Add include precondition

CHANGELOG.md

@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to Semantic Versioning](https://semver.org/spec/v2.0.0.html)
 
+## 4.2
+
+- Add precondition to include to improve performance
+
+## 4.1.1
+
+- Add include to TypeScript definitions
+
 ## 4.1.0
 
 - Add include processor

README.md

@@ -326,9 +326,10 @@ Shallow copies the specified paths into a new log record. This is useful to avoi
 
 It has the following options:
 
-| name  | type  | required | default | notes                                        |
-| ----- | ----- | -------- | ------- | -------------------------------------------- |
-| paths | array | no       | []      | Specifies the paths of the fields to include |
+| name         | type     | required | default    | notes                                                      |
+| ------------ | -------- | -------- | ---------- | ---------------------------------------------------------- |
+| paths        | array    | no       | []         | Specifies the paths of the fields to include               |
+| precondition | function | no       | () => true | A function which must return true for the processor to run |
 
 #### example
 

lib/processors/include.js

@@ -3,9 +3,13 @@ const get = require("get-value");
 const set = require("set-value");
 const toPath = require("to-path");
 
+const ALWAYS_PASS = () => true;
+
 module.exports = (params = {}) => {
-  const { paths = [] } = params;
-  return ({ record }) => {
+  const { paths = [], precondition = ALWAYS_PASS } = params;
+  return ({ level, message, context, record }) => {
+    if (!precondition({ level, message, context, record })) return record;
+
     const included = paths.reduce((acc, path) => {
       if (!has(record, path, { split: getSplit })) return acc;
       const value = get(record, path, { split: getSplit });

test/processors/include.test.js

@@ -37,4 +37,16 @@ describe("include", () => {
     fn({ record });
     eq(record, { a: { b: 1, c: 2 }, m: 1, x: { y: 1, z: 2 } });
   });
+
+  it("should run the processor the precondition passes", () => {
+    const fn = include({ precondition: ({ record }) => record.a.b === 1, paths: ["a.b", "x"] });
+    const result = fn({ record: { a: { b: 1, c: 2 }, m: 1, x: { y: 1, z: 2 } } });
+    eq(result, { a: { b: 1 }, x: { y: 1, z: 2 } });
+  });
+
+  it("should bypass the processor the precondition fails", () => {
+    const fn = include({ precondition: () => false, paths: ["a.b", "x"] });
+    const result = fn({ record: { a: { b: 1, c: 2 }, m: 1, x: { y: 1, z: 2 } } });
+    eq(result, { a: { b: 1, c: 2 }, m: 1, x: { y: 1, z: 2 } });
+  });
 });