errorist

Package errorist provides useful error handling utilities inspired by Thanos Coding Style Guide and Uber go style guide.

Closing Resources

errorist provides hassle-free functions closing io.Closer with defer.

With Error Capture

The most recommended way is using error capture. An error caused by Close will be captured on the given error pointer unless it already has an error as the value.

func printFile(path string) (err error) {
    f, err := os.OpenFile(path)
    if err != nil {
        return errors.Wrapf(err, "open %s", path)
    }
    defer errorist.CloseWithErrCapture(f, &err)
    ...
}

With Error Channel

An error also can be captured and sent to an error channel (chan error). It is a good fit with resources in goroutines.

errChan := make(chan error)
go func() {
    f, err := os.OpenFile(path)
    defer errorist.CloseWithErrChan(f, errChan)
}()

With Error Log

Otherwise, why don't we just log and ignore it? Default logger is log.Println but you are able to customize it with options.

defer errorist.CloseWithLogOnErr(f)

// with logrus
defer errorist.CloseWithLogOnErr(f, errorist.LogWithLogrus(logger.Warn))

Adding Contexts with Error Wrapping

If you're familiar with errors.Wrap or fmt.Errorf, you may want to do the same error handling with errorist. errorist provides the option wrapping errors with context.

func printFile(path string) (err error) {
    f, err := os.OpenFile(path)
    if err != nil {
        return errors.Wrapf(err, "open %s", path)
    }
    defer errorist.CloseWithErrCapture(f, &err, errorist.Wrapf("close %s", path))
    ...
}

Note that errorist.Wrapf is just an option specifier for errorist; it cannot be used solely. If you want to just wrap errors, you can use pkg/errors or fmt.Errorf with %w pattern added in Go 1.13.

Recovering from Panics

errorist provides panic recovery functions that can be used with defer.

wg, ctx := errgroup.WithContext(context.Background())
wg.Go(func() (err error) {
    defer errorist.RecoverWithErrCapture(&err)
    ...
})

Stacktrace is prettified, and calls from non-project source will be filtered by default. You can customize stacktrace format with options. For details, please refer options.go.

fmt.Println("%+v", err)

panic: assignment to entry in nil map
    github.com/therne/errorist.panicStation (panic_test.go:67)
    github.com/therne/errorist.TestWrapPanicWith.func1.1.1 (panic_test.go:19)
    github.com/therne/errorist.TestWrapPanicWith.func1.1 (panic_test.go:13)
    github.com/therne/errorist.TestWrapPanicWith.func1 (panic_test.go:12)
    github.com/therne/errorist.TestWrapPanicWith (panic_test.go:11)

Prettifying Stacktraces on Errors

pkg/errors is the most popular and powerful tool for handling and wrapping errors. errorist provides extracting and prettifying a stacktrace from errors created or wrapped by pkg/errors.

errorist.Stacktrace(err) ==
    []string{
        "github.com/some/app/api/Server.Handle (api.go:84)",
        "github.com/some/app/controller/Controller.Get (controller.go:11)",
    }

The below example shows how to use it in API responses for debugging purposes.

func handleGinError(c *gin.Context) {
    c.Next()
    if len(c.Errors) > 0 {
        err := c.Errors.Last().Err
        c.JSON(500, gin.H{
            "error":       err.Error(),
            "stacktraces": errorist.Stacktrace(err)
        })
    }
}

Options

You can use global options, package-wide, or with call arguments. Options set on a smaller scope can override options set on a wider scope.

errorist.SetGlobalOptions(
    errorist.IncludeNonProjectFiles(),
    errorist.WithDetailedTrace(),
)

// package-local options can override global options
errorist.SetPackageLevelOptions(
    errorist.IncludedPackages("github.com/my/pkg"),
    errorist.LogWithLogrus(pkgLogger),
)

// call options can override options above
errorist.CloseWithErrCapture(f, &err, errorist.Wrapf("close %s", path))

For detailed options, please refer Godoc or options.go.