Caught Object Report JSON

Motivation
Before Using This Library
Examples
API
Links

Motivation

JavaScript does not have a default way to represent Error object as JSON.
No standard way to extend error object with custom properties. It is natural to augment thrown error with details, but everybody is going to do it their own way. There is no standard details field.
Error object can have nested errors, see AggregateError and cause property. This can be a custom property of course like rootCauses. This means that occasionally an error you catch can be a deeply nested tree.
Even worse, in JavaScript, you can apply throw statement to any object, not just to Error instances. For example throw Infinity is valid JS code.
TypeScript does not attempt to make throwing errors type-safe. Every time you catch, the best you can say about caught object is that it is unknown.

All these things make serializing caught object to JSON a non-trivial problem.

This library attempts to provide a useful JSON representation for any JS object thrown and caught.

Intended use cases are

Structured logging
REST API or GraphQL response
Front-end sending an error report

Please don't hesitate to open an issue if your use case for this type of library is not met.

Before Using This Library

Consider

JSON.stringify(err, Object.getOwnPropertyNames(err)) is good enough if you don't necessarily want all edge cases covered.
JSON.stringify can throw, so make sure to wrap it in try catch or use safe-stable-stringify to avoid common errors of converting to JSON like circular references or converting BigInt value.

Compared to the method above, caught-object-report-json gives you the following benefits

Handles weird edge cases like throw null or when accessing a property on the error throws. Just slap caught-object-report-json on anything.
Logs errors that happen when producing JSON report (configurable). This means that even when caught-object-report-json fails to produce complete report, it will tell you why.
Handles nested errors
1. Replacer array obtained by Object.getOwnPropertyNames will apply to nested errors, but they can have a different set of property names, and you can miss on something important. caught-object-report-json does not have this problem.
2. caught-object-report-json flattens nested errors. Array is more suitable for processing than nested object. For example, you can write a pseudocode search condition like this with JSONPath query - $.children[:].constructor_name == "SyntaxError". It will search through all children in flattened array no matter how deeply nested. Same is not easily attainable for nested objects.
caught-object-report-json guarantees a JSON format which is
1. Same for any object processed.
2. Has metadata fields that hint into how it was produced (configurable).
3. Has JSON Schema as a source of truth.

Examples

1. Syntax error

_{(Run with npm run ts-file ./examples/example-1-syntax-error.ts)}

try {
  JSON.parse(undefined);
} catch (caught: unknown) {
  const report = makeCaughtObjectReportJson(caught);
  console.log(JSON.stringify(report, null, 2));
}

prints

{
  "instanceof_error": true,
  "typeof": "object",
  "constructor_name": "SyntaxError",
  "message": "Unexpected token u in JSON at position 0",
  "as_string": "SyntaxError: Unexpected token u in JSON at position 0",
  "as_json": {},
  "stack": "SyntaxError: Unexpected token u in JSON at position 0\n    at JSON.parse (<anonymous>)\n    at Object.<anonymous> (/home/user/work-dir/caught-object-report-json/examples/example-1-syntax-error.ts:6:8)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at phase4 (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)",
  "children_sources": [
    "cause",
    "errors"
  ],
  "as_string_format": "String",
  "as_json_format": "safe-stable-stringify@2.4.1",
  "v": "corj/v0.6"
}

2. Axios error

AxiosError#toJSON does not include response headers and response data (issue), so you'll have to add it yourself.

_{(Run with npm run ts-file ./examples/example-2-axios-error.ts)}

const axiosClient = axios.create();

class AxiosErrorWrapper extends AxiosError {
  error: AxiosError;

  constructor(error: AxiosError) {
    super(
      error.message,
      error.code,
      error.config,
      error.request,
      error.response,
    );
    this.error = error;
  }

  override toJSON = function (this: AxiosErrorWrapper) {
    return {
      ...this.error.toJSON(),
      ...(!this.error.response
        ? {}
        : {
          response_data: this.error.response.data,
          response_headers: this.error.response.headers,
        }),
    };
  };
}

axiosClient.interceptors.response.use(undefined, (error) => {
  if (error instanceof AxiosError) {
    return Promise.reject(new AxiosErrorWrapper(error));
  }
  return Promise.reject(error);
});

