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78 lines
2.5 KiB
Text
78 lines
2.5 KiB
Text
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Package warnings implements error handling with non-fatal errors (warnings).
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import path: "gopkg.in/warnings.v0"
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package docs: https://godoc.org/gopkg.in/warnings.v0
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issues: https://github.com/go-warnings/warnings/issues
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pull requests: https://github.com/go-warnings/warnings/pulls
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A recurring pattern in Go programming is the following:
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func myfunc(params) error {
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if err := doSomething(...); err != nil {
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return err
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}
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if err := doSomethingElse(...); err != nil {
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return err
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}
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if ok := doAnotherThing(...); !ok {
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return errors.New("my error")
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}
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...
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return nil
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}
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This pattern allows interrupting the flow on any received error. But what if
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there are errors that should be noted but still not fatal, for which the flow
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should not be interrupted? Implementing such logic at each if statement would
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make the code complex and the flow much harder to follow.
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Package warnings provides the Collector type and a clean and simple pattern
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for achieving such logic. The Collector takes care of deciding when to break
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the flow and when to continue, collecting any non-fatal errors (warnings)
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along the way. The only requirement is that fatal and non-fatal errors can be
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distinguished programmatically; that is a function such as
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IsFatal(error) bool
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must be implemented. The following is an example of what the above snippet
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could look like using the warnings package:
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import "gopkg.in/warnings.v0"
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func isFatal(err error) bool {
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_, ok := err.(WarningType)
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return !ok
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}
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func myfunc(params) error {
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c := warnings.NewCollector(isFatal)
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c.FatalWithWarnings = true
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if err := c.Collect(doSomething()); err != nil {
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return err
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}
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if err := c.Collect(doSomethingElse(...)); err != nil {
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return err
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}
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if ok := doAnotherThing(...); !ok {
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if err := c.Collect(errors.New("my error")); err != nil {
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return err
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}
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}
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...
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return c.Done()
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}
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For an example of a non-trivial code base using this library, see
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gopkg.in/gcfg.v1
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Rules for using warnings
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- ensure that warnings are programmatically distinguishable from fatal
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errors (i.e. implement an isFatal function and any necessary error types)
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- ensure that there is a single Collector instance for a call of each
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exported function
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- ensure that all errors (fatal or warning) are fed through Collect
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- ensure that every time an error is returned, it is one returned by a
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Collector (from Collect or Done)
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- ensure that Collect is never called after Done
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