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feat: add package to handle end-user error messages. (#13)
Because - Connector errors produce an unfriendly output in VDP. - In order to trigger a pipeline, several repositories are involved in the execution. This commit - Implements a way to add and extract end-user messages to errors.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,50 @@ | ||
| # errmsg | ||
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| Add end-user messages to errors. | ||
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| `err.Error()` doesn't usually provide a human-friendly output. `errmsg` allows | ||
| errors to carry an (extendable) end-user message that can be used in e.g. | ||
| handlers. | ||
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| Here is an example on how it can be used: | ||
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| ```go | ||
| package connector | ||
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| import ( | ||
| // ... | ||
| "github.com/instill-ai/x/errmsg" | ||
| ) | ||
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| func (c *Client) sendReq(reqURL, method, contentType string, data io.Reader) ([]byte, error) { | ||
| // ... | ||
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| res, err := c.HTTPClient.Do(req) | ||
| if err != nil { | ||
| err := fmt.Errorf("failed to call connector vendor: %w", err) | ||
| return nil, errmsg.AddMessage(err, "Failed to call Vendor API.") | ||
| } | ||
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| if res.StatusCode < 200 || res.StatusCode >= 300 { | ||
| err := fmt.Errorf("vendor responded with status code %d", res.StatusCode) | ||
| msg := fmt.Sprintf("Vendor responded with a %d status code.", res.StatusCode) | ||
| return nil, errmsg.AddMessage(err, msg) | ||
| } | ||
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| // ... | ||
| } | ||
| ``` | ||
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| ```go | ||
| package handler | ||
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| func (h *PublicHandler) DoAction(ctx context.Context, req *pb.DoActionRequest) (*pb.DoActionResponse, error) { | ||
| resp, err := h.triggerActionSteps(ctx, req) | ||
| if err != nil { | ||
| resp.Outputs, resp.Metadata, err = h.triggerNamespacePipeline(ctx, req) | ||
| return nil, status.Error(asGRPCStatus(err), errmsg.MessageOrErr(err)) | ||
| } | ||
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| return resp, nil | ||
| } | ||
| ``` |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,67 @@ | ||
| package errmsg | ||
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| import ( | ||
| "errors" | ||
| "fmt" | ||
| ) | ||
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| // endUserError is an error that holds an end-user message. | ||
| type endUserError struct { | ||
| message string | ||
| cause error | ||
| } | ||
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| // Error implements the error interface by returning the internal error message. | ||
| func (e *endUserError) Error() string { return e.cause.Error() } | ||
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| // Unwrap implements the Unwrap interface. | ||
| func (e *endUserError) Unwrap() error { return e.cause } | ||
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| // As implements the required function to ensure errors.As can properly match | ||
| // endUserEror targets. | ||
| func (e *endUserError) As(target any) bool { | ||
| if tgt, ok := target.(**endUserError); ok { | ||
| *tgt = e | ||
| return true | ||
| } | ||
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| return false | ||
| } | ||
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| // AddMessage adds an end-user message to an error, prepending it to any | ||
| // potential existing message. | ||
| func AddMessage(err error, msg string) error { | ||
| if msgInCause := Message(err); msgInCause != "" { | ||
| msg = fmt.Sprintf("%s %s", msg, msgInCause) | ||
| } | ||
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| return &endUserError{ | ||
| cause: err, | ||
| message: msg, | ||
| } | ||
| } | ||
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| // Message extracts an end-user message from the error. | ||
| func Message(err error) string { | ||
| for err != nil { | ||
| eu := new(endUserError) | ||
| if errors.As(err, &eu) && eu.message != "" { | ||
| return eu.message | ||
| } | ||
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| err = errors.Unwrap(err) | ||
| } | ||
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| return "" | ||
| } | ||
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| // MessageOrErr extracts an end-user message from the error. If no message is | ||
| // found, err.Error() is returned. | ||
| func MessageOrErr(err error) string { | ||
| msg := Message(err) | ||
| if msg == "" { | ||
| return err.Error() | ||
| } | ||
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| return msg | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,72 @@ | ||
| package errmsg | ||
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| import ( | ||
| "errors" | ||
| "fmt" | ||
| "testing" | ||
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| qt "github.com/frankban/quicktest" | ||
| ) | ||
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| func TestAddAndExtractMessage(t *testing.T) { | ||
| c := qt.New(t) | ||
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| testcases := []struct { | ||
| name string | ||
| wantMsg string | ||
| wantErr string | ||
| err error | ||
| }{ | ||
| { | ||
| name: "no message", | ||
| wantMsg: "boom", | ||
| wantErr: "boom", | ||
| err: errors.New("boom"), | ||
| }, | ||
| { | ||
| name: "message on top of stack", | ||
| wantMsg: "Something went wrong.", | ||
| wantErr: "boom", | ||
| err: AddMessage(errors.New("boom"), "Something went wrong."), | ||
| }, | ||
| { | ||
| name: "message in wrapped error (fmt)", | ||
| wantMsg: "Something went wrong.", | ||
| wantErr: "bang: boom", | ||
| err: fmt.Errorf( | ||
| "bang: %w", | ||
| AddMessage(errors.New("boom"), "Something went wrong."), | ||
| ), | ||
| }, | ||
| { | ||
| name: "message in joint error", | ||
| wantMsg: "Something went wrong.", | ||
| wantErr: "bang\nboom", | ||
| err: errors.Join( | ||
| errors.New("bang"), | ||
| AddMessage(errors.New("boom"), "Something went wrong."), | ||
| ), | ||
| }, | ||
| { | ||
| name: "multi-message error", | ||
| wantMsg: "An error happened. Something went wrong.", | ||
| wantErr: "bang: boom", | ||
| err: AddMessage( | ||
| // handle error coming from downstream | ||
| fmt.Errorf("bang: %w", | ||
| // downstream error also contains message | ||
| AddMessage(errors.New("boom"), "Something went wrong."), | ||
| ), | ||
| // add message to downstream error | ||
| "An error happened.", | ||
| ), | ||
| }, | ||
| } | ||
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| for _, tc := range testcases { | ||
| c.Run(tc.name, func(c *qt.C) { | ||
| c.Check(MessageOrErr(tc.err), qt.Equals, tc.wantMsg) | ||
| c.Check(tc.err, qt.ErrorMatches, tc.wantErr) | ||
| }) | ||
| } | ||
| } |
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