(async () => {
  try {
    await axiosClient.get('https://reqres.in/api/users/23');
  } catch (caught: unknown) {
    const report = makeCaughtObjectReportJson(caught);
    console.log(JSON.stringify(report, null, 2));
  }
})();

prints

{
  "instanceof_error": true,
  "typeof": "object",
  "constructor_name": "AxiosErrorWrapper",
  "message": "Request failed with status code 404",
  "as_string": "AxiosError: Request failed with status code 404",
  "as_json": {
    "message": "Request failed with status code 404",
    "name": "AxiosError",
    "stack": "AxiosError: Request failed with status code 404\n    at settle (/home/user/work-dir/caught-object-report-json/node_modules/axios/lib/core/settle.js:19:12)\n    at IncomingMessage.handleStreamEnd (/home/user/work-dir/caught-object-report-json/node_modules/axios/lib/adapters/http.js:505:11)\n    at IncomingMessage.emit (node:events:525:35)\n    at IncomingMessage.emit (node:domain:489:12)\n    at endReadableNT (node:internal/streams/readable:1359:12)\n    at processTicksAndRejections (node:internal/process/task_queues:82:21)",
    "config": {
      "transitional": {
        "silentJSONParsing": true,
        "forcedJSONParsing": true,
        "clarifyTimeoutError": false
      },
      "adapter": [
        "xhr",
        "http"
      ],
      "transformRequest": [
        null
      ],
      "transformResponse": [
        null
      ],
      "timeout": 0,
      "xsrfCookieName": "XSRF-TOKEN",
      "xsrfHeaderName": "X-XSRF-TOKEN",
      "maxContentLength": -1,
      "maxBodyLength": -1,
      "env": {},
      "headers": {
        "Accept": "application/json, text/plain, */*",
        "User-Agent": "axios/1.2.1",
        "Accept-Encoding": "gzip, compress, deflate, br"
      },
      "method": "get",
      "url": "https://reqres.in/api/users/23"
    },
    "code": "ERR_BAD_REQUEST",
    "status": 404,
    "response_data": {},
    "response_headers": {
      "date": "Sat, 28 Jan 2023 19:10:32 GMT",
      "content-type": "application/json; charset=utf-8",
      "content-length": "2",
      "connection": "close",
      "x-powered-by": "Express",
      "access-control-allow-origin": "*",
      "etag": "W/\"2-vyGp6PvFo4RvsFtPoIWeCReyIC8\"",
      "via": "1.1 vegur",
      "cache-control": "max-age=14400",
      "cf-cache-status": "EXPIRED",
      "report-to": "{\"endpoints\":[{\"url\":\"https:\\/\\/a.nel.cloudflare.com\\/report\\/v3?s=1L5F50uGk8AGGDKIk2WHHM8L2xV13XnA%2FJbD9EVofkAK0nW9uVfqOZOtPTg2amWpxM17WWe2IM%2BYRBE6Vyr49Z6nELCdbyEuEHkOVpz%2F8U5Stl3BQK93EgFNhw%3D%3D\"}],\"group\":\"cf-nel\",\"max_age\":604800}",
      "nel": "{\"success_fraction\":0,\"report_to\":\"cf-nel\",\"max_age\":604800}",
      "vary": "Accept-Encoding",
      "server": "cloudflare",
      "cf-ray": "790c075efba977b0-KBP"
    }
  },
  "stack": "AxiosError: Request failed with status code 404\n    at /home/user/work-dir/caught-object-report-json/examples/example-2-axios-error.ts:35:27\n    at processTicksAndRejections (node:internal/process/task_queues:95:5)",
  "children_sources": [
    "cause",
    "errors"
  ],
  "as_string_format": "String",
  "as_json_format": "safe-stable-stringify@2.4.1",
  "v": "corj/v0.6"
}

3. Not an error object thrown

If you do not provide onCaughtMaking callback, then errors are reported by default reporter using console.warn function. Provide onCaughtMaking: null to opt out of it.

