-multi/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@openfn/engine-multi",
-  "version": "1.10.5",
+  "version": "1.10.6",
   "description": "Multi-process runtime engine",
   "main": "dist/index.js",
   "type": "module",

packages/lightning-mock/CHANGELOG.md

@@ -1,5 +1,13 @@
 # @openfn/lightning-mock
 
+## 2.4.8
+
+### Patch Changes
+
+- Updated dependencies [0ed97be]
+  - @openfn/runtime@1.8.5
+  - @openfn/engine-multi@1.10.6
+
 ## 2.4.7
 
 ### Patch Changes

packages/lightning-mock/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@openfn/lightning-mock",
-  "version": "2.4.7",
+  "version": "2.4.8",
   "private": true,
   "description": "A mock Lightning server",
   "main": "dist/index.js",

packages/runtime/CHANGELOG.md

@@ -1,5 +1,11 @@
 # @openfn/runtime
 
+## 1.8.5
+
+### Patch Changes
+
+- 0ed97be: Improve error reporting to resolve the dreaded "fn is not a function" error that occurs when writing `console.log()` at the top of job code
+
 ## 1.8.4
 
 ### Patch Changes

packages/runtime/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@openfn/runtime",
-  "version": "1.8.4",
+  "version": "1.8.5",
   "description": "Job processing runtime.",
   "type": "module",
   "exports": {

packages/runtime/src/errors.ts

@@ -18,7 +18,10 @@ export function assertRuntimeError(e: any) {
 // See https://nodejs.org/api/errors.html for errors
 export function assertRuntimeCrash(e: any) {
   // ignore  instanceof SystemError, AssertionError
-  if (e.constructor.name.match(/ReferenceError|SyntaxError/)) {
+  if (
+    e.severity === 'crash' ||
+    e.constructor.name.match(/ReferenceError|SyntaxError/)
+  ) {
     throw new RuntimeCrash(e);
   }
 }
@@ -106,6 +109,10 @@ export class RTError extends Error {
   name: string = 'Error';
   pos?: ErrorPosition;
   step?: string;
+  /** Hint to the user how to fix the problem */
+  fix?: string;
+  /** More details about the error  */
+  details?: string;
 
   constructor() {
     super();
@@ -123,6 +130,34 @@ export class ValidationError extends RTError {
     this.message = message;
   }
 }
+export class InvalidExportsError extends RTError {
+  severity = 'crash';
+  name = 'ValidationError';
+
+  constructor() {
+    super();
+    this.message = `Invalid exports in job expression: exports must be an array`;
+
+    this.fix = 'Ensure job code has been compiled before calling the runtime';
+
+    delete this.stack;
+  }
+}
+
+export class InvalidOperationError extends RTError {
+  severity = 'crash';
+  name = 'ValidationError';
+
+  constructor(idx: number) {
+    super();
+    this.message = `Invalid operation at statement ${idx}`;
+
+    this.fix =
+      'Ensure all top-level function or method calls are wrapped in an operation, like fn()';
+
+    delete this.stack;
+  }
+}
 
 // Generic runtime execution error
 // This is a wrapper around any node/js error thrown during execution
@@ -155,13 +190,19 @@ export class RuntimeCrash extends RTError {
   subtype: string;
   name = 'RuntimeCrash';
 
-  constructor(error: Error) {
+  constructor(error: any) {
     super();
     this.subtype = error.constructor.name;
     this.message = `${this.subtype}: ${error.message}`;
 
     this.pos = extractPosition(error);
     this.stack = extractStackTrace(error);
+    if (error.fix) {
+      this.fix = error.fix;
+    }
+    if (error.details) {
+      this.details = error.details;
+    }
   }
 }
 

packages/runtime/src/execute/expression.ts

@@ -20,6 +20,8 @@ import {
   assertRuntimeError,
   assertSecurityKill,
   AdaptorError,
+  InvalidOperationError,
+  InvalidExportsError,
 } from '../errors';
 import type { JobModule, ExecutionContext, GlobalsModule } from '../types';
 import { ModuleInfoMap } from '../modules/linker';
@@ -234,6 +236,17 @@ const prepareJob = async (
       log: opts.logger,
     });
     const operations = exports.default;
+
+    if (!Array.isArray(operations)) {
+      throw new InvalidExportsError();
+    }
+
+    operations.forEach((op: unknown, idx: number) => {
+      if (typeof op !== 'function') {
+        throw new InvalidOperationError(idx);
+      }
+    });
+
     return {
       operations,
       ...exports,

packages/runtime/src/util/log-error.ts

@@ -92,9 +92,13 @@ const createErrorReporter = (logger: Logger): ErrorReporter => {
       logger.error(error.message);
     }
 
+    if (error.fix) {
+      logger.error(error.fix);
+      logger.break();
+    }
     if (error.details) {
       logger.error('Additional error details:');
-      logger.print(error.details);
+      logger.error(error.details);
       logger.break();
     }
 

packages/runtime/test/errors.test.ts

@@ -14,6 +14,7 @@ const createPlan = (expression: string, options: WorkflowOptions = {}) => ({
   workflow: {
     steps: [
       {
+        id: 'a',
         expression,
       },
     ],
@@ -101,6 +102,22 @@ test('extractStackTrace: basic test', (t) => {
   );
 });
 
+test('crash on invalid operation (the iconic "fn is not a function" error)', async (t) => {
+  // Note that this will output 'x' to stdout and look a bit weird!
+  const expression = 'export default [console.debug("x")]';
+  const plan = createPlan(expression, { timeout: 1 });
+
+  let error;
+  try {
+    await run(plan);
+  } catch (e) {
+    error = e;
+  }
+
+  t.is(error.severity, 'crash');
+  t.regex(error.message, /invalid operation at statement 0/i);
+});
+
 test('crash on timeout', async (t) => {
   const expression = 'export default [(s) => new Promise((resolve) => {})]';
 

packages/ws-worker/CHANGELOG.md

@@ -1,5 +1,14 @@
 # ws-worker
 
+## 1.22.2
+
+### Patch Changes
+
+- 0ed97be: Improve error reporting to resolve the dreaded "fn is not a function" error that occurs when writing `console.log()` at the top of job code
+- Updated dependencies [0ed97be]
+  - @openfn/runtime@1.8.5
+  - @openfn/engine-multi@1.10.6
+
 ## 1.22.1
 
 ### Patch Changes

packages/ws-worker/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@openfn/ws-worker",
-  "version": "1.22.1",
+  "version": "1.22.2",
   "description": "A Websocket Worker to connect Lightning to a Runtime Engine",
   "main": "dist/index.js",
   "type": "module",