killerr

Kill "if err"(killerr) package is a simple implementation of exceptions for go language.

How to use it

Add "github.com/g-s-m/killerr" package to your project.

go get -v github.com/g-s-m/killerr

Description

There is a method

Try(f func(h Scope)) Scope

in the package. It is supposed to use in that place where you are expecting an exception. Scope is a structure contained 3 methods:

Catch(f func(err error))
CatchIs(target error, f func(err error))
Throw(err error)

Try receives your function that implements some logic and returns a Scope. That function must receive a Scope as an argument to be able to raise an exception. Pass this Scope to all calles may to throw an exception(like context.Context). In all the pieces of codes where a concrete error is generated you are able to call Throw to raise an exception. Call Catch to catch an exception. Call CatchIs to receive a concrete error.

Example:

func MyRepo1(ctx context.Context, ex killerr.Scope) {
  record, err := db.Insert()
  if err != nil {
    ex.Throw(fmt.Errorf("repo2 err: %w", err))
  }
}

func MyRepo2(ctx context.Context, ex killerr.Scope) {
  record, err := db.Find()
  if err != nil {
    ex.Throw(fmt.Errorf("repo2 err: %w", err))
  }
}

func MyInternalPackageLogic1(ctx context.Context, ex killerr.Scope) {
  MyRepo2(ctx, ex)
}

func MyInternalPackageLogic2(ctx context.Context, ex killerr.Scope)  {
  MyRepo1(ctx, ex)
  MyRepo2(ctx, ex)
  if somethingBadHappen {
    ex.Throw(ErrInternalPackage)
  }
}

func MyAppLogic(ctx context.Context, ex killerr.Scope) {
  MyInternalPackage1(ctx, ex)
  MyInternalPackage2(ctx, ex)
}

func RunMyApp() {
  ctx := context.Background()

  killerr.Try(func(ex killerr.Scope) {
    MyAppLogic(ctx, ex)
  }).CatchIs(ErrInternalPackage, func(err error){
    log.Error("internal error: %s", err.Error())
  }).CatchIs(ErrRepo, func(err error){
    log.Error("repo error: %s", err.Error())
  }).Catch(func(err error) {
    log.Error("another error: %s", err.Error())
  })
}

Restrictions

• If you doesn't place catch block, you will lose your error
• Try, Catch and Throw won't work in different goroutines, like try-catch in other languages works in the same thread, they would work properly only in the same goroutine. The following code will not work correctly:

// do not do this:
killerr.Try(func(ex killerr.Scope) {
  go func() {
    ex.Throw()
  }()
}).Catch(func(err error){
  ...
})

• Order of Catch and CatchIs matters. For example if function throws ErrInternal1 you may call CatchIs(ErrInternal, ...) first and then Catch(...) to catch ErrInternal separately of other errors. Always place CatchIs before Catch block. See example.

killerr.Try(func(ex killerr.Scope) {
    ex.Throw(ErrInternalPackage)
  }).CatchIs(ErrInternalPackage, func(err error){
    //this block will catch the error
    log.Error("internal error: %s", err.Error())
  }).Catch(func(err error) {
    log.Error("another error: %s", err.Error())
  })

  killerr.Try(func(ex killerr.Scope) {
    ex.Throw(ErrInternalPackage)
  }).Catch(func(err error) {
    //this block will catch the error
    log.Error("another error: %s", err.Error())
  }).CatchIs(ErrInternalPackage, func(err error){
    log.Error("internal error: %s", err.Error())
  })

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Released under the LICENSE.txt.