_{(Run with npm run ts-file ./examples/example-3-not-error-object.ts)}

try {
  throw undefined;
} catch (caught: unknown) {
  const report = makeCaughtObjectReportJson(caught, {
    onCaughtMaking: (caught, context) => {
      console.log("onCaughtMaking::", { context });
      console.log("onCaughtMaking::", { caught });
    }
  });
  console.log(JSON.stringify(report, null, 2));
}

prints form onCaughtMaking callback

onCaughtMaking:: {
  context: {
    reason: 'error-converting-caught-to-json',
    caughtObjectNestingInfo: null,
    caughtWhenProcessingReportKey: 'as_json'
  }
}
onCaughtMaking:: {
  caught: Error: Could not convert caught object to json string using safe-stable-stringify@2.4.1.
      at makeProp_as_json (/home/user/work-dir/caught-object-report-json/src/index.ts:546:19)
      at makeEntriesWithoutNested (/home/user/work-dir/caught-object-report-json/src/index.ts:903:20)
      at CorjMaker.entries (/home/user/work-dir/caught-object-report-json/src/index.ts:951:46)
      at CorjMaker.makeReportObject (/home/user/work-dir/caught-object-report-json/src/index.ts:965:36)
      at makeCaughtObjectReportJson (/home/user/work-dir/caught-object-report-json/src/index.ts:353:42)
}

and then prints form catch block

{
  "instanceof_error": false,
  "typeof": "undefined",
  "as_string": "undefined",
  "as_json": null,
  "children_sources": [
    "cause",
    "errors"
  ],
  "as_string_format": "String",
  "as_json_format": "safe-stable-stringify@2.4.1",
  "v": "corj/v0.6"
}

Use metadataFields option to control what metadata to add to report. There is a similar option childrenMetadataFields that controls metadata fields for children reports. By default metadata is not set for children reports.

_{(Run with npm run ts-file ./examples/example-4-metadata-fields.ts)}

try {
  throw new Error(`Hi, I'm a regular Error object.`);
} catch (caught: unknown) {
  const report = makeCaughtObjectReportJson(caught, {
    metadataFields: {
      $schema: true,
      as_json_format: false,
      as_string_format: false,
      children_sources: false,
      v: false
    },
  });
  console.log(JSON.stringify(report, null, 2));
}

prints

{
  "instanceof_error": true,
  "typeof": "object",
  "constructor_name": "Error",
  "message": "Hi, I'm a regular Error object.",
  "as_string": "Error: Hi, I'm a regular Error object.",
  "as_json": {},
  "stack": "Error: Hi, I'm a regular Error object.\n    at Object.<anonymous> (/home/user/work-dir/caught-object-report-json/examples/example-4-metadata-fields.ts:4:9)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at phase4 (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)",
  "$schema": "https://raw.githubusercontent.com/dany-fedorov/caught-object-report-json/main/schema-versions/corj/v0.7-report-object.json"
}

5. Nested errors: Basic

JS has two standard ways to represent nested/children errors.

AggregateError has nested errors accessible in errors property
cause property of Error class.

Caught Object Report JSON abstracts this into children property.

In the following example AggregateError has both errors and cause properties set.

On a JSON report children_sources metadata field tells which property names were used to obtain children array.

Children in array have three additional fields - child_id, child_path and child_level.

child_id is an integer id assigned to a nested error object, starts from 0
child_path is a JSONPath from root caught object to this object.
child_level shows a level of this object in a tree of nested error objects.

_{(Run with npm run ts-file ./examples/example-5-nested-errors-1-basic.ts)}

const caught = new AggregateError(
  [
    new Error('AggregateError child 0'),
    'AggregateError child 1 (not an Error object)',
  ],
  'AggregateError message',
  { cause: new Error('Cause Error object') },
);
const report = makeCaughtObjectReportJson(caught, {
  metadataFields: {
    $schema: false,
    as_json_format: false,
    as_string_format: false,
    v: false,
    children_sources: true,
  },
});
console.log(JSON.stringify(report, null, 2));

prints

{
  "instanceof_error": true,
  "typeof": "object",
  "constructor_name": "AggregateError",
  "message": "AggregateError message",
  "as_string": "AggregateError: AggregateError message",
  "as_json": {},
  "stack": "AggregateError: AggregateError message\n    at Object.<anonymous> (/home/user/work-dir/caught-object-report-json/examples/example-5-nested-errors-1-basic.ts:7:16)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at phase4 (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)",
  "children": [
    {
      "id": "0",
      "path": "$.cause",
      "level": 1,
      "instanceof_error": true,
      "typeof": "object",
      "constructor_name": "Error",
      "message": "Cause Error object",
      "as_string": "Error: Cause Error object",
      "as_json": {},
      "stack": "Error: Cause Error object\n    at Object.<anonymous> (/home/user/work-dir/caught-object-report-json/examples/example-5-nested-errors-1-basic.ts:13:12)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at phase4 (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)"
    },
    {
      "id": "1",
      "path": "$.errors[0]",
      "level": 1,
      "instanceof_error": true,
      "typeof": "object",
      "constructor_name": "Error",
      "message": "AggregateError child 0",
      "as_string": "Error: AggregateError child 0",
      "as_json": {},
      "stack": "Error: AggregateError child 0\n    at Object.<anonymous> (/home/user/work-dir/caught-object-report-json/examples/example-5-nested-errors-1-basic.ts:9:5)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at phase4 (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)"
    },
    {
      "id": "2",
      "path": "$.errors[1]",
      "level": 1,
      "instanceof_error": false,
      "typeof": "string",
      "constructor_name": "String",
      "as_string": "AggregateError child 1 (not an Error object)",
      "as_json": "AggregateError child 1 (not an Error object)"
    }
  ],
  "children_sources": [
    "cause",
    "errors"
  ]
}

