add types and docs

docs/api.md

@@ -375,6 +375,23 @@ const hooks = {
 }
 ```
 
+
+<a id="streamWrite"></a>
+##### `streamWrite`
+
+Allows for manipulating the _stringified_ JSON log data just before writing to various transports.
+
+The method receives the stringified JSON and must return valid stringified JSON.
+
+For example:
+```js
+const hooks = {
+  streamWrite (s) {
+    return s.replaceAll('sensitive-api-key', 'XXX')
+  }
+}
+```
+
 <a id=opt-formatters></a>
 #### `formatters` (Object)
 

pino.d.ts

@@ -641,6 +641,12 @@ declare namespace pino {
              * using apply, like so: method.apply(this, newArgumentsArray).
              */
             logMethod?: (this: Logger, args: Parameters<LogFn>, method: LogFn, level: number) => void;
+
+            /**
+             * Allows for manipulating the stringified JSON log output just before writing to various transports.
+             * This function must return a string and must be valid JSON.
+             */
+            streamWrite?: (s: string) => string;
         };
 
         /**

pino.js

@@ -70,7 +70,8 @@ const defaultOptions = {
     }
   }),
   hooks: {
-    logMethod: undefined
+    logMethod: undefined,
+    streamWrite: undefined
   },
   timestamp: epochTime,
   name: undefined,