TypeScript error when using PrettyOptions.customPrettifiers.level with extras

[Frederick888]

For example,

function pinoPrettyTransport(opts: PrettyOptions): PrettyStream {
  return PinoPretty({
    ...opts,
    translateTime: 'UTC:yyyy-mm-dd"T"HH:MM:ss.l"Z"',
    customPrettifiers: {
      level: (_level, _levelKey, _log, { labelColorized }) => labelColorized.toLowerCase(),
    },
  })
}

...leads to

error TS2322: Type '{ level: (_level: string | object, _levelKey: string, _log: object, { labelColorized }: PrettifierExtras<LevelPrettifierExtras>) => string; }' is not assignable to type 'Record<string, Prettifier<object>> & { level?: Prettifier<LevelPrettifierExtras> | undefined; }'.
  Type '{ level: (_level: string | object, _levelKey: string, _log: object, { labelColorized }: PrettifierExtras<LevelPrettifierExtras>) => string; }' is not assignable to type 'Record<string, Prettifier<object>>'.
    Property 'level' is incompatible with index signature.
      Type '(_level: string | object, _levelKey: string, _log: object, { labelColorized }: PrettifierExtras<LevelPrettifierExtras>) => string' is not assignable to type 'Prettifier<object>'.
        Types of parameters '__3' and 'extras' are incompatible.
          Type 'PrettifierExtras<object>' is not assignable to type 'PrettifierExtras<LevelPrettifierExtras>'.
            Type '{ colors: Colorette; }' is missing the following properties from type 'LevelPrettifierExtras': label, labelColorized

115     customPrettifiers: {
        ~~~~~~~~~~~~~~~~~

It seems since Record<string, Prettifier> doesn't restrict what keys it can have, Prettifier must be assignable to Prettifier<LevelPrettifierExtras>?

I'm new to TypeScript so maybe it's me that's using it wrong. Please help, thanks!

Edit: I'm using TypeScript v4.8.4, Node.js v18.9.1.

[mcollina]

Thanks for opening a PR! Can you please add a unit test? We use tsd for types.

[Frederick888]

Hi @mcollina, I'm happy to contribute a test but I'm not sure what the best way is to fix it.

The test change can be as simple as:

diff --git a/test/types/pino-pretty.test-d.ts b/test/types/pino-pretty.test-d.ts
index 9f2acd7..2f41344 100644
--- a/test/types/pino-pretty.test-d.ts
+++ b/test/types/pino-pretty.test-d.ts
@@ -32,9 +32,9 @@ const options: PinoPretty.PrettyOptions = {
   customPrettifiers: {
     key: (value) => {
       return value.toString().toUpperCase();
     },
-    level: (level, label, colorized) => {
+    level: (level, levelKey, log, { label, labelColorized, colors }) => {
       return level.toString();
     }
   },
   customLevels: 'verbose:5',

And I tried to still use Record or interface X { [key: string]: Y } however after some research, I'm under the impression that this is not possible. We essentially want to model a key to be any string but level (then intersect the Record with such a key with another Record<'level', ...>), which was discussed at e.g. https://stackoverflow.com/questions/51442157/type-for-every-possible-string-value-except; also https://stackoverflow.com/questions/57208330/extend-a-recordstring-string-with-a-different-type-of-property seems to be exactly the same problem, where the conclusion was again that it was possible to define such a type but it would lead to errors once you put it into use.

We can though, leverage a Map<'level', Prettifier<LevelPrettifierExtras>> & Map<string, Prettifier> type (full patch at the end), but this will be a breaking change.

We can also simply merge PrettifierExtras<object> and LevelPrettifierExtras into one {colors: Colorette.Colorette, label?: string, labelColorized?: string}, which is a compromise but hopefully not too confusing. Maybe we can do this in v13.0.1 and release the above Map method in v14?

Again I'm new to TypeScript and Node.js so please let me know if you have anything better in mind. I'll be happy to submit PR(s) with your guide.

Appendix: Map<'level', Prettifier<LevelPrettifierExtras>> & Map<string, Prettifier> full patch

diff --git a/index.d.ts b/index.d.ts
index 2c4c5c8..cc44241 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -182,12 +182,9 @@ declare namespace PinoPretty {
      *  // do some prettify magic
      * }
      * ```
      */
-    customPrettifiers?: Record<string, Prettifier> &
-      {
-        level?: Prettifier<LevelPrettifierExtras>
-      };
+    customPrettifiers?: CustomPrettifiers;
     /**
      * Change the level names and values to an user custom preset.
      *
      * Can be a CSV string in 'level_name:level_value' format or an object.
@@ -217,8 +214,9 @@ declare namespace PinoPretty {
   }
 
   function build(options: PrettyOptions): PrettyStream;
 
+  type CustomPrettifiers = Map<'level', Prettifier<LevelPrettifierExtras>> & Map<string, Prettifier>
   type Prettifier<T = object> = (inputData: string | object, key: string, log: object, extras: PrettifierExtras<T>) => string;
   type PrettifierExtras<T = object> = {colors: Colorette.Colorette} & T;
   type LevelPrettifierExtras = {label: string, labelColorized: string}
   type MessageFormatFunc = (log: LogDescriptor, messageKey: string, levelLabel: string, extras: PrettifierExtras) => string;
@@ -227,8 +225,8 @@ declare namespace PinoPretty {
   type PrettyFactory = typeof prettyFactory;
   type Build = typeof build;
   type isColorSupported = typeof Colorette.isColorSupported;
 
-  export { build, PinoPretty, PrettyOptions, PrettyStream, colorizerFactory, prettyFactory, isColorSupported };
+  export { build, CustomPrettifiers, PinoPretty, PrettyOptions, PrettyStream, colorizerFactory, prettyFactory, isColorSupported };
 }
 
 export = PinoPretty;
diff --git a/test/types/pino-pretty.test-d.ts b/test/types/pino-pretty.test-d.ts
index 9f2acd7..87874c1 100644
--- a/test/types/pino-pretty.test-d.ts
+++ b/test/types/pino-pretty.test-d.ts
@@ -3,8 +3,9 @@ import { expectType } from "tsd";
 import pretty from "../../";
 import PinoPretty, {
   PinoPretty as PinoPrettyNamed,
   PrettyOptions,
+  CustomPrettifiers,
   colorizerFactory,
   prettyFactory
 } from "../../";
 import PinoPrettyDefault from "../../";
@@ -12,8 +13,15 @@ import * as PinoPrettyStar from "../../";
 import PinoPrettyCjsImport = require("../../");
 import PrettyStream = PinoPretty.PrettyStream;
 const PinoPrettyCjs = require("../../");
 
+const customPrettifiers: CustomPrettifiers = new Map()
+customPrettifiers.set('key', (value) => {
+  return value.toString().toUpperCase();
+})
+customPrettifiers.set('level', (level, levelKey, log, {label, labelColorized, colors}) => {
+  return level.toString();
+})
 const options: PinoPretty.PrettyOptions = {
   colorize: true,
   crlf: false,
   errorLikeObjectKeys: ["err", "error"],
@@ -28,16 +36,9 @@ const options: PinoPretty.PrettyOptions = {
   timestampKey: "timestamp",
   minimumLevel: "trace",
   translateTime: "UTC:h:MM:ss TT Z",
   singleLine: false,
-  customPrettifiers: {
-    key: (value) => {
-      return value.toString().toUpperCase();
-    },
-    level: (level, label, colorized) => {
-      return level.toString();
-    }
-  },
+  customPrettifiers,
   customLevels: 'verbose:5',
   customColors: 'default:white,verbose:gray',
   sync: false,
   destination: 2,