6. Nested errors: Nesting levels

The following example showcases some nuances of processing nested errors.

Because of maxChildrenLevel option set to 2, "lvl 3" errors are not included
When there are nested error object detected, but level is greater than maxChildrenLevel setting, children_omitted_reason field is added
Because childrenSources option includes nestedError field, it is included in children array
Because childrenSources option includes nestedError field, it is excluded from as_json field
Because nested objects are flattened, children prop for nested objects includes list of child_ids and not objects
If a value found by a property from childrenSources is an array, then report is made for each element and not for an array as a whole.

_{(Run with npm run ts-file ./examples/example-6-nested-errors-2-nesting-levels.ts)}

const caught = new Error("lvl 0", {
  cause: new Error("lvl 1; obj 0", {
    cause: [
      new Error("lvl 2; obj 0.0", { cause: new Error("lvl 3; obj 0.0.0") }),
      new Error("lvl 2; obj 0.1")
    ]
  })
});
caught.nestedErrors = 'lvl 1; obj 1';
caught.extraField = 'error info';
const report = makeCaughtObjectReportJson(caught, {
  maxChildrenLevel: 2,
  childrenSources: ['cause', 'errors', 'nestedErrors'],
  metadataFields: {
    $schema: false,
    as_json_format: false,
    as_string_format: false,
    v: false,
    children_sources: true
  }
});
console.log(JSON.stringify(report, null, 2));

prints

{
  "instanceof_error": true,
  "typeof": "object",
  "constructor_name": "Error",
  "message": "lvl 0",
  "as_string": "Error: lvl 0",
  "as_json": {
    "extraField": "error info"
  },
  "stack": "Error: lvl 0\n    at Object.<anonymous> (/home/user/work-dir/caught-object-report-json/examples/example-6-nested-errors-2-nesting-levels.ts:5:16)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at phase4 (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)",
  "children": [
    {
      "id": "0",
      "path": "$.cause",
      "level": 1,
      "instanceof_error": true,
      "typeof": "object",
      "constructor_name": "Error",
      "message": "lvl 1; obj 0",
      "as_string": "Error: lvl 1; obj 0",
      "as_json": {},
      "stack": "Error: lvl 1; obj 0\n    at Object.<anonymous> (/home/user/work-dir/caught-object-report-json/examples/example-6-nested-errors-2-nesting-levels.ts:9:5)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at phase4 (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)",
      "children": [
        "2",
        "3"
      ]
    },
    {
      "id": "1",
      "path": "$.nestedError",
      "level": 1,
      "instanceof_error": false,
      "typeof": "string",
      "constructor_name": "String",
      "as_string": "lvl 1; obj 1",
      "as_json": "lvl 1; obj 1"
    },
    {
      "id": "2",
      "path": "$.cause.cause[0]",
      "level": 2,
      "instanceof_error": true,
      "typeof": "object",
      "constructor_name": "Error",
      "message": "lvl 2; obj 0.0",
      "as_string": "Error: lvl 2; obj 0.0",
      "as_json": {},
      "stack": "Error: lvl 2; obj 0.0\n    at Object.<anonymous> (/home/user/work-dir/caught-object-report-json/examples/example-6-nested-errors-2-nesting-levels.ts:13:9)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at phase4 (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)",
      "children_omitted_reason": "Reached max depth - 2"
    },
    {
      "id": "3",
      "path": "$.cause.cause[1]",
      "level": 2,
      "instanceof_error": true,
      "typeof": "object",
      "constructor_name": "Error",
      "message": "lvl 2; obj 0.1",
      "as_string": "Error: lvl 2; obj 0.1",
      "as_json": {},
      "stack": "Error: lvl 2; obj 0.1\n    at Object.<anonymous> (/home/user/work-dir/caught-object-report-json/examples/example-6-nested-errors-2-nesting-levels.ts:16:9)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at phase4 (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)"
    }
  ],
  "children_sources": [
    "cause",
    "errors",
    "nestedError"
  ]
}

