72 lines
2.8 KiB
Markdown
72 lines
2.8 KiB
Markdown
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---
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date: "2019-02-12:00:00+02:00"
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title: "Custom Errors"
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draft: false
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type: "doc"
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menu:
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sidebar:
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parent: "practical instructions"
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---
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# Custom Errors
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All custom errors are defined in `pkg/models/errors.go`.
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You should add new ones in this file.
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Custom errors usually have fields for the http return code, a [vikunja-specific error code]({{< ref "../usage/errors.md">}})
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and a human-readable error message about what went wrong.
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An error consists of multiple functions and definitions:
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{{< highlight golang >}}
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// This struct holds any information about this specific error.
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// In this case, it contains the user ID of a nonexistand user.
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// This type should always be a struct, even if it has no values in it.
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// ErrUserDoesNotExist represents a "UserDoesNotExist" kind of error.
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type ErrUserDoesNotExist struct {
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UserID int64
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}
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// This function is mostly used in unit tests to check if a returned error is of that type.
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// Every error type should have one of these.
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// The name should always start with IsErr... followed by the name of the error.
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// IsErrUserDoesNotExist checks if an error is a ErrUserDoesNotExist.
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func IsErrUserDoesNotExist(err error) bool {
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_, ok := err.(ErrUserDoesNotExist)
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return ok
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}
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// This is the definition of the actual error type.
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// Your error type is _required_ to implement this in order to be able to be returned as an "error" from functions.
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func (err ErrUserDoesNotExist) Error() string {
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return fmt.Sprintf("User does not exist [user id: %d]", err.UserID)
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}
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// This const holds the vikunja error code used to be able to identify this error without having to
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// rely on an error string.
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// This needs to be unique, so you should check whether the error code exists or not.
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// The general convention for error codes is as follows:
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// * Every "group" errors lives in a thousend something. For example all user issues are 1000-something, all
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// list errors are 3000-something and so on.
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// * New error codes should be the current max error code + 1. Don't take free numbers to prevent old errors
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// which are depricated and removed from being "new ones". For example, if there are error codes 1001, 1002, 1004,
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// a new error should be 1005 and not 1003.
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// ErrCodeUserDoesNotExist holds the unique world-error code of this error
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const ErrCodeUserDoesNotExist = 1005
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// This is the implementation which returns an http error which is then passed to the client.
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// Here you define the http status code with which one the error will be returned, the vikunja error code and
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// a human-readable error message.
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// HTTPError holds the http error description
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func (err ErrUserDoesNotExist) HTTPError() web.HTTPError {
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return web.HTTPError{
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HTTPCode: http.StatusNotFound,
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Code: ErrCodeUserDoesNotExist,
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Message: "The user does not exist.",
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}
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}
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{{< /highlight >}}
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