errstack

ErrStack

ErrStack is a linter for Go that checks for unnecessary error wrapping using errors.Wrap, errors.Wrapf, and errors.WithStack.

It is created as a complement to the wrapcheck linter.

Installation

Go >= v1.22

go install github.com/AdamBrianBright/errstack/cmd/errstack@latest

ErrStack can be used as a module for golangci-lint.

.custom-gcl.yml

version: v1.64.0

destination: ./testdata/src

plugins:
  - module: 'github.com/AdamBrianBright/errstack'
    import: 'github.com/AdamBrianBright/errstack/cmd/gclplugin'
    version: v0.2.0

.golangci.yml

linters-settings:
  custom:
    errstack:
      type: "module"
      description: Walks through the AST and finds all functions that return an error.
      settings:
        wrapperFunctions:
          - pkg: github.com/pkg/errors
            names: [ New, Errorf, Wrap, Wrapf, WithStack ] 
        cleanFunctions:
          - pkg: errors
            names: [ New ]
          - pkg: fmt
            names: [ Errorf ]
          - pkg: github.com/pkg/errors
            names: [ WithMessage, WithMessagef ]

linters:
  disable-all: true
  enable:
    - errstack

Configuration

You can configure ErrStack using the .errstack.yaml file in your project root, or in your home directory.

# List of functions that are considered to wrap errors.
# If you're using some fancy error wrapping library like github.com/pkg/errors,
# you may want to add it to this list.
# If you want to ignore some functions, simply don't add them to the list.
wrapperFunctions:
  - pkg: github.com/pkg/errors
    names:
      - New
      - Errorf
      - Wrap
      - Wrapf
      - WithStack
# List of functions that are considered to clean errors without stacktrace.
cleanFunctions:
  - pkg: errors
    names:
      - New
  - pkg: fmt
    names:
      - Errorf
  - pkg: github.com/pkg/errors
    names:
      - WithMessage
      - WithMessagef

Usage

To lint all the packages in your project, run:

errstack ./...

Testing

This linter is tested using analysistest, you can view all the test cases under testdata directory.

Why?

If you're using some fancy error wrapping library like github.com/pkg/errors, you may have stumbled upon doubling or tripling the amount of stacktrace duplicates in your logs.

This happens because the library wraps errors in context style, hiding stacktraces from the user in unexported structs and fields like russian dolls.

When doing so, libraries don't check for stacktraces already present in the error, since it is usually not necessary and only slows down your code.

However, if you're using libraries out of your control, you may not be able to easily identify whether some functions may return wrapped errors or not, and just wrap errors from external packages like wrapcheck suggests anyways.

This linter helps you to identify such cases, and help you remove unnecessary wrapping.

How does it work?

1. Preloads all packages and parses their ASTs.
2. Finds all functions that return errors.
3. Finds all calls to functions that return errors.
4. Marks functions that return wrapped errors.
5. Analyzes original function CFG and reports if unnecessary wrapping is used.

Example

package main

import (
	"github.com/pkg/errors"
)

func main() {
	_ = testDoubleReturnWrapStack()
}

func testDoubleReturnWrapStack() error {
	return errors.Wrap(errors.WithStack(nil), "wrapped") // want `Wrap call unnecessarily wraps error with stacktrace\. Replace with errors\.WithMessage\(\) or fmt\.Errorf\(\)`
}