7. Using CorjMaker instance to provide options just once

_{(Run with npm run ts-file ./examples/example-7-using-corj-maker-instance.ts)}

const corj = CorjMaker.withDefaults({
  metadataFields: false
});

try {
  throw new Error(`Hi, I'm a regular Error object.`);
} catch (caught: unknown) {
  const report = corj.makeReportObject(caught);
  console.log(JSON.stringify(report, null, 2));
}

prints

{
  "instanceof_error": true,
  "typeof": "object",
  "constructor_name": "Error",
  "message": "Hi, I'm a regular Error object.",
  "as_string": "Error: Hi, I'm a regular Error object.",
  "as_json": {},
  "stack": "Error: Hi, I'm a regular Error object.\n    at Object.<anonymous> (/home/user/work-dir/caught-object-report-json/examples/example-5-using-corj-maker-instance.ts:8:9)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at phase4 (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/user/work-dir/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)"
}

8. Flat array report with Zod error

ZodError has nested errors in the errors prop. caught-object-report-json logs both top-level and nested error.

_{(Run with npm run ts-file ./examples/example-8-zod-error-flat-report.ts)}

const corj = CorjMaker.withDefaults({
  metadataFields: false,
});

const User = zod.object({
  name: zod.string(),
  age: zod.number().min(-250).max(250),
});

try {
  const validatedStallmanObject = User.parse({ name: 'Richard Stallman' });
  console.log('Hello, validated', validatedStallmanObject.name);
} catch (caught: unknown) {
  const reportArray = corj.makeReportArray(caught);
  console.log(JSON.stringify(reportArray, null, 2));
}

prints

[
  {
    "id": "root",
    "path": "$",
    "level": 0,
    "instanceof_error": true,
    "typeof": "object",
    "constructor_name": "ZodError",
    "message": "[\n  {\n    \"code\": \"invalid_type\",\n    \"expected\": \"number\",\n    \"received\": \"undefined\",\n    \"path\": [\n      \"age\"\n    ],\n    \"message\": \"Required\"\n  }\n]",
    "as_string": "[\n  {\n    \"code\": \"invalid_type\",\n    \"expected\": \"number\",\n    \"received\": \"undefined\",\n    \"path\": [\n      \"age\"\n    ],\n    \"message\": \"Required\"\n  }\n]",
    "as_json": {
      "issues": [
        {
          "code": "invalid_type",
          "expected": "number",
          "received": "undefined",
          "path": [
            "age"
          ],
          "message": "Required"
        }
      ],
      "name": "ZodError"
    },
    "stack": "ZodError: [\n  {\n    \"code\": \"invalid_type\",\n    \"expected\": \"number\",\n    \"received\": \"undefined\",\n    \"path\": [\n      \"age\"\n    ],\n    \"message\": \"Required\"\n  }\n]\n    at handleResult (/home/df/hdd/wd/caught-object-report-json/node_modules/zod/lib/types.js:29:23)\n    at ZodObject.safeParse (/home/df/hdd/wd/caught-object-report-json/node_modules/zod/lib/types.js:142:16)\n    at ZodObject.parse (/home/df/hdd/wd/caught-object-report-json/node_modules/zod/lib/types.js:122:29)\n    at Object.<anonymous> (/home/df/hdd/wd/caught-object-report-json/examples/example-8-zod-error-flat-report.ts:14:40)\n    at Module._compile (node:internal/modules/cjs/loader:1120:14)\n    at Module.m._compile (/home/df/hdd/wd/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/df/hdd/wd/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:998:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:839:12)",
    "children": [
      "0"
    ],
    "children_sources": [
      "cause",
      "errors"
    ],
    "as_string_format": "String",
    "as_json_format": "safe-stable-stringify@2.4.1",
    "v": "corj/v0.8"
  },
  {
    "id": "0",
    "path": "$.errors[0]",
    "level": 1,
    "instanceof_error": false,
    "typeof": "object",
    "constructor_name": "Object",
    "message": "Required",
    "as_string": "[object Object]",
    "as_json": {
      "code": "invalid_type",
      "expected": "number",
      "received": "undefined",
      "path": [
        "age"
      ],
      "message": "Required"
    }
  }
]

9. Winston integration

_{(Run with npm run ts-file ./examples/example-9-winston-integration.ts)}

This integration uses a feature of winston that allows to specify transports that will react to uncaughtException event emitted by the process - https://www.npmjs.com/package/winston#exceptions

Integration by monkey patching the exported class is not pretty, but this is the only way I found to make it work.

