batcherror

Keep track of individual errors within a batched process.

Why?

Sometimes a batch operation is required to implement an existing interface that has a singular error return type. This package can help with conveying and consulting individual errors in the returned error. It works well with the errors package by the standard library.

Why not?

Often it is simpler to return a custom type from a batch process, something like:

type batchResult struct {
	outputData any
	err error
}

func myBatchFunc(inputData []any) []batchResult {
	// ...
}

Usage

package main

import (
	"errors"
	"fmt"

	"github.com/zgiber/batcherror"
)

func main() {
	items := []any{1, 2, 3, "foo", 4, "bar", 5, 6}
	if err := processItems(items); err != nil {
		fmt.Println(err)
		// not an integer at [3]
		// not an integer at [5]

		fmt.Println(batcherror.At(err, 1) == nil)
		// true

		fmt.Println(batcherror.At(err, 3))
		// not an integer at [3]

		for k, v := range batcherror.Map(err) {
			fmt.Println(k, v)
			// 3 not an integer at [3]
			// 5 not an integer at [5]
		}
	}
}

func processItems(items []any) error {
	var batchErr error
	for idx, item := range items {
		if _, ok := item.(int); !ok {
			batchErr = errors.Join(batchErr, batcherror.New(fmt.Errorf("not an integer"), idx))
		}
	}
	return batchErr
}