This method keeps all the processing that is done by winston for the error object, but it replaces the message prop on the resulting JSON with an extended report instead of error message + stack that winston uses by default.

This is the string that winston gives by default for this example.

"AggregateError\n    at Object.<anonymous> (/home/df/wd/personal/caught-object-report-json/examples/example-9-logging-uncaught-exceptions-and-rejections-with-winston.ts:33:7)\n    at Module._compile (node:internal/modules/cjs/loader:1267:14)\n    at Module.m._compile (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1321:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:1125:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:965:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:83:12)\n    at phase4 (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)"

caught-object-report-json does not loose any info, see the final JSON message below the code snippet.

Also, winston breaks when you throw null or throw undefined. caught-object-report-json saves you from this edge case.

import { createLogger, transports, ExceptionHandler } from 'winston';

const origGetAllInfo = ExceptionHandler.prototype.getAllInfo;
ExceptionHandler.prototype.getAllInfo = function getAllInfoExtended(
  err: unknown,
): object {
  const errorInfoByWinston = origGetAllInfo.call(
    ExceptionHandler.prototype,
    err instanceof Error
      ? err
      : `I'm a hacky stub error that does not break getAllInfo method, unlike undefined or null.`,
  );
  return {
    ...errorInfoByWinston,
    error: err,
    message: makeCaughtObjectReportJson(err),
  };
};

const logger = createLogger({
  transports: [new transports.Console()],
  exceptionHandlers: [new transports.Console()],
});

logger.info({ 'just-an-info-message': 'hey' });

throw new AggregateError([new Error('cause 1'), new Error('cause 2'), null]);

prints an inline version of the following JSON

{
  "date": "Wed May 24 2023 01:17:44 GMT+0300 (Eastern European Summer Time)",
  "error": {},
  "exception": true,
  "level": "error",
  "message": {
    "as_json": {},
    "as_json_format": "safe-stable-stringify@2.4.1",
    "as_string": "AggregateError",
    "as_string_format": "String",
    "children": [
      {
        "as_json": {},
        "as_string": "Error: cause 1",
        "constructor_name": "Error",
        "id": "0",
        "instanceof_error": true,
        "level": 1,
        "message": "cause 1",
        "path": "$.errors[0]",
        "stack": "Error: cause 1\n    at Object.<anonymous> (/home/df/wd/personal/caught-object-report-json/examples/example-9-winston-integration.ts:30:27)\n    at Module._compile (node:internal/modules/cjs/loader:1267:14)\n    at Module.m._compile (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1321:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:1125:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:965:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:83:12)\n    at phase4 (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)",
        "typeof": "object"
      },
      {
        "as_json": {},
        "as_string": "Error: cause 2",
        "constructor_name": "Error",
        "id": "1",
        "instanceof_error": true,
        "level": 1,
        "message": "cause 2",
        "path": "$.errors[1]",
        "stack": "Error: cause 2\n    at Object.<anonymous> (/home/df/wd/personal/caught-object-report-json/examples/example-9-winston-integration.ts:30:49)\n    at Module._compile (node:internal/modules/cjs/loader:1267:14)\n    at Module.m._compile (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1321:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:1125:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:965:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:83:12)\n    at phase4 (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)",
        "typeof": "object"
      },
      {
        "as_json": null,
        "as_string": "null",
        "id": "2",
        "instanceof_error": false,
        "level": 1,
        "path": "$.errors[2]",
        "typeof": "object"
      }
    ],
    "children_sources": [
      "cause",
      "errors"
    ],
    "constructor_name": "AggregateError",
    "instanceof_error": true,
    "message": "",
    "stack": "AggregateError\n    at Object.<anonymous> (/home/df/wd/personal/caught-object-report-json/examples/example-9-winston-integration.ts:30:7)\n    at Module._compile (node:internal/modules/cjs/loader:1267:14)\n    at Module.m._compile (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1321:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:1125:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:965:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:83:12)\n    at phase4 (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)",
    "typeof": "object",
    "v": "corj/v0.8"
  },
  "os": {
    "loadavg": [
      1.04,
      1.3,
      1.16
    ],
    "uptime": 262285.15
  },
  "process": {
    "argv": [
      "/home/df/wd/personal/caught-object-report-json/node_modules/.bin/ts-node",
      "/home/df/wd/personal/caught-object-report-json/examples/example-9-winston-integration.ts"
    ],
    "cwd": "/home/df/wd/personal/caught-object-report-json",
    "execPath": "/home/df/.volta/tools/image/node/20.1.0/bin/node",
    "gid": 1000,
    "memoryUsage": {
      "arrayBuffers": 3595822,
      "external": 5796716,
      "heapTotal": 100966400,
      "heapUsed": 69475360,
      "rss": 146800640
    },
    "pid": 88513,
    "uid": 1000,
    "version": "v20.1.0"
  },
  "stack": "AggregateError\n    at Object.<anonymous> (/home/df/wd/personal/caught-object-report-json/examples/example-9-winston-integration.ts:30:7)\n    at Module._compile (node:internal/modules/cjs/loader:1267:14)\n    at Module.m._compile (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts:1618:23)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1321:10)\n    at Object.require.extensions.<computed> [as .ts] (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts:1621:12)\n    at Module.load (node:internal/modules/cjs/loader:1125:32)\n    at Function.Module._load (node:internal/modules/cjs/loader:965:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:83:12)\n    at phase4 (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts:649:14)\n    at bootstrap (/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts:95:10)",
  "trace": [
    {
      "column": 7,
      "file": "/home/df/wd/personal/caught-object-report-json/examples/example-9-winston-integration.ts",
      "function": null,
      "line": 30,
      "method": null,
      "native": false
    },
    {
      "column": 14,
      "file": "node:internal/modules/cjs/loader",
      "function": "Module._compile",
      "line": 1267,
      "method": "_compile",
      "native": false
    },
    {
      "column": 23,
      "file": "/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts",
      "function": "Module.m._compile",
      "line": 1618,
      "method": "_compile",
      "native": false
    },
    {
      "column": 10,
      "file": "node:internal/modules/cjs/loader",
      "function": "Module._extensions..js",
      "line": 1321,
      "method": ".js",
      "native": false
    },
    {
      "column": 12,
      "file": "/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/index.ts",
      "function": "Object.require.extensions.<computed> [as .ts]",
      "line": 1621,
      "method": "ts]",
      "native": false
    },
    {
      "column": 32,
      "file": "node:internal/modules/cjs/loader",
      "function": "Module.load",
      "line": 1125,
      "method": "load",
      "native": false
    },
    {
      "column": 12,
      "file": "node:internal/modules/cjs/loader",
      "function": "Module._load",
      "line": 965,
      "method": "_load",
      "native": false
    },
    {
      "column": 12,
      "file": "node:internal/modules/run_main",
      "function": "Function.executeUserEntryPoint [as runMain]",
      "line": 83,
      "method": "executeUserEntryPoint [as runMain]",
      "native": false
    },
    {
      "column": 14,
      "file": "/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts",
      "function": "phase4",
      "line": 649,
      "method": null,
      "native": false
    },
    {
      "column": 10,
      "file": "/home/df/wd/personal/caught-object-report-json/node_modules/ts-node/src/bin.ts",
      "function": "bootstrap",
      "line": 95,
      "method": null,
      "native": false
    }
  ]
}

API

makeCaughtObjectReportJson(caught)

A wrapper for CorjMaker#makeReportObject with default options.

makeCaughtObjectReportJsonArray(caught)

A wrapper for CorjMaker#makeCaughtObjectReportJsonArray with default options.

new CorjMaker(options)

Use CorjMaker.withDefaults static method to construct a CorjMaker with default options.
Use CorjMaker#makeReportObject instance method to produce CaughtObjectReportJson.
Use CorjMaker#makeReportArray instance method to produce CaughtObjectReportJsonChild[].

type CaughtObjectReportJson

Report object produced by CorjMaker#makeReportObject.

type CaughtObjectReportJsonChild

Report object produced in array by CorjMaker#makeReportArray, or in top-level children property on CaughtObjectReportJson.